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External Biofidelity Evaluation of Pedestrian Leg-Form Impactors

SAE International Journal of Transportation Safety

University of Virginia-Daniel Perez-Rapela, Jason Forman, Jeff Crandall
Hyundai Kia R&D-Haeyoung Jeon
  • Journal Article
  • 2017-01-1450
Published 2017-03-28 by SAE International in United States
Current state-of-the-art vehicles implement pedestrian protection features that rely on pedestrian detection sensors and algorithms to trigger when impacting a pedestrian. During the development phase, the vehicle must “learn” to discriminate pedestrians from the rest of potential impacting objects. Part of the training data used in this process is often obtained in physical tests utilizing legform impactors whose external biofidelity is still to be evaluated. This study uses THUMS as a reference to assess the external biofidelity of the most commonly used impactors (Flex-PLI, PDI-1 and PDI-2). This biofidelity assessment was performed by finite element simulation measuring the bumper beam forces exerted by each surrogate on a sedan and a SUV. The bumper beam was divided in 50 mm sections to capture the force distribution in both vehicles. This study, unlike most of the pedestrian-related literature, examines different impact locations and velocities. The results show how the Flex-PLI and the PDI-1 exert greater forces on the bumper beam than the THUMS, while the PDI-2 produced bumper beam forces similar to the THUMS. The PDI-2 is…
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Recreational Off-Highway Vehicle Safety: Countermeasures for Ejection Mitigation in Rollover

University of Virginia-Bronislaw D. Gepner, Jack Cochran, Patrick Foltz, Carolyn Roberts, Jacek Toczyski, Qi Zhang, Jason Kerrigan
Honda R&D Americas, Inc.-Matthew Taracko, Jacob Borth, Robert Wilson, Adam Upah
Published 2016-04-05 by SAE International in United States
Recreational Off-Highway Vehicles (ROVs), since their introduction onto the market in the late-1990s, have been related to over 300 fatalities with the majority occurring in vehicle rollover. In recent years several organizations made attempts to improve ROV safety. This paper is intended to evaluate ejection mitigation measures considered by the ROV manufacturers. Evaluated countermeasures include two types of occupant restraints (three and four point) and two structural barriers (torso bar, door with net). The Rollover protection structure (ROPS) provided by the manufacturer was attached to a Dynamic Rollover Test System (DRoTS), and a full factorial series of roll/drop/catch tests was performed. The ROV buck was equipped with two Hybrid III dummies, a 5th percentile female and a 95th percentile male. Additionally, occupant and vehicle kinematics were recorded using optoelectronic stereophotogrammetric camera system. Two distinctive rollover conditions (200deg/s and 360deg/s at 3.5-5g vertical drop acceleration) used to simulate vehicle rollover were extracted from the field testing presented in the literature. The results show that for both rollover conditions the unbelted occupants experienced the largest excursion from…
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Development of a Biofidelic Rollover Dummy-Part II: Validation of the Kinematic Response of THOR Multi-Body and Finite Element Models Relative to Response of the Physical THOR Dummy under Laboratory Rollover Conditions

SAE International Journal of Transportation Safety

University of Virginia-Qi Zhang, Bronislaw Gepner, Jacek Toczyski, Jason Kerrigan
  • Journal Article
  • 2016-01-1486
Published 2016-04-05 by SAE International in United States
While over 30% of US occupant fatalities occur in rollover crashes, no dummy has been developed for such a condition. Currently, an efficient, cost-effective methodology is being implemented to develop a biofidelic rollover dummy. Instead of designing a rollover dummy from scratch, this methodology identifies a baseline dummy and modifies it to improve its response in a rollover crash. Using computational models of the baseline dummy, including both multibody (MB) and finite element (FE) models, the dummy’s structure is continually modified until its response is aligned (using BioRank/CORA metric) with biofidelity targets. A previous study (Part I) identified the THOR dummy as a suitable baseline dummy by comparing the kinematic responses of six existing dummies with PMHS response corridors through laboratory rollover testing. In this study (Part II), the whole-body kinematic responses of the THOR MB and FE models were validated with responses of the physical THOR dummy in experiments that simulated rollover conditions. This step is necessary to ensure accuracy of the computer-aidedengineering dummy design, thereafter improving confidence in the proposed rollover dummy design…
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Geometrical Personalization of Pedestrian Finite Element Models Using Morphing Increases the Biofidelity of Their Impact Kinematics

University of Virginia-David Poulard, Huipeng Chen, Matthew Panzer
Published 2016-04-05 by SAE International in United States
Pedestrian finite element models (PFEM) are used to investigate and predict the injury outcomes from vehicle-pedestrian impact. As postmortem human surrogates (PMHS) differ in anthropometry across subjects, it is believed that the biofidelity of PFEM cannot be properly evaluated by comparing a generic anthropometry model against the specific PMHS test data. Global geometric personalization can scale the PFEM geometry to match the height and weight of a specific PMHS, while local geometric personalization via morphing can modify the PFEM geometry to match specific PMHS anatomy. The goal of the current study was to evaluate the benefit of morphed PFEM compared to globally-scaled and generic PFEM by comparing the kinematics against PMHS test results. The AM50 THUMS PFEM (v4.01) was used as a baseline for anthropometry, and personalized PFEM were created to the anthropometric specifications of two obese PMHS used in a previous pedestrian impact study using a mid-size sedan. Personalization was done using either global scaling or morphing, and the kinematics of each PFEM model were compared to the experiments using a correlation analysis (CORA).…
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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

