ABS A ST TRA ACCTS S - Shock and Vibration Exchange Symposium/86th Abstract Book.pdf · Modeling and Simulation with User Material Models using ABAQUS ... Investigation of an Extension

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ACRATION SYBER 5 – 8

CTSYMPOSIUM

8, 2015

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CONTENTS SESSION 1: UNDEX I

Response of Composite Plates to Near Field Underwater Explosions Including Polyurea Coating Effects ................... 1

An Experimental Study of Loading from UNDEX Bubble Collapse ................................................................................. 1

Application of the Coupled Eulerian‐Lagrangian (CEL) technology in Abaqus/Explicit for near field UNDEX ............... 1

Physics Based Modeling & Simulation For Shock & Vulnerability Assessments; Navy Enhanced Sierra Mechanics (NESM) ........................................................................................................................................................................... 2

Equipment and Deck Fixture Response Prediction Using A 2‐DOF Oscillator ............................................................... 2

SESSION 2: STRUCTURAL RESPONSE

Progress on Verification and Acceptance of the Residual Mass Dynamic Design Analysis Model ................................ 2

AT Planner for Bridges: Computationally Efficient Software For Assessing The Response Of Bridge Components Subjected To Blast Loads ............................................................................................................................................... 2

Detailing of Steel Structures Subjected to Blast Loading ............................................................................................... 3

Shock Optimized Foundation Designs ........................................................................................................................... 4

Precision Guidance Kit (PGK) Power Electronics Module Gun Launch .......................................................................... 4

The Damage Procedure of a H‐type Beam to a Inclined Dynamic Force ....................................................................... 4

SESSION 3: MATERIAL CHARACTERIZATION AND EVALUATION UNDER MECHANICAL SHOCK

Development of a Dynamic Mechanically Matched Explosive Simulant for Shock Testing Embedded Electronic Components .................................................................................................................................................................. 5

Shock Testing of Conductive and Electronic Materials .................................................................................................. 5

Polymeric Composite Characterization Using Embedded Instrumentation in High‐G Loading ..................................... 5

Evaluation of Damage Induced by Embedded Masses in Polymeric Composites ......................................................... 6

Wave Propagation Methods for Modeling Pyrotechnic Shock Attenuation across Material and Joints ....................... 6

SESSION 4: MECHANICAL SHOCK: ADVANCED MODELING AND TESTING METHODS

Medium Weight Shock Machine (MWSM) Equipment Kill Criteria: Test Results .......................................................... 7

Medium Weight Shock Machine (MWSM) Equipment Kill Criteria: Model Development ............................................ 7

An Updated Medium Weight Shock Machine And Ballasted Spring Deck Fixture FEA Model ...................................... 7

Effects Of Geometric Nonlinearity On Shock Response Of The Antenna Structure ...................................................... 7

Response Limited Shaker Shock Testing ........................................................................................................................ 8

Development of a Single Input Multiple Output (SIMO) Input Derivation Algorithm for Oscillatory Decaying Shocks 8

SESSION 5: ISOLATION

A New Short Mount for Barge Shock Isolation .............................................................................................................. 8

Selection of Shock Tech IIsolation Systems for Populated 901d Racks ......................................................................... 9

Design and Evaluation of a Support Platform for a Bulkhead Mounted Electronic Unit ............................................... 9

Using Wire Rope Isolators for Seismic Protection ....................................................................................................... 10

Modelling The Response to Underwater Explosions of Internal Platforms Resiliently Mounted with Rubber Shock Isolators ....................................................................................................................................................................... 10

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Wire Rope vs. Elastomer Isolators for Naval Applications ........................................................................................... 11

SESSION 6: UNDEX ANALYSIS APPLICATIONS

Analysis of an Implosion Mitigation Device ................................................................................................................. 11

Proof‐of‐Concept Testing for Implosion Mitigation Device ......................................................................................... 12

Computational Modeling of Shock Initiated Implosion of a Metal Tube within a Closed Tube .................................. 12

Testing and analysis of a Water‐Borne IED (WBIED) to characterize the above and below waterline explosive loading environment ................................................................................................................................................... 12

Determination of a Design Pressure for External Volumes to Resist Implosion Failure when Subjected to Combined Shock and Submergence Loading ................................................................................................................................ 12

SESSION 7: MECHANICAL SHOCK USING ENERGY METHODS

Use of Energy & Temporal Duration to Synthesize SRS Compatible Acceleration ...................................................... 13

Shock sequence at a forward location in a large boat‐ analysis and generation of a laboratory simulation regime .. 13

Mechanical Shock Failure Predictions of a Cantilever Structure Using Energy Response Spectra Methods .............. 14

A Method for Extrapolating Haversine Shock Test Input Levels .................................................................................. 14

Calculation of the Dissipated Energy Spectrum from a Fourier Amplitude Spectrum ................................................ 15

SESSION 8: VIBRATION AND ACOUSTIC TESTING/ANALYSIS

6 DOF Shock and Vibration: Testing and Analysis ....................................................................................................... 15

Phase Influence on the Response of a Slender Beam Structure under Combined Rotational and Transverse Base Excitations ................................................................................................................................................................... 16

The Derivation of Multiple‐Input‐Multiple Output (MIMO) Acoustic Test Specifications to Simulate a Missile Flight ..................................................................................................................................................................................... 16

The Effects Of Vibration On Measurement Microphones ........................................................................................... 16

The Use of Quaternions to Compensate for Geometric Distortion in Dynamic Seismic and Satellite Testing ............ 17

SESSION 9: EXPERIMENTAL TESTING METHODS AND INSTRUMENTATION IN HIGH‐G ENVIRONMENTS

Using Multiple G‐Switches for Target Detection ......................................................................................................... 17

Mechanical Survivability of Embedded Mass in Quasi‐Static and Dynamic High‐Pressure Environment ................... 17

Experimental Evaluation of Additively Manufactured Supports Under High‐g Loads ................................................. 18

Measuring Embedded Dynamic Pressure: Design, Characterization and Implementation ......................................... 18

SESSION 10: ADVANCED DATA ANALYSIS IN VIBRATION

The Solution to Random Over‐Testing ........................................................................................................................ 18

Employing Monte Carlo Techniques to Explore the Spectral Density Matrix Solution Space ..................................... 19

Natural Frequencies of Layered Beams Using a Continuous Variation Model ............................................................ 19

Tactical Transportation Vibration Characterization and Comparison to MIL‐STD‐810G ............................................. 20

SESSION 11: RESPONSE TO DETONATIONS / ANALYSIS OF DETONATIONS

Development of a Scalable/Selectable Wall Breaching Munition ............................................................................... 21

Analysis of Blast Overpressure from Ammunition Compartment Events ................................................................... 21

Analysis of Craters from Large Buried Charges ........................................................................................................... 21

A Lagrangian particle formulation for modeling fragmentation processes ................................................................. 22

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Simulation of experiments which show that reflection pressure time history from ground shock depends on the reflected structure's stiffness and mass ...................................................................................................................... 22

SESSION 12: THE NAVY ENERGETIC MODELING ORACLE (NEMO)

Introducing The Navy Energetic Modeling Oracle (NEMO) ......................................................................................... 23

Sierra Mechanics & Its Critical Contributions to NESM ............................................................................................... 23

NEMO Parallel Code Communication & The Navy Standard Coupler (NSC) ................................................................ 23

Approach to Fluid‐Structure Interactions within a Fixed Eulerian CFD Grid ............................................................... 24

Verification & Validation of NEMO .............................................................................................................................. 24

SESSION 13: AIRBLAST TESTING AND M&S OF SYSTEMS / MODELING FOR STRUCTURAL RESPONSE

Experimental Series to Evaluate the Performance of the Modular Protective System (MPS) Against Airblast Loading ..................................................................................................................................................................................... 24

Development and Experimental Evaluation of the Modular Protective System (MPS) Multi‐Purpose Guard Tower 25

The Role of Geometric Imperfections on Quasi‐static Axial Crushing of Bisected Honeycomb Structures ................ 25

Steady State Response of Pipes with Various End Supports and Geometric Imperfections ....................................... 26

Simplified Model Generation for Exodus II .................................................................................................................. 26

SESSION 14: ACOUSTIC AND VIBRATION ENVIRONMENTS: CHARACTERIZATION AND ANALYSIS

Performance Evaluation of Flow Induced Noise Models for a Cylinder in Axial Flow ................................................. 27

The Derivation of Appropriate Laboratory Vibration Test Durations and Number of Shock Hits from Non Stationary Field Test Data ............................................................................................................................................................. 27

Analysis of the vibration measured during exposure of a launcher to an in‐laboratory simulated dynamic regime at the rear of a fast boat .................................................................................................................................................. 27

Vibrations at an aft location on a large boat‐ analysis and generation of a laboratory simulation regime ................ 28

SESSION 15: BALLISTICS EFFECTS: MODELING AND TESTING

Modeling and Simulation with User Material Models using ABAQUS ......................................................................... 29

Variables Impacting the Projectile Dynamics near Muzzle Exit ................................................................................... 29

Stress Testing of Mortar Baseplates – Method and Validation ................................................................................... 29

Weapon Ricochet as a Continuously Decaying Process ............................................................................................... 30

SESSION 16: UNDEX ASSESSMENT TOOLS / NAVY SHOCK REQUIREMENTS AND TESTING

Decision‐Aid Software for UNDEX Qualification and Optimization ............................................................................. 31

ADQUES Validation ...................................................................................................................................................... 31

Shock Environment Comparison Methods .................................................................................................................. 31

Investigation of an Extension of DDAM for External Components .............................................................................. 32

Impact of Recent Revision of US Navy Instruction and Standard on Navy Ship Equipment Shock Qualification and Navy Ship Shock Hardness Certification ...................................................................................................................... 33

A Practical Band Based Approach for Determination of Shock Response Frequence (SRF) of Class II Equipment for use with MIL‐S‐901E in Cases Where SRF is Useful for Optimal Shock Qualification Testing of Class II Equipment ... 33

SESSION 17: INSTRUMENTATION AND MEASUREMENTS

Yield Estimate of Wasp Prime Using Digitized Nuclear Fireball Films ......................................................................... 33

Assessment of Dynamic Performance Characteristics of Piezoelectric Strain Gauges ................................................ 34

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Contamination of and Solution for Cable Generated Noise in Accelerometer Signals ............................................... 34

Acoustic Measurements In Air Flow ............................................................................................................................ 34

Dynamic Materials Testing to Blast Testing, Equipment Qualifications ...................................................................... 34

SESSION 18: FLIGHT SYSTEM TESTING / TESTING METHODS AND CORRELATION

Finite Element Simulation of a Direct‐Field Acoustic Test of a Flight System Using Acoustic Source Inversion ......... 35

The Significance of Combined Vibration and Acceleration Environments for Flight Testing ...................................... 35

The Future of Testing in Combined Environments for Flight Hardware ...................................................................... 35

Analysis of the Crack Strain Difference of Two Size Experiment Specimen to Shock Load ......................................... 36

SESSION 19: POST BLAST FORENSIC

Investigation of Relationships between Crater Geometry and Soil Type and Condition ............................................ 36

Experimental Analysis of Vehicle‐Borne Improvised Explosive Devices ...................................................................... 37

Investigation of Key Parameters for Post‐Blast Crater Analysis .................................................................................. 37

Effect of Barrier Wall Shielding on the Relationship between Overpressure and Dynamic Pressure from a Detonation ................................................................................................................................................................... 38

Forensic Characterization of Small Arms and Propelled Munitions using Image, Chemical, and Metallurgical Analysis ..................................................................................................................................................................................... 38

SESSION 20: UNDEX II

The recovery method of the measured signal curve of an underwater explosion shock pressure ............................. 38

The Coupling Effect Of The Static And Shock Load On The Responses Of A Ring‐Stiffened Cylinder .......................... 39

Study for Effective Shock Analysis Methodology with UNDEX Experimental Data using Down Scale Ship Model ..... 39

The equivalence of shock environments of the real ship and the SFSP to a heavy resilient mount equipment ......... 40

Shock Analysis of an Antenna Structure Subjected to Underwater Explosions .......................................................... 40

SESSION 21: BLAST RISKS TO VEHICLES AND STRUCTURES

Comparison of Results from Experiments with Impulse Measuring Device that Quantify Effects of Soil Placement Parameters on Aboveground Impulse ......................................................................................................................... 41

Comparisons of Results from Experiments and Simulations with Impulse Devices that Quantify Effects of Charge Parameters, Depth of Burial, and Soil Type ................................................................................................................. 41

Dual State Energy Absorbing Mechanism to Mitigate Vertical Shock Loading ............................................................ 41

SESSION 22: MECHANICAL SHOCK: INSTRUMENTATION AND MODELING/SIMULATION

Analysis of Various Simulations of Complex Components under Mechanical Shock .................................................. 42

The Effect of Boundary Condition Assumptions on the Predicted Dynamic Response of Packaged Electronic Assemblies ................................................................................................................................................................... 42

Characterization of the Endevco 7280A Transverse Sensitivity Performance to Full Scale Range .............................. 42

Characterization of Meggitt Sensing Systems’ Updated Hopkinson Bar Capability .................................................... 43

A Novel Micro‐CT Data Based Finite Element Modeling Technique to Study Reliability of Densely Packed Fuze Assemblies ................................................................................................................................................................... 43

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UNDEX I

RESPONSE OF COMPOSITE PLATES TO NEAR FIELD UNDERWATER EXPLOSIONS INCLUDING POLYUREA COATING EFFECTS Dr. James LeBlanc, Naval Undersea Warfare Center, Division Newport The response of composite plates, including polyurea coatings, subjected to near field underwater explosion (UNDEX) loading has been studied through experiments and corresponding numerical simulations. A water filled blast tank is used for the conduct of all experiments with the transient plate response captured through the use of high speed photography coupled with Digital Image Correlation. Improved plate response is observed through the use of a thicker plate or through the application of a polyurea coating, although there is a weight penalty associated with the additional material which should be considered. Computational models of the experiments have been developed utilizing the commercial finite element code LS‐Dyna. A high level of correlation is observed between the numerical simulations and the experimental data. AN EXPERIMENTAL STUDY OF LOADING FROM UNDEX BUBBLE COLLAPSE Mr. John M. Brett, Defence Science & Technology Mr. George Yiannakopoulos, Defence Science & Technology Mr. Andrew Krelle, Defence Science & Technology The loading experienced by a submerged structure in close proximity to an underwater explosion is complex and sensitive to the distance of the explosion from the structure. To study this loading, the authors have conducted experiments in which small scale charges were detonated in close proximity to a flat plate target instrumented with an array of surface mounted pressure transducers. High speed imaging was used to track the dynamics of the gas bubble as it interacted with and loaded the target structure. In this paper we describe the experiment and present some preliminary results detailing the complex loading phenomena at play, including cavitation collapse, the bubble pulse, pressure wave and water jetting. APPLICATION OF THE COUPLED EULERIAN‐LAGRANGIAN (CEL) TECHNOLOGY IN ABAQUS/EXPLICIT FOR NEAR FIELD UNDEX Mr. Mike Sasdelli, Dassault Systemes SIMULIA Corp Mr. Dave Woyak, Dassault Systemes SIMULIA Corp UNDEX applications can be broadly classified as near field (close‐in) or far field. From a simulation standpoint, the proximity of the blast to the structure (i.e. whether far‐field or near‐field) dictates whether an acoustic based modeling approach can be taken or whether it is necessary to go to a more detailed modeling approach which may include direct modeling of the explosive charge and modeling approaches to allow for moderate to significant deformation of the structure and associated fluid‐structure interface. In Abaqus, the acoustic based modeling approach has been utilized for far‐field UNDEX applications since its introduction in Abaqus version 6.1, released in 2001. Earlier releases of Abaqus used a coupling to the 3rd‐party USA code for modeling of underwater shock applications. This study investigates the use of the Coupled Eulerian‐Lagrangian (CEL) approach in Abaqus/Explicit for near field blast, and in this initial work focuses on the characterization of the explosive and water materials to accurately capture the shock pulse without a structure included. The results are compared to analytical and experimental data.

