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Technical Paper

The Effect of Occupant Size on Head Displacement in Frontal Collisions

This paper builds on previous research on the development of a head displacement model for restrained occupants in frontal collisions. Physical and mathematical simulations were performed utilizing the 5th percentile female and 50th percentile male Hybrid III dummies to measure the effect of occupant size, seat belt system design and crash severity on resultant head displacement of occupants in frontal collisions. Sled and simulation accelerations ranged from 10 g to 20 g with delta-V's from 6.6 m/s to 10.0 m/s. Results indicate a difference between the 5th percentile female and 50th percentile male dummies. Preliminary assessment of head displacement as a function of occupant kinetic energy demonstrated good correlation.
Technical Paper

Development of a Finite Element Model of the Human Shoulder

Previous studies have hypothesized that the shoulder may be used to absorb some impact energy and reduce chest injury due to side impacts. Before this hypothesis can be tested, a good understanding of the injury mechanisms and the kinematics of the shoulder is critical for occupant protection in side impact. However, existing crash dummies and numerical models are not designed to reproduce the kinematics and kinetics of the human shoulder. The purpose of this study was to develop a finite element model of the human shoulder in order to achieve a deeper understanding of the injury mechanisms and the kinematics of the shoulder in side impact. Basic anthropometric data of the human shoulder used to develop the skeletal and muscular portions of this model were taken from commercial data packages. The shoulder model included three bones (the humerus, scapula and clavicle) and major ligaments and muscles around the shoulder.
Technical Paper

Kinematics of Human Cadaver Cervical Spine During Low Speed Rear-End Impacts

The purposes of this study were to measure the relative linear and angular displacements of each pair of adjacent cervical vertebrae and to compute changes in distance between two adjacent facet joint landmarks during low posterior- anterior (+Gx) acceleration without significant hyperextension of the head. A total of twenty-six low speed rear-end impacts were conducted using six postmortem human specimens. Each cadaver was instrumented with two to three neck targets embedded in each cervical vertebra and nine accelerometers on the head. Sequential x-ray images were collected and analyzed. Two seatback orientations were studied. In the global coordinate system, the head, the cervical vertebrae, and the first or second thoracic vertebra (T1 or T2) were in extension during rear-end impacts. The head showed less extension in comparison with the cervical spine.
Technical Paper

A Study of Cervical Spine Kinematics and Joint Capsule Strain in Rear Impacts using a Human FE Model

Many efforts have been made to understand the mechanism of whiplash injury. Recently, the cervical facet joint capsules have been focused on as a potential site of injury. An experimental approach has been taken to analyze the vertebral motion and to estimate joint capsule stretch that was thought to be a potential cause of pain. The purpose of this study is to analyze the kinematics of the cervical facet joint using a human FE model in order to better understand the injury mechanism. The Total Human Model for Safety (THUMS) was used to visually analyze the local and global kinematics of the spine. Soft tissues in the neck were newly modeled and introduced into THUMS for estimating the loading level in rear impacts. The model was first validated against human test data in the literature by comparing vertebrae motion as well as head and neck responses. Joint capsule strain was estimated from a maximum principal strain output from the elements representing the capsule tissues.
Technical Paper

A Study of Knee Joint Kinematics and Mechanics using a Human FE Model

Posterior translation of the tibia with respect to the femur can stretch the posterior cruciate ligament (PCL). Fifteen millimeters of relative displacement between the femur and tibia is known as the Injury Assessment Reference Value (IARV) for the PCL injury. Since the anterior protuberance of the tibial plateau can be the first site of contact when the knee is flexed, the knee bolster is generally designed with an inclined surface so as not to directly load the projection in frontal crashes. It should be noted, however, that the initial flexion angle of the occupant knee can vary among individuals and the knee flexion angle can change due to the occupant motion. The behavior of the tibial protuberance related to the knee flexion angle has not been described yet. The instantaneous angle of the knee joint at the timing of restraining the knee should be known to manage the geometry and functions of knee restraint devices.
Technical Paper

