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Impact & Crashworthiness Laboratory
Meeting Materials
3rd MIT Workshop on Experimental and
Computational Fracture Mechanics
compiled by
Tomasz Wierzbicki
Massachusetts Institute of Technology
Cambridge, MA 02139 Phone: 617-253-2104 Email: [email protected] http://web.mit.edu/icl
October 16-17, 2006
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WELCOME ADDRESS
The present workshop is the third in a series of informal annual gathering of members of the Impact and Crashworthiness Lab (ICL) and international experts in the area of ductile fracture. The first workshop (October 2004) was attended by over 40 people, and was dominated by representatives of the aircraft industry. The second workshop (October 2005) featured a large contingent of the developers of leading commercial codes (ABAQUS, LS-DYNA, PAM-CRASH, RADIOSS, and ANSYS). The emphasis of the present third MIT Workshop on the Experimental and Computational Fracture Mechanics is put on fracture characterization of advanced high strength steels (AHSS), including armor steels and Navy steels. A part of the workshop will also be devoted to the launching of an international industrial AHSS consortium. Understandably, large delegations were sent by worldwide automotive and steel industries. The accomplishments of the MIT team in the areas of aluminum fracture, impact and blast loading of structures, and biaxial testing of AHSS, will be summarized in ten presentations of the ICL team. We will also have eight invited talks by renowned experts in the respected fields related to the theme of the workshop. This will create a forum for the exchange of thoughts and ideas in the very informal setting of the MIT Faculty Club. On a more personal note, the 2006 workshop is a very special event for me as this year marks the 25th anniversary of my work as a professor at MIT. I am very thankful to international fracture community for responding to my invitation without knowing the special anniversary that this represents. With great pleasure and expectations, I would like to welcome the representatives of academia, industry, national labs, government sponsoring organizations, and developers of leading commercial codes for this two-day workshop. Tomasz Wierzbicki Cambridge, October 2006
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TABLE OF CONTENTS
Welcome Address 3
Agenda 5
List of Participants 9
Personnel of Impact and Crashworthiness Lab 11
Brief Biographical Sketch of ICL Personnel 12
Summary of 2006 Research Accomplishment of ICL 15
Fundamental research on ductile fracture
Development of new experimental techniques
Numerical simulation of fracture initiation and propagation
International and Domestic Collaboration 18
Collaboration with FE Code Developers 21
Launching of a New Advanced High Strength Steel (AHSS) Consortium 22
List of Reports of ICL 25
List of ICL Journal Publications on Fracture 37
Abstracts of all ICL Reports Completed after October, 2005 39
The full text of all PowerPoint presentations will be included on a CD and distributed to all participants
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AGENDA
3rd MIT Workshop on Experimental and Computational Fracture Mechanics
Impact and Crashworthiness Lab, MIT
MIT Faculty Club 50 Memorial Drive (Building E-52), 6th Floor, Cambridge, MA
First Day – Monday, October 16th
8:00-9:00 CONTINENTAL BREAKFAST
Session 1 – Protection against Improvised Explosive Devices (IED) 9:00-9:10 Tomasz Wierzbicki (MIT) Welcome Address and Overview of the 2- day Workshop 9:10-9:40 Jonas Faleskog Fracture Characterization of an Armored (Royal Institute of Steel using Combined Tension/Torsion Technology, Sweden) Tests 9:40-10:10 Yuanli Bai (MIT) Fracture Characterization of Tungsten Alloy Dirk Mohr (MIT) in Bi-axial Testing. Preliminary Results for Carey Walters (MIT) DH-36 Navy Steel Stefan Hiermaier (EMI) 10:10-10:40 JongMin Shim (MIT) Effect of Polyurea Coating on Blast Tomasz Wierzbicki (MIT) Resistance of Plates – Analytical vs. Numerical Solution 10:40-11:00 COFFEE BREAK 11:00-11:30 John Lettow DARPA's Needs in the area of Fracture and
(Direct Technologies, Inc.) Failure 11:30-12:00 Carey Walters (MIT) Anatomy of IED-induced Damage of Field Tomasz Wierzbicki (MIT) Vehicles 12:00-12:30 Min Huang (MIT) Optimizing Impact Resistance of Xiaoqing Teng (MIT) Double-layer Armor Against IED Fragments 12:30-1:30 LUNCH (catered in)
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Session 2 – Aluminum Fracture 1:30-2:00 Hiroyuki Mae (Honda R&D) Fracture Testing of Aluminum Castings Xiaoqing Teng (MIT) and RADIOSS Simulation Yuanli Bai (MIT) 2:00-2:30 Christian Roth Plastic and Fracture Properties of (Bundeswehr University) Aluminum Overlap Fillet Welds Mario Lochmueller (BMW R&D Center) Dirk Mohr (MIT) Session 3 – Computational Fracture 2:30-3:00 Lars Greve Multi-scale Crash Simulation including (Volkswagen AG) Failure 3:00-3:30 Xiaoqing Teng (MIT) A New Coupled Plasticity/Fracture Model in ABAQUS 3:30-4:00 COFFEE BREAK 4:00-4:30 Liang Xue (MIT) A New Coupled Plasticity/Fracture Model in LS-DYNA 4:30-5:00 JongMin Shim (MIT) Mesh Size Effect on Fracture Calibration Tomasz Wierzbicki (MIT) 5:00 Adjourn 7:30-9:30 Dinner has been arranged at the Charles Hotel on One Bennett Street in the Harvard Square area for the workshop attendees. Breakfast and lunch are provided at the host’s expense, but the dinners will not be covered.
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Second Day – Tuesday, October 17th 8:00-9:00 CONTINENTAL BREAKFAST Session 4 – Fracture Characterization of Advanced Steels 9:00-9:30 Benda Yan Industry Perspective on Fracture of AHSS (Mittal Steel) Components 9:30-10:00 Dirk Mohr (MIT) Development of a New Bi-axial Testing Martin Oswald (ETH) Technique for AHSS Sheets 10:00-10:30 Yuanli Bai (MIT) A Pilot Study on the History Effect on Fracture of Sheets 10:30-11:00 COFFEE BREAK 11:00-11:30 Pierre-Olivier Santacreu Prediction of Forming Limit Curves for (Arcelor) Austenitic Steels 11:30-12:00 Richard Pecherski Modeling of Shear Banding for Enhanced (Technical University Ductility in Advanced High Strength Krakow) Materials 12:00-1:00 LUNCH (catered in) Start-up Meeting of the MIT/Industry AHSS Consortium 1:00-1:40 Tomasz Wierzbicki Task-by-task presentation of the Core (MIT) Project and two Expansion Projects 1:40-2:10 Roland Gustafsson Integration of the Current NGV Program (Volvo Technology on Stainless Steel with the MIT AHSS Corporation) Consortium 2:10-2:30 Lucie Piazza (MIT) Questions and Answers to the Office of Denise Moody (MIT) Sponsored Programs at MIT about intellectual property issues and rules and practice of running industrial consortia
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2:30-3:00 COFFEE BREAK 3:00-5:00 Tomasz Wierzbicki Round table discussion on the content of the (Moderator) intended work and industrial input Formation of the Project Technical Committee (PTC) Determination of the major milestones for the first year 5:00 Adjourn
Third Day – Wednesday, October 18th (optional)
9:00-10:00 Demonstration tests at the Impact and Crashworthiness Lab on biaxial plasticity and fracture testing in ICL Lab, Room 5-011. 10:00-12:00 Further discussion with individual Consortium members on possible joint projects, Room 5-314. (Sorry; no lunch!)
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LIST OF PARTICIPANTS
David W. Anderson Autosteel [email protected] Todd W. Bjerke US Army Research Lab [email protected] Ming Chen US Steel [email protected] Edmund Chu Alcoa [email protected] Katie Cook Pratt & Whitney [email protected] Jonas Faleskog Royal Institute of Technology [email protected] Partha Ganguly Schlumberger [email protected] Jorg Gerlach ThyssenKrupp [email protected] Lars Greve Volkswagen [email protected] Roland N-G Gustafsson Volvo Technology Group [email protected] Byeong-Ryeol Ham Hyundai-Kia Motors R&D Division [email protected] Alan Humphreys Schlumberger [email protected] Juan A. Hurtado ABAQUS Inc. [email protected] Wojciech Jesien Pratt & Whitney Canada [email protected] Christopher Joseph Northrop Grumman [email protected] Robert Kalan Sandia National Lab [email protected] Daniel Kim Nissan [email protected] Tae-Jeong Kim Hyundai-Kia Motors R&D Division [email protected] Goran Kugler Technical University-Clausthal [email protected] Bruce LaMattina Army Research Office [email protected] Young-woong Lee GE Global Research Center [email protected] John Lettow Directed Technologies Inc.(DARPA) [email protected] Mario Lochmuller BMW Group [email protected] Jeff Lund Aerovision [email protected] Hiroyuki Mae Honda [email protected] Scott McClennan Weidlinger Associates, Inc. [email protected] Olivier Morisot ESI Group [email protected] Scott Natkow Office of Naval Research [email protected] Brian O'Hara Honda R&D Americas Inc. [email protected]
Palani Palaniappan Toyota Motor Engineering and Manufacturing [email protected]
Heinz Palkowski Institute of Metallurgy, TU Clausthal [email protected] Ryszard B. Pecherski Kracow University of Technology [email protected] Rodney Peterson NSWC Carderock Division [email protected]
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Charles Roe NSWC Carderock Division [email protected] Christian Roth Bundeswehr University [email protected] Nripen K. Saha Ford [email protected]
Pierre-Olivier Santacreu Ugine&Alz, Arcelor-Mittal [email protected]
Reed R. Skaggs US Army Research Lab [email protected] Joey Staza Aerovision [email protected] Stfan Szyniszewski University of Florida [email protected] Dylan Thomas Honda R&D Americas Inc. [email protected] Shigeo Tobaru Honda [email protected] Akira Toyama Nissan [email protected] Kangping (Kathy) Wang GM [email protected] Gerard Winkelmuller Mecalog [email protected] Benda Yan Mittal Steel [email protected] Li Zhang DaimlerChrysler [email protected] Li Zheng GE Global Research Center [email protected] Hong Zhu Mittal Steel [email protected]
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PERSONNEL OF THE IMPACT AND CRASHWORTHINESS LAB AS OF OCTOBER 2006
Tomasz Wierzbicki Professor [email protected] Chiara Bisagni Visiting Professor from Politecnico di Milano [email protected] Dirk Mohr Post. Doc. [email protected] Xiaqing Teng Post. Doc. (As of September 29 with HESS) [email protected] Liang Xue Ph.D. Candidate [email protected] Yuanli Bai Ph.D. Candidate [email protected] Carey Walters Ph.D. Candidate [email protected] JongMin Shim Ph.D. Candidate [email protected] Min Huang Graduate Student [email protected] Allison Beese Graduate Student [email protected] Martin Oswald Visiting Student from ETH [email protected] Steve Rudolph Technical Director [email protected] Sheila McNary Administrative Assistant [email protected]
FORMER POST. DOC. OF THE IMPACT AND CRASHWORTHINESS LAB
Sigit Santosa GM Weigan Chen Ford Heung-Soo Kim Arther D. Little Consulting Yingbin Bao GE Global Research Center Young-Woong Lee GE Global Research Center Li Zheng GE Global Research Center
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BRIEF BIOGRAPHICAL SKETCH OF ICL PERSONNEL
Professor Tomasz Wierzbicki received his MS degree from the Department of Mechanical Engineering of the Warsaw Technical University. He earned his PhD degree in 1965 from the Institute of Fundamental Technological Research under the supervision of Professor Piotr Perzena of the Polish Academy of Sciences. Soon after that, he went for a one year postdoctoral study at Stanford University and collaborated with Professor E. H. Lee. In 1981, he was promoted to a full professor at the Polish Academy of Sciences and in the same year, he left for the United States, which has become his home. In 1983, he was appointed as a full professor at MIT, where he is currently directing the Impact and Crashworthiness Lab. He is the author of over 150 papers published in the major international journals. In 1986, he received the Alexander von Humboldt senior US scientist award. Professor Wierzbicki spent over three years working in the BMW R&D Department in Munich. He directed a number of large industry-orientated programs at MIT with the support of over 50 major automotive, aluminum and shipbuilding companies. Professor Wierzbicki’s research and consulting interests are in the area of dynamic plasticity, structural failure, crashworthiness, ultralight material, and more recently ductile fracture.
