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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.

Vehicle front-end geometry and stiffness characteristics have been shown to influence pedestrian lower extremity response and injury patterns. The goal of this study is to compare the lower extremity response and injuries of post mortem human surrogates (PMHS) tested in full-scale vehicle-pedestrian impact experiments with a small sedan and a large sport utility vehicle (SUV). The pelves and lower limbs of six PMHS were instrumented with six-degree-of-freedom instrumentation packages. The PMHS were then positioned laterally in mid-stance gait and subjected to vehicle impact at 40 km/h with either a small sedan (n=3) or a large SUV (n=3). Detailed descriptions of the pelvic and lower extremity injuries are presented in conjunction with global and local kinematics data and high speed video images. Injured PMHS knee joints reached peak lateral bending angles between 25 and 85 degrees (exceeding published injury criteria) at bending rates between 1.1 deg/ms and 3.7 deg/ms.

Two post-mortem human subjects were subjected to dynamic, non-injurious (up to 20% chest deflection) anterior shoulder belt loading at 0.5 m/s and 0.9 m/s loading rates. The human surrogates were mounted to a stationary apparatus that supported the spine and shoulder in a configuration comparable to that achieved in a 48 km/h sled test at the time of maximum chest deformation. A hydraulically driven shoulder belt was used to load the anterior thorax which was instrumented with a load cell for measuring reaction force and uniaxial strain gages at the 4th and 8th ribs. In addition, the deformation of the chest was measured using a 16- camera Vicon 3D motion capture system. In order to investigate the chest deformation pattern and ribcage loading in greater detail, a human finite element (FE) model of the thorax was used to simulate the tests.

This study presents a detailed comparison of internally and externally measured chest deflections resulting from eight tests conducted on three male post mortem human subjects. A hydraulically driven shoulder belt loaded the anterior thorax under a fixed spine condition while displacement data were obtained via a high-speed 16-camera motion capture system (VICON MX™). Comparison of belt displacement and sternal displacement measured at the bone surface provided a method for quantifying effective change in superficial soft tissue depth at the mid sternum under belt loading. The relationship between the external displacement and the decrease in the effective superficial tissue depth was found to be monotonic and nonlinear. At 65 mm of mid-sternal posterior displacement measured externally, the effective thickness of the superficial tissues and air gap between the belt and the skin had decreased by 14 mm relative to the unloaded state.

This investigation explored THOR's force-deflection response to upper abdomen/lower ribcage steering wheel rim impacts in comparison to the Hybrid III and cadaver test subjects. The stationary subjects were impacted by a ballasted surrogate wheel propelled at 4 m/s, a test condition designed to approximate the upper abdomen impacting a steering wheel rim in a frontal crash. Both the standard THOR and the Hybrid III crash dummies were substantially stiffer than the cadavers. Removing THOR's torso skin and foam from the upper abdomen and replacing the standard Hybrid III abdomen with a prototype gel-filled unit produced force-deflection results that were more similar to the cadavers. THOR offers advantages over the Hybrid III because of its ability to measure abdominal deflection. THOR, with modification, would be a useful instrument with which to assess the crashworthiness of steering assemblies and restraint systems in frontal crashes.

A finite element human model has been developed to simulate occupant behavior and to estimate injuries in real-world car crashes. The model represents an average adult male of the US population in a driving posture. Physical geometry, mechanical characteristics and joint structures were replicated as precise as possible. The total number of nodes and materials is around 67,000 and 1,000 respectively. Each part of the model was not only validated against human test data in the literature but also for realistic loading conditions. Additional tests were newly conducted to reproduce realistic loading to human subjects. A data set obtained in human volunteer tests was used for validating the neck part. The head-neck kinematics and responses in low-speed rear impacts were compared between the measured and calculated results. The validity of the lower extremity part was examined by comparing the tibia force in a foot impact between the test data and simulation results.

This paper discusses struck-side occupant thoracic response to side-impact loading and the requirements of a sled system capable of reproducing the relevant motions of a laterally impacted vehicle. A simplified viscoelastic representation of a thorax is used to evaluate the effect of the door velocity-time profile on injury criteria and on the internal stress state of the thorax. Simulations using a prescribed door velocity-time profile (punch impact) are contrasted against simulations using a constant-velocity impact (Heidelberg-type impact). It is found that the stress distribution and magnitude within the thorax, in addition to the maximum thorax compression and viscous response, depend not only on the door-occupant closing velocity, but also on the shape of the door velocity-time profile throughout the time of contact with the occupant. A sled system capable of properly reproducing side-impact door and seat motion is described.

Studies show that the pedestrian population at high risk of injury consists of both young children and adults. The goal of this study is to gain understanding in the mechanisms that lead to injuries for children and adults. Multi-body pedestrian human models of two specific anthropometries, a 6year-old child and a 50th percentile adult male, are applied. A vehicle model is developed that consists of a detailed rigid finite element mesh, validated stiffness regions, stiff structures underlying the hood and a suspension model. Simulations are performed in a test matrix where anthropometry, impact speed and impact location are variables. Bumper impact occurs with the tibia of the 50th percentile adult male and with the thigh of the 6-year-old child. The head of a 50th percentile male impacts the lower windshield, while the 6-year-old child's head impacts the front part of the hood.

This research investigates the variation of pedestrian stance in pedestrian-automobile impact using a validated multi-body vehicle and human model. Detailed vehicle models of a small family car and a sport utility vehicle (SUV) are developed and validated for impact with a 50th percentile human male anthropometric ellipsoid model, and different pedestrian stances (struck limb forward, feet together, and struck limb backward) are investigated. The models calculate the physical trajectory of the multi-body models including head and torso accelerations, as well as pelvic force loads. This study shows that lower limb orientation during a pedestrian-automobile impact plays a dominant role in upper body kinematics of the pedestrian. Specifically, stance has a substantial effect on the subsequent impacts of the head and thorax with the vehicle. The variation in stance can change the severity of an injury incurred during an impact by changing the impact region.

