CASE STUDY III: MULTI-PURPOSE VEHICLES/HMMWVarc.engin.umich.edu/events/archive/annual/conf97/case3.pdf · CASE STUDY III: MULTI-PURPOSE VEHICLES/HMMWV KK Choi Greg Hulbert ... n Reduced-order

Center for Computer Aided Design

Automotive Research Centerarc

CASE STUDY III: MULTI-PURPOSE VEHICLES/HMMWV

KK ChoiGreg Hulbert

Ed Haug

Automotive Research Center



OUTLINE

l HMMWV Product Model Generation

l HMMWV Dynamic Model Simulationn Durability tire model

n Integrating DADS and ABAQUS simulation tools

l Duty Cycle and Dynamic Load Predictionn Real-time dynamics for soldier-in-the-loop simulation

n High fidelity load prediction with stiff bushed model

l Crack Initiation Fatigue Life Analysisn Preliminary and refined analysis methods

n Fatigue life without and with bushing elements

l Design Sensitivity Analysis and Optimizationn Design sensitivity analysis

n Design optimization

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PRO/E MODEL OF HMMWV



ICEE MAIN WINDOW



HMMWV PRODUCT MODEL

AUTOMOTIVE RESEARCH CENTER

HMMWV Dynamic Simulation

n Rough road / off road tire model

n Simulation tool integration

• DADS - HMMWV vehicle model

• ABAQUS - 4 tire models



n Fatigue life prediction requires accurate dynamic loads

prediction

n Dynamic simulation objective: compute load histories

for given terrain profiles

n Off road terrains produce severe duty cycles

n Proper tire model needed to compute load transfer

through tires for off road terrains


Proper Tire Model

n Reduced-order finite element model

n Tread modeled with shell elements

n Special purpose sidewall model

• variable stiffness beam

• lookup table for efficiency


Tire Model Parameters

n Sidewall length, curvature and attachment angles


Tire Model Parameters

n Sidewall bending stiffness

n Tread bending and membrane stiffnesses


Step Rollover(1 in. step at 0 deg)


Step Rollover(Longitudinal force)

200

150

100

50

0

Long

itud

inal

Forc

e (l

bf)

14121086420-2Longitudinal Displacement (in)

Experiment FEA Model


Step Rollover(Vertical force)

2000

1800

1600

1400

1200

1000

800

600

Ver

tica

l Forc

e (l

bf)

14121086420-2Longitudinal Displacement (in)

ExperimentFEA Model



n Vehicle dynamics simulated using DADS

n Tire response simulated using 4 separate ABAQUS executions


DADS / ABAQUS Integration

n Minimal data transfer between codes

n Time stepping strategy needed to avoid analysis “locking”

n Coordination must be explicit: restarts currently not feasible



n Tire passes forces / moments to vehicle

n Vehicle passes hub position / orientation to tire

Forces/Moments

Position /

Orientation



t n t n+2t n+1

Extrapolated vehicle position

Computed vehicle position

n Tire forces and moments linearly interpolated between tire computations



n Successful integration of DADS HMMWV model and 4 ABAQUS tire models

n Simulation performed for 0.48 in. RMS representation of Yuma Test Center Terrain

n Results show transient response of tires transferred to spindles

NSF-TACOMI/UCRC


PROPER MODELS OF HMMWV FOR DUTY CYCLE AND LOAD

PREDICTION

l Basic 14 Body Model: Tire Modeling and Load Approximation for Subsystem Preliminary Design

l Real-Time 10 Body Model: Virtual Proving Ground Simulation with the Soldier-in-the-Loop for Duty Cycle Prediction

l Bushed 14 Body Model: Accurate Loads for Component Durability Analysis and Design

NSF-TACOMI/UCRC


REAL-TIME MODEL FOR VIRTUAL PROVING GROUND

SIMULATION

l Globally Independent Coordinate Approach Developed in ARC Research

l Runs in Real-Time on Workstation Computer

l Enables Engineering Fidelity Soldier-in-the-Loop Simulation for Duty Cycle Prediction

NSF-TACOMI/UCRC


GLOBALLY INDEPENDENT COORDINATES

l Generalized Coordinates Dual to Suspension Forcesn Based on vehicle stability

n Natural physical meaning

n Efficient linear algebra

n Topology based dependent coordinate recovery

l Variational Cartesian Coordinate Formulationn Consistent with design

models

n Avoids recursive method

NSF-TACOMI/UCRC


REAL-TIME PERFORMANCE FOR VEHICLE VIRTUAL PROVING

GROUND SIMULATION

l Implementation in Real-Timen Workstation demonstration

l Soldier-in-the-Loop Virtual Proving Ground Simulation with High Fidelity Modelsn Compatible with design models

n Compatible with IDS/NADS based proving grounds

n Predict duty cycles for system/subsystem design

NSF-TACOMI/UCRC


ON-COURSE VS. IDS VIEWS

On-CourseOn-Course SimulatorSimulator

NSF-TACOMI/UCRC


VVPG DEMONSTRATION--EXAMPLE RESULTS

Vehicle VelocityVehicle Velocity

Vehicle SteeringVehicle Steering

SimulatorSimulator

On-courseOn-course

NSF-TACOMI/UCRC


NSF-TACOMI/UCRC


VIRTUAL PROVING GROUND DUTY CYCLE PREDICTION

l Driver Inputs, Vehicle Speed, and Vehicle Trajectory Represent Realistic Use History in the Hands of the Soldier

l Estimates of Load History Predicted Suitable for Subsystem Preliminary Design

l Results Transmitted to Higher Fidelity Vehicle Models for Accurate Component Load Prediction