Dr. Chiara Bisagni is an Associate Professor in Aerospace Structures and Materials at the Department of Aerospace Engineering of Politecnico di Milano, Italy. Presently, she is a Visiting Associate Professor at the Department of Mechanical Engineering of Massachusetts Institute of Technology for six months as a holder of a Fulbright Foundation Grant. Dr. Bisagni received her Master’s Degree in Aeronautical Engineering and her Ph.D. in Aerospace Engineering at Politecnico di Milano. She received different international recognitions and fellowships, including a scholarship from DAAD (Deutscher Akademischer Austauschdienst) in 1996, Amelia Earhart Fellowship in 1996/97, and TMR Marie Curie Research Training Grant given by the programme Training and Mobility
of Researchers of the European Union in 1998. Dr. Bisagni is an author of over 60 papers in international journals and conference proceedings. She is a member of AIAA (American Institute of Aeronautics and Astronautics), the editorial board of International Journal of Crashworthiness, the Working Group for European Space Agency Buckling Handbook, and the MIL-HDBK 17 Working Group for crashworthiness of composite structures. Her research interests spans the fields of aerospace and automotive structures, with particular emphasis on buckling and post-buckling, and on crashworthiness, with emphasis on both metallic and composite structures, from the point of view of modeling and testing. Dr. Bisagni has projects and collaborations with several different universities, research centers and industries. Among others, they are DLR (German Aerospace Center, Germany), Technion (Technical University in Haifa, Israel), Riga Technical University (Latvia), RWTH Aachen University (Germany), Agusta/Westand (Italy), IAI (Israel Aircraft Industries, Israel), and Ferrrari (Italy).
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Dr. Dirk Mohr is currently a postdoctoral associate at ICL. He joined the lab as an MIT master student in 2000 and completed his PhD on the “Experimental Investigation and Constitutive Modeling of Metallic Honeycombs in Sandwich Structures” under the supervision of Professor Wierzbicki in 2003. He extensively contributes to several leading journals such as the Journal of Applied Physics or the International Journal of Solids and Structures. One of the topics which he is currently investigating is the crashworthiness, stiffness and formability of sandwich structures. Dr. Xiaoqing Teng is a postdoctoral associate, who received his Ph.D in December, 2004. His Ph. D. thesis was entitled “High Velocity Impact Fracture” and focused on analytical and numerical methods for predicting ductile fracture in various problems involving in high velocity impact. Prior to coming to MIT, Dr. Teng received his Masters degree in Naval Architecture from Shanghai Jiao Tong University. He was an instructor at Shanghai Jiao Tong University for three years, teaching structural mechanics and conducting research on strength analysis of complex engineering structures. He is currently working on the development and implementation of computer software to predict fracture of metals and other materials. He is an author or co-author of about ten original papers published in leading peer-reviewed journals.
Mr. Liang Xue is a sixth year doctoral student, who comes to MIT after graduating the prestigious Shanghai Jiao Tong University. His studies there concentrated on automotive engineering. His professional experience includes production engineering with respect to automotive safety for Volkswagen. After coming to MIT, he worked closely with Professor Wierzbicki on the reconstruction of the aircraft penetration into the World Trade Center. The title of his proposed thesis is “Theory and Application in Ductile Fracture Modeling.”
Mr. Yuanli Bai is a fourth year doctoral student, who comes to MIT after graduating with a Masters degree in Vehicle Engineering from Tsinghua University in Beijing. His research at Tsinghua was about vehicle safety, especially with respect to automotive airbag modeling. His research at MIT has concentrated on the development of a novel specimen geometry for the calibration of a material fracture locus. His thesis is anticipated to be on the subject of the loading history effect on fracture.
Mr. JongMin Shim is a fifth year doctoral student, who comes to MIT after graduating with a Masters degree in Civil Engineering from Korea Advanced Institute of Science and Technology (KAIST). His research at KAIST was on the subject of structural dynamics with an application of structural health monitoring. Prior research at MIT has been on the development of a constitutive model which includes thermo-chemo-mechanical effects. Mr. Shim’s thesis is anticipated to be on the subject of polymer/steel composite failure.
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Mr. Carey Walters is a third year graduate student, who comes to MIT after four years in Industry. His professional experience includes simulation of the crash of a full helicopter for Sikorsky Aircraft. Since he has been at MIT, his research has concentrated on the evaluation of a polymer as a blast resistant material through full field vehicle simulations. Mr. Walters’ thesis is anticipated to be on the subject of the dependence of fracture on strain rate.
Mr. Min Huang is a second year graduate student, who comes to MIT after graduating from Tsinghua University. There, he studied material sciences and engineering with a concentration in industrial processing and grain refinement of light metals. Mr. Huang expects to concentrate his studies at MIT in the propagation of cracks through a ductile material under the combined supervision of Professors Wierzbicki and Parks using numerical and analytical techniques.
Ms. Allison Beese is a first year graduate student, who comes to MIT after graduating from the Pennsylvania State University in May 2005 and working for a year in industry. At Penn State, she majored in Mechanical Engineering with a minor in Engineering Mechanics. Between her graduation in 2005 and now, she spent a year working at Knolls Atomic Power Laboratory outside of Albany, NY. Ms. Beese expects to concentrate her studies at MIT researching the effect of material anisotropy on ductile fracture.
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SUMMARY OF 2006 RESEARCH ACCOMPLISHMENTS OF ICL The present set of meeting material will be distributed to all participants of the fracture workshop along with a CD with all of the presentations listed in the Agenda. Printing the entire power point presentations will have taken too much space. Instead, the meeting material will include only title pages and abstracts of all reports of the Impact and Crashworthiness Lab (ICL) Team compiled since the October 2005 review meeting. Therefore, in order to avoid repetition, the present summary of research accomplishments will be very brief and will serve only as a guide to where a given research topic can be found. The presentations at the workshop are divided into the following four sessions: Session 1 – Protection against Improvised Explosive Devices (IED) Session 2 – Aluminum Fracture Session 3 – Computational Fracture Session 4 – Fracture Characterization of Advanced Steels The present short review of the accomplishments of the ICL is arranged in a slightly different way emphasizing the fundamental aspects of the work performed here at MIT as well as a broad range of industrial applications. Fundamental research on ductile fracture: Investigating team: X. Teng L. Xue Y. Bai T. Wierzbicki The following topics studied at ICL during 2006 fall under the general heading of Fundamental Work on Fracture.
1. Development of advanced plasticity models which brings the effect of the first and third invariant of the stress tensor into the classical J2 plasticity theory. Those results are documented in ICL Reports No. 151 and 155.
2. An in-depth study of the relationship between the plastic damage and fracture. The question that has been asked is whether the damage accumulates in a linear way with the equivalent plastic strain. The answer is no, it does not. Interest readers are referred to ICL Reports No.148, 150, and 154.
3. The effect of the loading history on fracture has first been taken up in the Ph.D thesis of Y. Bao, ICL Report No. 100. Subsequently, this problem received a considerable amount of attention in the lab because in many manufacturing processes, the loading history could be quite complicated. This in turn can lead to premature fracture during stamping operations or subsequent crash loading. The problem becomes especially acute in relation to the so-called Advanced High-Strength Steels which are characterized by relatively low ductility. There is a Ph.D thesis on the way in the lab to address this problem. Some preliminary results can be found in ICL Report No. 124. See also the presentation of Y. Bai entitled “A Pilot Study on the History Effect on Fracture of Sheets.”
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4. Development of a procedure for constructing a 3-D fracture locus and consideration of two limiting cases, plane stress 2-D fracture locus, and plane strain 2-D fracture locus. Those results are described in ICL Reports No. 148, 149, 150, 151, 153, 154, 155, and 156.
Development of new experimental techniques: Investigating team: D. Mohr
Y. Bai M. Oswald C. Roth
T. Wierzbicki
1. In addition to standard tensile tests on un-notched and notched round bars as well as un-grooved and grooved flat dog-bone specimens, a number of unique types of specimens were developed in the lab. These include butterfly specimens (described in 2005 progress report), reduced size butterfly specimens to study fracture of aluminum castings, tubular tension/torsion specimens, and miniature flat specimens to study plastic properties of aluminum weldments and steel sheets. All these types of specimens are working in conjunction with our unique Universal Biaxial Testing Device (UBTD) or with our custom-made double actuator loading frame. Information on these new testing techniques can be found in ICL Reports No. 146, 151, 154, and 155.
2. A number of new materials have been calibrated for fracture since the October 2005 review meeting. These include:
(i) Tungsten alloy (ii) Navy steel DH-36 (iii) Two types of cast aluminum alloys (iv) 1045 Steel (v) 2024 T351 Aluminum alloy
The experimental procedure as well as new sets of data are scattered throughout all new 2006 reports listed in the present meeting material.
Numerical simulation of fracture initiation and propagation: Investigating team: X. Teng
L. Xue J. Shim C. Walters
M. Huang
1. Contribution to CAE The following general purpose commercial FE codes are currently installed at the ICL:
ABAQUS LS-DYNA PAM-CRASH and PAM-STAMP RADIOSS
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Each of the above software has its own, sometimes quite sophisticated, fracture model. We have found that those fracture models are insufficient in many practical situations, such as penetration mechanics, prediction of cup-and-cone and slant fracture, etc.. In order to remedy those deficiencies, more advanced fracture models were incorporated into ABAQUS (ICL Report No. 153), LS-DYNA (ICL Report No. 150), and RADIOSS (ICL Report No. 154).
2. Investigation of the effect of strain rate on deformation and fracture of polyurea/steel composite plate (ICL Report No. 152).