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PHYSICS BASED MODELING & SIMULATION FOR SHOCK & VULNERABILITY ASSESSMENTS; NAVY ENHANCED SIERRA MECHANICS (NESM) Dr. E. Thomas Moyer, NSWC Carderock No abstract provided. EQUIPMENT AND DECK FIXTURE RESPONSE PREDICTION USING A 2‐DOF OSCILLATOR Mr. Rick Griffen, HII‐NNS Mr. Matt Davis, HII‐NNS

An effort to develop equipment design spectra for the Deck Simulator Fixtures used with the MIL‐S‐901D Floating Shock Platform required assessment of several hundred equipment and DSF frequency, mass and damping combinations. Such a parametric study can be accelerated if this test arrangement can be adequately simulated by a simple two degree of freedom particle model. Several models of simulated equipment attached to the midspan of a uniform pinned‐end beam driven by a measured FSP inner bottom motions established a set of baseline responses. Comparison to varied 2‐DOF models established that a base oscillator with mass equaling 81% of the deck mass provides a reasonable equipment response approximation provided the equipment fixed base frequency is not significantly greater than the deck frequency. For higher frequency equipment, the response of a second model representing the deck third bending mode must be applied.

STRUCTURAL RESPONSE

PROGRESS ON VERIFICATION AND ACCEPTANCE OF THE RESIDUAL MASS DYNAMIC DESIGN ANALYSIS MODEL Mr. Rick Griffen, Huntington Ingalls Industries – Newport News Shipbuilding The standard naval shock analysis methodology for the assessment of equipment and foundations is the Dynamic Design Analysis Method (DDAM). This method is an evolution of the response spectrum analysis technique developed for earthquake assessment. Some procedures for implementing this method set modal mass recovery requirements that are difficult to meet in many common models. A modification of this method, called RM‐DDAM, was presented at the 83rd Shock & Vibration Symposium that offers to resolve this issue by altering the DDAM such that its evaluation phase always includes the full model mass through the assignment of all unrecovered residual modal mass to an additional synthetic n+1 mode. This short topic presents progress to date in a National Shipbuilding Research Program task to verify the utility of the RM‐DDAM approach and define a procedure for its implementation. AT PLANNER FOR BRIDGES: COMPUTATIONALLY EFFICIENT SOFTWARE FOR ASSESSING THE RESPONSE OF BRIDGE COMPONENTS SUBJECTED TO BLAST LOADS Dr. Eric Williamson, University of Texas at Austin Mr. Eric L. Sammarco, Protection Engineering Consultants Mr. Joeny Q. Bui, Protection Engineering Consultants Dr. David J. Stevens, Protection Engineering Consultants Dr. C. Kennan Crane, US Army Corps of Engineers, ERC Terrorist attacks against transportation infrastructure have generated significant interest in the topic of bridge security. The protective design of bridges involves unique loading and response characteristics

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that cannot be easily adopted from the wealth of information that already exists for the protective design of buildings. Over the past decade, research on bridge security has addressed vulnerability assessments, risk‐based prioritization methods, characterization of blast loads on different bridge components, computational modeling, and blast mitigation techniques. Although much research is still needed, the field has matured to the point where it is appropriate to start incorporating protective design principles in the design of bridges. Hence, research results must be made available to appropriate users within the bridge analysis and design community. The objective of the research described in this presentation is to develop user‐friendly and computationally efficient software that, given a threat scenario and structural bridge component of interest, characterizes demand on the selected component and provides an estimate of peak dynamic response and incurred damage. Such software will allow practicing bridge engineers to assess the vulnerability of critical bridge components without having to rely on more time‐consuming, costly, and complex resources such as physical testing or high‐fidelity finite element simulations. In this presentation, a general overview of the software, including a discussion of the available threats and bridge components, will be provided. Results obtained from the software will be compared with test data and detailed nonlinear finite element models to demonstrate its accuracy for the considered cases. DETAILING OF STEEL STRUCTURES SUBJECTED TO BLAST LOADING Mr. David A. Holgado, M. Sc., P.E. Ms. Rachel Stansel, Ph. D., ABS Consulting Mr. Darrell Barker, P.E., ABS Consulting Structures in petrochemical facilities or DoD installations are often used in areas that may be subjected to blast loading. In most cases, steel structures are preferred for their ductile capability during dynamic response. A structure subjected to blast loading that is adequately designed and detailed can achieve very large deformations prior to reaching its limit capacity. These large deflections generate secondary effects which are not normally addressed in conventional design. These secondary effects include: a) large axial forces generated in all components, b) framing nodes displaced producing dynamic eccentricity, and c) additional moments at the supports due to the latter, e.g. P‐delta effects. The tensile axial force built into the system due to the large‐deflection effect not only stretches the components but also the support connections and component splices. Even a small axial deformation along the component axis could produce significant tensile force in that same component. During the analysis, if some of the axial deformation could be relieved fully or partially incorporating the stiffness connection concept the axial force along the component and connection could also be reduced. Structural systems designed for conventional loading are always restricted to deflection limits, mainly intended for serviceability (i.e., small deflection). Conventional detailing addresses effects related to only small deflections in the system. Furthermore, depending of the demand on the structural system under blast loading, the material response could be beyond the yielding limits. The commonly used Single Degree of Freedom (SDOF) approach assumes ideal material non‐linear behavior (i.e. elastic ‐ perfect plastic). However, depending of the grade of steel, the steel tensile strength could be 25% – 30% higher than the yielding one. Then, using only the yielding stress could be conservative enough for designing the component itself but un‐conservative for the corresponding connection design.

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Depending on the provided detailing, components supports may generate tensile forces, shear forces and moments which vary in time. Those forces and moments will produce interactions of stresses on each connection element. When using a more refined analysis such as Multi‐Degree of Freedom (MDOF), the internal forces output may be inappropriate while neglecting that dynamic interaction which will result in an inadequate connections design. Therefore, the detailing of steel structures subjected to blast loading has not been properly addressed by blast standards and design guidelines. This paper intends to highlight the possible effects that could generate secondary effects in the analysis on the main framing as well as secondary framing. Furthermore, several recommendations are provided on how to address those highlighted effects through proposed detailing. SHOCK OPTIMIZED FOUNDATION DESIGNS Mr. Carlos, de Lima, Altair Engineering Mr. Danie, Pusey, Altair Engineering

Underwater explosions may cause dynamic loads that can structurally damage essential components and equipment on board submarines and naval vessels. In order to design these items for military use, they must be qualified for underwater shock loads. DDAM (Dynamic Design Analysis Method) is a form of response spectrum analysis developed by the US Navy to evaluate the structural performance of such components. It estimates the dynamic response of a component to a shock load caused by the motion of the hull. In this paper, optimization will be used to drive the design of a foundation model using DDAM as a validation criteria. OptiStruct is a commercially available simulation software that not only can validate structures using DDAM, but has unique built in optimization capabilities to effectively maximize performance while reducing weight, cost and design cycles. Results will be compared to baseline model and optimization methods and definitions will be discussed PRECISION GUIDANCE KIT (PGK) POWER ELECTRONICS MODULE GUN LAUNCH Mr. Miroslav Tesla, US ARMY ARDEC Mr. Eric Marshall, US ARMY ARDEC Mr. Michael Hollis, US ARMY ARDEC As part of a root cause analysis, modeling and simulation was used to predict strains of a printed wiring board (PWB) during cannon launch environment. Predicted strains were used to asses if the capacitors on the PWB would be at risk of mechanical failure. The PWB is a power conditioning board used in an artillery system. There are nine capacitors of interest on the particular PWB. Capacitors were not physically modeled; instead elements at the location of the capacitors were selected and the principle strains were monitored. The failure criteria was to compare the strain magnitude with a strain range that was based on work performed at the Center for Advanced Life Cycle Engineering (CALCE) University of Maryland. Results from the analysis predict that the capacitor which failed is at a location on the PWB that exceeds the strain failure criteria. THE DAMAGE PROCEDURE OF A H‐TYPE BEAM TO A INCLINED DYNAMIC FORCE Mr. Haikun Wang, China Ship Scientific Research Center Mr. Jianhu Liu, China Ship Scientific Research Center

Most of ship hull structures can be simplified as a H‐type beam when dealing with the local damage to blast. Nowadays some new explosion protection structures are employed the membrane mechanism to

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enhance the anti‐shock capability and this structure can usually endure large deformation. When the ship hull jointed with the membrane structure is exposed to strong explosion loads, the joint structure is the key point to damage. The damage of the membrane part of the joint structure has widely investigated previously, however, the damage of the H‐type beam has rarely studied and it is typically loaded by an inclined dynamic force. If the H‐type beam suffers an inclined load, there will be bending moment, shearing force and axial force inside the beam and an obvious coupling effect between dynamic elastic‐plastic buckling and yield rupture is existed that is of very important influence to the ultimate loading capability. In order to set up the criteria of a H‐type beam to inclined dynamic loading, the damage procedures are the primary item that can find the main cause of the damage. The damage procedure of H‐type beam under a inclined dynamic force was investigated by experimental and numerical method, and the influence of beam section geometry, beam span, loading position and incline angle on the damage procedure were investigated. On this basis, the failure criterion and ultimate loading capability evaluating method of H‐type beam structure were proposed that can be used for improving the hull structure strength to explosions.

DEDICATED SESSION: MATERIAL CHARACTERIZATION AND EVALUATION UNDER MECHANICAL SHOCK

DEVELOPMENT OF A DYNAMIC MECHANICALLY MATCHED EXPLOSIVE SIMULANT FOR SHOCK TESTING EMBEDDED

ELECTRONIC COMPONENTS Dr. Tammy Metroke, AFRL, Dr. Jacob Dodson, AFRL, and Dr. Janet Wolfson, DTRA No abstract provided. SHOCK TESTING OF CONDUCTIVE AND ELECTRONIC MATERIALS Mr. Curtis McKinion, Doolittle Institute/AFRL Dr. Jason Foley, AFRL/RWMF

AFRL is performing research on how integrated circuits and electronics perform in extremely transient mechanical environments. In an effort to develop resilient electronics, conductive polymer composites are being developed as electronic interconnects. Conductive polymers are evaluated as solder material for electronic components surface mounted to printed circuit boards (PCB). Test articles consist of PCBs with commercial off‐the‐shelf (COTS) components such as transistors and capacitors. These test articles are subjected to increasing shock levels from an MTS drop tower; peak accelerations up to 40,000 g are achieved. The conductive polymer material is then compared to COTS solder material via strain, acceleration, and electrical measurements at the point of failure of components. High‐speed imaging is also implemented to observe component failure under shock. POLYMERIC COMPOSITE CHARACTERIZATION USING EMBEDDED INSTRUMENTATION IN HIGH‐G LOADING Dr. Jacob Dodson, Air Force Research Laboratory Lt. Hayley Chow, Air Force Research Laboratory Dr. Janet Wolfson, Air Force Research Laboratory Understanding the relative movement of the fill in weapon systems in harsh dynamic environments is crucial for effective fuzing systems. The movement of the fill inside the case can generate large internal forces and pressures on both hard mounted and embedded electronic components. While existing computational models can give some idea about the dynamic state in the explosive fill, there are

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currently no existing experimentally validated models which accurately capture energy attenuation in high‐g events in polymer composites. AFRL is leading a continuing effort to develop the tools and characterize the dynamic material response of the embedded environment in polymer composites subject to high‐g loadings. These tools utilize laboratory and field tests to: experimentally measure the embedded response (acceleration and pressure) in operational loadings, measure the severity of the shock and vibration in the embedded mechanical environment, and use the experimental data to calculate the amplitude dependent energy attenuation and propagation properties of polymeric composites. This presentation will discuss the current status of the tools characterizing the environment and the material properties determined from the operational response of the polymer composite. EVALUATION OF DAMAGE INDUCED BY EMBEDDED MASSES IN POLYMERIC COMPOSITES Lt. Hayley Chow, AFRL/RWMF It is critical to be aware of the mechanical interaction between embedded fuze components and the explosive fill to support the development of revolutionary hard target fuzing designs. In a dynamic event the motion of embedded fuze components may plastically deform the surrounding filler material, while the system’s internal pressure has the potential to crush the embedded fuze’s external housing. Primary design considerations include the density tolerance and the optimal shape of the embedded components. In order to define density tolerance for embedded fuzes, AFRL/RW is developing a methodology to assess the mechanical survivability of the surrounding polymer composite using embedded masses of differing densities. RWMF researchers utilize cannon testing with subscale projectiles fired into concrete walls to subject the embedded masses to large dynamic environments. Pre and post x‐rays are compared to determine any movement of the embedded mass during the test. Then, the embedded masses are extracted from the polymer composite and examined for damage. In upcoming tests, a drop tower will be used to subject a fixture, filled with a polymer composite and potential shapes of the embedded components, to high impact events. The final goal is to determine the embedded mass density tolerance and optimal shape that does not damage the surrounding media. This paper will discuss the current status, including polymeric composite density measurements, and future work on developing an optimal embedded mass shape for operational functionality. WAVE PROPAGATION METHODS FOR MODELING PYROTECHNIC SHOCK ATTENUATION ACROSS MATERIAL AND JOINTS Mr. Tom Irvine, Vibration Data This paper uses wave methods to model distance and joint attenuation for pyrotechnic shock propagation. A key objective to provide an analytical basis for historical NASA attenuation factors which were compiled from empirical data in the 1960s era. This legacy data is still widely used today but often with a lack of understanding of the assumptions and limitations.

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MECHANICAL SHOCK: ADVANCED MODELING AND TESTING METHODS

MEDIUM WEIGHT SHOCK MACHINE (MWSM) EQUIPMENT KILL CRITERIA: TEST RESULTS Mr. Brian Lang, NSWC Carderock Mr. Chris Szczur, American Society of Engineering Education No abstract provided. MEDIUM WEIGHT SHOCK MACHINE (MWSM) EQUIPMENT KILL CRITERIA: MODEL DEVELOPMENT Mr. Brian Lang, NSWC Carderock Mr. Chris Szczur, American Society of Engineering Education No abstract provided. AN UPDATED MEDIUM WEIGHT SHOCK MACHINE AND BALLASTED SPRING DECK FIXTURE FEA MODEL Mr. Matt Davis, Newport News Shipbuilding Mr. Rick Griffen, Newport News Shipbuilding This effort discusses refinements to a Medium Weight Shock Machine and Ballasted Spring Deck Fixture finite‐element prediction model to extend its utility to both lower and higher frequency equipment. Model modifications to date in this on‐going effort included a nonlinear force‐deflection representation of the air jacks and a two‐mode anvil representation. Testing was conducted with varying equipment masses and frequencies. The rationale for these changes are discussed and preliminary test comparisons are presented that show good correlation across a wide frequency range. EFFECTS OF GEOMETRIC NONLINEARITY ON SHOCK RESPONSE OF THE ANTENNA STRUCTURE

Mr. Yunus Ozcelik, ASELSAN Antenna structures used in electronic warfare, radar, naval, satellite, spacecraft systems encounter mechanical shock from various sources such as near miss under water explosion, pyrotechnic and ballistic shocks. Since most of the antenna structure has larger dimension in longitudinal direction and experience high frequency, high amplitude shock energy, geometric nonlinearity become crucial to predict dynamic behavior in real life. In this study, the antenna structure is modeled by Euler‐Bernoulli beam theory in order to validate finite element simulation with ANSYS, which is one of the commercial finite element software. After that, shock response of the antenna structure including geometric nonlinearity is investigated. The results for the linear system obtained from time integration and approximate methods such as Absolute Method, Square Root of Sum of Squares (SRSS), Naval Research Method, Combined Quadratic Combination (CQC) and Shock Response Spectrum Method (SRS) are compared to the nonlinear ones. Moreover, these results are compared with the ones obtained from experimental results from a drop test table.

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RESPONSE LIMITED SHAKER SHOCK TESTING Mr. Troy J. Skousen, Sandia National Laboratories Mr. Ronald G. Coleman, Sandia National Laboratories Mr. David O. Smallwood, Consultant When conducting dynamic testing on shakers is often prudent to limit the response of the test article to protect the unit from over test and to more closely represent the environment. This is an accepted practice with random vibration testing. A methodology will be presented for response limiting shaker shock testing. The method allows multiple response limit channels with independent shock response spectra limit profiles. The notches to the input shock response spectra are determined with iterative solutions of the inputs with the system transfer functions to the responses with limits. DEVELOPMENT OF A SINGLE INPUT MULTIPLE OUTPUT (SIMO) INPUT DERIVATION ALGORITHM FOR OSCILLATORY

DECAYING SHOCKS Mr. Chad A Heitman, Sandia National Laboratories Mr. Jack B. Reid, Sandia National Laboratories Mr. Vit Babuska, Sandia National Laboratories During shaker shock testing of a complex system it may be desirable to match a Shock Response Spectra (SRS) at one location while controlling the test at a different location. Further, it may be desirable to match SRSs at multiple locations. This paper describes an algorithm for deriving an optimum shaker shock input such that a weighted combination of the responses for multiple locations is matched with respect to the field data measured at those locations. This work assumes the shock environment is characterized by a SRS. Since the SRS is a nonlinear transformation of the underlying acceleration waveform, the optimization process will be based on the decayed sine synthesis algorithms developed by David Smallwood.