Sled Test Evaluation of Racecar Head/Neck Restraints Revisited

At the 2002 MSEC, we presented a paper on the sled test evaluation of racecar head/neck restraint performance (Melvin, et al. 2002). Some individuals objected to the 3 msec clip filtering procedures used to eliminate artifactual spikes in the neck tension data for the HANS® device. As a result, we are presenting the same test data with the spikes left in the neck force data to reassure those individuals that these spikes did not significantly affect the results and conclusions of our original paper. In addition we will add new insights into understanding head/neck restraint performance gained during two more years of testing such systems. This paper re-evaluates the performance of three commercially available head/neck restraint systems using a stock car seating configuration and a realistic stock car crash pulse. The tests were conducted at an impact angle of 30 degrees to the right, with a midsize male Hybrid III anthropomorphic test device (ATD) modified for racecar crash testing.
Technical Paper

Effect of Head-Neck Position on Cervical Facet Stretch of Post Mortem Human Subjects during Low Speed Rear End Impacts

The purpose of this study was to determine the effect of head-neck position on cervical facet stretch during low speed rear end impact. Twelve tests were conducted on four Post Mortem Human Subjects (PMHS) in a generic bucket seat environment. Three head positions, namely Normal (neutral), Zero Clearance between the head and head restraint, and Body Forward positions were tested. A high-speed x-ray system was used to record the motion of cervical vertebrae during these tests. Results demonstrate that: a) The maximum mean facet stretch at head restraint contact occurs at MS4 and MS5 for the Body Forward condition, b) The lower neck flexion moment, prior to head contact, shows a non-linear relationship with facet stretch, and c) “Differential rebound” during rear end impact increases facet stretch.
Technical Paper

Investigation of Upper Body and Cervical Spine Kinematics of Post Mortem Human Subjects (PMHS) during Low-Speed, Rear-End Impacts

A total of eight low-speed, rear-end impact tests using two Post Mortem Human Subjects (PMHS) in a seated posture are reported. These tests were conducted using a HYGE-style mini-sled. Two test conditions were employed: 8 kph without a headrestraint or 16 kph with a headrestraint. Upper-body kinematics were captured for each test using a combination of transducers and high-speed video. A 3-2-2-2-accelerometer package was used to measure the generalized 3D kinematics of both the head and pelvis. An angular rate sensor and two single-axis linear accelerometers were used to measure angular speed, angular acceleration, and linear acceleration of T1 in the sagittal plane. Two high-speed video cameras were used to track targets rigidly attached to the head, T1, and pelvis. The cervical spine kinematics were captured with a high-speed, biplane x-ray system by tracking radiopaque markers implanted into each cervical vertebra.
Technical Paper

A Study of Driver Injury Mechanism in High Speed Lateral Impacts of Stock Car Auto Racing Using a Human Body FE Model

This paper analyzed the mechanisms of injury in high speed, right-lateral impacts of stock car auto racing, and interaction of the occupant and the seat system for the purpose of reducing the risk of injury, primarily rib fractures. Many safety improvements have been made to stock car racing recently, including the Head and Neck Support devices (HANS®), the 6-point restraint harnesses, and the implementation of the SAFER Barrier. These improvements have contributed greatly to mitigating injury during the race crash event. However, there is still potential to improve the seat structure and the understanding of the interaction between the driver and the seat in the continuation of making racing safety improvements. This is particularly true in the case of right-lateral impacts where the primary interaction is between the seat supports and the driver and where the chest is the primary region of injury.
Technical Paper

Occupant Kinematics and Estimated Effectiveness of Side Airbags in Pole Side Impacts Using a Human FE Model with Internal Organs