3. Optimization of a composite metal/metal double-layered armor plate impacted by an IED fragment (ICL Report No. 157, to be completed in November 2006). Also see the presentation by M. Huang and X. Teng entitled “Optimizing Impact Resistance of Double-layered Armor Against IED Fragments.”
4. All calibration for fracture performed at the ICL were using hybrid experimental/computational metals to determine all components of stresses and strain in a fracturing specimen. The computations were performed using small-sized solid elements. However, in many applications, the size of solid elements is larger, or even worse, solid elements are replaced by shell elements. Therefore, all the calibration curves and the so-called fracture loci have to be readjusted depending on the size of finite element discritization. This important topic is a subject of ongoing research. Some preliminary results will be presented at the workshop by J. Shim and T. Wierzbicki at the end of the first day of the workshop. The title of this presentation is “Mesh Size Effect on Fracture Calibration.”
In summary, ICL research on ductile fracture has been addressing several important and unresolved problems in macroscopic and computational fracture mechanics. The fact that the present workshop has attracted attention from steel, aluminum, automotive, ship, aerospace, and oil and gas industries, as well as developers of CAE codes, and federal agencies indicates that our work has been recognized by the domestic and international community and is making an impact on many practical fields.
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DOMESTIC AND INTERNATIONAL COLLABORATION Army Research Lab: ARL provided the ICL with a research grant to investigate fracture properties of tungsten alloys for application to kinetic energy penetrators. The main point of contact for the ICL at ARL is Dr. Todd Bjerke. Despite the work of Dr. Tusit Weerasooriya of ARL, only limited data exists on fracture of tungsten rods. With the existing data, it is still difficult to predict the process of penetration and breaking of the long rod on exiting an armor plate. MIT has just performed new quasi-static biaxial tests to characterize fracture properties of the tungsten alloy. Harvard University: Professor John Hutchinson is the Principal Investigator of the MURI Project sponsored by ONR. ICL is a subcontractor of Harvard University and is currently conducting a pilot study on the effect of polyurea coating on the blast resistance of the bottom structure of field vehicles. Professor Hutchinson is also a member of the doctoral committee of Mr. Liang Xue, who is a fourth year doctoral student at ICL. Funding for the project will expire in April 2007. Naval Surface Warfare Center (NSWC): ICL has established a contact with a team at NSWC working on fracture characterization of Navy steels. Dr. Charles Roe, the leader of the team, visited MIT last April. Subsequently, NSWC provided MIT with a set of 20 round and flat specimens made of DH-36 steel. ICL has already performed the necessary testing and calibration. The results of this project are summarized in ICL Report No. 156 (see also the presentation in the agenda). Newport News Shipyard (NNS): A joint venture has just been initiated between ICL and NNS on fracture characterization of two grades of construction steel, HSLA 100 and HSLA 80. This is a low-budget pilot study in which the shipyard will manufacture all specimens according to MIT specification, and fracture calibration will be performed at ICL. University of Bundeswehr in Munich: Professor Wierzbicki has a long history of collaboration with Professor Helmut Rapp of the Institute of Lightweight Structures. A very successful project was initiated between ICL, Alusuisse, and the University of Bundeswehr on deformation and fracture of large welded extruded aluminum panels. Large-scale tests were performed in Munich while some small-scale experiments and all numerical simulation were completed at MIT. The results of this very successful project were summarized in the Ph.D. thesis of Dr. Li Zheng (see ICL Report #140). During 2006, two students from Professor Rapp’s Institute (Christian Roth and Andre Chripunow) completed their respective MS theses under joint supervision of Professor Wierzbicki. Those theses were published as ICL Reports No. 145 and 146. Politecnico di Milano: There is an ongoing collaboration between the ICL and Professor Chiara Bisagni of the Department of Aerospace Engineering in Milan on crashworthiness and fracture of metal and composite structures. Dr. Bisagni spent several months at MIT as a postdoctoral associate before being appointed to the faculty at the University of Milan. She is currently at MIT for six months as a recipient of the Fulbright Foundation Fellowship, and will be working with the ICL team from now until the end of March 2007. Together with Professor Wierzbicki,
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she visited the Ferrari car company in August 2006 in order to initiate a new collaborative project between these three institutions. BMW R&D Center, Munich: Professor Wierzbicki’s relationship with BMW goes back into the mid-80s. He spent more than three years of his professional career working with his German colleagues in Munich during his three consecutive sabbaticals and many summers. More recently, two of his doctoral students were received by various departments at BMW as summer interns. During 2005, Dr. Dirk Mohr, who is a Postdoc at ICL, completed two projects dealing with the fracture of aluminum weldments. In 2004, ICL hosted Wolfgang Guenthner, who was co-supported by BMW, and who has since completed his MS thesis and authored ICL Report No. 121. Another important contribution to the collaboration between BMW and MIT was made by Christian Roth whose MS thesis was jointly supervised by Professor Wierzbicki on the MIT side. Mr. Roth’s thesis was completed in April 2006, and it is printed as ICL Report No. 146. Another important event is that Mario Lochmueller, who is working in Material Concepts and Modeling at the BMW R&D Center in Munich, is currently at MIT as a visiting scientist for a period of two months. He will be working with the ICL team on fracture of aluminum weldments which will be a part of his Ph.D thesis in Germany. Honda R&D Center: Mr. Hiroyuki Mae of the Honda R&D Center in Japan invited Professor Wierzbicki to participate in a joint project on fracture of a cast aluminum alloy. Mr Mae has visited MIT three times previously, and he is participating in the present workshop. Honda has provided MIT with different types of specimens for uni-axial and bi-axial testing. Actual experiments and numerical simulation of the tests have been completed at MIT. It is planned that the results of this project will be presented at the Experimental Mechanics Conference in Greece in 2007. The results of this study are summarized in ICL Report No. 154. Norwegian University of Science and Technology (NTNU), Department of Structural Engineering: Professor Tore Borvik is one of the world’s leading researchers in the area of ballistics. He and Professor Wierzbicki have been interacting in this field for a number of years now. During the August 2005 stay of Professor Wierzbicki at NTNU, it was decided to launch a joint project on fracture characterization of Weldox steel. This is an armor steel which has been extensively studied and calibrated at NTNU. However, there is insufficient data on the fracture properties of this material for small or negative stress triaxialities. In ICL Report No. 134, Dr. Teng calibrated the properties of the Weldox steel using an inverse method. In the new project, tension/sheer as well as torsion/tension tests on the material provided by NTNU will be performed at MIT together with the necessary numerical simulation. Based on the more exact fracture locus, the problem of projectile penetration and perforation will be solved numerically by both research teams. Also starting in January 2007 Professor Borvik will perform a new set of perforation tests on double-layer armor plate to validate numerical simulation performed at MIT and summarized in ICL Report No. 157. Ecole Polytechnique: One of the important research topics at ICL is the effect of strain rate on the initiation and propagation of cracks. Few papers on this subject have been published in the literature, but the difference between static and dynamic fracture is one of the few main obstacles in the progress of the computer simulation methods of accidental events. Recognizing the importance of this subject, Dr. Dirk Mohr is currently working in Professor Gary’s dynamics lab
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at Ecole Poytechnique in France. This lab has a great deal of experience in dynamic testing of materials and developed several novel experimental techniques. Specifically, at the time of this writing, a new type of specimen has been designed for high strain rate tensile testing which could be used in both split Hopkinson pressure bar at Ecole Polytechnique as well as drop tower facility at ICL. This collaboration will continue into 2007. Ernst Mach Institute (EMI): The collaboration between Professor Wierzbicki and Professor Klaus Thoma, the Director of EMI, initiated in 2002 when Professor Wierzbicki spent part of his sabbatical in Freiburg, Germany. At that time he met Dr. Stefan Hiermaier who is the Deputy Director of EMI and leads the computational and crashworthiness group there. Since then, Professor Wierzbicki has made semi-annual visits to EMI. As a result of these interactions, a joint project has been initiated on fracture characterization of the tungsten alloy. The butterfly specimens were prepared at EMI and the biaxial testing and simulation was performed at MIT. The results of this pilot study are summarized in ICL Report No. 157. Volkswagen/Audi Group: A joint experimental and computational project has been initiated between VW and ICL on fracture characterization of a new front bumper made of AHSS. On the German side, the project is managed and supervised by Dr. Lars Greve. MIT will be responsible for extracting specimens out of the bumper and testing the coupons under complex loading paths for plasticity and fracture. Ferrari: Professor Wierzbicki and Professor Bisagni were invited last August to visit the Ferrari plant in Maranello, Italy for a day of presentations and discussions. Ferrari is interested in predicting fracture of cast aluminum components. The scope of the joint project between ICL, Politecnico di Milano, and Ferrari is being negotiated. Also, Ferrari will sponsor a summer internship of Mr. Carey Walters, who is a third-year doctoral student in the lab.
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COLLABORATION WITH FE CODE DEVELOPERS Over the past few years, Professor Wierzbicki has established a close relationship with the developers of leading nonlinear FE codes. The representative of ESI participated in the annual ICL review meetings in 2002 and 2003 with presentations. Likewise, Dr. Juan Hurtado of ABAQUS made a presentation at the 2004 review meeting. In addition, Professor Wierzbicki was invited to contribute to the 2004 EuroPAM in Meinz, 2004 ABAQUS review meeting in Cambridge, MA, 2005 RADIOSS Users’ Meeting in Nice, and Altar/Mecalog user meeting in Japan in December 2006. He also gave a seminar in 2004 at LSTC. Finally, Dr. Winkelmuller of Mecalog made a presentation for last years’ ICL Workshop. Clearly, ductile fracture is one of the high-priority topics for the software development houses. There is also recognition that ICL has a lot to offer for the future improvements of various codes. As an important step in launching the “AHSS Fracture Consortium” at MIT, Professor Wierzbicki used his extensive contacts within the developers of various codes and invited them to actively participate in the Consortium. The response to this invitation was very positive. Five companies, including LSTC, ABAQUS, Meclog, ESI, and ANSYS, proved ICL with letters of intent, and sent their representatives for the 2005 Workshop. The present 2006 Workshop is attended by representatives of ABABUS, ESI, and Mecalog. Besides an active participation in this a future workshops, it is anticipated that respective companies will be willing to include the user-defined subroutines for fracture developed at MIT in future commercial releases of their software. ICL will select several high-visibility validation tasks. Then, various codes will be invited to use their best fracture technology in order to predict the failure process and compare their results against the pertinent experimental data to be generated at MIT.