ISOLATION

A NEW SHORT MOUNT FOR BARGE SHOCK ISOLATION Mr. Kevork Kayayan, Shock Tech Mr. JJ Osmecki, Shock Tech Inc A new series of short, low profile, high capacity Seamounts™ has been developed at Shock Tech that meet allowable deflection in less space than with the original tall Arch mounts while still achieving effective shock reduction in the Navy’s barge test. These newer mounts makes it possible to gain additional space [1U / 1.75 inch] for equipment within the rack. This was a main objective for the isolator’s design. The short mount is reviewed in this presentation and its development program is described. The mounts are molded of Shock Damp™ – a proprietary Shock Tech elastomer. The short mount is 5 plus inches high versus 7.5 inches for the tall isolator. In one example, calculations using base and stabilizer short mounts with a 1124 lb cabinet showed 3.0 inch in compression and 15.12 g’s at the cg ‐ 14 hz barge test. The new series of mounts has been released to production, additionally has broadly enlarged the Shock Tech product line, and has extended isolator applications to the protection of electronics and special machinery in other severe shock environments. Test data and engineering characteristics of the mount are given. In its development, along with reduced height, focus was on meeting acceleration criteria in barges shock as well ensuring stability to off‐axis loads. Additionally, the ongoing development work at Shock

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Tech has resulted in improved Seamount™ design for increased energy capacity in limited space, closer control of dynamic to static stiffness characteristics, and more predictable load deflection range at temperature extremes. Multi‐axis stiffness and hysteretic curves of the newer family of Seamounts are presented and calculated response to barge test shock is reviewed. SELECTION OF SHOCK TECH IISOLATION SYSTEMS FOR POPULATED 901D RACKS Mr. Herb LeKuch, Consultant– 901D and Shock Tech Mr. Neil Donovan, Shock Tech In this presentation we highlight Shock Tech’s newer isolation systems and rugged 901d lightweight, stiffened racks to successfully protect COTS equipment to the Navy’s barge shock test. We also describe typical problems and load amplification at equipment that can occur with improperly designed isolated rack/mount systems. Simulation models and test data are used to show the shock response of isolated racks to different deck conditions We review several tests from Shock Tech/901d’s highly successful history in protecting equipment from barge shock. For example – a low frequency isolated rack system qualified for the 8 hz deck can also satisfactorily meet 14 hz and stiffer deck tests in many installations. It then has universal application on a variety of ships and locations. Engineering considerations, dynamic modeling and interaction of coupled modes are reviewed. In addition, data from several recent tests is presented. A highlight of this presentation includes calculations and visuals using Shock Tech’s proprietary (STI) software for vibration and shock analysis of isolation systems. Case studies include modeling, calculations and display of accelerations, deflections and relative motion. Capabilities of the new software are shown. The STI software is an advance in the analysis of isolated rack performance to a variety of shock loads. It is an example of what we are doing to improve and being new analytical techniques to the design of electronic enclosures and isolation systems DESIGN AND EVALUATION OF A SUPPORT PLATFORM FOR A BULKHEAD MOUNTED ELECTRONIC UNIT Mr. Fred Sainclivier, 901d Mr. Aldric Seguin, 901d Small enclosures and special machinery are sometimes bulkhead mounted onboard ship. In this arrangement the equipment is fixed to the bulkhead or support structure by means of an adapter fixture or platform. Shock isolation mounts can be installed between the bulkhead and platform or between platform and equipment. In this presentation we describe a shelf‐supported base and stabilizer mounted isolation design for a small enclosure with equipment weighing less than 200 lbs. The design involved a fabricated structural frame and an arrangement of two base mounts in compression and two stabilizer mounts in roll to a vertical load. The isolators are from among Shock Tech’s Arch series. The L‐shaped frame was directly bolted to the bulkhead support. The shelf, its mounts, their axial and cross‐axis stiffness and damping characteristics are described. Stiffness and strength of the shelf are important to the performance of the mounts. The input at each isolator can vary because the barge shock input at the elevated location of the unit on the bulkhead can be significantly different from measured deck input. This can affect the stability of the unit and ability to correctly calculate the expected response. The flexibility of the shelf and/or the degree to which the unit and shelf becomes dynamically unbalanced also influences the shock response of the unit. Results of FEA and SV analysis are given. Test specifications are Mil‐Std‐167 Vibration and Mil‐S‐901D Barge Shock, 14 hz deck

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USING WIRE ROPE ISOLATORS FOR SEISMIC PROTECTION Mr. Claude Prost, Vibro /Dynamics LLC Mr. Joshua Partyka, Vibro /Dynamics LLC Wire rope isolators are well known for shock and vibration protection of sensitive equipment in defense applications. Their unique features and predictable response by means of numerical simulation have made them a standard solution for many shock and vibration problems. Less known are their capabilities in seismic applications, although the same equations and methodology apply. Through extensive studies over the years, a vast amount of data on earthquakes has been gathered. Accordingly, the shock and vibration community, including involved governmental entities and contractors, is becoming increasingly aware of the need for better isolation products against such hazards, among which wire rope isolators are gaining popularity. One widely accepted design consisting of un‐damped springs with snubbers in seismic applications may result in substantial magnification of the seismic input when the snubbers are engaged. This is not an issue in terms of safety, but may lead to special reinforcement of the equipment at high cost, which is contradictory to today's approach of reducing cost with the use of off‐the‐shelf components (COTS). The advantage of coil springs is the capability to offer better vibration isolation, which makes them suited for generating sets, pumps, and compressors. Another solution is to reinforce the equipment to avoid the earthquake frequencies, which is impractical or at least very costly in most cases. Wire rope isolators offer substantial damping, which reduces the unavoidable magnification of seismic inputs at low frequencies. The shock response spectrum is a widely used concept and clearly shows that damping is of paramount importance for seismic protection, but doesn't provide sufficient insight into the dynamic behavior of a system under seismic conditions. Therefore, it is ideal to conduct a dynamic analysis using time histories and a non‐linear numerical model. It is the purpose of this paper to present briefly two physical case studies from Socitec's large application track record with wire rope isolators, a circuit breaker and an electronics cabinet. Both cases have been installed by highly known international contractors. Input /output diagrams and animations will be presented, along with comparisons of calculated response with experimentally measured data. MODELLING THE RESPONSE TO UNDERWATER EXPLOSIONS OF INTERNAL PLATFORMS RESILIENTLY MOUNTED WITH

RUBBER SHOCK ISOLATORS Mr. Steven De Candia, Australian Maritime College Dr. Craig Flockhart, Defence Science & Technology Rubber elastomer materials are commonly employed in passive shock isolator mounts used on board naval vessels to protect sensitive systems and equipment from shock loading. UNDEX (underwater explosion) experiments were conducted on a scaled cylindrical vessel to measure the response of an internal platform/raft structure. Tests were conducted with the platform in a hard‐mounted (bolted) configuration and when shock isolated using commercially available filled rubber mounting blocks to support the platform. Measured platform acceleration and velocity data were compared against FEA simulations using the coupled USA/LS‐Dyna codes. The FEA results for hard‐mounted configurations showed good correlation with the experiment. Modelling, however, of the shock isolated configuration

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proved more challenging due to the requirement for a rubber constitutive model capable of accurately describing the nonlinear large strain, visco‐elastic, strain rate and cyclic strain dependency of the rubber material. It is also required that the finite element type used for analysis be compatible with the material model and allow the almost incompressible volumetric behaviour of the rubber material to be captured without introducing numerical instabilities. In this paper, results will be presented from the UNDEX tests as well as a description of the author’s current progress and remaining challenges towards developing validated modelling procedures for the UNDEX shock assessment of resiliently mounted platforms incorporating rubber shock isolators. WIRE ROPE VS. ELASTOMER ISOLATORS FOR NAVAL APPLICATIONS Mr. Claude Prost, Vibro /Dynamics LLC Mr. Joshua Partyka, Vibro /Dynamics LLC Shock and Vibration have always been a concern in commercial and naval vessels, whether for the comfort of passengers or simply as a matter of survivability for the ship. While shipbuilding has benefited from many technological improvements over the years, the level of vibration and shock inputs to which onboard equipment aboard are subjected have not substantially decreased, due to the ever increasing capability of vessels. In addition, the widespread use of non‐rugged commercial off the shelf (COTS) equipment has made shock and vibration isolation even more necessary. A ship is exposed to many different inputs, such as shock from underwater explosions (UNDEX) or the vibration induced by its’ propellers, main and auxiliary engines. An isolation system that supports equipment on the ship is required to protect against both types of input. A shock isolator requires a certain amount of dynamic displacement capability in order to cope with the induced displacement step subsequent to the above mentioned type of shock, while a vibration isolator should exhibit a low dynamic stiffness in order to achieve the required amount of isolation. Selection of a shock and vibration isolator typically requires a tradeoff between both, which makes it critical to completely understand all isolator characteristics during the selection process. This paper will discuss two well‐known technologies used on naval ships, wire rope and elastomer shock and vibration isolators. The benefits and drawbacks of each type will be detailed through a number of application cases involving the medium weight shock testing machine of MIL‐S‐901D and its modelling with Socitec software SYMOS..

UNDEX ANALYSIS APPLICATIONS

ANALYSIS OF AN IMPLOSION MITIGATION DEVICE Dr. Joseph Ambrico, Naval Undersea Warfare Center Mr. Ryan Chamberlin, Naval Undersea Warfare Center Mr. Stephen Turner, Naval Undersea Warfare Center Implosion within a confined space is analyzed using equations and numerical methods. When an object implodes within a flooded space partially or totally confined by structure, the structure restricts the water flow. This can dramatically alter the pressure waves that result from the implosion. Simplified equations are written to describe a particular confined implosion case. The equations are used to investigate methods to mitigate the implosion pressure waves. Additionally, detailed computational

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simulations are used to investigate a few mitigation methods. Results are included to show the trends for the effectiveness in reducing the implosion pressure waves. PROOF‐OF‐CONCEPT TESTING FOR IMPLOSION MITIGATION DEVICE Mr. Stephen Turner, NUWC Previous experiments have demonstrated that underwater implosion within a confined space can cause severe water hammer loading. Hydrostatic implosion of unstiffened aluminum alloy 6061‐T6 cylinders within a flooded confined space has resulted in large amplitude pressure waves, which travel within the confined space. In an effort to reduce the magnitude of the pressure waves, NUWC engineers have designed and tested several implosion mitigation device concepts. Results of the testing program, which directly compare pressure waves with and without the implosion mitigation device, will be presented. COMPUTATIONAL MODELING OF SHOCK INITIATED IMPLOSION OF A METAL TUBE WITHIN A CLOSED TUBE Dr. Emily Guzas, Naval Undersea Warfare Center, Division Newport Dr. Joseph Ambrico, Naval Undersea Warfare Center, Division Newport Dr. James LeBlanc, Naval Undersea Warfare Center, Division Newport The Office of Naval Research is currently funding a collaborative effort between NUWCDIVNPT and the University of Rhode Island to perform implosion experiments within a confining tube and to develop computational models of implosions occurring within a tube. This paper covers computational modeling of a series of experiments investigating the shock initiated implosion of a metal tube (implodable volume) occurring within a closed outer tube. Experiments were carried out within a cylindrical tank (7 in diameter by 72 in length) at the University of Rhode Island, and involved concentrically placed aluminum 6061‐T6 implodable volumes. For each test, the implodable volume is hydrostatically loaded to a fraction of the critical collapse pressure before being subjected to a shock wave generated by a RP‐80 detonator cap in the fluid. At certain hydrostatic pressures, the resulting shock wave initiates collapse of the implodable volume. The pressure histories generated by the explosion and resulting implosion are captured using dynamic pressure transducers mounted on the inner surface of the outer tube. Computational models of the implosion experiments were developed using the DYSMAS software package, and the computational pressure profiles as well as collapsed shapes were compared to the experimental data. TESTING AND ANALYSIS OF A WATER‐BORNE IED (WBIED) TO CHARACTERIZE THE ABOVE AND BELOW WATERLINE

EXPLOSIVE LOADING ENVIRONMENT Mr. Ken Nahshon, NSWC Carderock Division Mr. N. Reynolds Mr. D.T. Wilson

No abstract provided. DETERMINATION OF A DESIGN PRESSURE FOR EXTERNAL VOLUMES TO RESIST IMPLOSION FAILURE WHEN SUBJECTED TO COMBINED SHOCK AND SUBMERGENCE LOADING Mr. Christopher Abate, Electric Boat Corporation Mr. Dashiell Parsons, Electric Boat Corporation No abstract provided.

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MECHANICAL SHOCK USING ENERGY METHODS

USE OF ENERGY & TEMPORAL DURATION TO SYNTHESIZE SRS COMPATIBLE ACCELERATION Mr. J. Edward Alexander, BAE Systems The Shock Response Spectrum (SRS) has been used as a structural dynamics method to characterize seismic and mechanical shock for the past eight decades. Conceived by Maurice Biot (Biot, 1932) the SRS is a method to characterize a transient acceleration in terms of the peak response of a single degree of freedom (SDOF) systems as a function of frequency. Early research of the SRS was conducted in the 1950's by the seismic community (Hudson, 1956), (Housner, 1959) to study the behavior of structures during earthquakes. Since then, the use of the SRS has become pervasive and is now used by the seismic, aerospace and defense communities. The SRS is frequently employed to specify the requirements for the structural dynamic environment that a physical system must survive (Bureau of Ships, DDAM, 1961), (MIL‐STD‐810G, 2008), (NASA‐STD‐7003, 1999), (NASA‐HDBK‐7005, 2001). When structural dynamic requirements are specified in terms of a design shock response spectrum, termed SRSD, the ability of the structure to meet this requirement can be demonstrated by either analysis or test. When the system to be shock qualified can be represented by a linear structure (i.e., linear equations of motion), a mode‐superposition analysis can be performed directly using SRSD to estimate the dynamic response of the structure. However, if the structure is be shock qualified by testing on an electro‐dynamic shaker, or if the structure is nonlinear (nonlinear equations of motion), the SRSD cannot be used directly. In these instances, an SRSD compatible base acceleration must be synthesized to either:

drive the armature of an electro‐dynamic test machine, or

be used in conjunction with a nonlinear transient analysis The synthesis of SRS compatible accelerations is not difficult and numerous procedures have been documented which do this. However, past research has demonstrated that synthesis of an SRSD compatible acceleration time‐history does not, by itself, guarantee that the dynamic response of the structure will be accurate, either by analysis or test. The motivation for the research described herein is to augment the acceleration synthesis process in order to improve physical model response accuracy. Additional constraints beyond that of compatibility with SRSD have been added to the synthesis process. These are:

Improved matching the energy input to the structure based on synthesized acceleration's compatibility with an Energy Input Spectrum (EIS).

