Real World Derived Simulation Methodology for the Evaluation of Fleet Crash Protection of New Vehicle Designs

Real World Derived Simulation Methodology for the Evaluation of Fleet Crash Protection of New Vehicle Designs by Randa Radwan B. S. in Electrical Engineering, May 1982, Rice University Masters of Electrical Engineering, May 1984, Rice University A Dissertation submitted to The Faculty of The School of Engineering and Applied Science of The George Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy May 17, 2015 Dissertation directed by Azim Eskandarian Professor of Engineering and Applied Science The School of Engineering and Applied Science of The George Washington University certifies that Randa Radwan has passed the Final Examination for the degree of Doctor of Philosophy as of February 6, 2015. This is the final and approved form of the dissertation. Real World Derived Simulation Methodology for the Evaluation of Fleet Crash Protection of New Vehicle Designs Randa Radwan Dissertation Research Committee: Azim Eskandarian, Professor of Engineering and Applied Science, Dissertation Director Kennerly H. Digges, Research Professor of Engineering, Committee Member Muhammad I. Haque, Professor of Engineering and Applied Science, Committee Member Samer H. Hamdar, Assistant Professor of Civil Engineering, Committee Member William T. Hollowell, President, WTH Consulting, Committee Member ii © Copyright 2015 by Randa Radwan All rights reserved iii Dedication To My Sons Alexander and Peter, To My Mom Whose Spirit Will Always be with Me, To My Friends, Colleagues and Family, Thank You for Your Boundless Encouragement, Support, & Faith in me! iv Acknowledgments The author wishes to thank Professor Azim Eskandarian for his work chairing the committee and all of his effort as academic advisor, and Professors Kennerly Digges, Muhammad Haque, and Samer Hamdar for their feedback and support as committee members. The author wishes to thank Dr. Tom Hollowell for his work as committee member and his encouragement over the years. The author gratefully appreciates the financial support of the National Highway Traffic Safety Administration (NHTSA) of the U.S. Department of Transportation (DOT) in the sponsored project under which most of the research was performed. The author wishes to thank Dr. Cing-Dao Kan for his support and guidance during his tenure as director of the National Crash Analysis Center (NCAC) of the School of Engineering and Applied Science. The author wishes to thank her NCAC colleagues, NHTSA support staff, and NCAC consulting staff including Dr. Dhafer Marzougui, Dr. Chongzhen Cui, Ms. Lilly Nix, Ms. Aida Barsan-Anelli, Dr. Fadi Tahan, Dr. Chung-Kyu Park, Dr. Pradeep Mohan, Dr. Tejas Ruparel, Mr. Abdul Khan, Mr. Sarath Kamalakkannan, Mr. Vamsi Kommineni, and Mr. Stefano Dolci for performing extended vehicle and occupant model development and validations, and conducting hundreds of simulations whose output served as input to the methodology developed in this research. The author wishes to thank her sponsors at NHTSA including Mr. Stephen Summers and Ms. Lixin Zhao for their invaluable discussions and feedback on this research. Finally, the author is immensely grateful for Dr. Priya Prasad’s guidance, mentorship, and insights throughout this research. The author also wishes to thank Professor Kennerly Digges for his support and collegiate inspiration throughout her tenure at the NCAC. v Abstract of Dissertation Real World Derived Simulation Methodology for the Evaluation of Fleet Crash Protection of New Vehicle Designs At the present time, the crash safety of new and concept vehicle designs, i.e., with advanced materials or structure or powertrains, is primarily assessed through computer simulations of single- vehicle crash test protocols specified by existing regulations and consumer information programs. Although such protocols are representative of real-world crash configurations, the tests are typically impacts into fixed object and are performed at single speeds with a single size of dummy occupants. In the real world, vehicles are involved in crashes with fixed objects and with other vehicles in the fleet. These crashes occur at various speeds and involve occupants of many sizes and ages. To date, assessment of the real-world safety of vehicle designs has not been attempted through simulations because a systematic approach is not currently defined or developed. In this research, a novel methodology for Evaluating Fleet, i.e., self and partner, Protection (EFP) of new vehicle designs has been developed through a systems modeling approach driven by structural and occupant modeling, and real-world crash and full-scale test data. The fleet societal injury risk in EFP is defined as the total injury risk of occupants in both the target vehicle and partner vehicles aggregated over a range of impact speeds, occupant sizes, and crash configurations, and weighted by relative frequency of the specific crash incident in the real world. The self-protection provided by a target vehicle is derived as the aggregate injury risk for its occupants in both single- and two-vehicle crashes. Partner protection is derived as the aggregate injury risk for the occupants of the vehicles in the fleet against which the target vehicle collides. The integral feature of EFP is that the methodology is based on real-world crash configurations, severity exposures and occupant injury risks in each crash incident, and is also based on physically realistic vehicle structural, occupant, and restraint system models. The main hypothesis of EFP is as follows: Given that the approach is grounded in the physical world with sufficient detail (i.e., real-world derived with sufficient granularity), EFP will serve as a useful method vi to assess the overall safety of vehicle designs in the fleet and for directing future vehicle safety research efforts. As proof-of-concept and initial application, EFP was implemented to assess real-world fleet societal risk in frontal crashes. The modeled frontal crash configurations and EFP weighting factors were derived from an innovative crash taxonomy based on real-world structural engagement from the National Automotive Sampling System Crashworthiness Data System (NASS CDS). The EFP crash configuration weighting factors for two-vehicle crash simulations were modulated by real-world crash exposure by vehicle class. The weighting factors for the impact speeds of the simulated crash incidents were based on real-world distributions for the target vehicle class. Simulation data to drive the methodology were obtained from finite element vehicle structural models with sufficient physical detail that allow implementation of new designs such as lightweight materials, new powertrains, and new structural architectures. Occupant responses were based on three-dimensional articulated rigid body models of the occupant and the passenger compartment. Both the structural and the occupant models are subjected to validation and robustness checks for the modeled crash configurations. Occupant injury potentials were derived from occupant responses using state-of-the-art biomechanical injury risk probability functions. EFP was applied to compute the change in driver societal injury risk between baseline and concept light-weighted vehicle design variants. EFP was also applied to obtain insights of the safety interactions in frontal crashes in an assumed light-weighted fleet as compared with a baseline fleet, both consisting of two vehicle segments. Overall, there is a net decrease in safety on a fleet level and by vehicle segments modeled in the light-weighted fleets. While the proof-of-concept and initial implementation of EFP was to drivers in frontal crashes, the EFP methodology can be extended to all crash modes and occupants. vii Table of Contents Dedication ................................................................................................................................. iv Acknowledgments...................................................................................................................... v Abstract of Dissertation ............................................................................................................ vi List of Figures ........................................................................................................................ xiii List of Tables ........................................................................................................................... xx Chapter 1. Introduction .............................................................................................................. 1 1.1. Fleet Crash Safety Performance Assessment: A Historical Perspective ................ 1 1.2. Changing U.S. Fleet ............................................................................................... 2 1.3. State of the Art: Evaluation of Crash Safety of New Vehicle Designs .................. 3 1.4. Objective and Summary of Dissertation Research ................................................. 4 1.5. Contributions of this Work ..................................................................................... 6 1.6. Roadmap of Dissertation Chapters ......................................................................... 9 Chapter 2. Literature Review ................................................................................................... 11 2.1. Ford SSOM .......................................................................................................... 11 2.2. Volpe’s Systems Model.......................................................................................

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