22
LAUNCHING A NEW ADVANCED HIGH STRENGTH STEELS (AHSS) CONSORTIUM
The second day of the workshop will be devoted to the overview of research needs in the area of fracture predictions of AHSS and presentations of the results of several pilot studies on the topic initiated at ICL. A complete research proposal was presented to the international steel and automotive industries back in August 2006. The proposal received a generally positive response and as a result, many potential sponsors are sending their representatives to the present workshop. The executive summary of the AHSS proposal is reproduced below. The full text of the proposal can be found on the following website: http//web.mit.edu/icl . Executive Summary of AHSS Proposal The present proposal is concerned with a full characterization of plastic and fracture properties of Advanced High Strength Steels (AHSS). The most formidable representatives of this family are the Dual Phase (DP) steel and TRansformation Induced Plasticity (TRIP) steel. AHSS, which was nowhere to be found in the car body five years ago, is predicted to replace 45% of the traditional deep drawing or HSLA (High Strength Low Alloy) steels vehicle components by 2012 (Shi, 2005). One major difficulty in dealing with AHSS is their low ductility. Fracture often occurs before necking, thus making the entire forming predictive capabilities based on FLD not applicable (Fig. 1). The proposed MIT research program is going right to the heart of the problem and is aimed to help press shops at this transition stage by developing the new testing and computational predictive technology for forming and crash design and simulation. The following important topics are addressed in the present proposal:
• Development of an adequate plasticity model which includes kinematic/isotropic hardening, anisotropy, Bauschinger effects, temperature-dependent phase transformation under simple and complex loading paths.
• Development of a new multi-axial testing technique for plasticity and fracture of sheets using MIT’s unique dual actuator testing equipment. Assist industrial partners in the development of a simplified, standardized testing procedure using standard or inexpensive test equipment and a reduced number of tests.
• Identification of key material parameters controlling fractures and determination of a general fracture criteria valid under monotonic loading and complex loading paths. This will also include assessment of the manufacturing process on subsequent fracture in crash loading as well as the effect of loading rate on fracture.
• Investigation of the relationship between the laboratory fracture data obtained using small solid element FE discretization and press shop and full car body simulation by means of larger shell elements.
• Implementation of the new fracture technology into commercial FE codes.
23
Localized neck before fracture in a DP600 steel sample (left), slant fracture prior to necking in a DP980 steel sample (right), after Shi and Gelisse (2006). This proposal not only tells what will be done but also explains how and why various tasks will be accomplished. Such a presentation of results is necessary because most of the issues and techniques are relatively new for the sheet metal forming community. Therefore, the proposed work will not follow established paths. For the above reason, the technical proposal is relatively long (50 pages), but the presentation of results should be appreciated by both managers and technical experts in the industry. The proposal addresses fundamental issues pertinent to the worldwide steel and automotive industry and thus must be carried out at the pre-competitive level. It is proposed to pull together resources of various industries and agencies by forming an industrial consortium at MIT. The standard participation fee in the consortium is $50,000 per company per year. The project will be of 3 year duration Because of the unknown number of project participants and the floating budget, the scope of the program was divided into the Core Project and two Expansion Projects, each with its own objective, set of deliverables, and budget. The PTC will prioritize various tasks at the start-up meeting. The schedule for launching the new program is given below.
24
Timetable for launching the research program on AHSS June 1, 2006 MIT launched a pilot study on AHSS. August 14, 2006 Proposal sent to prospective sponsors. August-October Proposal reviewed and comments sent to PI. October 17, 2006 Start-up meeting at MIT and formation of the Project Technical
Committee (PTC). At this meeting, various tasks will be prioritized and necessary changes to the proposed scope of the program will be discussed.
November 15, 2006 Deadline for informing MIT about acceptance/rejection of the proposal November 30, 2006 The revised proposal to be sent to the prospective sponsors along with
the MIT Standard Consortium Agreement signed by the MIT representative.
December 14, 2006 Fully executed Consortium Agreement Form should be received by the Office of Sponsored Programs at MIT. January 1, 2007 Starting date of the program.
25
C
OR
E P
RO
JEC
T M
ILE
STO
NE
S
TAS
K 1
TAS
K 2
1stye
ar2n
dye
ar3r
dye
ar
Plas
ticity
Te
stin
g &
Mod
elin
g
Frac
ture
Te
stin
g
TAS
K 3
Failu
re
mod
els
&
valid
atio
n
TAS
K 4
Rea
l-life
ap
plic
atio
ns
Dev
elop
men
t of b
iaxi
al te
stin
g te
chni
que
Dev
elop
men
t of e
nhan
ced
plas
ticity
mod
els
Test
ing
prog
ram
on
DP,
SS,
and
TR
IP (o
ne ty
pe e
ach)
Test
ing
prog
ram
of a
dditi
onal
AH
SS
Dev
elop
men
t of t
estin
g te
chni
que
for
in-p
lane
she
ar fr
actu
re
Dev
elop
men
t of e
nhan
ced
fract
ure
mod
els
for m
onot
onic
& re
vers
e lo
adin
g
But
terfl
y sp
ecim
en te
stin
g pr
ogra
m o
n D
P, S
S, a
nd T
RIP
(one
type
eac
h)
Dev
elop
men
t of i
ndus
trial
test
ing
prog
ram
and
add
ition
al
calib
ratio
n of
AH
SS g
rade
s
Appl
icat
ion
to p
ress
sho
p pr
oble
ms
in te
rms
of F
LD a
nd F
FLD
Mod
el im
plem
enta
tion
into
com
mer
cial
cod
es
Cas
e st
udie
s on
form
ing
and
cras
h w
ith a
ctiv
e pa
rtici
patio
n of
co
nsor
tium
mem
bers
26
EX
PA
NS
ION
PR
OJE
CTS
MIL
ES
TON
ES
Expa
nsio
n Pr
ojec
t 1
1stye
ar2n
dye
ar3r
dye
ar
Test
on
dyna
mic
frac
ture
usi
ng h
ydra
ulic
dua
l act
uato
r sys
tem
(lo
w to
inte
rmed
iate
stra
in ra
tes)
Dev
elop
men
t of e
nhan
ced
fract
ure
mod
els
inco
rpor
atin
g th
e ef
fect
of s
train
rate
&
tem
pera
ture
Dev
elop
men
t of a
met
hodo
logy
to tr
ansf
er fr
actu
re d
ata
from
sol
id to
she
ll m
odel
ing
Test
on
dyna
mic
frac
ture
usi
ng S
plit
Hop
kins
on P
ress
ure
Bar
tech
niqu
e (h
igh
stra
in ra
tes)
Exp
ansi
on
Pro
ject
2V
alid
atio
n ex
perim
ents
at t
he c
ompo
nent
leve
l and
com
paris
on
(join
tly w
ith F
E-so
ftwar
e de
velo
pers
)
Effe
ct o
f st
rain
rate
an
d te
mp.
on
fra
ctur
e
Mes
h si
ze
effe
ct o
n fra
ctur
e
27
LIST OF REPORTS OF THE IMPACT AND CRASHWORTHINESS LAB Report No. 1 Experimental, Numerical, and Analytical Study of Honeycomb
Material. Tomasz Wierzbicki, March 1997.(Circulation limited to supporting institutions.)
Report No. 2 Crash Behavior of Box Column Filled with Aluminum Honeycomb or
Foam. Sigit P. Santosa and Tomasz Wierzbicki, April 1997. Report No. 3 On the Modeling of Crush Behavior of a Closed-cell Aluminum
Structure. Sigit P. Santosa and Tomasz Wierzbicki, June 1997. Report No. 4 Crash Behavior of Box Columns Filled with Aluminum Honeycomb
or Foam. Sigit P. Santosa, (Masters Thesis, Department of Mechanical Engineering), June 1997.
Report No. 5 Effect of an Ultralight Metal Filler on the Torsional Crushing
Behavior of Thin-walled Prismatic Columns. Sigit P. Santosa and Tomasz Wierzbicki, July 1997.
Report No. 6 Effect of an Ultralight Metal Filler on the Bending Collapse of Thin-
walled Prismatic Columns. Sigit P. Santosa and Tomasz Wierzbicki, November 1997.
Report No. 7 Crush Behavior of Box Columns Filled with Aluminum Honeycombs
or Foams. Tomasz Wierzbicki and Sigit P. Santosa, October 1997. Report No. 8 Simplified Analysis of Torsional Crushing Behavior of Thin-walled
square Columns. Weigang Chen and Tomasz Wierzbicki, February, 1998
Report No. 9 Axial Crushing of Foam-filled Sections: Numerical Predictions vs.
Experiments. Sigit P. Santosa, April 1998. Report No. 10 Numerical Study on Deep Biaxial Bending Collapse of Thin-walled
Beams. Heung-Soo Kim and Tomasz Wierzbicki, April 1998. Report No. 11 A Pilot Study on Forming of Sandwich Plates with a Crushable Core.
Chiara Bisagni and Tomasz Wierzbicki, May 1998. Report No. 12 Crushing Behavior of Double-walled Sandwich Columns. Sigit P.
Santosa and Tomasz Wierzbicki, May 1998. Report No. 13 Preliminary Experiments on Oblique Crushing of Honeycombs. Jorge
Barrera and Tomasz Wierzbicki, May 1998.
28
Report No. 14 Petalling of Plates under Explosive and Impact Loading. Tomasz
Wierzbicki, May 1998. Report No. 15 Energy Equivalent Flow Stress in Crash Calculations. Tomasz Wierzbicki and F. Schneider, May 1999. Report No. 16 Cockcroft and Latham Revisited. Tomasz Wierzbicki and Heinrich
Werner, September 1998. Report No. 17 Axial Crushing of Foam-filled Columns with Arbitrary Cross Sections.
Sigit P. Santosa, October 1998. Report No. 18 Numerical Study on Deep Biaxial Bending of Complex Cross Section
Beams. Heung-Soo Kim and Tomasz Wierzbicki, November 1998. Report No. 19 Numerical Study on Torsional Crushing of Foam-filled Sections.
Weigang Chen and Tomasz Wierzbicki, November 1998. Report No. 20 Experimental and Numerical Analyses of Bending of Foam-filled
Sections. Sigit P. Santosa, John Banhart, and Tomasz Wierzbicki, November 1998.
Report No. 21 Calibration of Ductile Fracture from Compression and Tension Tests.
Tomas Wierzbicki and Osamu Muragishi, February 1999. Report No. 22 Biaxial Bending Collapse of Thin-walled Beams Filled Partially or
Fully with Aluminum Foam. Heung-Soo Kim, May 1999. Report No. 23 Pilot Study on Optimization for Minimum Weight. Weigang Chen, May 1998. Report No. 24 Summary Report on Crush Response of Ultralight Structures. Sigit P.
Santosa, May 1999. Report No. 25 Analytical, Numerical, and Experimental Study of Double-walled
Sandwich Columns. Jorge Barrera, Sigit Santosa, Tomasz Wierzbicki, May 1999.
Report No. 26 Experimental Study on the Crushing Behavior of Aluminum Closed-
hat, Foam-filled Sections. Weigang Chen and Tomasz Wierzbicki, November 1999.
Report No. 27 Failure Locus of Prismatic Columns under Combined Bending and
Compression. Heung-Soo Kim and Tomasz Wierzbicki, November 1999.
29
Report No. 28 A Pilot Study on Crash Optimization of Foam-filled Front Rail. Heung-Soo Kim, C. H. Tho, and R. J. Kim, November 1999.
Report No. 29 Weight Optimization of Foam-filled, Thin-walled Crash Members.