Constraining the synthesized acceleration to match a predefined temporal duration requirement TE defined by a MIL‐STD‐810G, Method 516

SHOCK SEQUENCE AT A FORWARD LOCATION IN A LARGE BOAT‐ ANALYSIS AND GENERATION OF A LABORATORY SIMULATION REGIME Mr. Zeev Sherf, RAFAEL Environmental Engineering Center Dr. Arie Elka, RAFAEL Environmental Engineering Center Mr. Philip Hopstone, RAFAEL Environmental Engineering Center Mr. L. Klebanov, RAFAEL Environmental Engineering Center Methods of non‐stationary time‐series analysis and extreme value counting are applied to a measured shock sequence at a forward location on a large boat. The RMS time‐history, PSD matrix, kurtosis and

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probability of shock maxima, shock duration, and of energy per shock were calculated by applying appropriate analysis methods. Laboratory simulation programs have been planned, using energy considerations (avoiding the need of physics of failure models with unknown parameters), achieving reduction factors in the number of the shocks to be applied of 18 and 27 respectively. MECHANICAL SHOCK FAILURE PREDICTIONS OF A CANTILEVER STRUCTURE USING ENERGY RESPONSE SPECTRA METHODS Mr. Vit Babuska, Sandia National Laboratories Mr. Carl Sisemore, Sandia National Laboratories Mr. Jason Booher, Sandia National Laboratories

Shock Response Spectra (SRS) are the standard for describing mechanical shock events and are used for design, analysis, and defining test specifications. The basic premise behind the SRS is that all time histories with the same SRS have the same shock damage potential. Energy response spectra have been used for some time as an alternate approach to describing mechanical shock events. This paper will describe an analytical, numerical, and experimental study that compares traditional SRS with energy response spectra. A test structure supporting up to eight 3‐D printed cantilever test rods was designed for either shaker shock testing or drop table testing. Shock environments are developed such that the cantilever rods are predicted to fail during testing. Various options for tuning the frequency and failure stress of the test rods are incorporated to enable an adequate study of statistical parameters. The test results will be compared to the model predictions with a focus on using the test results to evaluate the failure prediction capabilities of the SRS and the energy response spectra for this simple problem. A METHOD FOR EXTRAPOLATING HAVERSINE SHOCK TEST INPUT LEVELS Mr. Carl Sisemore, Sandia National Laboratories Mr. Troy Skousen, Sandia National Laboratories

Fitting a haversine shock response spectrum to field collected shock data is an accepted method for subsequently performing laboratory tests or numerical system level analyses. However, in a situation where a system is required to demonstrate performance at one level but asked to simulate or evaluate performance at another, higher level, it is often uncertain how to extrapolate the shock response to different severities. To perform this analysis, an understanding of how the shock response spectrum is changed from one input level to another is necessary. In this example, a single system level drop shock test was performed in the field. A haversine shock response spectrum was fit to the experimental data for use in evaluating the system and sub‐components. Since no further system level testing was conducted, an analytical methodology for extrapolating the resulting shock input was required for evaluation of the system at different drop heights. An analytical method for extrapolating the shock response spectrum of a system sub‐component was developed using the conservation of energy relationships for a system in free‐fall. This resulted in a shock response spectrum extrapolation technique based on a combined scaling of the input velocity and shock period. Subsequent laboratory testing of a similar instrumented system at several different shock input levels was compared against the extrapolation method to evaluate the proposed scaling methodology.

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CALCULATION OF THE DISSIPATED ENERGY SPECTRUM FROM A FOURIER AMPLITUDE SPECTRUM Mr. Carl Sisemore, Sandia National Laboratories Ms. Julie Harvie, Sandia National Laboratories Mr. Troy Skousen, Sandia National Laboratories

The idea of using energy spectrum metrics in the analysis of shock data is almost as old as the shock response spectrum. Work and energy methods for the analysis of shock data was originally proposed in the 1950’s and has gained increased acceptance in recent years. Most analysis focuses on determination of the input energy spectrum as a measure of the energy imparted to the system. The input energy spectra is typically defined as a summation of the kinetic energy spectra, absorbed energy spectra, and dissipated energy spectra. The calculation of these spectra is typically performed through numerical integration in the time domain. While this works well, it can be computationally expensive for long, finely sampled time records. A methodology for calculating the input energy spectrum using a smoothed Fourier amplitude spectrum was proposed several years ago. In addition to being significantly faster computationally, the relationship between the Fourier spectrum and the input energy spectrum is important to bring additional understanding to the problem. This paper presents the mathematical derivation showing that the dissipated energy spectra can also be derived as a function of a smoothed Fourier amplitude spectrum. This calculation presents significant computational speed improvement over time integration method and again helps to highlight the inter relationships of the energy and Fourier methods.

VIBRATION AND ACOUSTIC TESTING/ANALYSIS

6 DOF SHOCK AND VIBRATION: TESTING AND ANALYSIS Dr. Brian C. Owens, Sandia National Laboratories Dr. D. Gregory Tipton, Sandia National Laboratories Mr. Matthew McDowell, Sandia National Laboratories

Shock and vibration testing has long been used for qualification of structural components under a variety of environments. These environments are typically defined along fundamental axes of a component or system. The availability of six degree of freedom (6 DOF) “shaker” hardware allows for a greater flexibility in test inputs in three translational as well as three rotational axes. This allows for a more accurate representation of true environments than can be provided by single axis input. It also allows the response of a component or system to be more accurately characterized using multi‐axis input. While testing is often used for qualification efforts, it is also an important resource for model development and calibration. Simulation allows for test predictions to be made “after the fact” to examine responses at un‐instrumented locations. A calibrated model also allows for the construction of full stress/strain fields in a component. A calibrated model is also of value in designing better tests and investigating responses under various environments. Nevertheless, thorough model calibration requires an understanding of test input and cross‐axis inputs in the case of 6 DOF testing. This work will discuss experimental instrumentation and data acquisition methodologies for informing model input from 6 DOF testing. Challenges associated with this type of testing and simulation will be discussed. Approaches for deriving simulation input from test data will be demonstrated and the

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importance of including full 6 DOF in model predictions will be emphasized. The opportunities for using 6 DOF testing for a more accurate representation of true environments will also be highlighted. PHASE INFLUENCE ON THE RESPONSE OF A SLENDER BEAM STRUCTURE UNDER COMBINED ROTATIONAL AND TRANSVERSE BASE EXCITATIONS Dr. Ed Habtour, US Army Research Laboratory Mr. Raman Sridharan, Center for Advanced Life Cycle Engineering, University of Maryland Mr. Abhijit Dasgupta, Center for Advanced Life Cycle Engineering, University of Maryland The response of a cantilever metallic beam structure under combined rotational and translational harmonic base excitation is investigated experimentally. The study demonstrates the importance of cross‐axis coupling, especially as a function of the relative phase angle between the two excitations. The experiments are performed using a unique six degree‐of‐freedom (6‐DoF) electrodynamic shaker with high degree of controllability. The experimental results show that increasing the phase angle between the rotational and translational excitations from 0‐135deg increases the beam tip response and the beam nonlinear stiffening effect. The combined excitation results are compared to both uniaxial rotational and translational base vibration. Fatigue damage buildup occurred in uniaxial and multiaxial excitation experiments, which is manifested by a shift in the resonance frequency and a progressive increase in the response amplitude as a function of the accumulated number of vibration cycles. The beam deflection is sensitive to the phase angle; thus, the phase contribution cannot be neglected when assessing fatigue damage. Furthermore, applying the principle of superposition (mathematical addition of the response for each uniaxial excitation) may lead to erroneous dynamic predictions. Exploiting the sensitivity of the phase angle between the rotation and transverse base excitation may also enable structural control without changing the loading amplitudes. The experimental results presented in this paper are the first to identify the qualitative and quantitative differences between three types of nonlinear harmonic excitations of a cantilever beam structure: transverse base excitation, rotational flexural base excitation, and combined rotation and transverse with varying phase differences. This novel set of experimentation has been possible because of the 6‐DoF shaker. THE DERIVATION OF MULTIPLE‐INPUT‐MULTIPLE OUTPUT (MIMO) ACOUSTIC TEST SPECIFICATIONS TO SIMULATE A

MISSILE FLIGHT Mr. Jerome Cap, Sandia National Laboratories Ms. Shantisa Norman, Sandia National Laboratories Mr. David Smallwood, Consultant System level acoustic tests are often performed to simulate the environments associated with the powered flight phase of a missile flight. The traditional approach is to generate a uniform acoustic field around the structure. Sandia recently participated in a unique test series for which we derived the input Spectral Density Matrix for a 12 source acoustic system to simulate flight data measured on 12 internal accelerometers for three unique phases of flight: 1) lift‐off, 2) transonic, and 3) resonant burn. The paper will discuss the challenges associated with deriving a stable set of inputs for a MIMO acoustic test and show how well the flight responses were reproduced. THE EFFECTS OF VIBRATION ON MEASUREMENT MICROPHONES Mr. Robert K. O'Neil, GRAS Sound and Vibration When measurement microphones are exposed to high levels of vibrations or mechanical shocks, the influence may vary from small signal degradations, to permanent changes in sensitivity and frequency

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response or permanent mechanical destruction of the microphone. The effects on measurement microphones from the different excitations will be determined by the type and size of the specific microphone but also from the choice of materials, mechanical processing grades and assembly method selected. In some cases, mainly for free field type measurements, it is possible to mount the microphone and preamplifier combination in vibration insulating supports and this may effectively dampen the vibrations reaching the microphone. In many other situations, especially in dynamic pressure type measurements, the microphone needs to be firmly mounted on a test structure. This may range from aircrafts, vehicles, ship structures and other large, vibrating machinery. THE USE OF QUATERNIONS TO COMPENSATE FOR GEOMETRIC DISTORTION IN DYNAMIC SEISMIC AND SATELLITE TESTING Dr. Marcos Underwood, Tutuli Enterprises Seismic testing waveforms sometimes require significant rotations in the reference waveforms that are used for the tests. When this motion occurs, the control transducers that are mounted on the surface of the tables and that are used for this type of testing, will no longer point in the world (non moving) coordinate system as the table rotates. Because of this, X, Y, Z control and auxiliary accelerometers used during a MIMO vibration test may produce outputs, which contain the effects of significant geometric distortion and thus will not produce acceleration measurements that are aligned with the fixed world coordinates, but rather will produce measurements that are aligned with the moving body coordinates of the table. If, perhaps because of insufficient actuation resources, unwanted rotations are not being suppressed, a Time‐Dependent Input/Output Transformation capability may be needed. (This may be particularly important when Horizontally testing satellites with a high Center of Gravity, which can be prone to large over‐turning moments.) Although MIMO Control Systems function by formulating and solving the system Spectral Density Matrix in real‐time, geometric distortion presents additional complexity to an already demanding control situation. Thus, since the representation of rotations by Quaternions are more compact, accurate and efficient to computationally compensate for the effects of geometric distortion than with the use of rotation matrices, they have found a unique and highly successful application in multi‐degree‐of‐freedom control systems as described by this paper.

DEDICATED SESSION: EXPERIMENTAL TESTING METHODS AND INSTRUMENTATION IN HIGH‐G ENVIRONMENTS

USING MULTIPLE G‐SWITCHES FOR TARGET DETECTION Dr. Jeff Hill, Sandia National Laboratories No abstract provided. MECHANICAL SURVIVABILITY OF EMBEDDED MASS IN QUASI‐STATIC AND DYNAMIC HIGH‐PRESSURE ENVIRONMENT Lt Josh Campbell, US Air Force, Dr. Jacob Dodson, AFRL, Dr. Janet Wolfson, AFRL Understanding the mechanical response of fuze components in weapon systems is critical to ongoing research, and provides insight into the dynamics experienced within high‐pressure environments. The dynamic movement of the fill inside the warhead can generate large internal forces and pressures

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leading to complex fuzing environments. For the future applications, the impact of static and dynamic pressure loading on the mechanical integrity of the fuze housing is critical. While computational models give some insight about the dynamic pressure response inside the explosive fill, there are currently no experimental methods that produce validation data for a high‐pressure dynamic event. In order to initially determine mechanical survivability of an embedded mass due to high dynamic pressure inside an embedded environment, AFRL/RW designed a quasi‐static high‐pressure experiment. This method utilizes a pressure chamber filled with an inert explosive simulant containing an embedded component. An industrial press is used to incrementally load the simulant up to 40,000 psi. Test design primarily focuses on resulting base pressure in the fixture and internal strain data. Next, the dynamic high‐pressure event will be replicated. In upcoming tests, a large chamber air gun will shoot a projectile to impact a similar test fixture. This test will effectively simulate the dynamic impulse that is present during an actual penetration event. The final goal is provide validation data to computational models and augment our understanding of the survivability envelope for current and future embedded fuze components. This presentation will discuss the current status, including inert fill measurements, and future work on developing the dynamic pressure testing method. EXPERIMENTAL EVALUATION OF ADDITIVELY MANUFACTURED SUPPORTS UNDER HIGH‐G LOADS Dr. Ryan Lowe, Applied Research Associates No abstract provided. MEASURING EMBEDDED DYNAMIC PRESSURE: DESIGN, CHARACTERIZATION AND IMPLEMENTATION Dr. Alain Beliveau, Applied Research Associates, Inc Mr. Jonathan Hong, Applied Research Associates, Inc. Lt. Hayley Chow, AFRL Dr. Jacob Dodson, AFRL AFRL Munitions Directorate research activities in fuze embedded in fill material includes efforts in measuring the dynamic pressure in the fill during an impact. Both high deceleration level (thousands of Gs) and large pressure (ten thousands of psi) can be present at the same time. This presentation first reports laboratory measurement of the performance of various acceleration compensated pressure gages under impact conditions. Results from reverse ballistic impact and sub‐scale cannon tests will also be discussed.

ADVANCED DATA ANALYSIS IN VIBRATION

THE SOLUTION TO RANDOM OVER‐TESTING Mr. Philip Van Baren, Vibration Research Mr. Joel Minderhoud, Vibration Research Mr. Jacob Maatman, Vibration Research

Random vibration control systems produce a PSD plot by averaging FFTs. Modern controllers can set the DOF, or number of frames involved in the averaged PSD signal. The PSD is a way to present a random signal—which by nature “bounces” about the mean, at times making high excursions from the mean—in a format that makes it easy to determine the validity of a test. This process takes time as many frames of data are collected in order to generate the PSD and a test can appear to be out of tolerance until the

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controller has enough data. Something is awry with a PSD that achieves total in‐tolerance immediately after starting or during level changes, and this can create dangerous over or under test conditions within specific frequency bands and should be avoided. This paper intends to treat some of the inherent properties of the PSD and some faulty PSD methods that attempt to circumvent these inherent properties. EMPLOYING MONTE CARLO TECHNIQUES TO EXPLORE THE SPECTRAL DENSITY MATRIX SOLUTION SPACE Dr. Luke A. Martin, NSWC Dahlgren Mr. Shawn Schneider, NSWC Dahlgren

Multiple exciter vibration testing has been addressed by MIL‐STD‐810 since 2008 with the inclusion of Method 527, “Multi‐Exciter Testing”. This method begins the dialog and documentation of the added complexities associated with multiple degree of freedom testing (MDOF) when compared to traditional single degree of freedom (SDOF) testing. One added complexity in MDOF testing is the requirement to define a spectral density matrix (SDM). This presentation will review required mathematical properties of an SDM to insure the SDM can be implemented in a laboratory test. Developing SDMs from measured field data will be reviewed along with Monte Carlo techniques for finding the suitable solution space from the measured field data. NATURAL FREQUENCIES OF LAYERED BEAMS USING A CONTINUOUS VARIATION MODEL Dr. Arnaldo J. Mazzei, Jr, Kettering University Mr. Richard A. Scott, University of Michigan This work involves the determination of the bending natural frequencies of beams whose properties vary along the length. Of interest are beams with different materials and varying cross‐sections, which are layered in cells.These can be uniform or not, leading to a configuration of stacked cells of distinct materials and size. Here the focus is on cases with two, or three cells, and shape variations that include smooth (tapering) and sudden (blocktype) change in cross‐sectional area. Euler‐Bernoulli theory is employed.The variations are modeled using approximations to unit step functions, here logistic functions. The approach leads to a single differential equation with variable coefficients. A forced motion strategy is employed in which resonances are monitored to determine the natural frequencies. Forcing frequencies are changed until large motions and sign changes are observed. Solutions are obtained using MAPLER's differential equation solvers. The overall strategy avoids the cumbersome and lengthy Transfer Matrix method.Pin‐pin and clamp‐clamp boundary conditions are treated. Accuracy is partially assessed using a Rayleigh‐Ritz method and, for completeness, FEM.Results indicate that the forced motion approach works well for a two‐cell beam, three‐cell beam and a beam with a sinusoidal profile. For example, in the case of a uniform two‐cell beam, with pin‐pin boundary conditions, results differ less than 1%.

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TACTICAL TRANSPORTATION VIBRATION CHARACTERIZATION AND COMPARISON TO MIL‐STD‐810G Mr. Galit Kipervaser‐Levit, RAFAEL Mr. R. Moshe, RAFAEL Mr. I. Sofer, RAFAEL Mr. L. Klebanov, RAFAEL Mr. Arie Elka, RAFAEL Mr. Zeev Sherf, Consultant The paper describes the analysis of the vibration regime on a launcher truck. It was noted that the vibrations do not resemble the levels of the MIL‐STD 810 guide lines. The measured levels at the system's first natural frequency were close to, and at some measurement points, higher than the MIL‐STD810G levels. The measured levels vary with driving speed, road type, loading configurations (fully/ partially loaded launcher), launcher model and Missile in Canister (MIC) configuration (dummy, inert or operational). The overall GRMS increases with speed for all measurement directions. For similar driving speeds, the GRMS levels are higher on gravel road and at the lower canister loading point. The highest GRMS levels were observed in the transverse direction, contrary to the guidelines and the common understanding of transportation induced vibrations. Additional measurements were performed on a modified launcher truck; the improvements to the truck resulted in lower GRMS vibration levels, roughly about an order of magnitude in the transverse direction and about 50% in the vertical direction. Different loading configurations of the canisters resulted also in different vibration levels. Regression models of the overall GRMS were generated as a function of driving speed and road type. The regression models served in the definition of the overall GRMS input, for laboratory life cycle simulation conditions. Kurtosis time‐histories were calculated from the measured time‐history. From the kurtosis statistical analysis it was learned that about 40% of the time, the kurtosis levels were below 2, for about 55% the levels were between 2 and 4, and for the remaining time, kurtosis levels of up to 7 were observed. The kurtosis analysis results indicate only a mild "spiky" behavior of the time‐history. Following the measured data analysis which showed that the data was almost stationary, functional and endurance testing conditions were defined. For the purpose of generating a vibration testing spectrum, a mean+3σ PSD vibration program that covers 99.7% of the population, was generated. Planning of the system's accelerated life simulation was based on the Miner‐Palmgren hypothesis. The presentation starts with a short introduction, followed by a description of the measurement setup. Next the analysis results are presented and discussed followed by the generation of the simulation program. Several summarizing remarks conclude the presentation.