When a car collides against a pole-like obstacle, the deformation pattern of the vehicle body-side tends to extend to its upper region. A possible consequence is an increase of loading to the occupant thorax. Many studies have been conducted to understand human thoracic responses to lateral loading, and injury criteria have been developed based on the results. However, injury mechanisms, especially those of internal organs, are not well understood. A human body FE model was used in this study to simulate occupant kinematics in a pole side impact. Internal organ parts were introduced into the torso model, including their geometric features, material properties and connections with other tissues. The mechanical responses of the model were validated against PMHS data in the literature. Although injury criterion for each organ has not been established, pressure level and its changes can be estimated from the organ models.
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

Forensic Determination of Seat Belt Usage in Automotive Collisions: Development of a Diagnostic Tool

The primary purpose of this research was to generate a “linked set” of data between collision severity, occupant weight and collision-induced seat belt markings to assist in reconstruction of motor vehicle accidents. The secondary purpose was to establish a preliminary threshold of belt load to produce known collision-induced seat belt markings. Sled tests were performed utilizing Hybrid III 5th and 50th percentile crash test dummies. Sled accelerations ranged from 10.0 g to 23.6 g and Delta-V’s from 6.4 m/s to 11.3 m/s. Post-test inspections and photographs taken of the seat belts documented collision-induced markings on components such as the D-Ring, latch plate, webbing and stitching. Belt loads were analyzed to establish preliminary thresholds for the production of observable markings.
Technical Paper

Research of the Relationship of Pedestrian Injury to Collision Speed, Car-type, Impact Location and Pedestrian Sizes using Human FE model (THUMS Version 4)

Injuries in car to pedestrian collisions are affected by various factors such as the vehicle body type, pedestrian body size and impact location as well as the collision speed. This study aimed to investigate the influence of such factors taking a Finite Element (FE) approach. A total of 72 collision cases were simulated using three different vehicle FE models (Sedan, SUV, Mini-Van), three different pedestrian FE models (AM50, AF05, AM95), assuming two different impact locations (center and the corner of the bumper) and at four different collision speeds (20, 30, 40 and 50 km/h). The impact kinematics and the responses of the pedestrian model were validated against those in the literature prior to the simulations. The relationship between the collision speed and the predicted occurrence of head and chest injuries was examined for each case, analyzing the impact kinematics of the pedestrian against the vehicle body and resultant loading to the head and the chest.
Technical Paper

Finite Element Simulation of Ankle/Foot Injury in Frontal Crashes

Finite element models of human body segments have been developed in recent years. Numerical simulation could be helpful when understanding injury mechanisms and to make injury assessments. In the lower leg injury research in NISSAN, a finite element model of the human ankle/foot is under development. The mesh for the bony part was taken from the original model developed by Beaugonin et al., but was revised by adding soft tissue to reproduce realistic responses. Damping effect in a high speed contact was taken into account by modeling skin and fat in the sole of the foot. The plantar aponeurosis tendon was modeled by nonlinear bar elements connecting the phalanges to the calcaneus. The rigid body connection, which was defined at the toe in the original model for simplicity, was removed and the transverse ligaments were added instead in order to bind the metatarsals and the phalanges. These tendons and ligaments were expected to reproduce a realistic response in compression.
Journal Article

Analysis of Driver Kinematics and Lower Thoracic Spine Injury in World Endurance Championship Race Cars during Frontal Impacts

This study used finite element (FE) simulations to analyze the injury mechanisms of driver spine fracture during frontal crashes in the World Endurance Championship (WEC) series and possible countermeasures are suggested to help reduce spine fracture risk. This FE model incorporated the Total Human Model for Safety (THUMS) scaled to a driver, a model of the detailed racecar cockpit and a model of the seat/restraint systems. A frontal impact deceleration pulse was applied to the cockpit model. In the simulation, the driver chest moved forward under the shoulder belt and the pelvis was restrained by the crotch belt and the leg hump. The simulation predicted spine fracture at T11 and T12. It was found that a combination of axial compression force and bending moment at the spine caused the fractures. The axial compression force and bending moment were generated by the shoulder belt down force as the driver’s chest moved forward.
Journal Article

