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Boruah S.,University of Virginia | Subit D.L.,Center for Applied Biomechanics | Crandall J.R.,State University of New York at Buffalo | Salzar R.S.,University of Virginia | And 2 more authors.
2014 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury | Year: 2014

Brain injury resulting from exposure to blast continues to be a significant problem in the military community, often leading to death or long-term disability. The presence of high-frequency energy content in pressure waves generated in explosive blasts necessitates understanding the transmissibility and damping characteristics of skull bone. Current finite element models (FEM) of the skull do not include material damping and therefore fail to capture the correct attenuation spectrum or rate dependency of skull bone. Cylindrical through-the-thickness specimens of skull bone were obtained from ten adult (55 ± 10 years old) male post mortem human surrogates. A test apparatus was developed to apply cyclic loading to potted cores at frequencies ranging from 1 to 50 kHz using a piezoelectric shaker. High bandwidth transducers were used to record accelerations and forces at the boundary. A lumped mass model was optimized to match the recorded boundary conditions. This paper reports composite material properties of the skull as a frequency-dependent complex modulus. The calculated material loss tangent was distributed in a log-normal fashion and ranged from 0.027 to 0.194 (95 % CI). A generalized Maxwell model, represented using a Prony series, has been developed and the model parameters have been reported. Source

Lobo B.,University of Virginia | Lin R.,University of Virginia | Brown D.,University of Virginia | Kim T.,Center for Applied Biomechanics | Panzer M.,Center for Applied Biomechanics
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

Simulations provide vehicle designers with the capability to evaluate the safety of their designs in a wide variety of scenarios. However, the high-fidelity simulations required for safety assessment carry significant computational costs. As such, the engineering team must carefully select automotive designs to simulate, and use the results obtained to accurately predict the performance of new designs over a wide range of metrics. This paper describes the modeling of automotive simulation outputs to accurately predict a large number of widely used pedestrian injury metrics given the vehicle front-end design. The models in this paper allow the vehicle designer to identify and focus on the variables that most affect the different injury metrics, and determine which variables are most important to the overall safety performance of the vehicle. © Springer International Publishing Switzerland 2015. Source

Kerrigan J.R.,Center for Applied Biomechanics | Jordan A.,Jordan and Co. | Parent D.,Center for Applied Biomechanics | Zhang Q.,Center for Applied Biomechanics | And 5 more authors.
SAE Technical Papers | Year: 2011

A dynamic rollover test system (DRoTS) capable of simulating rollover crashes in a laboratory was designed for research use at the University of Virginia. The goal of the current study is to describe the system's capabilities and specifications as well as to explore the limitations of the system's ability to simulate rollover crashes. The test apparatus was designed to permit simulation of a single roof-to-ground interaction of a rollover crash with the potential to be modified for evaluation of pre-roof contact occupant motion. Special considerations were made to permit testing of both dummies and post-mortem human surrogates in both production vehicles and a parametric test buck. DRoTS permits vertical translation, pitch, and roll of the test vehicle while constraining longitudinal and lateral translations and yaw. The study details the ranges of test parameters capable with the DRoTS and evaluates the limitations of the system relative to rollover crash conditions. Considerations on the use of the test system and the constraints applied to the vehicle are evaluated through analytical analysis and computational modeling. The results of the analyses suggest that the DRoTS design is capable of testing vehicles in a wide variety of conditions while maintaining reasonable fidelity to rollover crashes during the duration of a single vehicle roof-to-ground interaction. © 2011 SAE International. Source

Lockerby J.,Center for Applied Biomechanics | Kerrigan J.,Center for Applied Biomechanics | Seppi J.,Center for Applied Biomechanics | Crandall J.,Center for Applied Biomechanics
SAE Technical Papers | Year: 2013

The goals of this study were to examine the dynamic force-deformation and kinematic response of a late model van subjected to an inverted drop test and to evaluate the accuracy of three-dimensional multi-point roof deformation measurements made by an optical system mounted inside the vehicle. The inverted drop test was performed using a dynamic rollover test system (Kerrigan et al., 2011 SAE) with an initial vehicle pitch of 5 degrees, a roll of +155 degrees and a vertical velocity of 2.7 m/s at initial contact. Measurements from the optical system, which was composed of two high speed imagers and a commercial optical processing software were compared to deformation measurements made by two sets of three string potentiometers. The optical and potentiometer measurements reported similar deformations: peak resultant deformations varied by 0.7 mm and 3 ms at the top of the A-pillar, and 1.7 mm and 2 ms at the top of the B-pillar. The top of the vehicle B-pillar sustained peak resultant deformation of 146.2 mm 116 ms after contact, and unloaded to 77.1 mm (47% of peak) at 291 ms. Peak reaction forces at contact were approximately 100 kN, and the force-deflection response between the drop test and the IIHS roof crush test on the same make and model vehicle showed comparable dynamic and quasi-static stiffness. The results presented in this study showed that the optical system can be used to measure dynamic roof deformations, in three dimensions, at high rates, across a large area of the vehicle structure, from inside a vehicle subjected to rollover crash test. Copyright © 2013 SAE International. Source

Kerrigan J.R.,Center for Applied Biomechanics | Seppi J.,Center for Applied Biomechanics | Lockerby J.,Center for Applied Biomechanics | Foltz P.,Center for Applied Biomechanics | And 5 more authors.
SAE Technical Papers | Year: 2013

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 the actual vehicle CG and transformation of the kinematics parameters from the local to global reference frame. Actual touchdown parameters varied from goal test parameters due to limitations of the roll drive and drop-release systems. As a result of these limitations, these systems were modified or redesigned to eliminate variations between the goal and actual test parameters. Road load cells recorded peak contact loads that varied from 58 to 117 kN. Peak forces normalized by vehicle weight were shown to be both vehice-specific and test-condition specific. The translating road surface and constrained roll-axis configuration of the test system was shown to produce similar energy transfer between translational and rotational energy as in unconstrained rollover crashes. Copyright © 2013 SAE International. Source

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