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RESPONSE TO DETONATIONS/ANALYSIS OF DETONATIONS

DEVELOPMENT OF A SCALABLE/SELECTABLE WALL BREACHING MUNITION Mr. Timothy Shelton, US Army Corps of Engineers – ERDC Dr. John Ehrgott, US Army Corps of Engineers ‐ ERDC Mr. Andrew Woetzerl, ARDEC ‐ Picatinny Arsenal After completion of the Military Operations in Urban Terrain Army Technical Objective (MOUT ATO), the focus of the U.S. Army’s wall breaching effort was directed toward developing an inert system capable of providing scalable or selectable charges to produce man‐sized breaches in the entire array of MOUT targets and missions. Utilizing the findings of the previous MOUT ATO research and development effort, the focus of the continued research was to provide a single, lightweight, packable, inert breaching system that could be tailored for particular targets or missions in within the entire array of MOUT targets using readily available demolition explosives. Specifically, the objective of the research was to provide a man portable, one‐time on target munition that produces man‐sized breaches in common MOUT targets, while minimizing both the safe standoff distance and collateral damage by optimizing the explosive mass and configuration necessary for each wall type. The development of the scalable and selectable wall breacher will allow for implementation of the inert breaching system into any existing Army breaching kit for use in a variety of situations and potential theatres. The results of the research executed during this program will be presented. ANALYSIS OF BLAST OVERPRESSURE FROM AMMUNITION COMPARTMENT EVENTS Mr. James Eridon, General Dynamics Land Systems Ammunition compartments are significant sources of risk to occupants of combat vehicles. The Army Research Laboratory recently published results of a number of experiments using simulated 30mm ammunition in a heavily instrumented, re‐usable blast compartment, estimating the amount of propellant that reacts promptly as a result of overmatching attack. The results of this work include an analysis that relies on a model of pressure generated during propellant reaction which is appropriate for internal ballistics (in a gun breech). Recognizing that a compartment environment differs greatly from a gun breech, we have re‐analyzed the test data produced by ARL using a compartment reaction model, and found that it significantly affects the results of the previous work. In particular, the estimates of the amount of propellant reacting in each event are greatly reduced. In addition, the work indicates a potential mechanism to reduce the threat posed by an overmatching event, thereby increasing crew survivability in a compartmented vehicle. ANALYSIS OF CRATERS FROM LARGE BURIED CHARGES Mr. James Eridon, General Dynamics Land Systems Mr. Tom Zeleznik, General Dynamics Land Systems Mr. Matt Miiller, General Dynamics Land Systems This paper presents the results of a series of controlled tests conducted with large explosive charges in which a number of threat parameters were systematically varied. After each test, careful measurements were made of the crater dimensions. A statistical analysis was conducted in order to relate the measured crater dimensions to the threat characteristics. The test plan examined the effects of charge size, soil type, shape of the charge, and burial depth. The results of the analysis showed that all of the threat parameters had a significant effect on the most commonly measured dimension, the crater lip diameter. Analysis of the data shows that any model which attempts to estimate charge size based

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solely on crater measurements will necessarily have large predictive errors, on the order of a factor of two or more. A LAGRANGIAN PARTICLE FORMULATION FOR MODELING FRAGMENTATION PROCESSES Mr. Youcai Wu, Karagozian& Case Mr. Joseph M Magallanes, Karagozian& Case Mr. Hyung‐Jin Choi, Karagozian& Case

A particle formulation is developed for the analysis of fragmentation processes. The formulation [1, 2] couples the finite element (FE) and reproducing kernel (RK) formulation dynamically. It starts with the more computationally efficient FE formulation and converts the more computationally robust RK formulation when certain triggering criteria are satisfied. The weak form of the coupled approximation is integrated uniquely by the stabilized conforming nodal integration technique (SCNI) [3, 4] and thus termed as “particle formulation”. The SCNI not only assures the efficiency but also maintains the accuracy during the conversion since state variable transition from a Gauss point (which is usually used in the standard FE method) to a node in the particle formulation is avoided. State variables such as material damage or effective plastic strain can be employed as the triggering criteria so that the RK approximation is only applied in the highly distorted / cracked regions (i.e., ones exhibiting high damage or effective plastic strain). By doing so, such a coupled formulation takes advantage of the benefits afforded by both the FE and RK formulations while minimizes the disadvantages of each. Moreover, the particulate nature of particle methods preserved by the SCNI is ideal for analyzing fragmentation processes where large degree of material damage and separation occurred, which are very difficult for FE method. The debris evolution, which is of great interest in many impact penetration analyses, can be captured naturally by the particle formulation. Examples including fragmentation of concrete structures and steel materials are examined using the Lagrangian form of proposed particle formulation and excellent correlation with experimental observations is obtained. SIMULATION OF EXPERIMENTS WHICH SHOW THAT REFLECTION PRESSURE TIME HISTORY FROM GROUND SHOCK DEPENDS

ON THE REFLECTED STRUCTURE'S STIFFNESS AND MASS Mr. Leo Laine, LL Engineering AB Mr. Morgan Johansson, ReinertsenSverige AB Mr. Ola Pramm Larsen, CAEwiz Consulting This paper simulates by using Autodyn, experiments from 1980s conducted by S. Hultgren FORTV where Hultgren studied the structural response of a well‐defined structure, a suspended piston‐spring system buried in sand subjected for ground shock from an explosive charge. The experiments showed that if one increases the suspended mass of the piston, initial reflected pressure increases. Similarly the experiments showed that if the stiffness of the suspended piston is increased the reflected pressure time history increases for the latter part of the reflected pressure curve. The aim of the simulations is to find simple analytical relationships for conducting structural response from ground shock if the ground shock is predicted by simplified relationships such as Conwep and if the protective structure's effective mass and effective stiffness is known, for example a buried concrete wall. The sand is modelled with an Equation of State (EOS) designed for porous soils was implemented in Autodyn. The major benefit with earlier implementations is that the unloading wave speed can easily be made both density and pressure dependent. The modification results in a more accurate way to calculate the shock wave propagation and attenuation in dry sand compared to the Compaction EOS

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found in the standard library. Previously, only an elastic unloading was available in the Compaction EOS in Autodyn by specifying the elastic bulk sound speed as a function of density. Currently, a nonlinear modification is available which relates the slope to a user defined bulk module as a function of density. However, neither of these options captures properly the nonlinear behaviour seen in tri‐axial test data during unloading and how the unloading curve shape varies with both density and pressure. Nor is attenuation of the shock wave large enough for scaled distances above 1 m/kg1/3 The implementation presented in L. Laine and O. Larsen(2012) SAVIAC uses two main equations to define the unloading wave speed in the whole density and pressure space. The input data of the model has been made flexible which allows fitting to tri‐axial soil stress tests.

DEDICATED SESSION: THE NAVY ENERGETIC MODELING ORACLE (NEMO)

INTRODUCING THE NAVY ENERGETIC MODELING ORACLE (NEMO) Dr. E. Thomas Moyer, NSWC/Carderock Division No abstract provided. SIERRA MECHANICS & ITS CRITICAL CONTRIBUTIONS TO NESM Dr. Garth Reese, Sandia National Laboratories Dr. Kendall Pierson, Sandia National Laboratories

A coupled fluid‐structure application depends upon high performance capabilities in the fluid solver, the structural application and the coupler. Key structural applications capabilities include fundamental tools for modeling complex ship or other structures, managing linear and nonlinear elastic responses, scalable parallel performance and highly accurate solutions. In addition, capabilities for structural damage and fragmentation, eigen analysis, frequency response and structural acoustics are necessary for predictive response to a variety of environments. Effective management of constraints and/or contact is essential. For integration into a package like NESM, the structural application must be readily modified and customized while retaining all the software quality engineering (SQE) capabilities of a production application. The DOE Sierra Mechanics application addresses these requirements by integrating solid mechanics and structural dynamics modules. Agile SQE practices provide the engineering framework for development. These practices also position the application for transition to next generation hardware which will require complex communication patterns. Accurate coupling to fluid applications requires a somewhat intrusive API. Each application must be capable of accurate solutions, controlled advancement of an iterative multiphysics step (projector/corrector), and parallel communication of data to/from the fluid domain. Relevant convergence metrics must be provided. An important element of the implementation is the development of adequate unit, integration and system level tests to verify conformance at all levels. The Sierra Mechanics application builds upon related couplings in shock physics, acoustics, and fluid flow to address these requirements with NEMO. NEMO PARALLEL CODE COMMUNICATION & THE NAVY STANDARD COUPLER (NSC) Dr. Badri Hiriyur, Weidlinger Associates, Inc. NEMO is a CFD code under development at NSWC Carderock Division and is focused on providing a modern platform for underwater fluid‐structure coupled shock analyses. It specifically aims to provide a

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platform for convenient and rapid prototyping of new and candidate algorithms that can enhance Navy capabilities while assessing their robustness and their readiness for production‐level analyses. We discuss the code architecture of NEMO which is designed for massively parallel scalability leveraging the architectures of the latest high‐performance computing platforms at the Department of Defense. To solve Fluid‐Structure interaction problems, NEMO couples with the Sandia National Laboratories' Sierra Mechanics suite (Sierra/SM and Sierra/SD) via a new MPI‐based code‐coupling interface called NSC (Nemo‐Sierra‐Coupler). The NSC API is a flexible framework which allows for parallel‐fluid to parallel‐structure communication of data‐intensive messages between the fluid and structure codes. The NSC API architecture is built to enable a flexible and extensible environment for investigation of coupling schemes of different orders of accuracy. APPROACH TO FLUID‐STRUCTURE INTERACTIONS WITHIN A FIXED EULERIAN CFD GRID Mr. Paul Hassig, Weidlinger Associates, Inc. Dr. Badri Hiriyur, Weidlinger Associates, Inc. Key to simulating Fluid‐Structure Interactions when coupling CFD and CSD codes is the treatment at the Fluid‐Structure interface. The approach in NEMO is to model moving CSD surfaces as embedded within a fixed Eulerian CFD grid. F‐S grid intersections are used to identify a surrogate surface on which FSI calculations are performed. Specifically, the local FSI problem at each CFD grid intersection is treated in one of three directional components, producing a 1‐D F‐S Riemann problem in that direction. The solution to these individual 1‐D F‐S Riemann problems serve as local internal boundary conditions for the 1‐D Euler equations solved during each directional pass though the CFD grid; solution pressures are passed to the CSD code. Depending on the fluid EOS, solutions to this F‐S Riemann problem can be obtained analytically, iteratively, or by more efficient approximate methods. This approach is one of several second‐order accurate coupling schemes developed by Farhat et al. [1] during the course of a recently completed ONR Future Naval Capabilities program targeting the implosion phenomenology. VERIFICATION & VALIDATION OF NEMO Mr. Jonathan Stergiou, NSWCCD Mr. Michael Miraglia, NSWCCD No abstract provided.

AIRBLAST TESTING AND M&S OF SYSTEMS

EXPERIMENTAL SERIES TO EVALUATE THE PERFORMANCE OF THE MODULAR PROTECTIVE SYSTEM (MPS) AGAINST AIRBLAST LOADING Mr. Bradford Steed, US Army ERDC Mr. Matthew S. Holmer, US Army ERDC Mr. Donald Nelson, US Army ERDC Mr. Omar Esquilin‐Mangual, US Army ERDC Mr. Billy Bullock, US Army ERDC U.S. forces conducting military operations in remote areas characterized by complex terrain require low logistics, reusable, rapidly‐deployable passive force protection technologies for expedient establishment of perimeter security at extra‐small base camps. The Modular Protective System (MPS) developed by the U.S. Army Engineer Research and Development Center (ERDC) provides the warfighter with a technology‐based solution for rapidly‐deployable and reusable physical protection. The MPS can be

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configured to provide scalable levels of protection for many critical assets, and its performance has been validated for protection against small arms, mortars, rockets, and airblast loadings from personnel‐borne improvised explosive devices (PBIEDs). An objective of recent research has been to evaluate the performance of the MPS as a perimeter wall system against airblast loadings from vehicle‐borne improvised explosive devices (VBIEDs). VBIEDs are a significant threat to U.S. and Coalition forces as terrorists often use them to weaken or breach protective perimeter defense measures at the onset of complex attacks. A series of open‐air arena experiments were designed and executed to investigate structural response and performance of the MPS when subjected to airblast loadings resulting from the detonation of explosive charges representative of small VBIEDs threats. The results of these experiments will be presented in this paper. DEVELOPMENT AND EXPERIMENTAL EVALUATION OF THE MODULAR PROTECTIVE SYSTEM (MPS) MULTI‐PURPOSE GUARD TOWER Mr. Matthew Holmer, US Army ERDC Mr. Bradford Steed, US Army ERDC Mr. Micael C. Edwards, US Army ERDC Mr. Patrick Kieffer, US Army ERDC U.S. military operations in recent conflicts have highlighted the need for innovative, light‐weight, low‐logistics, rapidly‐deployable, and reusable force protection technologies that are suited for use in remote, austere combat environments. The US Army Engineer Research and Development Center (ERDC) has developed the Modular Protective System (MPS) Multipurpose Guard Tower system that provides the Army with a novel expeditionary, logistically‐optimized force protection capability for rapidly establishing perimeter security and entry control. An extensive experimental program was executed to develop and optimize this system to meet protection, logistical, and functional requirements. This paper will discuss the results of several weapons effects experiments performed to evaluate and validate the performance of the MPS Multipurpose Guard Tower System against small arms, mortars, rockets, and vehicle‐borne improvised explosive devices (VBIEDs).

MODELING FOR STRUCTURAL RESPONSE

THE ROLE OF GEOMETRIC IMPERFECTIONS ON QUASI‐STATIC AXIAL CRUSHING OF BISECTED HONEYCOMB STRUCTURES Mr. Morris Berman, US Army Research Lab A bisected hexagonal honeycomb structure is modeled in the explicit formulation finite element code LS‐Dyna. The simulation models the dynamic compressive loading of the honeycomb structure. Fully integrated shell elements are used to model the AlcoreHigrid honeycomb structure. Delamination of the foil layers during large deformation is simulated using tie‐break interfaces between the foil layers. Further, geometric imperfections were imposed throughout the structure. The distribution and magnitude of the imperfections are defined by a combination of stochastic and deterministic processes. To assess the fidelity of the simulation, the honeycomb structure was dynamically loaded in its axial direction (parallel to the axis of the hexagonal cells). Corresponding quasi‐static compression experiments were also performed to validate the modeling results.

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STEADY STATE RESPONSE OF PIPES WITH VARIOUS END SUPPORTS AND GEOMETRIC IMPERFECTIONS Dr. Rudolph J. Scavuzzo, Consultant Mr. Domenic A. Urzillo, NSWCCD Philadelphia, 6690

At the 84th Symposium, a paper was presented to explain why pipes subject to vertical shock would first vibrate in the vertical direction from a vertical shock and then change to horizontal motion. It was found that the small imperfections in the pipe geometry or various end supports cause beating between vertical and horizontal modes of pipe vibration. In this paper, this work has been extended to examine the steady state response of piping under the same conditions.

First a cantilever pipe is excited at its base with a perfect geometry and then with a pipe where the pipe is not perfect. The frequency of the steady state excitation is examined at two frequencies: one below the first mode frequency, one at the first mode frequency, Secondly, a simply supported pipe is examined where both ends have the same vertical excitation and both the effect of the end supports and pipe geometry is also examined at two different frequencies. Pipe damping is assumed to be 5%. Also, a random input is applied to the supported pipe and the response is examined.

