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Kim, Taewung
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Influence of Driver Input on the Touchdown Conditions and Risk of Rollover in Case of Steering Induced Soil-Trip Rollover Crashes

Toyota Technical Center USA, Inc.-Mark Clauser
University of Virginia-Varun Bollapragada, Taewung Kim, Jeff Crandall, Jason Kerrigan
Published 2016-04-05 by SAE International in United States
Some rollover testing methodologies require specification of vehicle kinematic parameters including travel speed, vertical velocity, roll rate, and pitch angle, etc. at the initiation of vehicle to ground contact, which have been referred to as touchdown conditions. The complexity of the vehicle, as well as environmental and driving input characteristics make prediction of realistic touchdown conditions for rollover crashes, and moreover, identification of parameter sensitivities of these characteristics, is difficult and expensive without simulation tools. The goal of this study was to study the sensitivity of driver input on touchdown parameters and the risk of rollover in cases of steering-induced soil-tripped rollovers, which are the most prevalent type of rollover crashes. Knowing the range and variation of touchdown parameters and their sensitivities would help in picking realistic parameters for simulating controlled rollover tests. Additionally, understanding the sensitivity of the risk of rollover could potentially aid in developing countermeasures to prevent rollover. Monte Carlo simulations were performed using two multibody models (sedan and pickup) by varying the driving inputs (speed, steer angle, steer rate) for typical…
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Neck Validation of Multibody Human Model under Frontal and Lateral Impacts using an Optimization Technique

Tsinghua University-Yan Wang, Yibing Li
University of Virginia-Taewung Kim, Jeff Crandall
Published 2015-04-14 by SAE International in United States
Multibody human models are widely used to investigate responses of human during an automotive crash. This study aimed to validate a commercially available multibody human body model against response corridors from volunteer tests conducted by Naval BioDynamics Laboratory (NBDL). The neck model consisted of seven vertebral bodies, and two adjacent bodies were connected by three orthogonal linear springs and dampers and three orthogonal rotational springs and dampers. The stiffness and damping characteristics were scaled up or down to improve the biofidelity of the neck model against NBDL volunteer test data because those characteristics were encrypted due to confidentiality. First, sensitivity analysis was performed to find influential scaling factors among the entire set using a design of experiment. Second, the identified scaling factors were adjusted using a gradient-based optimization technique to minimize a Biofidelity rank score (smaller the better), which is one of common technique for correlation analysis between PMHS responses and ones of a dummy or a model. In the sensitivity analysis 4 scaling factors out of 7 were found to be influential to the…
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The Contribution of Pre-impact Spine Posture on Human Body Model Response in Whole-body Side Impact

University of Virginia-David Poulard, Damien Subit, John-Paul Donlon, David J. Lessley, Taewung Kim, Gwansik Park, Richard W. Kent
Published 2014-11-10 by The Stapp Association in United States
The objective of the study was to analyze independently the contribution of pre-impact spine posture on impact response by subjecting a finite element human body model (HBM) to whole-body, lateral impacts. Seven postured models were created from the original HBM: one matching the standard driving posture and six matching pre-impact posture measured for each of six subjects tested in previously published experiments. The same measurements as those obtained during the experiments were calculated from the simulations, and biofidelity metrics based on signals correlation were established to compare the response of HBM to that of the cadavers. HBM responses showed good correlation with the subject response for the reaction forces, the rib strain (correlation score=0.8) and the overall kinematics. The pre-impact posture was found to greatly alter the reaction forces, deflections and the strain time histories mainly in terms of time delay. By modifying only the posture of HBM, the variability in the impact response was found to be equivalent to that observed in the experiments performed with cadavers with different anthropometries. The patterns observed in…
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Evaluation of Biofidelity of Side Impact Computational Surrogates (ES-2re, WorldSID, GHBMC)

Automotive Safety Honda R&D Americas-Andy Svendsen, Nathaniel Saunders, Craig Markusic
University of Virginia-Gwansik Park, Taewung Kim, Jeff Crandall
Published 2014-04-01 by SAE International in United States
The goal of this study was to evaluate the biofidelity of the three computational surrogates (GHBMC model, WorldSID model, and the FTSS ES-2re model) under the side impact rigid wall sled test condition. The responses of the three computational surrogates were compared to those of post mortem human surrogate (PMHS) and objectively evaluated using the correlation and analysis (CORA) rating method. Among the three computational surrogates, the GHBMC model showed the best biofidelity based on the CORA rating score (GHBMC =0.65, WorldSID =0.57, FTSS ES-2re =0.58). In general, the response of the pelvis of all the models showed a good correlation with the PMHS response, while the response of the shoulder and the lower extremity did not. In terms of fracture prediction, the GHBMC model overestimated bone fracture. The results of this study can be effectively utilized in a research that mainly relies on the response of computational surrogates without experimental tests, especially initial development stage of countermeasures for occupant protection from vehicular accidents.
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Rollover Initiation Simulations for Designing Rollover Initiation Test System (RITS)

Hyundai America Technical Center-Ravi Tangirala, Michael Guerrero
University of Virginia-Taewung Kim, Jason Kerrigan, Varun Bollapragada, Jeff Crandall
Published 2014-04-01 by SAE International in United States
Some rollover test methods, which impose a touchdown condition on a test vehicle, have been developed to study vehicle crashworthiness and occupant protection in rollover crashes. In ground-tripped rollover crashes, speed, steering maneuver, braking, vehicle inertial and geometric properties, topographical and road design characteristics, and soil type can all affect vehicle touchdown conditions. It is presumed that while there may be numerous possible combinations of kinematic metrics (velocity components and orientation) at touchdown, there are also numerous combinations of metrics that are not likely to occur in rollover crashes. To determine a realistic set of touchdown conditions to be used in a vehicle rollover crash test, a lateral deceleration sled-based non-destructive rollover initiation test system (RITS) with a fully programmable deceleration pulse is in development.A full-size SUV vehicle dynamics model was developed and validated with static test data and curb-trip rollover test data. Then, design constraints of the RITS were set considering available space and given range of vehicle mass and geometric properties. Since accelerating a test vehicle consumes the limited travel distance, the effect…
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Test Methodology and Initial Results from a Dynamic Rollover Test System

UVA Center for Applied Biomechanics-Jason R. Kerrigan, Jeremy Seppi, Jack Lockerby, Patrick Foltz, Brian Overby, Jim Bolton, Taewung Kim, Nate J. Dennis, Jeff Crandall
Published 2013-04-08 by SAE International in United States
The goal of this study is to present the methods employed and results obtained during the first six tests performed with a new dynamic rollover test system. The tests were performed to develop and refine test methodology and instrumentation methods, examine the potential for variation in test parameters, evaluate how accurately actual touchdown test parameters could be specified, and identify problems or limitations of the test fixture. Five vehicles ranging in size and inertia from a 2011 Toyota Yaris (1174 kg, 379 kg m₂) to a 2002 Ford Explorer (2408 kg, 800 kg m₂) were tested. Vehicle kinematic parameters at the instant of vehicle-to-road contact varied across the tests: roll rates of 211-268 deg/s, roll angles of 133-199 deg, pitch angles of -12 deg to 0 deg, vertical impact velocities of 1.7 to 2.7 m/s, and road velocities of 3.0-8.8 m/s. Vehicle instrumentation included three angular rate sensors and three linear accelerometers mounted near the vehicle CG; data from the sensor pack and a coordinate measurement machine facilitated analytical translation of the kinematics sensors to…
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