Weigang Chen, November 1999. Report No. 30 Strain Analysis and Fracture of Crushed Aluminum Tubes. Hans
Kristian Dyrli, December 1999. Report No. 31 Failure and Crash Response of Aluminum Cruciforms. Jesper Urban,
Tomasz Wierzbicki, and Bo Cerup Simonsen, May 2000. Report No. 32 Modeling of Inelastic Properties of a Honeycomb Core. Dirk Mohr,
May 2000. Report No. 33 Bending Collapse of Thin-walled Beams with Ultralight Filler:
Numerical Simulation and Weight Optimization. Weigang Chen, Tomasz Wierzbicki, and Sigit Santosa, June 2000.
Report No. 34 Effect of the Cross-Sectional Shape on Crash Behavior of a Three-
Dimensional Space Frame. Heung-Soo Kim and Tomasz Wierzbicki, June 2000.
Report No. 35 Experimental and Numerical Studies on Deep Bending Collapse of
Foam-filled Hat Profiles. Weigang Chen, June 2000. Report No. 36 Crash Optimization of Aluminum Foam-filled Front Side Rail of a
Passenger Car. Heung-Soo Kim, Cheng-Ho Tho, Tomasz Wierzbicki, and Ren-Jye Yang, June 2000.
Report No. 37 Crushing of Double-Walled Sandwich Profiles with Honeycomb Core.
Dirk Mohr and Jan Meyer, June 2000. Report No. 38 Fracture of Aluminum Honeycombs and Foams under
Hemispherical-Punch Indentation. M. Doyoyo and T. Wierzbicki, June 2000.
Report No. 39 Buckling and Folding of Aluminum Sandwich Strips with a
Honeycomb Core. Dirk Mohr, November 2000. Report No. 40 Design of an Apparatus for Combined Normal and Shear Loading
and Preliminary Tests on Foam and Honeycomb Samples. Mulalo Doyoyo and Tomasz Wierzbicki, November 2000.
Report No. 41 Strength and Fracture of Foam-filled Cast Aluminum Profiles under 3-Point Bending. Yongbin Bao and Tomasz Wierzbicki, November 2000.
30
Report No. 42 Study on Relative Merits of Single Cell, Multi-cell, and Foam-filled
Structures. Weigang Chen, November 2000. Report No. 43 Analysis of Crash Response of an Aluminum Foam-filled Front Side
Rail of a Passenger Car. Heung-Soo Kim and Tomasz Wierzbicki, November 2000.
Report No. 44 Effect of the Cross-sectional Shape of a Hat-type Cross-section on
Crush Resistance of a Three-dimensional “S”-frame. Heung-Soo Kim and Tomasz Wierzbicki, November 2000.
Report No. 45 Optimization for Minimum Weight of Foam-filled Tubes under Large
Twisting Rotation. Weigang Chen, November 2000. Report No. 46 Premature Cleavage of Ship Plating under Reverse Bending. Osamu
Muragishi, September 2000. Report No. 47 Preliminary Crash Experiments on Stainless Steel Sandwich
Components. Dirk Mohr and Tomasz Wierzbicki, November 2000. Report No. 48 Strength and Fracture of Unidirectionally Stiffened Aluminum
Sandwich Panels under Crash Loading. Alf Kristensen, December 2000.
Report No. 49 Crashworthiness Optimization of Ultralight Structural Components.
Weigang Chen, February 2001. Report No. 50 Crash Behavior of Three-dimensional Thin-walled Structures under
Combined Loading. Heung-Soo Kim, February 2001. Report No. 51 Analysis of Crushing Response of Three-Dimensional Thin-walled “S”
Frames with Rectangular Cross-sections. Heung-Soo Kim and Tomasz Wierzbicki, May 2001.
Report No. 52 Numerical Simulation of Effects of Mismatch and Misfit on Response
of Butt-Welded Plates. Xiaoqing Teng and Tomasz Wierzbicki, May 2001.
Report No. 53 Fracture Initiation and Propagation in 3-Point Bending of Foam-filled
Castings. Yingbin Bao and Tomasz Wierzbicki, May 2001. Report No. 54 Effect of Material Distribution on Axial and Bending Response of
Extruded Aluminum Profiles. Young-Woong Lee and Tomasz Wierzbicki, May 2001.
31
Report No. 55 Failure of Ductile and Brittle Foams under a Biaxial State of Stress. Mulalo Doyoyo and Tomasz Wierzbicki, May 2001.
Report No. 56 Crash Optimization of Aluminum Foam-Filled Three-Dimensional
Thin-Walled “S” Frame. Heung-Soo Kim, Weigang Chen, and Tomasz Wierzbicki, May 2001.
Report No. 57 Fracture Calibration Procedure from Upsetting Test for Industrial
Applications. Yingbin Bao and Tomasz Wierzbicki, May 2001. Report No. 58 Shear Folding of Sandwich Box Columns under Axial Crushing.
DirkMohr and Tomasz Wierzbicki, May 2001. Report No. 59 Analytical Model for Axial Crushing of Stainless Steel Sandwich Core.
Li Zheng and Tomasz Wierzbicki, May 2001. Report No. 60 Biaxial Testing of Honeycomb in the W-T-plane : Numerical Analysis
of the Behavior of the Microstructure. Dirk Mohr and Mulalo Doyoyo, May 2001.
Report No. 61 Ship Hull Plating Weld Misalignment Effects When Subjected to
Tension. C. Weaver, May 2001. Report No. 62 Redefining the Concept of the Stress-Strain Curve for Foams. T.
Wierzbicki, M. Doyoyo, A. Markaki, June 2001. Report No. 63 New Extruded Multi-Cell Aluminum Profile for Maximum Crash
Energy Absorption and Weight Efficiency. H. S. Kim, July 2001. Report No. 64 Exact Solution for a Full Crush of a Single Stainless Steel Fiber. X.
Teng, September 2001. Report No. 65 A Pilot Study on the Improvements of Side Impact Protection by
Foam-filled Structures. Y.-W. Lee and T. Wierzbicki, November 2001. Report No. 66 Comparative Study of Various Fracture Criteria: Part I -
Experiments. Y. Bao and T. Wierzbicki, November 2001. Report No. 67 Comparative Study of Various Fracture Criteria: Part II - Finite
Element Analysis. Y. Bao and T. Wierzbicki, November 2001. Report No. 68 Study of the Mesh Size Effect on Fracture of V-shaped Notched
Specimens. X. Teng, November 2001.
32
Report No. 69 Analytical and Numerical Study on the Effect of Imperfection on the Crush Behavior of HSSA Fiber Core. L. Zheng and T. Wierzbicki, November 2001.
Report No. 70 Validation of Material Models for Aluminum Foams. Y. Bao,
D. Mohr, and M. Doyoyo, November 2001. Report No. 71 Development of New Ultralight Aluminum Sandwich Sheets for
Automotive Applications. D. Mohr, November 2001. Report No. 72 Multi-axial Yield and Fracture Behavior of Aluminum Foams.
M. Doyoyo, November 2001. Report No. 73 Analysis of the Arcan Apparatus in the Clamped Configuration, D.
Mohr and M. Doyoyo, November 2001. Report No.74 Aircraft Impact Damage of the World Trade Center Towers, T.
Wiezbicki,L. Xue, and M. Hendry-Brogan, February 2002. Report No. 75 How the Airplane Wing Cut Through the Exterior Columns of the
World Trade Center, T. Wierzbicki and X. Teng, March 2002. Report No. 76 Folding of a Plastic Fiber under Combined Shear Compression, X.
Teng, April 2002. Report No. 77 Numerical Study on the Lateral Crushing Behavior of an Automotive
Side Body Component, Y.-W. Lee and T. Wierzbicki, April 2002. Report No. 78 Thickness Dependence on Fracture Ductility in Aluminum Plates, Y.
Bao, May 2002.
Report No. 79 Enhanced Arcan Apparatus for the Biaxial Testing of Cellular Solids,D. Mohr and M. Doyoyo, April 2002.
Report No. 80 The Out-of-Plane Yield Behavior of an Aluminum Alloy Honeycomb
under a Biaxial State of Stress – Part I: Experimental Observations, M. Doyoyo and D. Mohr, May 2002.
Report No. 81 Effect of Stress Triaxiality on Fracture Ductility, Y. B. Bao and
T.Wierzbicki, May 2002.
Report No. 82 Numerical Simulation of the Impact Damage of a Box Column by a Rigid Mass, L. Zheng and T. Wierzbicki, May 2002.
Report No. 83 Interactive Failure of Two Impacting Beams, X. Teng and T.
Wierzbicki, May 2002.
33
Report No. 84 Effect of Geometrical Misfit on Ductile Fracture of Butt Welds, R.
Bebermeyer, May 2002. Report No. 85 Multiple Impact of Beam-to-Beam, X. Teng and T. Wierzbicki, June
2002. Report No. 86 Quasi-Static Tearing Test of Metal Plating, J. Woertz, August 2002. Report No. 87 Properties of Aluminum Honeycomb under Uniaxial Compression,
P.Young, C. Lloyd, and M. Doyoto, August 2002. Report No. 88 Large Deformation of an Inelastic Beam under High Velocity
Impact:Analytical vs. Numerical Solution, X. Teng and T. Wierzbicki,September 2002.
Report No. 89 Crush Response of an Inclined Beam, X. Teng and T. Wierzbicki,
September 2002. Report No. 90 Ductile Fracture – Theory, Calibration, and Application, T.
Wierzbicki, Y. B. Bao, and H. Werner, October 2002. Report No. 91 Analysis of Deformation and Fracture of Thin Plates under Localized
Dynamic Pressure Loading, Y.-W. Lee, November 2002. Report No. 92 Numerical Simulation of Crush Behavior of Aluminum Sandwich
Panels for Train Collision, L. Zheng, November 2002. Report No. 93 Elastic Buckling of a Fully Clamped Plate under Combined In-plane
Loading, D. Mohr, November 2002. Report No. 94 Numerical Study of Aluminum Honeycomb under Multiaxial
Loading, D. Mohr and M. Doyoyo, November 2002.
Report No. 95 Chain Link Model for Crashworthiness Analysis of Thin-Walled Tubes, L. Xue, November 2002.
Report No. 96 Fracture Ductility of Tensile Specimens with Different Cross Sections,
Y. Bao, November 2002. Report No. 97 Interactive failure in high velocity impact of two box beams, L. Xue, L.
Zheng and T. Wierzbicki, August 2003
34
Report No. 98 Effect of Fracture Criteria on High Velocity Perforation of Thin Beams. X. Teng and T. Wierzbicki, January 2003.
Report No. 99 Numerical Study of Crack Propagation in High Velocity Impact. X.
Teng and T. Wierzbicki, April 2003.
Report No. 100 Prediction of Ductile Crack Formation in Uncracked Bodies. (Ph.D. Thesis), Y. Bao, July 2003.
Report No. 101 Fracture Prediction of Thin Plates under Localized Impulsive
Loading, Part I: Calibration and Validation. Y.-W. Lee and T. Wierzbicki, June 2003.
