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Technical Paper

A Madymo Model of the Foot and Leg for Local Impacts

It has been reported that lower extremity injuries represent a measurable portion of all moderate-to-severe automobile crash- related injuries. Thus, a simple tool to assist with the design of leg and foot injury countermeasures is desirable. The objective of this study is to develop a mathematical model which can predict load propagation and kinematics of the foot and leg in frontal automotive impacts. A multi-body model developed at the University of Virginia and validated for blunt impact to the whole foot has been used as basis for the current work. This model includes representations of the tibia, fibula, talus, hindfoot, midfoot and forefoot bones. Additionally, the model provides a means for tensioning the Achilles tendon. In the current study, the simulations conducted correspond to tests performed by the Transport Research Laboratory and the University of Nottingham on knee-amputated cadaver specimens.
Technical Paper

A Normalization Technique for Developing Corridors from Individual Subject Responses

This paper presents a technique for developing corridors from individual subject responses contained in experimental biomechanical data sets. Force-deflection response is used as an illustrative example. The technique begins with a method for averaging human subject force-deflection responses in which curve shape characteristics are maintained and discontinuities are avoided. Individual responses sharing a common characteristic shape are averaged based upon normalized deflection values. The normalized average response is then scaled to represent the given data set using the mean peak deflection value associated with the set of experimental data. Finally, a procedure for developing a corridor around the scaled normalized average response is presented using standard deviation calculations for both force and deflection.
Technical Paper

Development and Validation of a Finite Element Model of a Vehicle Occupant

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.
Technical Paper

A Comparative Evaluation of Pedestrian Kinematics and Injury Prediction for Adults and Children upon Impact with a Passenger Car

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.
Technical Paper

Material Identification using Successive Response Surface Methodology, with Application to a Human Femur Subjected to Three-Point Bending Loading

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.
Technical Paper

The Causes of Head Injury in Vehicle-Pedestrian Impacts: Comparing the Relative Danger of Vehicle and Road Surface

This research uses simulations of vehicle-pedestrian collisions to determine if the risk of pedestrian head injury is greater from impact with the vehicle or from impact with the ground, and to determine the influence of vehicle speed, vehicle type, and pedestrian stance on the injury risk. Five speeds, two vehicle types and four pedestrian stances are examined. In addition, a smaller set of simulations is included to determine the influence of body orientation just prior to ground impact. As anticipated, risk of head injury from both the vehicle and the ground tends to increase with vehicle speed, but injury risk from the ground is less predictable. At lower speeds, the vehicle tends to pose a greater risk of injury than does the ground, while at higher speeds the probability of injury from both the vehicle and ground is typically very large.
Technical Paper

Sled System Requirements for the Analysis of Side Impact Thoracic Injury Criteria and Occupant Protection

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.
Technical Paper

Optical Measurement of High-Rate Dynamic Vehicle Roof Deformation during Rollover

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.
Technical Paper

Test Methodology and Initial Results from a Dynamic Rollover Test System

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.
Technical Paper

Evaluation of Biofidelity of Side Impact Computational Surrogates (ES-2re, WorldSID, GHBMC)

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.
Technical Paper

Rollover Initiation Simulations for Designing Rollover Initiation Test System (RITS)

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.
Technical Paper

The Effects of Vehicle Seat Belt Parameters on the Injury Risk for Children in Booster Seats

The correct restraint for children, age 4-10 years, is a booster seat restrained by the vehicle's seat belt system. The goal of this study is to investigate the effects of misuse of the restraint system by varying initial seat belt slack and to investigate the effects of modern countermeasures, like force limiting belts and pretensioners, on the injury risk of young children. A multi-body model of a Hybrid III 6-year old dummy positioned in a booster seat and restrained by the car seat belt was developed using MADYMO and validated using sled tests. As anticipated, adding initial slack resulted in higher peak accelerations and to an increase in forces and moments in the neck, both factors increasing the injury risk significantly. The countermeasures pretensioning and force limiting prove to be useful in lowering peak values but a high risk of injury persists. A combination of pretension and force limiting provides the safest restraint for this setup.
Technical Paper

Frequency Content Analysis and Filter Class Selection for the Small Female Instrumented Upper Extremity