Results indicate that the effect of pipe geometry do not cause any significant out of plane motion from steady state vibration input to the cantilever pipe which is very different from that of a shock transient. However, misaligned supports can cause the pipe to vibrate is a whirling motion when the forcing frequency is near a resonate frequency of the pipe. SIMPLIFIED MODEL GENERATION FOR EXODUS II Mr. Matthew King, Altair Engineering Many companies that perform shock and vibration analysis use government and open‐source tools and solvers to perform finite element analysis (FEA). Among these tools are the common Exodus II data file (to define geometry) and the Sierra Mechanics code suite (developed by Sandia National Laboratories). The concept of Exodus II is to have a common database for multiple solver codes rather than a solver code specific format. Sierra Mechanics includes simulation capabilities for thermal, fluid, aerodynamics, solid mechanics, and structural dynamics. One of the challenges analysts face with using Exodus II and Sierra solvers is the narrow options for model generation (mesh, material, property, boundary conditions, and other solver‐specific parameters). Altair HyperMesh is a commercial, high‐performance finite element pre‐processor that prepares models starting from the import of CAD geometry to exporting a solver run for various disciplines/solvers. Fundamental to HyperMesh are its open architecture and ability for customization. Within HyperMesh’s open architecture, users can build interfaces to any FEA format including Exodus II and Sierra solvers. This enables the powerful and efficient capabilities of HyperMesh to be applied when building Exodus II and Sierra models. These capabilities include high‐quality meshing in the shortest time possible, regardless of model size, a complete set of geometry‐editing tools to prepare CAD for meshing, conversion to/from commonly used FEA formats, and features that enable rapid design changes and optimization. This presentation details the current interface and benefits of the new HyperMesh v14.0 Exodus II user profile. Additionally, plans for support to the Sierra solver formats will be discussed. The result is a vastly improved process for building models in the Exodus II and Sierra formats.

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ACOUSTIC AND VIBRATION ENVIRONMENTS: CHARACTERIZATION AND ANALYSIS

PERFORMANCE EVALUATION OF FLOW INDUCED NOISE MODELS FOR A CYLINDER IN AXIAL FLOW Dr. Krishna Kumar, Defence Research & Development Organization Dr. Bhujanga Rao, Defence Research & Development Organization Self‐noise of a towed array sonar increases with an increase in the towing speed due to Turbulent Boundary Layer (TBL) induced pressure fluctuations and limits the sonar performance. Further, as the flow induced noise increases as a fifth power of speed, its significance as a design parameter is increasing as the demand for higher towing speeds is on the rise. For example, a reduction of 6 dB in self‐noise level will double the detection range under the same conditions. Therefore, characterizing the flow noise generating mechanisms and finding ways to mitigate it at the design stage itself is very important for an improved sonar performance. Hence, an accurate estimation of probable flow noise signature on a towed body will aid in formulating design strategy. Keeping this in view, the paper evaluates the performance of various existing TBL induced flow noise models with aim to identify a suitable model for the underwater applications. The authors have used published data of Arakeri and Mani (1990) to verify the model’s performance. Arakeri and Mani have measured surface pressure fluctuation levels at a water tunnel test facility of Institute of Science, Bangalore, using standard B&K transducer flush mounted on a cylinder in axial flow. Surface pressure fluctuation levels were measured at three different free stream velocities viz., 3.3 m/sec, 4.2 m/sec and 5.2 m/sec. Although, Arakeri and Mani have compared measured data with the theoretically computed data using Ko’s model, subsequent to their work several models were developed. Taking note of this fact, the newly developed models such as Chase‐Howe, Smol’yakovand Goody were verified for their performance. THE DERIVATION OF APPROPRIATE LABORATORY VIBRATION TEST DURATIONS AND NUMBER OF SHOCK HITS FROM NON

STATIONARY FIELD TEST DATA Mr. Jerome Cap, Sandia National Laboratories Ms. Melissa C' de Baca, Sandia National Laboratories It is often necessary to qualify systems to shock and vibration field environments that vary with time (i.e., non‐stationary). The techniques used to define the magnitude of the test specification tend to be based on an estimate of the Maximum Predicted Environment (e.g., maxi‐max envelop, statistical model, etc.). However, given this definition of the test levels, when the field environment is both long in duration and non‐stationary, it is clearly neither appropriate nor practical to set the duration of a laboratory vibration test or the number of hits for a laboratory shock test equal to the anticipated durations and hits for the total service life. The purpose of this paper is to present an approach implemented at Sandia to define the appropriate vibration test durations and number of shock hits associated with the P99/90 Maximum Predicted Environment laboratory test levels using a power law fatigue model to generate the same amount of damage that was observed during a 1000 mile road test. ANALYSIS OF THE VIBRATION MEASURED DURING EXPOSURE OF A LAUNCHER TO AN IN‐LABORATORY SIMULATED

DYNAMIC REGIME AT THE REAR OF A FAST BOAT Mr. Zeev Sherf, RAFAEL Environmental Engineering Center Dr. Arie Elka, RAFAEL Environmental Engineering Center Mr. Philip Hopstone, RAFAEL Environmental Engineering Center A launcher was tested in the laboratory to evaluate its capability to withstand the vibratory regime to which it is exposed while mounted on a fast boat. Spectral signatures (PSDs and Transfer Functions) as

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well as characteristic vibro–acoustic indexes were calculated and compared graphically and numerically for vibration measured prior to, and after 10 hours of vibration testing of the launcher. The numerical results were presented in tables, in absolute and dB format. In general no significant deviations were identified between the initial and final stages of the test. A deviation in absolute terms less than 20 % or relative terms less than 1 dB, was established as a pass criterion. A particular location was identified with a majority occurrence of deviations. The methodology applied in the work is promising. At this stage, data that relate failures to values of the vibro‐acoustic indexes are lacking. A more efficient use of these indexes requires a study of the relation between their values and a failure condition, or in other words a controlled study of induced failures, while evaluating the appropriate values of the indexes. The most conventional method is by comparing PSD or Transfer Functions. This comparison is inefficient for the cases in which the deviations are not prominent, the spectral content is complex, and when data are measured at many locations. Comparison of the PSDs and Transfer Function requires a comparison between all the spectral lines, while application of the vibratory indexes method concentrates the differences in a single number, making the comparison more efficient, more elegant and less cumbersome. The data accumulated prior to and after the 10 hour test were stationary. The methodology can be applied for non‐stationary data also, as was the case with the measurements at 5 different periods during narrow‐band on wide‐band sweeps, to which the system was exposed. The methodology was applied only for a single measurement location, for which an interesting, unexpected behavior was observed, namely that prominent deviations from the initial values can be observed toward the middle of testing, while toward the end the changes disappear and the indexes return to their initial values. It is worthwhile to pursue a study of the vibratory indexes behavior under non‐stationary loading conditions, stressing methods for discerning between changes as result of the non‐stationarity and changes due to the structural behavior. Finally, a new method for identification of structural changes during vibration tests was applied. This is a promising method, worthwhile of improvement and future use. VIBRATIONS AT AN AFT LOCATION ON A LARGE BOAT‐ ANALYSIS AND GENERATION OF A LABORATORY SIMULATION

REGIME Mr. Zeev Sherf, RAFAEL Environmental Engineering Center Dr. Arie Elka, RAFAEL Environmental Engineering Center Mr. Philip Hopstone, RAFAEL Environmental Engineering Center Mr. L. Klebanov, RAFAEL Environmental Engineering Center This paper describes the analysis of vibrations at an aft location on a large boat. It was noted that the vibrations are composed of combined narrow and wide‐band. The central frequency of the narrow band and the PSD level at this frequency vary with sailing speed. The overall GRMS increases with speed for all measurement directions. The GRMS increases with the angle to the waves for the longitudinal direction and decreases for the transverse and vertical directions. Two different sea levels do not induce significant differences in the vibration levels. Regression models of the overall GRMS of the central frequencies, of the narrow bands and the PSDs at those frequencies were generated as a function of sailing speed. Also regression models were created of the GRMS vs the angle to the waves. The regression models served in the definition of the overall GRMS, central frequencies and PSD levels at the narrow bands that were used in the definition of laboratory simulation conditions. Functional and endurance testing conditions were defined. Two methods were applied to establish the endurance testing duration, one that made use of energy considerations and one that made use of a GRMS damage accumulation model. The first method does not require data related to the system. The second method requires knowledge of physics of failure model parameters. The testing durations calculated by the two methods differ significantly. The recommended duration of the endurance testing per axis is larger than

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10 hrs. Generation of laboratory testing equivalent conditions is achieved by application of the "Swept Narrow Band" over "Wide Band" testing methodology.

BALLISTICS EFFECTS: MODELING & TESTING

MODELING AND SIMULATION WITH USER MATERIAL MODELS USING ABAQUS Dr. Jennifer Cordes, US Army, Picatinny Arsenal Mr. Pavol Stofko, US Army, Picatinny Arsenal Mr. Steve Recchia, US Army, Picatinny Arsenal A series of user subroutines, VUMATs, were developed for modeling and simulation of high strain‐rate events using the general‐purpose, finite element code ABAQUS. The subroutines and material library are derived from a government‐only hydrocode. The resulting subroutines provide high‐fidelity material models for simulating complex phenomena including impact on ceramic armor, soil/structural interactions, and hard target penetration. Several examples will compare Abaqus to other hydrocodes or experimental results. Example 1 compares penetration results using several of the HEP soil models. Example 2 compares target penetrations to experimental values on the Air Force’s Baby Blu projectile. A third example demonstrates the importance of the Johnson Cook pressure term in modeling polycarbonate structures impacting a hard target. VARIABLES IMPACTING THE PROJECTILE DYNAMICS NEAR MUZZLE EXIT Dr. Jennifer Cordes, US Army Picatinny Arsenal Dr. Donald Carlucci, US Army Picatinny Arsenal Mr. Matt Hawkswell, US Army Picatinny Arsenal The gun launch of projectiles is a highly dynamic event. Precision projectiles carry a variety of electronics to ensure accuracy. At muzzle exit, high accelerations can result in failure in electronic components if design loads aren't properly determined. Muzzle exit accelerations include transverse or balloting accelerations as well as axial accelerations. In this study, 30+ variables affecting muzzle exit kinematics are explored. The method incorporates variations in dimensions, pressures, ringing, and gun launch angle into the six equations of motion. Data from instrumented tests on 155‐mm projectiles were used to quantify the input variables. Muzzle exit pressure, blow‐by, several dimensions, and the severity of the pressure drop‐off were predicted to have the largest effects on the balloting accelerations for the 155‐mm projectile. The extreme values of muzzle exit accelerations were also determined based on the variables and Monte Carlo simulations. STRESS TESTING OF MORTAR BASEPLATES – METHOD AND VALIDATION Dr. Andrew Littlefield, US Army RDECOM‐ARDEC Benét Labs The increased use of mortars in current conflicts has placed a high priority in getting mortar baseplates to the field. To ensure that the baseplate is safe for use in the field it must undergo acceptance testing. The purpose of the acceptance testing, as defined by Test Operations Procedure (TOP) 3‐2‐050 Testing of Mortar Systems, is “to disclose any deficiency or malfunction that would preclude its further use.” For a baseplate these deficiencies could arise from either material or manufacturing methods. Traditionally acceptance testing has been carried out on all baseplates via live fire testing as defined in the TOP. There are a number of reasons why this is not desirable. First is that the test site is not collocated with the production site, so large numbers of plates must be boxed, shipped to the test site

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and any plates that fail must be returned to the production site. Second is availability and response time for the proof site. Higher priority workload, such as ammunition lot acceptance testing could cause baseplate testing to be delayed. Additionally weather conditions can often cause delays. Third is that every round that is used for testing is a round that is no longer available for use in the field. Finally and most importantly is the cost. The test site’s costs can vary greatly due to quantity and workload but have historically been over $2000 per baseplate, not including transportation or ammunition. To overcome these issues Watervliet Arsenal approached Benét to investigate an alternative test method for acceptance. For many years Benét had investigated different ways of duplicating the firing loads for a mortar baseplate utilizing pile drivers. Though no work had been done on duplicating a single hit acceptance test, this previous work provided an invaluable starting point. For each of these systems a different load is required. To generate the appropriate stress state, the load can vary from 14 kips for the small baseplate to 333 kips for the largest baseplate. Additionally they vary in size from 8 x 10 inches for the small baseplate to almost 36 inches in diameter for the largest one. Any method developed had to cover this range of conditions. This paper will cover the method developed and validate it against firing data for the 60mm M7A1 baseplate and the 81mm M3A2 baseplate. WEAPON RICOCHET AS A CONTINUOUSLY DECAYING PROCESS Ms. Anju Shah, DTRA Dr. Philip Randles, DTRA Considerable testing has been done by the Defense Threat Reduction Agency (DTRA) to determine the most effective techniques for defeating hard and deeply buried targets. In many cases, entrance into the facility is through rebounding weapons as they travel down a tunnel. DTRA has developed many tools for the Integrated Munitions Effectiveness Assessment tool for this type of attack; how the weapon travels down tunnels is the subject of this work. By creating a ricochet model in order to predict the motion of a projectile as it repeatedly hits a surface the warfighter will be provided a greater chance in defeating the target by knowing time of travel and velocities. In order to develop the model, we analyzed data from controlled penetration experiments. Data were obtained from experiments where projectiles were shot into rock targets having a fixed‐size hole to identify and measure multiple ricochets. The projectiles were instrumented and provided outstanding three dimensional decelerations (x, y and z) of the projectile during the continuous event. The decelerations clearly show the first event, subsequent bounces, and final bottom engagement. The model developed is accurate in predicting the integrated position and final arrival time (i.e. motion) and does not require analysis of each ricochet event after the initial bounce. The final model parameters will be related to the initial velocity and angle of flight for a complete IMEA model implementation.

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UNDEX ASSESSMENT TOLLS / NAVY SHOCK REQUIREMENTS AND TESTING

DECISION‐AID SOFTWARE FOR UNDEX QUALIFICATION AND OPTIMIZATION Dr. Jeffrey Cipolla, Weidlinger Associates Dr. Brett Benowitz, Weidlinger Associates Mr. Adam Hapij, Weidlinger Associates Mr. Fred Costanzo, Consultant Dr. Jay Martin, Penn State University Dr. Michael Yukish, Penn State University Naval engineers are under enormous pressure to minimize design, engineering and acquisition costs while complying with NAVSEA standards for underwater shock (UNDEX) survivability of equipment. Historically, critical shipboard equipment has been qualified by costly shock tests or engineering analysis; alternately, and preferably, critical items may be qualified by ‘extension’ (QBE). In QBE, Navy engineers assess that the new item is sufficiently similar to previously qualified items that it may be accepted without extensive testing or analysis. Our effort enhances QBE through quantitative analysis of databases of shipboard item qualification tests and results. The enhancement correlates readily observable traits of shipboard items, such as materials, rattlespace, mounts, et cetera and the test outcomes of the items. Software implementation allows a user – either an engineer developing new equipment, or a NAVSEA engineer performing QBE – can enter the traits of new equipment and obtain a statistical assessment of the probability of successful test outcome, together with a level of confidence in that probability. This will allow maximum confidence in a process of UNDEX qualification by extension. This paper addresses the prototype implementation of this software and its verification. ADQUES VALIDATION Dr. Michael Woodworth, Weidlinger Associates Mr. Adam Dick, Weidlinger Associates Dr. Jeff Cipolla, Weidlinger Associates ADQUES is a reduced order modeling tool for the rapid investigation of the response of submarines to underwater explosion events. Its purpose is the quick assessment of large UNDEX loading parameter spaces to recover the most severe loadings for further investigation by testing or more resolved transient analysis. ADQUES operates on user‐supplied beam models of the ship which can be sourced from many popular FEM programs, even those condensed from more intricate shell representations of ship structure. The analysis of these models is conducted in the frequency domain using loading determined from a Geers‐Hunter model for the impulsive loads including bubble pulses. The severity of the loads assessed can be sorted and visualized based on peak spectral responses of individual or collections of critical nodes representing hull structure or mounted equipment. The algorithms of ADQUES were assessed for validity by comparison to the results of full scale testing of the SSTV article. SHOCK ENVIRONMENT COMPARISON METHODS Dr. Michael Woodworth, Weidlinger Associates Dr. Jeff Cipolla, Weidlinger Associates Mr. Adam Hapij, Weidlinger Associates Naval design is often evolutionary for a variety of reasons. The modification of a class can be caused by the integration of new systems or technologies. Increasing the duration of a procurement program and the quantity of ships within it reduces per ship costs to the Navy. Engineering decisions reached at the

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onset of a program may be impacted by the changes to the design features and assumptions rendered obsolete by the cascading changes to the platform with each iteration. This is exemplified by the Virginia Class submarine program, which is currently executing a fifth (“Block V”) consequential evolution design and build phase. Each Block phase has included updates to systems and hull features, but the latest is very extensive. The planned lengthening of the vessels to include new system space may alter the shock environment in ways which may increase risks to previously‐qualified machinery and systems aboard. A methodology was developed to investigate the effects of significant changes between ship blocks on the platform level shock environment. The dynamic response of the existing basis and candidate platforms was evaluated using the rapid analysis tool ADQUES. ADQUES quickly assesses a submarine’s response in the frequency domain to a large sample (many thousands) of UNDEX events, including the initial shock pulse and multicycle bubble loading. The numerous results of the simulation were compiled and compared at a compartment level using geometric, node‐based responses and at a frequency level, using mode‐by‐mode comparison. The mode‐by‐mode comparison is related to the ‘Modal Acceptance Criterion’ (MAC) family of approaches, which enable responses at disparate resonant frequencies to be compared empirically. Both methods were implemented in software to create detailed reports on the consequences of design feature changes between the candidate and base designs. The reports give designers and reviewers the information needed to rationally asses the differences in the shock environment between basis and candidate designs.