Report No. 102 Fracture Prediction of Thin Plates under Localized Impulsive
Loading, Part II: Dishing, Y.-W. Lee and T. Wierzbicki, June 2003.
Report No. 103 Fracture Prediction of Thin Plates under Localized Impulsive Loading, Part III: Discing and Petalling, Y.-W. Lee and T. Wierzbicki, June 2003.
Report No. 104 Comparative Study of Crash and Transient Response of Double Hull
Panels with Various Core Arrangement, Y.-W. Lee and T. Wierzbicki, September 2002.
Report No. 105 Experimental Investigation And Constitutive Modeling Of Metallic
Honeycombs In Sandwich Structures, (Ph.D. Thesis), D. Mohr, September 2003.
Report No. 106 Quasi-Static Crushing Of S-Shaped Aluminum Front Rail, L. Zheng,
September 2003. Report No. 107 Correlation Between Analytical And Numerical Solution In High
Velocity Tearing Fracture, T. Wierzbicki and Y.-W. Lee, July 2003. Report No. 108 High Speed Impact Of Fluid-Filled Cylinders, L. Xue and T.
Wierzbicki, November 2003. Report No. 109 Numerical Prediction of Fracture in the Taylor Test, X. Teng, T.
Wierzbicki, S. Hiermaier and I. Rohr, December 2003 Report No. 110 On The Transition From Shear To Tensile Failure In High Velocity
Impact Of Beams And Plates, X. Teng and T. Wierzbicki, December 2003.
Report No. 111 Interactive Failure Of Two Empty And Fluid-Filled Beams Subjected
To High Velocity Impact, L. Xue, December 2003.
35
Report No. 112 Bridgman Revisited: On the History Effects on Ductile Fracture, T.
Wierzbicki and Y. Bao, January, 2004. Report No. 113 A New Method for Calibrating Phenomenological Crack Formation
Criteria for Metals, D. Mohr and S. Henn, Febuary, 2004. Report No. 114 Necking, Fracture Initiation, and Crack Propagation in Flat Tensile
Specimen, Y.W. Lee, T. Wierzbicki and Y. Bao, February, 2004. Report No. 115 Quick Fracture Calibration for Industrial Use, Y.W. Lee, and T.
Wierzbicki, August 2004. Report No. 116 Fracture of Crashworthy Aluminum Structures under Reverse
Loading, T. Wierzbicki, Y. Bao and Y. Bai, April 2004. Report No. 117 Effect of Fracture Criteria on Impact Driven Spallation of Metal
Plates, X. Teng and T. Wierzbicki, March, 2004. Report No. 118 Prediction of High Velocity Impact Fracture of Large Structural
Systems, T. Wierzbicki, March, 2004
Report No. 119 Numerical Study on the Material Mismatch of the Welded Aluminum Joints Considering the HAZ Effect, L. Zheng, and T. Wierzbicki, May, 2004
Report No. 120 Evaluation of the Wilkins (and other) Fracture Model, Y. Bao, Y.W. Lee and T. Wierzbicki, May 2004
Report No. 121 Finite Element Modeling Techniques for the Failure Prediction of
Aluminum Overlap Fillet Welds, W. Guenthner, March, 2004 Report No. 122 Numerical Simulation with Fracture of Small-Scale Impact Tests into
WTC External Columns, L. Xue, and T. Wierzbicki, March, 2004 Report No. 123 Draw Bending of All-Metal Sandwich Sheets, D. Mohr, May, 2004 Report No. 124 Fracture of Extruded Aluminum Columns Considering Effects of
Strain Reversal, Y. Bai, Y. Bao, and T. Wierzbicki, May, 2004 Report No. 125 Experimental Investigation of Tearing Fracture in Sheets under
Quasi-static Loading, M. Roach, May, 2004 Report No. 126 Effect of Hull-to-Bulkhead Flexible Connections on Blast Resistance
of Double Hulled Ships, C. Brown, May, 2004
36
Report No. 127 A Comparative Study of Shell Element Deletion and Element Split, H.
Alsos, June, 2004 Report No. 128 Structural Optimization against Fracture Damage of Double Hulls
under Localized Impulsive Loading, Y.W. Lee, and T. Wierzbicki, August 2004.
Report No. 129 Splitting Fracture of Honeycomb Blocks, T. Wierzbicki and D. Mohr,
October 2004. Report No. 130 Small-Strain and Finite-Strain Plasticity of Low-Density Fiber Core
Materials, D. Mohr, September 2004. Report No. 131 On the Transition from Adiabatic Shear Banding to Fracture , X.
Teng, T. Wierzbicki, and H. Couque, October 2004. Report No. 132 Development and Manufacturing of Formable Ultra-Thin All-Metal
Sandwich Sheets for Automotive Applications, D. Mohr, G.Straza, October 2004.
Report No. 133 Fracture Prediction in Metal Sheets, (PhD Thesis), Y.W. Lee,
December 2004. Report No. 134 High Velocity Impact Fracture, (PhD Thesis), X. Teng, December 2004. Report No. 135 Calibration of A710 Steel for Fracture, Y. Bao, Y. Bai, and T.
Wierzbicki, December 2004. Report No. 136 On the Effect of the Third Invaraint of the Stress Deviator on Ductile
Fracture, T. Wierzbicki and L. Xue, February 2005. Report No. 137 Pilot Study on Strength and Fracture of a Composite Steel/Polymenr
Plate under Impact and Impulsive Loading, T. Wierzbicki, C. Walters, Y.W. Lee, and J.M. Shim, February 2005.
Report No. 138 Calibration and Evaluation of Seven Fracture Models, T. Wierzbicki,
Y. Bao, Y.W. Lee, and Y. Bai, March 2005. Report No. 139 Evaluation of Six Fracture Models in High Velocity Perforation, X.
Teng and T. Wierzbicki, June 2005. Report No. 140 Fracture of Welded Aluminum Thin-Walled Structures, (PhD Thesis),
L. Zheng, June 2005.
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Report No. 141 Failure of a Polyurea/Steel Composite Plate under Blast Loading, J.-M. Shim, July 2005
Report No. 142 Preliminary Study on the Response of a Field Vehicle to Land Mine
Explosion, Y.-W. Lee, C. Walters, Tom Wierzbicki, July 2005 Report No. 143 Gouging and Fracture of Aluminum Panel under Oblique Impact, X.
Teng and T. Wierzbicki, October 2005. Report No. 144 Energy Absorption of Prismatic Columns Made from Thin Sandwich
Sheets with Different Types of Cores, D. Mohr and T. Wierzbicki, October 2005.
Report No. 145 Gouging and Fracture of Aluminum Panel under Oblique Impact, X.
Teng, February 2006. Report No. 146 Characterization of Plastic and Fracture Properties of Aluminum
Overlap Fillet Welds, C. Roth, April 2006. Report No. 147 Numerical Experimental and Analytical Study on Plastic Buckling of
Thick-Walled Tubes, A. Chripunow, April 2006. Report No. 148 Ductile Fracture Initiation and Propagation Modeling Using a New
Fracture Criterion, L. Xue and T. Wierzbicki, May 2006. Report No. 149 Void Shearing Effect in Ductile Fracture of Porous Materials, L. Xue,
May 2006. Report No. 150 Verification of a New Fracture Criterion Using LS-DYNA, L. Xue and
T. Wierzbicki, June 2006. Report No. 151 Study on the effect of the third stress invariant on ductile fracture, Y.
Bai, X. Teng, and T. Wierzbicki, June 2006. Report No. 152 Failure of an impulsively-loaded composite steel/polyurea plates, J.
Shim and T. Wierzbicki, June 2006. Report No. 153 Numerical Prediction of Slant Fracture with Continuum Damage
Mechanics, X. Teng, July 2006. Report No. 154 Calibration of Ductile Fracture Properties of a Cast Aluminum Alloy,
H. Mae, X. Teng, Y. Bai and T. Wierzbicki, September 2006. Report No. 155 On the asymmetric metal plasticity and fracture, Y. Bai and T.
Wierzbicki, September 2006.
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Report No. 156 Fracture of tungsten alloy under combined loading, Y. Bai, C. Walters, T. Wierzbicki, S. Hiermaier and I. Rohr, October 2006.
Report No. 157 Optimization of armor plates under projectile impact, X. Teng and T.
Wierzbicki, October 2006.
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LIST OF ICL JOURNAL PUBLICATIONS ON FRACTURE
1. Mae, H., Teng, X., Bai, Y., and Wierzbicki, T. Calibration of ductile fracture properties of a cast aluminum alloy. To be submitted to Materials Sciences and Engineering A., 2006.
2. Teng, X. Numerical prediction of slant fracture with continuum damage mechanics. Submitted to Computer Methods in Applied Mechanics and Engineering, 2006.
3. Teng, X., Wierzbicki, T., and Couque, H. On the transition from adiabatic shear banding to fracture. Mechanics of Materials, 2007. 39(2): p 107-125.
4. Teng, X. and Wierzbicki T. Evaluation of six fracture models for high velocity perforation, Engineering Fracture Mechanics, 2006. 73: p. 1653-1678.
5. L. Xue and T. Wierzbicki, Ductile fracture initiation and propagation modeling using a new fracture criterion, 9th European Mechanics and Materials Conference, May 8-12 2006, Moret-sur-Loing, France
6. L. Xue, Void shearing effect in ductile fracture of porous materials, 9th European Mechanics and Materials Conference, May 8-12 2006, Moret-sur-Loing, France
7. L. Xue and T. Wierzbicki, Verification of a new fracture criterion using LS-DYNA, 9th International LS-DYNA Users Conference, June 4-6, 2006, Dearborn, MI
8. J. Shim and T. Wierzbicki, Failure of an impulsively-loaded composite steel/polyurea plates, ASME International Mechanical Engineering Congress and Exposition, November 5-10, 2006, Chicago, IL
9. Y. Bai and T. Wierzbicki, On the asymmetric metal plasticity and fracture, International Journal of Plasticity (Submited)
10. Bao, Y.B. and Wierzbicki, T. On the cut-off value of negative triaxiality for fracture. Engineering Fracture Mechanics, 2005. 72(7): p. 1049-1069.
11. Bao, Y.B., Dependence of ductile crack formation in tensile tests on stress triaxiality, stress and strain ratios. Engineering Fracture Mechanics, 2005. 72(4): p. 505-522.
12. Lee, Y.W. and Wierzbicki, T. Fracture prediction of thin plates under localized impulsive loading. Part I: dishing. International Journal of Impact Engineering, 2005. 31(10): p. 1253-1276.
13. Lee, Y.W. and Wierzbicki, T. Fracture prediction of thin plates under localized impulsive loading. Part II: discing and petalling. International Journal of Impact Engineering, 2005. 31(10): p. 1277-1308.
14. Teng, X., Wierzbicki, T., Hiermaier, S., and Rohr, I. Numerical prediction of fracture in the Taylor test. International Journal of Solids and Structures, 2005. 42(9-10): p. 2929-2948.
15. Teng, X. and Wierzbicki, T. Numerical study on crack propagation in high velocity perforation. Computers & Structures, 2005. 83(12-13): p. 989-1004.