University of Virginia-Varun Bollapragada, Taewung Kim, Jeff Crandall, Jason Kerrigan
Toyota Technical Center USA, Inc.-Mark Clauser
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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Analysis of Vehicle Kinematics, Injuries and Restraints in DRoTS Tests to Match Unconstrained Rollover Crashes

University of Virginia-Carolyn W. Roberts, Jacek Toczyski, Jack Cochran, Qi Zhang, Patrick Foltz, Bronislaw Gepner, Jason Kerrigan
Toyota Technical Center USA, Inc.-Mark Clauser
Published 2016-04-05 by SAE International in United States
Multiple laboratory dynamic test methods have been developed to evaluate vehicle crashworthiness in rollover crashes. However, dynamic test methods remove some of the characteristics of actual crashes in order to control testing variables. These simplifications to the test make it difficult to compare laboratory tests to crashes. One dynamic method for evaluating vehicle rollover crashworthiness is the Dynamic Rollover Test System (DRoTS), which simulates translational motion with a moving road surface and constrains the vehicle roll axis to a fixed plane within the laboratory. In this study, five DRoTS vehicle tests were performed and compared to a pair of unconstrained steering-induced rollover tests. The kinematic state of the unconstrained vehicles at the initiation of vehicle-to-ground contact was determined using instrumentation and touchdown parameters were matched in the DRoTS tests. This study was performed to (1) evaluate the ability of the DRoTS to mimic the conditions of unconstrained rollover inside a laboratory, (2) demonstrate the repeatability of the DRoTS, and (3) to assess differences in ATD motion and related injury criteria for different vehicles with various…
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Whole-body Response for Pedestrian Impact with a Generic Sedan Buck

University of Virginia-Jason L. Forman, Hamed Joodaki, Ali Forghani, Patrick O. Riley, Varun Bollapragada, David J. Lessley, Brian Overby, Sara Heltzel, Jason R. Kerrigan, Jeff R. Crandall, Seth Yarboro, David B. Weiss
Published 2015-11-09 by The Stapp Association in United States
To serve as tools for assessing injury risk, the biofidelity of whole-body pedestrian impact dummies should be validated against reference data from full-scale pedestrian impact tests. To facilitate such evaluations, a simplified generic vehicle-buck has been recently developed that is designed to have characteristics representative of a generic small sedan. Three 40 km/h pedestrian-impact tests have been performed, wherein Post Mortem Human Surrogates (PMHS) were struck laterally in a mid-gait stance by the buck. Corridors for select trajectory measures derived from these tests have been published previously. The goal of this study is to act as a companion dataset to that study, describing the head velocities, body region accelerations (head, spine, pelvis, lower extremities), angular velocities, and buck interaction forces, and injuries observed during those tests. Scaled, transformed head accelerations exceeded 80 g prior to head contact with the windshield for two of the three tests. Head x-axis angular velocity exceeded 40 rad/s prior to head contact for all three tests. In all cases the peak resultant head velocity relative to the vehicle was greater…
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Detached Eddy Simulation on a Swept Hybrid Model in the IRT

University of Virginia-Cameron Butler, Eric Loth
Published 2015-06-15 by SAE International in United States
In recent years, there has been a growing desire to incorporate computational methods into aircraft icing certification practices. To improve understanding of ice shapes, a new experimental program in the NASA Icing Research Tunnel (IRT) will investigate swept hybrid models which are very large relative to the test section and are intended to operate at high lift coefficients. The present computations were conducted to help plan the experiments and to ascertain any effects of flow separation and unsteady forces. As they can be useful in robustly and accurately predicting large separation regions and capturing flow unsteadiness, a Detached Eddy Simulation (DES) approach has been adopted for simulating the flow over these large high-lift wing sections. The DES methodology was first validated using experimental data from an unswept NACA 0012 airfoil with leading-edge ice accretion, showing reasonable performance. For the hybrid geometries in the IRT, the present predictions yielded a large separation bubble that develops at the junction between the model and the IRT ceiling. However, the separation region does not negatively impact the flow around…
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Neck Validation of Multibody Human Model under Frontal and Lateral Impacts using an Optimization Technique

University of Virginia-Taewung Kim, Jeff Crandall
Tsinghua University-Yan Wang, Yibing Li
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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Rollover Testing of a Sport Utility Vehicle (SUV) with an Inertial Measurement Unit (IMU)

University of Virginia-James Funk
Asay Engineering-Alan F. Asay
Published 2015-04-14 by SAE International in United States
A follow-up case study on rollover testing with a single full-size sport utility vehicle (SUV) was conducted under controlled real-world conditions. The purpose of this study was to conduct a well-documented rollover event that could be utilized in evaluating various methods and techniques over the phases associated with rollover accidents. The phases documented and discussed, inherent to rollovers, are: pre-trip, trip, and rolling phases.With recent advances in technology, new devices and techniques have been designed which improve the ability to capture and document the unpredictable dynamic events surrounding vehicle rollovers. One such device is an inertial measurement unit (IMU), which utilizes GPS technology along with integrated sensors to report and record measured dynamic parameters real-time. The data obtained from a RT-4003 IMU device are presented and compared along with previous test data and methodology.For this case study, an instrumented 1996 GMC Jimmy SUV was towed to 53.6 mph (86.3 kph) and released. An automated pre-programmed controller steered the vehicle through maneuvers intended to result in rollover. The SUV rolled 2 revolutions and was documented with…
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