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.

Fatalities resulting from vehicle rollover events account for over one-third of all U.S. motor vehicle occupant fatalities. While a great deal of research has been directed towards the rollover problem, few studies have attempted to determine the sensitivity of occupant injury risk to variations in the vehicle (roof strength), crash (kinematic conditions at roof-to-ground contact), and occupant (anthropometry, position and posture) parameters that define the conditions of the crash. A two-part computational study was developed to examine the sensitivity of injury risk to changes in these parameters. The first part of this study, the Crash Parameter Sensitivity Study (CPSS), demonstrated the influence of parameters describing the vehicle and the crash on vehicle response using LS-DYNA finite element (FE) simulations.

Material and structural properties of human tissues under impact loading are needed for the development of physical and computational models used in pedestrian and vehicle occupant protection. Obtaining these global properties directly from the data of biomechanical tests is a challenging task due to nonlinearities of tissue-test setup systems. The objective of this study was to develop subject-specific finite element (FE) techniques for material identification of human tissues using Successive Response Surface Methodology. As example, the test data of a human femur in three-point bending is used to identify parameters of cortical bone. Good global and local predictions of the optimized FE model demonstrate the utility and effectiveness of this new material identification approach.

The widespread implementation of air bags has increased the incidence of upper extremity injuries in the automotive crash environment. The first step in reducing these injuries is to determine applicable upper extremity injury criteria. The purpose of this paper is to develop injury risk functions for the fifth percentile female forearm, humerus, wrist, and elbow. Injury tolerance data for each anatomical region were gathered from experiments with controlled impact loading of disarticulated small female cadaver upper extremities. This technique allowed for the applied load to be directly quantified. All data were mass scaled to the fifth percentile female. In order to develop the risk functions, the logit distribution was integrated for the uncensored data, while logistic regression and generalized estimating equations statistical analysis techniques were used for censored data.

This paper compares restrained Hybrid III and THOR thoracic kinematics and cadaver injury outcome in 30° oblique frontal and in full frontal sled tests. Peak shoulder belt tension, the primary source of chest loading, changed by less than four percent and peak chest resultant acceleration changed by less than 10% over the 30° range tested. Thoracic kinematics were likewise insensitive to the direction of the collision vector, though they were markedly different between the two dummies. Mid-sternal Hybrid III chest deflection, measured by the standard sternal potentiometer and by supplemental internal string potentiometers, was slightly lower (∼10%) in the oblique tests, but the oblique tests produced a negligible increase in lateral movement of the sternum. In an attempt to understand the biofidelity of these dummy responses, a series of 30-km/h human cadaver tests having several collision vectors (0°, 15°, 30°, 45°) was analyzed.

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 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.

The goal of this study was to develop and validate a finite element (FE) model of the Polar-II pedestrian dummy. An upper body model consisting of the head, neck, shoulder, thorax, and abdomen was coupled with a previously validated model of the lower limb The viscoelastic material properties of the dummy components were determined from dynamic compression tests of shoulder urethane, shoulder rubber and abdominal foam. For validation of the entire upper body, the model was compared with NHTSA response requirements for their advanced frontal dummy (Thor) including head and neck pendulum tests as well as ribcage and abdominal impact tests. In addition, the Polar-II full body FE model was subjected to simulated vehicle-pedestrian impacts that recreated published experiments. Simulated head and pelvis accelerations as well as upper body trajectories reasonably reproduced the experiment.

Given the quantity and severity of head injuries to pedestrians in vehicle-to-pedestrian collisions, human pedestrian finite element models and pedestrian dummies must possess a biofidelic head/neck response to accurately reproduce head-strike kinematics and kinetics. Full-scale pedestrian impact experiments were performed on post-mortem human surrogates (PMHS) using a mid-sized sport utility vehicle and a small sedan. Kinematics of the head and torso were obtained with a six-degree-of-freedom (6DOF) cube, which contained three orthogonally mounted linear accelerometers and three angular rate sensors. The goal of the current study was to present a methodology for analyzing the data obtained from the sensors on each cube, and to use the kinematics data to calculate spatial trajectories, as well as linear velocities and angular accelerations of the head and T1 vertebra.

Pedestrian impact protection has been a growing area of research over the past twenty or more years. The results from many studies have shown the importance of providing protection to vulnerable road users as a means of reducing roadway fatalities. Most of this research has focused on the vehicle fleet as a whole in datasets that are dominated by passenger cars (cars). Historically, the influence of vehicle body type on injury distribution patterns for pedestrians has not been a primary research focus. In this study we used the Pedestrian Crash Data Study (PCDS) database of detailed pedestrian crash investigations to identify how injury patterns differ for pedestrians struck by light trucks, vans, and sport utility vehicles (LTVs) from those struck by cars. AIS 2+ and 3+ injuries for each segment of vehicles were mapped back to both the body region of the pedestrian injured and the vehicle source linked to that injury in the PCDS database.

Child restraint head padding is designed for the child's comfort under normal use. Under vehicle crash conditions, however, the padding in a rear facing child restraint may not be designed to sufficiently absorb impact energy. The objective of this paper is to evaluate the effects of various head padding conditions in rear facing child restraints in frontal impacts. Five sled tests were performed to measure the response of a CRABI 12 month dummy to different padding conditions in a rear facing child restraint. Static loading tests were performed on the padding materials. Results show that using padding of low stiffness increases head acceleration and HIC15 values.