16. Teng, X. and Wierzbicki, T. Dynamic shear plugging of beams and plates with an advancing crack. International Journal of Impact Engineering, 2005. 31(6): p. 667-698.
17. Wierzbicki, T., et al. Calibration and evaluation of seven fracture models. International Journal of Mechanical Sciences, 2005. 47(4-5): p. 719-743.
18. Wierzbicki, T., Bao, Y., and Bai, Y. A new experimental technique for constructing a fracture envelope of metals under multi-axial loading. Annual Conference of the Society of Experimental Mechanics (SEM), Portland, OR. USA. June 2005
40
19. Bao, Y.B. and Wierzbicki, T. A comparative study on various ductile crack formation criteria. Journal of Engineering Materials and Technology-Transactions of the ASME, 2004. 126(3): p. 314-324.
20. Bao, Y.B. and Wierzbicki, T. On fracture locus in the equivalent strain and stress triaxiality space. International Journal of Mechanical Sciences, 2004. 46(1): p. 81-98.
21. Teng, X. and Wierzbicki, T. Effect of Fracture Criteria on High Velocity Perforation of Thin Beams. International Journal of Computational Methods, 2004. 1(1): p. 171-200.
22. Wierzbicki, T. and Teng, X. How the airplane wing cut through the exterior columns of the World Trade Center. International Journal of Impact Engineering, 2003. 28(6): p. 601-625.
23. Wierzbicki, T., Petalling of plates under explosive and impact loading. International Journal of Impact Engineering, 1999. 22(9-10): p. 935-954.
24. Wierzbicki, T., K.A. Trauth, and A.G. Atkins, On diverging concertina tearing. Journal of Applied Mechanics-Transactions of the ASME, 1998. 65(4): p. 990-997.
25. Bracco, M.D. and T. Wierzbicki, Tearing resistance of advanced double hulls. Journal of Ship Research, 1997. 41(1): p. 69-80
26. Simonsen, B.C. and T. Wierzbicki, Plasticity, fracture and friction in steady-state plate cutting. International Journal of Impact Engineering, 1997. 19(8): p. 667-691.
27. Wierzbicki, Simonsen, B.C. Grounding Bottom Damage and Ship Motion over a Rock. International Journal of Offshore and Polar Engineering, 1996. 6(3): p. 195-202.
28. Zheng, Z.M. and Wierzbicki, T. A theoretical study of steady-state wedge cutting through metal plates. International Journal of Fracture, 1996. 78(1): p. 45-66.
29. Zhou, Q. and Wierzbicki, T. An incremental analysis of plane strain fully plastic crack growth in strain-hardening materials under extension. International Journal of Fracture, 1996. 79(1): p. 27-48.
30. Zhou, Q. and Wierzbicki, T. A tension zone model of blanking and tearing of ductile metal plates. International Journal of Mechanical Sciences, 1996. 38(3): p. 303-&.
31. McClintock, F.A., Zhou, Q., and Wierzbicki, T. Necking in Plane-Strain under Bending with Constant Tension. Journal of the Mechanics and Physics of Solids, 1993. 41(8): p. 1327-1343.
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ABSTRACTS OF ALL ICL REPORTS COMPLETED AFTER OCTOBER 2005
42
Report No: 145
43
Gouging and Fracture of Aluminum Panel
under Oblique Impact: LSDYNA vs. ABAQUS
Xiaoqing Teng
Abstract
This is the third report on the project on gouging and fracture response of an aluminum alloy obliquely impacted by a titanium fragment. The problem is numerically studied using LS-DYNA. Three cases are considered: (1) pure plastic deformation without fracture; (2) the constant critical plastic strain to fracture; and (3) the Bao-Wierzbicki fracture criterion. At the same time, the calculation based on the input file provided by the GE GRC team is also performed. A user defined material plasticity and fracture subroutine is developed to introduce the Bao-Wierzbicki fracture criterion into LS-DYNA. In the first two cases, the LS-DYNA simulations are comparable with the ABAQUS/Explicit results. However, there are large differences in the case with the Bao-Wierzbicki fracture model. The disagreement may be due to various contact formulations in the two solutions. The penalty contact constraint is defined in the LSDYNA simulation, in which penetration of the nodes of the master surface into the slave surface is allowed. Severe penetration leads to large negative sliding interface energy and thus the total energy is not conserved. This is true for the case with the Bao-Wierzbicki fracture criterion. The problem of how to effectively model interaction between the projectile and the target plate within LS-DYNA for the gouging process remains to be explored. Key words: LS-DYNA; ABAQUS/Explicit; Oblique impact; Gouging; Fracture criterion.
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Impact & Crashworthiness Laboratory
Report No. 146
Characterization of Plastic and Fracture Properties of Aluminum Overlap Fillet Welds
by
Christian C. Roth,
Bundeswehr University Munich & Massachusetts Institute of Technology
Cambridge, MA 02139 Email: [email protected]
April 2006
45
Characterization of Plastic and Fracture Properties of
Aluminum Overlap Fillet Welds
By
Christian C. Roth
Institute of Lightweight Structures, Bundeswehr University Munich &
Impact and Crashworthiness Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
ABSTRACT Aluminum overlap fillet weld specimens, similar to parts found in the undercarriage of a car, are studied both experimentally and numerically in three scale steps. First, the material properties throughout the welded specimen are determined in tensile tests by means of newly developed non-standardized micro-flat-tensile-strip (MFTS) specimens. Next, the “h”-slice specimens taken out of the welded specimen are examined in tensile tests and compared with numerical simulations, proving the correctness of the acquired material data and giving an insight on the plastic behavior of a weld specimen’s cross section. The Gurson-Tvergaard-Needleman plasticity model is introduced for the material behavior of the weld region and is compared to results using von Mises plasticity. Additionally, the Gurson-Tvergaard-Needleman failure criterion is implemented and calibrated for the simulation of the fracture of an “h”-slice specimen and compared to the experiments. Finally, the plastic behavior of a whole welded specimen is analyzed numerically and compared with experiments carried out at BMW R&D Center.
46
Impact & Crashworthiness Laboratory
Report No. 147
Numerical Experimental and Analytical Study on Plastic Buckling of Thick-Walled Tubes
by
André Chripunow
Bundeswehr University Munich & Massachusetts Institute of Technology
Cambridge, MA 02139 Email: [email protected]
April 2005
47
Deformation of a thick-walled tube
under compressive loading
By
André Chripunow Institute of Lightweight Structures, Bundeswehr University Munich &
Impact and Crashworthiness Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
ABSTRACT
From the point of view of designing a new core material, it is necessary to find a new class of so-called “stable cellular solids”. Preparing the ground for this development, it is at first essential to understand the plastic stability of the part system. The structures investigated in this thesis are thick cylindrical aluminum shells, as the plastic buckling of thick-walled tubes is not fully understood and a future cellular solid could consist out of many tubes or round holes. To provide a wide-ranging study, numerical, experimental and analytical methods were used in this thesis. Two-dimensional and three-dimensional numerical simulations were carried out. The study shows how the buckling mode depends on the relative density and thus on the wall thickness of the tubes. Furthermore it is shown how the buckling mode influences the value of the maximum load and especially the one of the critical shortening. To investigate the influence of the cross section shape on the response of tubes due to compressive loading, the behavior of several other shapes was investigated and compared to the one of a cylindrical tube. Thereby the cylindrical type turns out to be the most appropriate one to withstand compressive loading. To prove the reliability and accuracy of the numerical simulations, upsetting tests with tubes of various relative densities were carried out. Numerical simulations modeling the test conditions were performed. In conjunction with their calculated final deformation it can be summarized that the numerical simulations reproduce the response of the tubes due to compression very well. The analytical solution provides a rapid estimate for the critical load and its corresponding displacement. Despite several simplifying assumptions introduced in deriving this analytical solution, quite good results are obtained in a certain range of the relative densities.
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49
Ductile Fracture Initiation and Propagation Modeling Using
Damage Plasticity Model
Liang Xue and Tomasz Wierzbicki [email protected] and [email protected]
Impact and Crashworthiness Lab, Massachusetts Institute of Technology 77 Massachusetts Avenue, 5-011, Cambridge, MA 02139, USA
Abstract
Ductile fracture is often considered as the consequences of the accumulation of plastic damage. This paper is concerned with the formulation and application of a recently developed damage plasticity model that includes four effects: the pressure sensitivity, the Lode angle dependence, a nonlinear damage rule and the material deterioration effect. The ductile damaging process is calculated through the so-called cylindrical decomposition. Simulation results of compact tension and three-point bending tests are presented and good agreement with experiments is achieved. Keywords: Aluminum alloy; Damage plasticity model; Finite element simulation; Ductile fracture; Crack initiation.
50
51
Void Shearing Effect in Ductile Fracture
of Porous Materials
Liang Xue Impact and Crashworthiness Lab, Massachusetts Institute of Technology
77 Massachusetts Avenue, Room 5-011, Cambridge, MA 02139, USA
Abstract The Gurson-like material model has attracted a great deal of attention and various modifications to this model have been proposed. The solids are considered as a porous media. The constitutive equations are governed by the first and second stress invariants and the void volume fraction. Tvergaard and Needleman included the void-nucleation-growth-coalescence in a phenomenological way [1]. Meanwhile, little attention was given to the dependence of the damage evolution on the third stress invariant. McClintock et al [2] proposed damage model based on the void evolution in localized shear band. In the present paper, the GTN model is further extended to incorporate the void shearing mechanism. A new interval variable of damage is introduced and separated from the void volume fraction. Additional damage associated with void shearing deformation is incorporated. Numerical aspects are addressed concerning the integration of the constitutive relations. A unit cell simulation is used to illustrate the mechanical behavior of the modified model. Calculations of the axisymmetric and the transverse plane strain tension are also performed. Realistic crack modes in these simulations are achieved. Keywords: Ductile fracture; Porous materials; Void shearing; Lode angle dependence; Finite element analysis
52
53
Verification of a New Fracture Criterion Using
LS-DYNA
Liang Xue and Tomasz Wierzbicki ([email protected] and [email protected] )
Impact and Crashworthiness Lab, Massachusetts Institute of Technology, Room 5-007, Cambridge, MA 02139, USA
Abstract
Several fracture models are available in the material library of LS-DYNA. This paper is concerned with a newly developed constitutive model that covers the full range of plasticity till the onset of fracture. It is understood that the fracture initiation in uncracked solids is an ultimate result of a complex damage accumulation process. Such damage is induced by plastic deformations. A new damage model is proposed to incorporate the pressure sensitivity and the Lode angle dependence through a nonlinear damage rule using a reference fracture strain on a restricted loading path. The onset of fracture is predicted by integrating incremental damage along the actual loading path. In this cumulative fashion, fracture can be predicted for complex loading paths, which are not limited to the restricted loading in which the pressure is constant. This modified model also incorporates the coupling between the damage and the strain hardening function.