Although filter class specifications have been defined for most anthropomorphic test devices, no recommendation exists for the instrumented upper extremity. A three-part study was performed to determine the best channel filter class (CFC) to use for the instrumented upper extremity. By analyzing frequency content of signals from accelerometers and load cells, filtering data through three of the four possible CFC's to compare effects on the signals, and performing an injury comparison between cadaver data and the filtered load cell data, CFC 600 was chosen and recommended as the optimum filter class to use for upper extremity testing.
Technical Paper

Influence of Vehicle Body Type on Pedestrian Injury Distribution

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.
Technical Paper

Neck Validation of Multibody Human Model under Frontal and Lateral Impacts using an Optimization Technique

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.
Technical Paper

Whole-Body Response to Pure Lateral Impact

The objective of the current study was to provide a comprehensive characterization of human biomechanical response to whole-body, lateral impact. Three approximately 50th-percentile adult male PMHS were subjected to right-side pure lateral impacts at 4.3 ± 0.1 m/s using a rigid wall mounted to a rail-mounted sled. Each subject was positioned on a rigid seat and held stationary by a system of tethers until immediately prior to being impacted by the moving wall with 100 mm pelvic offset. Displacement data were obtained using an optoelectronic stereophotogrammetric system that was used to track the 3D motions of the impacting wall sled; seat sled, and reflective targets secured to the head, spine, extremities, ribcage, and shoulder complex of each subject. Kinematic data were also recorded using 3-axis accelerometer cubes secured to the head, pelvis, and spine at the levels of T1, T6, T11, and L3. Chest deformation in the transverse plane was recorded using a single chestband.
Technical Paper

Impact Response of Restrained PMHS in Frontal Sled Tests: Skeletal Deformation Patterns Under Seat Belt Loading

This study evaluated the response of restrained post-mortem human subjects (PMHS) in 40 km/h frontal sled tests. Eight male PMHS were restrained on a rigid planar seat by a custom 3-point shoulder and lap belt. A video motion tracking system measured three-dimensional trajectories of multiple skeletal sites on the torso allowing quantification of ribcage deformation. Anterior and superior displacement of the lower ribcage may have contributed to sternal fractures occurring early in the event, at displacement levels below those typically considered injurious, suggesting that fracture risk is not fully described by traditional definitions of chest deformation. The methodology presented here produced novel kinematic data that will be useful in developing biofidelic human models.
Technical Paper

Occupant Kinematics in Laboratory Rollover Tests: PMHS Response

The objective of the current study was to characterize the whole-body kinematic response of restrained PMHS in controlled laboratory rollover tests. A dynamic rollover test system (DRoTS) and a parametric vehicle buck were used to conduct 36 rollover tests on four adult male PMHS with varied test conditions to study occupant kinematics during the rollover event. The DRoTS was used to drop/catch and rotate the test buck, which replicated the occupant compartment of a typical mid-sized SUV, around its center of gravity without roof-to-ground contact. The studied test conditions included a quasi-static inversion (4 tests), an inverted drop and catch that produced a 3 g vertical deceleration (4 tests), a pure dynamic roll at 360 degrees/second (11 tests), and a roll with a superimposed drop and catch produced vertical deceleration (17 tests). Each PMHS was restrained with a three-point belt and was tested in both leading-side and trailing-side front-row seating positions.
Technical Paper

Correlation of Strain and Loads Measured in the Long Bones With Observed Kinematics of the Lower Limb During Vehicle-Pedestrian Impacts

The purpose of this study is to determine the loads in the long bones of the lower extremities during vehicle pedestrian impact tests, and to correlate load data with observed kinematics in an effort to understand how stature and vehicle shape influence pedestrian response. In tests with a large sedan and a small multi-purpose vehicle (MPV), four postmortem human surrogates (PMHS) in mid-stance gait were struck laterally at 40 km/h. Prior to the tests, each PMHS was instrumented with four uniaxial strain gages around the mid-shaft cross section of the struck-side (right) tibia and the femora bilaterally. After the tests, the non-fractured bones were harvested and subjected to three-point bending experiments. The effective elastic moduli were determined by relating the applied bending loads with the measured strains using strain gage locations, detailed bone geometry, and elastic beam theory.