Development of the MADYMO Race Car Driver Model for Frontal Impact Simulation and Thoracolumbar Spine Injury Prediction in Indianapolis-type Racing Car Drivers

This paper describes the results of a project to develop a MADYMO occupant model for predicting thoracolumbar (TL) spine injuries during frontal impacts in the Indianapolis-type racing car (ITRC) environment and to study the effect of seat back angle, shoulder belt mounting location, leg hump, and spinal curvature on the thoracolumbar region. The newly developed MADYMO Race Car Driver Model (RCDM) is based on the Hybrid III, 50th percentile male model, but it has a multi-segmented spine adapted from the MADYMO Human Facet Model (HFM) that allows it to predict occupant kinematics and intervertebral loads and moments along the entire spinal column. Numerous simulations were run using the crash pulses from seven real-world impact scenarios and a 70 G standardized crash pulse. Results were analyzed and compared to the real-world impacts and CART HANS® model simulations.
Journal Article

Determination of the Pressure Distribution Beneath Two- and Three-Inch Wide Racing Safety Belts

This study examines the static pressure distribution under both width belts in the shoulder and the pelvis of 15 volunteer subjects. The subjects applied the belt loads to themselves through a lever and pulley system. The configuration of the belts simulated the typical arrangement of a six-point belted upright-seated racing driver. The pressure distribution between the belt and the volunteer's body was determined and recorded with Tek-Scan pressure sensing grids. The paper presents the results of the measurements by comparing the actual area of significant loading beneath the two widths and materials of both lap and shoulder belts. In, general, there no significant increase in loaded area for the wider belts.
Technical Paper

Biomechanical Evaluation and Driver Experience with the Head and Neck Support

Auto and boat racers suffer fatigue and injury from loading of their necks. While racing, a driver's neck often becomes fatigued because it must support the weight of the head and helmet. In crashes, extreme motions of a driver's unrestrained head relative to the restrained torso cause excessive loads in the driver's neck. These neck loads between the head and torso can cause severe or fatal injuries such as spinal dislocations and basilar skull fractures. A new type of head and neck support has been developed that restrains the driver's head relative to their torso to reduce undesirable head motions and neck loads that cause fatigue and injury. This paper describes recent work, using computer crash simulations, crash dummy tests, and driver experiences, to better understand head and neck injury in racing and to evaluate the performance of a new head and neck support.
Technical Paper

Steering Assembly Impacts Using Cadavers and Dummies

Studies have shown that dummies can be used to study various issues relating to an unrestrained driver's interaction with the steering system in frontal crashes. However, current dummies have limitations in simulation of car occupants and to assess the spectrum of injury types and mechanisms. Human cadaver subjects were used to study abdominal injury and “severe” steering wheel deformation as part of an evaluation of energy absorbing steering systems. A predominant factor influencing abdominal injury in these tests was the impact location of the lower rim, injury being associated with the rim aligned 50 mm below the xiphoid. The dummies developed approximately twice the impact force than the cadaver subjects in these severe tests with a noncompressible column, in part due to the chest of the dummies “bottoming” out on a rigid spine.
Technical Paper

Biomechanical Performance of a New Head and Neck Support

The heads of auto racing drivers and military pilots are usually not supported so that neck fatigue and injury can be a serious problem. A new Head And Neck Support (HANS) is being developed to reduce head motions and neck loads. The biomechanical performance of HANS has been evaluated by crash victim modeling with CAL 3-D and by impact sled testing with a Hybrid III dummy. Modeling and testing were conducted at 30 and 35 mph BEV and with acceleration directions from the front, right front, and right lateral. The model and test results show that head motions, neck loading, and the potential for neck injury are all significantly reduced with HANS compared to without HANS.