The new fracture model is implemented to LS-DYNA as a user defined material subroutine. A series of benchmark tests and simulations have been performed to verify this model. The loading situations of these tests cover a wide range of standard laboratory testing, which include uniaxial tension of a round bar, uniaxial tension of a hollow bar and the three-point bending of a rectangular bar. A remarkable agreement between the experimental and numerical results is achieved.
54
Impact & Crashworthiness Laboratory
Report No. 151
Study on the effect of the third stress invariant on ductile fracture
by
Yuanli Bai, Xiaoqing Teng, and Tomasz Wierzbicki
Massachusetts Institute of Technology Room 5-218
Cambridge, MA 02139 Phone: 617-253-6055 Email: [email protected]
June 2006
55
Study on the effect of the third stress invariant on ductile
fracture
By
Yuanli Bai, Xiaoqing Teng, and Tomasz Wierzbicki
Impact and Crashworthiness Laboratory, Room 5-007 Massachusetts Institute of Technology, Cambridge, MA 02139, USA
ABSTRACT Equivalent plastic strain to fracture is widely used to describe the ductility of materials, but it is not a constant under different loading conditions. It is well known that stress triaxiality is the most important parameter controlling the fracture strain at the point of fracture initiation. Whether the third stress invariant (or the Lode parameter) will affect the equivalent fracture strain or not is an interesting question. In this paper, the anisotropy of two types of metal material (2024-T351 aluminum and 1045 steel) were investigated first, then two groups of specimens of these two types of materials were analyzed, designed and tested to investigate the interaction of these two parameters. From the derived theoretical formulas, the magnitudes of equivalent strain at the point of fracture initiation, stress triaxiality and the normalized third stress invariant were determined. Finite element simulations were performed to reproduce the experimental results. It was found that, for these two materials, in the high stress triaxiality region, the stress triaxiality is the most important parameters controlling the fracture strain, and the third stress invariant has little effect on fracture initiation strain. For 2024-T351 aluminum, the material anisotropy has also a significant effect on ductile fracture, which should be included in the future ductile fracture model. Keywords: fracture initiation, stress triaxiality, third stress invariant, lode parameter.
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Impact & Crashworthiness Laboratory
Report No. 152
Failure of an Impulsively-Loaded Composite Steel/Polyurea Plates
by
JongMin Shim and Tomasz Wierzbicki
Massachusetts Institute of Technology Room 5-218
Cambridge, MA 02139 Phone: 617-253-6055 Email: [email protected]
June 2006
57
Failure of an Impulsively-Loaded Composite Steel/Polyurea Plates
By
JongMin Shim andTomasz Wierzbicki
Impact and Crashworthiness Laboratory, Room 5-007 Massachusetts Institute of Technology, Cambridge, MA 02139, USA
ABSTRACT The concept of spraying thick layer of polymer material onto metal plate has recently received considerable interest in many civilian and military applications. There are numerous analytical and numerical solutions for single thin plates (membrane) made of either a steel or an elastomer. However, solutions for composite plate made of both of the above constituents are lacking. The objective of the present paper is to formulate a model for composite steel/elastomer plate, derive an analytical solution of the impulsive loading problem and compare it with a more exact numerical solution. It is assumed that the circular plate is fully clamped around its peripheral and it is loaded by uniformly distributed transverse pressure of high intensity and short duration. The pressure is imparting initial impulse which is proportional to initial transverse velocity of the plate. As an example, DH-36 is used for steel backing plate while polyurea is chosen to represent a typical polymer coating. In the analytical model, an iterative method is developed in which steel layer treated as a rigid perfectly-plastic material with magnitude of flow stress adjusted according to calculated magnitude of average strain. A linear elastic material is assumed with elastic modulus in the tensile range calculated from the Arruda-Boyce model for an specific type of polyurea. It was found that the magnitude of the average strain rate is relatively low, about 100 sec-1. Therefore, the effect of strain rate is not considered in this paper. A comprehensive parametric study was performed by varying various material and structural parameters of the model. A closed form solution was compared with the results of detailed FE simulations of composite plates. It was found that the polyurea coating could improve the failure resistance of the composite plate by some 20 % provided the thickness of the coating is 5-10 times larger than the plate.
58
Report No: 153
59
Numerical Prediction of Slant Fracture with
Continuum Damage Mechanics
Xiaoqing Teng
Abstract
Ductile specimens always exhibit an inclined fracture surface with an angle relative to the loading axis. This paper reports a numerical study on the cup-cone fracture mode in round bar tensile tests and the slant fracture in plane-strain specimens based on continuum damage mechanics. An implicit-explicit numerical scheme is developed within ABAQUS through user material subroutines, in which ABAQUS/Standard and ABAQUS/Explicit are sequentially used to simulate one single damage/fracture process. It is demonstrated that this numerical approach is able to significantly reduce computational cost for the simulation of fracture tests under low rate loading. Comparison with various tensile tests on 2024-T351 aluminum alloy is made showing good correlations in terms of the load-displacement curves and the fracture patterns. However, some errors exist in the prediction of the critical displacement of the specimens at the point of fracture. The results indicate that a new evolution rule of damage should be introduced. Key words: Continuum damage mechanics; Slant fracture; Cup-cone fracture; Damage evolution rule.
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Report No: 154
61
Calibration of Ductile Fracture Properties
of a Cast Aluminum Alloy
H. Maea, X. Tengb, Y. Baib, T. Wierzbickib a Honda R&D Co., Ltd. Japan
b Impact & Crashworthiness Lab, Massachusetts Institute of Technology, USA
Abstract
To numerically predict crack formation and growth of cast components under accidental loading, it is necessary to characterize fracture properties at the macroscopic level. In this paper, a ductile fracture locus formulated in the space of the effective plastic strain to fracture and the stress triaxiality for a cast aluminum alloy was obtained using a combined experimental-numerical approach. A total of twelve tests were conducted including six tensile tests on notched and unnotched round bars and six biaxial loading tests on flat butterfly specimens. Corresponding finite element analysis was performed to determine the evolution of stress and strain states. It was found that the material ductility strongly depends on the stress triaxiality for the present cast alloy. The fracture strain is as high as 0.54 when the stress state is predominately compressive. At the same time, the fracture strain drops to a very low value of 0.05 under uniaxial tension. The obtained fracture locus covers a wide range of the stress triaxiality and thus it be applicable to various loading cases. A large spread of fracture data was observed indicating a need of using a probability method to describe the fracture properties of the cast alloy. Key words: Cast aluminum alloy; Ductile fracture locus; Butterfly specimens.
62
Impact & Crashworthiness Laboratory
Report No. 155
On the asymmetric metal plasticity and fracture
by
Yuanli Bai and Tomasz Wierzbicki
Massachusetts Institute of Technology Room 5-218
Cambridge, MA 02139 Phone: 617-253-6055 Email: [email protected]
September 2006
63
On the asymmetric metal plasticity and fracture
By
Yuanli Bai and Tomasz Wierzbicki
Impact and Crashworthiness Laboratory, Room 5-007 Massachusetts Institute of Technology, Cambridge, MA 02139, USA
ABSTRACT
Classical metal plasticity theory assumes that the hydrostatic pressure has no or negligible effect on the material strain hardening, and that the flow stress is independent of the third stress invariant. However, recently reported experiments have shown that both the pressure effect and the effect of the third stress invariant should be included in the metal plasticity for more exact predictions of local stresses and strains. A general form of asymmetric metal plasticity, considering both the pressure sensitivity and the lode dependence, is postulated. Calibration method for the new metal plasticity is discussed. Experimental results on aluminum 2024-T351 verified the new metal plasticity model. From the similarity between yielding surface and fracture locus, a new 3-D asymmetric fracture locus, in the space of equivalent fracture strain, stress triaxiality and the normalized third stress invariant, is postulated based on the new form of metal plasticity. Two methods for the determination of fracture locus are discussed. One uses classical specimens (such as round notched bars or tubes), another one uses the newly designed butterfly specimen. The test data points of A710 steel verified the postulated 3D fracture locus. Keywords: pressure effect, lode dependance, yield surface, fracture locus, calibration method.
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Impact & Crashworthiness Laboratory
Report No. 156
Fracture of tungsten alloy under combined loading
by
Yuanli Bai, Carey Walters, and Tomasz Wierzbicki Impact and Crashworthiness Lab, MIT
In collaboration with Stefan Hiermaier and Ingmar Rohr Ernst Mach Institute, Freiburg, Germany
Massachusetts Institute of Technology Room 5-218
Cambridge, MA 02139 Phone: 617-253-6055 Email: [email protected]
October 2006
65
Fracture of tungsten alloy under combined loading
By
Yuanli Bai, Carey Walters, and Tomasz Wierzbicki
Impact and Crashworthiness Lab, MIT In collaboration with Stefan Hiermaier and Ingmar Rohr
Ernst Mach Institute, Freiburg, Germany
ABSTRACT Tungsten alloy is a representative of a family of high strength steel with the yield stress in excess of 1GPa. A specially designed set of grips was used to fix the specimen onto the Instron biaxial testing machine. Using the displacement control and force control modes in the biaxial testing machine, different combination of loading from two actuators (horizontal actuator and vertical actuator) were applied on the butterfly specimens of tungsten alloy. The specimens were tested under five different loading conditions characterizing by the loading angle. They are 90° tension, 30° tension with shearing, 10° tension with shearing, 0° shearing and -10° compression with shearing. An optical system was used to record the specimen deformation and measure the local displacement field. In particular the displacement to fracture in both directions was recorded with great accuracy. The butterfly specimen was descretized by very fine 8-nodes solid elements using ABAQUS/Standard. The stress strain curve was obtained from several iterative runs of 90° tension loading case. Numerical simulations on all the five cases show good correlations on both the horizontal and vertical force-displacement responses. From the corresponding displacement to fracture initiation, the corresponding fracture strain at the fracture initiation site can be obtained, as well as the history of stress triaxiality and the third stress parameter. Finally, the fracture locus of tungsten alloy was constructed in the space of equivalent strain to fracture and stress triaxiality. Keywords: tungsten alloy, fracture locus, biaxial testing.
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67
Optimization of Double-Layered Armor Plates
against Projectile Impact
X. Teng, and T. Wierzbicki Impact & Crashworthiness Lab, Room 5-218, Massachusetts Institute of Technology,
Cambridge, MA02139, USA
Abstract
In this paper, the protection performance of double-layered shields against projectile impact is critically evaluated using finite element methods. Four types of projectiles of different weight and nose shape are considered, representing fragments generated from Improvised Explosive Devices (IEDs) and standard 7.62 mm bullet ball rounds, respectively. The ballistic limits of twelve projectile-target systems are determined by conducting an extensive parametric study. It is found that compared to the monolithic plate, the double layer configuration is able to improve the ballistic resistance by 8.0-25.0% for the flat-nose projectile due to the transition of the failure modes from shear plugging to tensile tearing. Under impact by the conical-nose projectile, the double-layered target is almost as capable as the monolithic plate. The present research helps resolve the long outstanding issue of the protection effectiveness of the double layer configuration.
Key words: Double layer; Projectile; Perforation; Fragments.
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