INVESTIGATION OF AN EXTENSION OF DDAM FOR EXTERNAL COMPONENTS Dr. Jeff Cipolla, Weidlinger Associates Dr. Michael Woodworth, Weidlinger Associates Mr. Mahesh Bailakanavar, Weidlinger Associates Externally mounted submerged components include an increasing variety of appendages mounted exterior to the hulls of both surface ships and submarines. Mounting systems externally can more rapidly leverage new technologies in acoustics, UUVs, weapons and other system innovations. Instead of being one‐off designs, many of these components are being engineered for multiple installations by shipbuilders and other suppliers. Design and Qualification for shock for these items has previously required extensive testing and/or simulation of transient shock response, which are costly and time consuming. DDAM is an existing methodology for a rapid and simpler shock assessment used to reduce costs for suppliers and reviewers. Applying DDAM to externally mounted components would reduce costs for suppliers and ultimately for NAVSEA. External components will share the same hull‐driven base motion loads as internal components, as in conventional DDAM. However, external components experience a direct excitation from the fluid path of the UNDEX, as well as reactive loads due to the interaction of the component with the fluid. A single degree of freedom (SDOF) system was used to assess the viability and utility of applying a modification of the DDAM paradigm to external components. The linear elastic assumption of DDAM allows for the inclusion of direct fluid path loads by simple extension of the method by superposition. The SDOF response to pressure loading is solved analytically and the DDAM Shock Design Values are computed and compared to reference values from literature. It is shown that the direct fluid loading path is a significant source of load to the components, on parity with the base excitation induced forces determined from DDAM. A method of integration of the direct fluid loading effects into the DDAM paradigm is proposed. The method corrects each modal mass for fluid loading, and introduces an extra (direct‐fluid) response term into the NRL sum calculation of component response. Determining the value of the new terms for each

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mode requires the generation of Direct Fluid Loading design spectra which may be accomplished through higher resolution simulation supported by existing test data. Determination of the fluid modal mass correction can be performed using surface integrals or other computational approaches, as will be shown. IMPACT OF RECENT REVISION OF US NAVY INSTRUCTION AND STANDARD ON NAVY SHIP EQUIPMENT SHOCK QUALIFICATION AND NAVY SHIP SHOCK HARDNESS CERTIFICATION Dr. Christopher Merrill, NAVSEA 05P1 Recent revisions to “Survivability Policy and Standards for Surface Ships and Craft of the US Navy ‐(OPNAVINST 9070.1A, Sep 2012)”, “Shock Hardening of Surface Ships ‐ OPNAVINST 9072.2A, Feb 2013”, and “Shock Tests, H.I. Shipboard Machinery, Equipment, and Systems, Requirements for ‐ MIL‐S‐901E pending” impact interpretation of Shock Requirements for US Navy ships. Specifically, these revised documents impact interpretation of shock requirements for New Construction Navy ships, mandate a ship shock certification process while simultaneously enabling changes to the ship shock trial process, and have modernized ship equipment and system shock qualification shock qualification testing. This short paper characterizes and summarizes these changes and provides a synopsis of Navy policy impacts of these revision to Shock Qualification testing of ship system and equipment for US Navy ships, as well as, US Navy ship shock certification for New Construction and deployed ships in the fleet. A PRACTICAL BAND BASED APPROACH FOR DETERMINATION OF SHOCK RESPONSE FREQUENCE (SRF) OF CLASS II EQUIPMENT FOR USE WITH MIL‐S‐901E IN CASES WHERE SRF IS USEFUL FOR OPTIMAL SHOCK QUALIFICATION TESTING OF CLASS II EQUIPMENT Dr. Christopher Merrill, NAVSEA 05P1 Use of SRF is a relatively recent development in MIL‐S‐901 testing of Class II equipment. Numerous methods have been developed and used to determine explicit values for the SRF parameter. This paper proposes a practical approach for identifying the critical band of frequencies that the Class II equipment’s SRF falls within consistent with the usage of SRF in MIL‐S‐901E that does not necessitate determination of an explicit SRF value by analysis, as well as, identifies limitations and restrictions on use of the band based process.

INSTRUMENTATION & MEASUREMENTS

YIELD ESTIMATE OF WASP PRIME USING DIGITIZED NUCLEAR FIREBALL FILMS MAJ Matthew Gettings, Defense Threat Reduction Agency A methodology is developed for approximating the yield of the nuclear fireball by analyzing nine digitized nuclear test films. Several image processing techniques are employed to collect the timing mark locations and radii measurements recorded on the film. Compared to a manual frame‐by‐frame approach, the automated techniques reduce the time required for data collection. The methodology involved several key tasks, which ultimately led to calculation of weapon yield. Among these key tasks are: calculating absolute time, measuring the diameter of the opaque shockwave, and calculating yield using the Phi‐5th Method. For all films, the difference in the measured initial frame rates compare to previous published reports is less than one percent. For all films, the measured time span of detonation in the first frame was within 0.13 ms of previously accepted values. The measured radii of the shock wave generally agree with Taylor’s model and previously accepted values. The measured radii using the Caliper Method were not consistently greater than or less than Eilers’ data, which seems to indicate an

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unbiased error. The mean calculated yield for shot Wasp Prime was 17% greater than the published unclassified yields. ASSESSMENT OF DYNAMIC PERFORMANCE CHARACTERISTICS OF PIEZOELECTRIC STRAIN GAUGES Mr. Steven Rios, TCU Engineering Dr. Patrick Walter, TCU/PCB Piezotronics Piezoelectric strain gages offer output signal levels 10,000 times higher than conventional strain gages. Understanding the dynamic performance characteristics of piezoelectric strain gauges is an important concept in measurements engineering. In extremely high frequency structural environments piezoelectric strain gages may provide higher frequency intelligence than that available from accelerometers. This paper details experimentation and analysis to characterize the dynamic performance of piezoelectric strain gauges. By measuring propagating stress waves in a long, slender, steel bar, the performance of the piezoelectric gauge is compared to a traditional, variable resistive gauge by examining the frequency content of their individual outputs. CONTAMINATION OF AND SOLUTION FOR CABLE GENERATED NOISE IN ACCELEROMETER SIGNALS Dr. Patrick L. Walter, TCU/PCB Piezotronics While triboelectric generated noise has been discussed for years in terms of the deleterious additive effects it can have on piezoelectric accelerometers operated in a charge mode, its influence on silicon based (PR/MEMS) based accelerometers has not been studied. This paper reports on an extensive study of triboelectric effects in low impedance resistive circuits analogous to those encountered in MEMS accelerometers. While small, these effects have the potential to influence processed accelerometer signals. The magnitude of this effect is shown and corrective cable actions are discussed. ACOUSTIC MEASUREMENTS IN AIR FLOW Mr. Robert O'Neil, GRAS Sound and Vibration An acoustic signal may be combined with a flow‐induced turbulent noise, and there is an interest in quantifying the measurements of both the acoustic and flow‐induced turbulent noise. Increasing distance from a boundary will typically yield flows that deviate from that at the surface. A flush‐ mount Turbulence Screen was utilized that houses a flush‐mount microphone,, recessed in a small dome shaped cavity.The screen is a fine wired mesh that helps to dampen flows and the Turbulent Screen construction minimizes turbelent flows allowing for acoustic measurements in boundary layers. Data will be shown that supports attenuation of turbulent noise by as much as 15 dB, by utilizing a wind tunnel. DYNAMIC MATERIALS TESTING TO BLAST TESTING, EQUIPMENT QUALIFICATIONS Mr. Mike Hoyer, HBM Test and Measurement Whether performing dynamic materials testing in a Split Hopkinson Bar application, drilling and blasting a river bed in a environmentally‐sensitive area or testing warheads, munitions, explosives or rockets, it is imperative that appropriate equipment and procedures are used to reliably, accurately and safely acquire all necessary data plus efficiently produce calculated results and reports within a timely manner. Three applications will be examined to show how vital appropriate equipment and analysis software comes into play to; reliably record data during a $75 million rocket test, help limit any possible damage

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to fish using controlled blasting methods and improve US manufacturing through better characterization of material properties and tools plus account for vibration during the manufacturing process.

FLIGHT SYSTEM TESTING/TESTING METHODS AND CORRELATION

FINITE ELEMENT SIMULATION OF A DIRECT‐FIELD ACOUSTIC TEST OF A FLIGHT SYSTEM USING ACOUSTIC SOURCE INVERSION Mr. Ryan Schultz, Sandia National Laboratories Mr. Eric Stasiunas, Sandia National Laboratories Making predictions of structural response in flight‐type environments is desirable for many aerospace structures. First, however, the predictive capability of the structural dynamics model in that type of environment must be assessed, for example by simulating a laboratory acoustic test and comparing the model’s predicted response to the response measured in‐test. Recently, a laboratory direct‐field acoustic test was performed on a large system for the purposes of assessing a high‐fidelity finite element model subject to an acoustic field. This paper will discuss the process used to simulate this laboratory test, including determination acoustic loads for the finite element model using a source inversion capability in Sandia’s Sierra/SD structural dynamics code. THE SIGNIFICANCE OF COMBINED VIBRATION AND ACCELERATION ENVIRONMENTS FOR FLIGHT TESTING Mr. Richard Jepsen, Sandia National Labs Mr. Edward Romero, Sandia National Labs For the past decade, a test capability combining the acceleration environment from a centrifuge and the vibration environment from a unique shaker system was developed and utilized. The new capability, called the Vibrafuge, has been proven over a wide range of test environments and has been applied to several fight components and systems. The results of this testing have shown the flight test simulation capability to be robust and very valuable in system development and qualification programs. More significantly, the application of the new test capability clearly demonstrates the importance of more realistic testing in combined environments compared to the traditional approach of testing these separately. A history of the capability development along with several examples of results for testing actual flight hardware will be presented. THE FUTURE OF TESTING IN COMBINED ENVIRONMENTS FOR FLIGHT HARDWARE Mr. Edward Romero, Sandia National Labs Mr. David Siler, Sandia National Labs Mr. Richard Jepsen, Sandia National Labs Over the past decade, new test capabilities combining vibration and acceleration (Vibrafuge) and vibration, acceleration, and spin (Superfuge) have been developed and proof tested. The work thus far has demonstrated the importance of testing in a more realistic flight environment as results are frequently quite different than when tested separately. However, there are gaps in these capabilities that remain and could be improved upon to provide the most representative environment possible. Such gaps are associated with the available frequency range of the vibration, the test unit weight, and the secondary axis spin capabilities. Continued development and improvement in these areas will allow for more realistic flight testing and provide the most relevant data possible to evaluate flight hardware apart from conducting actual flight tests. A brief status of the present capability will be presented along

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with concepts and designs for future development to improve the test environment envelop that best simulates actual flight conditions. ANALYSIS OF THE CRACK STRAIN DIFFERENCE OF TWO SIZE EXPERIMENT SPECIMEN TO SHOCK LOAD Mr. Yuanzheng Cheng, China Ship Scientific Research Center Mr. Liping Meng, China Ship Scientific Research Center Mr. Jianhu Liu, China Ship Scientific Research Center Crack strain is a very important parameter to the material of a naval ship structure under shock loading which will determine absorbed energy with the yield stress. It is a difficult work to measure the crack strain correctly of a material. The Hopkinson bar, Instron and MTS test machine are used for measuring the crack strain in different strain rate thus different size of test specimen will be used that cause the difference in the values of the crack strain due to necking effect. This difference may cause some confusion in application the data for damage analysis by FEM method. In this paper, the steel specimens with two different size were investigated by experimental and FEM numerical methods. The specimens of two size were experimented and a series of relevant FEM models in various element size were set up for modeling the experimental phenomena, in which the Johnson‐Cook model was used. By fitting the experiment result, a method for determining the limited crack strain were achieved of different element size that can be used for crack evaluation of a structure to shock loading.

DEDICATED SESSION: POST BLAST FORENSIC

INVESTIGATION OF RELATIONSHIPS BETWEEN CRATER GEOMETRY AND SOIL TYPE AND CONDITION Mr. Joshua Payne, US Army ERDC Improvised Explosive Device (IED) attacks against our mounted and dismounted soldiers are an ongoing problem for deployed U.S. forces. Accurate estimates of the net explosive weight (NEW) employed by these IEDs are of critical importance, both in terms of identifying the exact nature of the threat and for use in designing protection schemes. NEW estimates are typically based on the observed dimensions of the soil crater produced by the IED detonation, identification of the soil type and conditions, and damage found at the scene. In order to address this need, the National Ground Intelligence Center and the U.S. Army Engineer Research and Development Center (ERDC) initiated the CALDERA program. The objective of the CALDERA program is to develop a scientific method to estimate the net explosive weight and depth‐of‐burial required to produce the crater size observed at the scene of an IED attack using forensic data. In order to develop this capability, a series of well‐controlled experiments were conducted in select soil backfills and in situ materials to define the key parameters that can affect the crater formation from shallow buried explosive charges. Soil type/condition has been proven to be one of the most influential parameters affecting crater size and shape, making it a valued piece of information collected at post‐blast scenes. The development of new relationships and methodologies to improve current techniques of soil type evaluation continues to be a critical need. This paper will examine relationships between soil crater geometry and soil type/condition to develop correlations that may improve soil type assessments with minimal data collected at post‐blast scenes.

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EXPERIMENTAL ANALYSIS OF VEHICLE‐BORNE IMPROVISED EXPLOSIVE DEVICES Dr. Kyle Crosby, US Army ERDC Mr. Josh Payne, US Army ERDC Dr. John Ehrgott, US Army ERDC Mr. Denis Rickman, US Army ERDC Vehicle‐borne improvised explosive devices (VBIEDs) have become an increasing threat in areas of conflict worldwide. The detonation of these devices has the potential to cause significant casualties as well as severe damage to nearby structures and support facilities. To address this threat, improved methods must be developed to help identify the size and type of these VBIEDs from forensic signatures collected at post‐blast scenes. The ability to assess the potential hazard levels associated with the various VBIED threats must also be improved to aid in the development of damage mitigation designs to protect structures and support facilities subjected to VBIED attacks. In order to improve our understanding and characterization of VBIED threats, the National Ground Intelligence Center (NGIC) and the U.S. Army Corps of Engineers, Engineer Research and Development Center (ERDC) have conducted a series of carefully controlled VBIED experiments. This series of experiments consisted of four large VBIEDs of various charge sizes and shapes. Explosive airblast pressures and impulses, ground crater formation, and damage to various barriers, structures, and witness targets were measured during the experiments to provide data for use in forensic analyses of VBIED attacks and for the development of blast mitigation schemes. INVESTIGATION OF KEY PARAMETERS FOR POST‐BLAST CRATER ANALYSIS Mr. William Myers, USACE Engineer Research and Development Center Mr. Joshua Payne, USACE Engineer Research and Development Center Dr. John Ehrgott, USACE Engineer Research and Development Center IED attacks against our mounted and dismounted soldiers are an ongoing problem for deployed U.S. forces. Accurate estimates of the net explosive weight (ENEW) employed by these IEDs are of critical importance, both in terms of identifying the threat and for use in designing protection schemes. ENEW estimates are typically based on the observed dimensions of the soil crater produced by the IED detonation, the description of the soil type, the soil conditions that the detonation occurs in, and damage found at the scene. In order to address this need, the National Ground Intelligence Center and the U.S. Army Engineer Research and Development Center (ERDC) initiated the CALDERA program. The objective of the CALDERA program is to develop a scientific method to estimate the net explosive weight and depth‐of‐burial required to produce the crater size observed at the scene of an IED attack using forensic data. In order to develop this capability, a series of well‐controlled experiments were conducting in select soil backfills and in situ materials to define the key parameters that can affect the crater formation from shallow‐buried explosive charges. This paper will compare some of the key parameters including soil type, soil conditions, explosive type, explosive mass, depth of burial, charge orientation, and overhead cover on the formation of a crater. and the paper will also identify key parameters that must be obtained in post‐blast forensic crater investigations.