NSF-TACOMI/UCRC


BUSHED MULTIBODY MODEL FOR ACCURATE LOAD PREDICTION

l Accurate Suspension Kinematic and Kinetic Representation with 14 Body Model

l Bushings Modeled to Enhance Load Accuracy for Component Durability Prediction

l High Bushing Stiffness and Damping Lead to Stiff Differential-Algebraic Equations (DAE) of Motion

l Stiff Numerical Integrator Required for Balance of Accuracy and Computational Affordability

NSF-TACOMI/UCRC


STIFFLY STABLE DAE INTEGRATOR DEVELOPED IN

ARC RESEARCHl Second Order, One Step Method Developed for

Efficient Simulation of Stiff Vehicle Models

l Method Based Onn Newmark integration approach from structural dynamics

n Generalized coordinate partitioning for satisfaction of all differential-algebraic equations in vehicle model

n Step-size and error control using embedded integration formula

l Formulation and Implementation Extended to Emerging Stiffly Stable Runge-Kutta Methods

NSF-TACOMI/UCRC


PERFORMANCE RELATIVE TO PREDICTOR-CORRECTOR EXPLICIT ALGORITHMS

l Both Implicit and Predictor-Corrector Methods Reduce Step Size During Intervals in Which High Frequency Variables have Significant Amplitude

l Explicit Method Tracks Small Amplitude High Frequency Variables; Prohibitive Cost

l Implicit Method Increases Step Size When Amplitude of High Frequency Variables is Less Than Error Tolerance, Reducing Cost

l Demonstration

NSF-TACOMI/UCRC


PERFORMANCE OF IMPLICIT METHOD: BUSHED HMMWV MODEL

l HMMWV Encounters 10 CM Bump

l Performance Enhanced (Sec.) n Simulation period 1 4 20 40

n Explicit method: 6,431 25,724 128,620 257,240

n Implicit method: 92 282 305 313

n Ratio of CPU times 70 91 423 821

l Error Control Maintained on All Model Variables

l Variable Step Size Control With Implicit Algorithm Effective for Stiff Model

NSF-TACOMI/UCRC


LOAD PREDICTION FOR DURABILITY ANALYSIS

l Simulation Scenario Consistent With Realistic Operational Duty Cycle

l Component Loads Due to Tire Forces, Suspension Elements, and Bushings Accurately Predicted

l Component Load Histories Transmitted to Durability and Reliability Analysis Workspace



DYNAMICS MODEL - DADSPoint Contact Tire Model

Three types of tire models •Basic (no inertia) •Intermediate •Full (inertia included)

Initial DADS HMMWV model usesfull tire model with single point contact



DYNAMICS MODEL - DADSLoad History

Acceleration at Driver’s Seat Position

Time (sec)

Acc

eler

atio

n (m

/ s)



DYNAMIC LOADING HISTORY OF LOWER-CONTROL ARM



STORING DYNAMICS RESULTS



RETRIEVING DYNAMICS RESULTS



GEOMETRY OF LOWER-CONTROL ARM



FATIGUE ANALYSIS FLOW OF LOWER-CONTROL ARM

Dynamic Stress Dynamic Stress Dynamic Stress Time History Time History Time HistoryStress

Time

Dynamic Loading

LifeLifeLife ContourContourContourGeometry/FE Model



DYNAMIC STRESS HISTORIES OF LOWER-CONTROL ARM



DURABILITY AND RELIABILITY ANALYSIS WORKSPACE -- DRAW

(Main Window)



PRELIMINARY ANALYSIS

l Linear Elastic Option

l Elastic/Plastic Option



REFINED ANALYSISl Critical Plane Methods

l Linear Elastic and Elastic/Plastic Options

Method 1Method 2Method 3Method 4Default - All

E/EE/P



FATIGUE LIFE AT CRITICAL POINTS(Preliminary Analysis)



LIFE CONTOUR AND CRITICAL REGION(Preliminary Analysis)



FATIGUE LIFE PREDICTIONS

NodalNumber Without Bushing Elements

Fatigue Crack Initiation Life (cycles)

With Bushing Elements

244

245

239

1.1104E2

1.5024E2

1.8422E2

3.6395E3212

2.4254E2

2.1367E3

1.7480E3

2.3524E7

PreliminaryAnalysis

RefinedAnalysis

PreliminaryAnalysis

RefinedAnalysis

6.9382E2

8.6289E2

1.0020E3

1.1302E4

1.5756E3

3.5476E4

2.2331E3

3.6817E9



FATIGUE DSA USING HYBRID METHOD

FE AnalysisQuasi-Staic Loadings

ContinuumDSA σ

DynamicLoading History

LifePrediction

≈i∂b

∂L(b) ∂L(b+δb) − L(b)

iδb

+δ δb

PredictionLife

L(b + δb) L(b)

AnalyticalApproach

FiniteDifferenceApproach

SIC

σSIC

σSIC σ

SIC



COMPUTATIONAL FLOW OF OPTIMIZATION

Geometric and FEModeling

PATRAN

Parametrization

DSA Computation

FEADADS

DRAW

DOTOptimum Design

DSO

DesignOptimization

Trade-offDetermination

What-ifStudy

SensitivityDisplay



DESIGN SENSITIVITY ANALYSIS AND OPTIMIZATION -- DSO

(Main Window)



TRACKED VEHICLE ROAD ARM

310 20-node solid elements

1,879 nodes

6,000 dof’s



FATIGUE LIFE PERFORMANCE



DESIGN PARAMETER AND COST FUNCTION HISTORY



OPTIMIZATION RESULT

Initial Design Optimum Design

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Documents

CASE STUDY III: MULTI-PURPOSE VEHICLES/HMMWVarc.engin.umich.edu/events/archive/annual/conf97/case3.pdf · CASE STUDY III: MULTI-PURPOSE VEHICLES/HMMWV KK Choi Greg Hulbert ... n Reduced-order