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EFFECT OF BARRIER WALL SHIELDING ON THE RELATIONSHIP BETWEEN OVERPRESSURE AND DYNAMIC PRESSURE FROM A

DETONATION Mr. Denis Rickman, USACE/ERDC Dr. Kyle Crosby, USACE/ERDC Mr. Joshua Payne, USACE/ERDC The dynamic pressure and impulse produced by a detonation is an important damage mechanism, particularly in terms of blast overturning of vehicles. Relationships exist to accurately determine the dynamic pressure produced by an above‐ground detonation based upon the measured overpressure at a given location. However, these relationships are predicated upon the assumption of free‐field conditions. In most real‐world scenarios of interest, structural elements such as walls and buildings may significantly disrupt the local airblast field in their wakes. This phenomenon is typically referred to as blast shielding. A number of studies have addressed the effect of blast shielding on overpressure, but its effect on dynamic pressure has not been reported in the literature. In this paper, the effect of blast shielding on the relationship between dynamic pressure and overpressure is explored. FORENSIC CHARACTERIZATION OF SMALL ARMS AND PROPELLED MUNITIONS USING IMAGE, CHEMICAL, AND METALLURGICAL ANALYSIS Mr. Cameron Thomas, US Army Corps of Engineers Dr. Kyle Crosby,US Army Corps of Engineers Dr. John Ehrgott, US Army Corps of Engineers Unknown weapon attacks against our mounted and dismounted soldiers are an ongoing problem for deployed U.S. forces. Accurate identification of the weapons employed in attacks is of critical importance, both in terms of identifying the exact nature of the threat and for use in designing protection schemes. In order to address this need, the National Ground Intelligence Center is funding the U.S. Army Engineer Research and Development Center (ERDC) to conduct a series of carefully controlled weapon target‐interaction experiments to gather critical forensic data. These tests series include the firing, under strict conditions, of selected weapon systems against pre‐determined targets and the collection of forensic data from those firings including but not limited to target photographs, munition fragments, penetration details, damage signatures, and chemical residue. The data collected will act as a baseline reference and provide guidance and comparisons to identify critical attack scene evidence that should be collected during post‐attack investigations. These data will also be used to develop forensic tools and technologies to enable the Army to quickly identify weapons and munitions used in attacks. This paper will provide an overview of the experiments conducted, critical post‐attack forensic data collection, and examples of weapons signatures found.

UNDEX II

THE RECOVERY METHOD OF THE MEASURED SIGNAL CURVE OF AN UNDERWATER EXPLOSION SHOCK PRESSURE Mr. Xianpi Zhang, China Ship Scientific Research Center Mr. Jianhu Liu, China Ship Scientific Research Center Mr. Jianqiang Pan, China Ship Scientific Research Center

For the measured underwater explosion pressure waveform we observed, it had been through a series of phases such as pressure field establishment, the pressure field transform and the signal transmission by circuit and so on. During this course, some differences between the output wave and input wave are

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usually unavoidable due to the non‐ideal condition of the measurement system, accordingly reduce the reliability of measured results. Existing processing method is only fitting for rising edge correction, and don’t take into account the waveform distortion due to insufficient system frequency response, thereby may introducing obvious deviation to impulse integral and energy integral. In this paper, based on the method of establishing the sensing function described previously, the recovery method combining the time and frequency characteristics is put forward. Firstly, by making feature identification to the measured waveform, the parameters such as rising time and time constant are extracted, and the smooth sample waveform is constructed. Secondly, based on the known sensing function of the measurement system and the sample waveform, the quasi original waveform is obtained by deconvolution, then a deviation zone is also got through contrasting the quasi original waveform and the sample waveform. Thirdly, the zone correction using deviation zone is carried out to the measured waveform, and the signal recovery is realization. Finally, recovery is made using above method to the measured underwater explosion pressure signals of TNT charge, and using the theory calculation as the basis of reference. The result showed that the method proposed in this paper has obvious advantage over the conventional method, and its efficiency is validated. The correcting method for measured signal is not only correcting the waveform in the frequency, but also reserve the characteristic in the time domain, it can obviously raise the measuring precision for underwater explosion. THE COUPLING EFFECT OF THE STATIC AND SHOCK LOAD ON THE RESPONSES OF A RING‐STIFFENED CYLINDER Mr. Jun Wang, China Ship Scientific Research Center Mr. Jianhu Liu, China Ship Scientific Research Center Mr. Yousheng Wu, China Ship Scientific Research Center

The ring‐stiffened cylindrical shell is the primary structures of a submarine or an offshore, and its safety is one of the most important characteristics for these naval and civil structures. It is very distinct and cannot be neglected that the coupling effect of hydrostatic pressure and UNDEX loads in the deep sea. Moreover there is a great difference in the damage mode and mechanism between the deep and shallow sea condition for cylindrical shells under UNDEX loading. In this paper, the coupling effect of the hydrostatic pressure and dynamic loads is revealed on the damage of the ring‐stiffened cylindrical structures, and it is shown the coupling effect on the damage radius to UNDEX is more obvious with the higher static pressure. STUDY FOR EFFECTIVE SHOCK ANALYSIS METHODOLOGY WITH UNDEX EXPERIMENTAL DATA USING DOWN SCALE SHIP MODEL Dr. Jeong‐Il Kwon, Korea Institute of Machinery &Materials Dr. Jung‐Hoon Chung, Korea Institute of Machinery &Materials Dr. Seok‐Jun Moon, Korea Institute of Machinery & Materials Many simulation program with hydrocodes using a combined Euler‐Lagrange model for surrounding water and ship structure is used for the analysis of the effects of an underwater explosion on their own naval ship. But to enhance the reliability of these analysis results, the validation course should be needed basically by the process of comparison with the calculated responses and measurements from the full or down scale shock trials of real naval vessel. For this purpose, this paper discusses that effective shock analysis calculation data was investigated using well known analysis code & program and compared with UNDEX experimental data using down scale ship model of ROKN frigate. It is concluded that calculations and measurements correspond quite well with each other.

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THE EQUIVALENCE OF SHOCK ENVIRONMENTS OF THE REAL SHIP AND THE SFSP TO A HEAVY RESILIENT MOUNT

EQUIPMENT Mr. Xuebing Chen, China Ship Scientific Research Center The low frequency shock environment down to 5 hertz of a naval ship to UNDEX is controlled by the shock wave load and that of the standard floating shock platform (SFSP) is controlled by the bubble pulsation load. The above difference may cause some discrepancy in the real shock loading to the heavy resilient mount equipment for shock validation test even if with the same shock spectrum at the rigid basis frequency. In order to investigate the equivalence of shock environments of the real ship and the SFSP to the heavy resilient mount equipment, the test and numerical method were employed in this paper. The difference of the loading mechanism between real ship and the SFSP to the heavy resilient equipment was compared. A series of UNDEX test were executed to the SFSP and the shock environment and the responses of a resilient mount equipment were measured. The responses of the same equipment on a ship to UNDEX were investigated by FEM numerical method. It is shown that the damping effects are the main factor that cause the different responses of the equipment with the same shock spectrum. SHOCK ANALYSIS OF AN ANTENNA STRUCTURE SUBJECTED TO UNDERWATER EXPLOSIONS Mr. Mehmet Emre Demir, ASELSAN Antenna structures constitute main parts of electronic warfare systems. Mechanical design is as crucial as electromagnetic design of antenna structures for proper functioning and meeting high system performance needs. Failure of mechanical and electronic structures operating under shock loading is a common occurrence in naval electronic warfare applications. A complete shock analysis of the dipole antenna structure subjected to underwater explosions is performed to foresee adverse effects of mechanical shock phenomena on the antenna structure. Theoretical models of the antenna structure; namely mathematical model and finite element model, are built on multi‐degree‐of‐freedom approach. Modal properties are derived from Classical Beam Theory and transient responses to input shock loading are obtained by Recursive Filtering Relationship (RFR) Method for the mathematical model. Input shock loading is synthesized from assessed shock specification to classical shock input. Transient responses exerted from RFR method are also approximated by simplified and SDOF models. Finite element analysis of the analytical model is performed on ANSYS® platform. Comparisons of analytical results are presented for interchangeably use of proposed models. Numerical results are verified with both modal and transient results collected from experimental analysis. Experimental analysis is performed for exact dimensions of antenna structure subjected to synthesized shock input criteria. Shock severity for antenna structure is presented for both electrical and mechanical components. Design roadmap is drawn within the limitations set for proper antenna functioning with desired performance. Design limitations are determined by the verified mathematical model. Thus, the complete shock analysis of the antenna structure is performed for antenna design to withstand underwater shock explosions.

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BLAST RISKS TO VEHICLES & STRUCTURES

COMPARISON OF RESULTS FROM EXPERIMENTS WITH IMPULSE MEASURING DEVICE THAT QUANTIFY EFFECTS OF SOIL PLACEMENT PARAMETERS ON ABOVEGROUND IMPULSE Mr. Garrett Doles, U.S. Army Engineer Research and Development Dr. John Ehrgott, U.S. Army Engineer Research and Development Dr. Jon Windham, SOL Engineering The dynamic airblast, fragmentation, and soil ejecta loading environments produced by the detonation of surface‐laid and shallow‐buried mines are major threats to lightweight military vehicles. During the past several years, the U.S. Army has focused considerable attention on developing improved methods for predicting the below‐vehicle environment from these threats for use by vehicle/armor analysts, thereby improving the survivability of these platforms. The U.S. Army Engineer Research and Development Center recently completed a multi‐year effort to experimentally quantify the blast and debris loading environments on vehicles due to surface and subsurface mine and IED detonations. As part of this research effort, a series of experiments was conducted to quantify the effects of soil placement parameters on the aboveground blast environments produced by the detonation of aboveground and shallow‐buried homemade explosive (HME) charges. The experiments were conducted using a well‐characterized clayey sand soil. The combined aboveground loads due to airblast and soil debris were measured by an impulse measuring device. This paper summarizes and compares the results of the experimental program with emphasis on defining the effects of soil placement parameters on the aboveground blast environment. COMPARISONS OF RESULTS FROM EXPERIMENTS AND SIMULATIONS WITH IMPULSE DEVICES THAT QUANTIFY EFFECTS OF CHARGE PARAMETERS, DEPTH OF BURIAL, AND SOIL TYPE Dr. Neil Williams, US Army Engineer Research and Development Mr. Garrett Doles, US Army Engineer Research and Development Mr. Stephen Akers, US Army Engineer Research and Development The U.S. Army Engineer Research and Development Center conducted a series of carefully controlled “underbelly blast” field experiments to quantify the loads delivered to aboveground rigid plates and the accompanying aboveground environments created by the detonation of near‐surface bare‐charge and cased‐charge explosives shallow buried in well‐controlled soil backfills. The experiments provided blast overpressure, impulse of the rigid plate, soil stress, and particle velocity data. By utilizing independent laboratory material characterization results of specimens of the testbed soils remolded to the as‐placed soil testbed quality control measurements, a model fit of the testbed soil with the Simple Hybrid‐Elastic‐Plastic constitutive model was developed to replicate the soil behavior. Simulations were run using EPIC for impulse of the rigid plates, soil stress, and particle velocity comparisons with the field experiment results. The simulations were also used to investigate the code’s ability to predict the trends in rigid plate impulse as a result of charge type, depth of burial, and soil type. DUAL STATE ENERGY ABSORBING MECHANISM TO MITIGATE VERTICAL SHOCK LOADING Mr. Jared Gardner, TKC Global Dr. Thomas Plaisted, US Army Research Laboratory Dr. Jerome Tzeng, US Army Research Laboratory No abstract provided.

AB‐42

MECHANICAL SHOCK: INSTRUMENTATION & MODELING/SIMULATION

ANALYSIS OF VARIOUS SIMULATIONS OF COMPLEX COMPONENTS UNDER MECHANICAL SHOCK Mr. Jonathan Hong, Applied Research Associates Dr. Janet Wolfson, AFRL Many challenges are associated with the modeling and simulation of complex components under mechanical shock. In order to baseline the computationalists’ ability to predict a complex shock environment utilizing established computational codes, the Joint Fuze Technology Program has funded a program to evaluate our ability to predict the response of an electrical system to a harsh mechanical shock. A series of laboratory tests were conducted on an electrical system comprised of accelerometers placed on Printed Circuit Boards placed on a Very High‐G (VHG) machine. The test series utilized two different input conditions of 1.8 kg peak with duration of 0.84 ms and 4.3 kg peak with duration of 0.24 ms. That data was subsequently provided to various modelers who were asked to simulate the output. Their predictions were analyzed against the experimental acceleration time history that was collected during the tests. The analysis methods that were used for comparison were: first pulse peak and duration comparison, Sum of Squared Errors (SoSE), Fast Fourier Transform (FFT) analysis, and Frequency Response Assurance Criterion (FRAC). This paper will show that the predictions agreed well with the experiment corresponding to the lower input and that challenges were encountered when the acceleration time history was compared to the predictions using the 4.3 kg peak with duration of 0.24 ms input values. THE EFFECT OF BOUNDARY CONDITION ASSUMPTIONS ON THE PREDICTED DYNAMIC RESPONSE OF PACKAGED ELECTRONIC ASSEMBLIES Dr. Matthew Neidigk, Sandia National Laboratories Finite element model boundary condition assumptions can dramatically change the predicted structural dynamic response of a packaged electronics assembly. For example, tearing or debonding of an elastomer coating within an assembly can have a dramatic influence on the fundamental frequency. Even if a coating is included in the model, if the boundary conditions are not accounted for appropriately, the model may respond in a manner similar to as if the coating was neglected altogether. How dynamic inputs are applied to a model can also dramatically affect the dynamic response as well as the predicted stresses. Important details such as a preloads must be considered for quantitative predictions in packaged electronics assemblies. CHARACTERIZATION OF THE ENDEVCO 7280A TRANSVERSE SENSITIVITY PERFORMANCE TO FULL SCALE RANGE Mr. Randy Martin, Meggitt Sensing Systems Mr. James Letterneau, Meggitt Sensing Systems This paper describes the transverse sensitivity testing of the Endevco® 7280A lightly damped, high‐g shock accelerometer. Transverse sensitivity (or crosstalk) testing is performed on a Hopkinson bar up to full scale range using two references; the first reference measures the acceleration input in the transverse axis of the accelerometer, and the second reference measures, and corrects for, the true acceleration present in the sensitive axis of the accelerometer. Results will be compared to the Endevco® 7270A transverse sensitivity measurements that were presented at the 85th Shock and Vibration Symposium. Additional considerations, such as mounting technique, will be discussed as they relate to the transverse sensitivity performance of the accelerometer.

AB‐43

CHARACTERIZATION OF MEGGITT SENSING SYSTEMS’ UPDATED HOPKINSON BAR CAPABILITY Mr. James Letterneau, Meggitt Sensing Systems Dr. Vesta Bateman, Mechanical Shock Consulting In the past year Meggitt Sensing Systems (MSS) has worked to expand upon the existing shock test capabilities at our Shock Test Laboratory in Orange County, CA by developing and implementing a second Hopkinson bar configuration. The primary feature of the second system is a one‐inch Hopkinson bar diameter that permits side‐by‐side comparisons of shock accelerometers in a variety of package types. Other improvements (over the existing capability) include expanded test capability at the lower shock levels, more uniform pulse shaping techniques, and pressure controller upgrades that result in improved repeatability. Additionally, the presentation will summarize the results of side‐by‐side testing of the Endevco® 7270A (undamped) and Endevco® 7280A (lightly damped) high‐g shock accelerometers, demonstrating similarities and differences of the relative response to a single shock event input, which was not possible before on smaller diameter bars. A NOVEL MICRO‐CT DATA BASED FINITE ELEMENT MODELING TECHNIQUE TO STUDY RELIABILITY OF DENSELY PACKED FUZE ASSEMBLIES Dr. Pradeep Lall, Auburn University Dr. Nakul Kothari, Auburn University Dr. Jason Foley, AFRL Dr. Ryan Lowe, Applied Research Associates, Inc. No abstract provided.

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