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Since 1994, the New Car Assessment Program (NCAP) of the National Highway Traffic Safety Administration (NHTSA) has compiled upper neck loads for the belt and air bag restrained 50th percentile male Hybrid III dummy. Over five years from 1994 to 1998, in frontal crash tests, NCAP collected upper neck data for 118 passenger cars and seventy-eight light trucks and vans. This paper examines these data and attempts to assess the potential for neck injury based on injury criteria included in FMVSS No. 208 (for the optional sled test). The paper examines the extent of serious neck injury in real world crashes as reported in the National Automotive Sampling System (NASS). The results suggest that serious neck injuries do occur at higher speeds for crashes involving occupants restrained by belts in passenger cars.

A finite element model of the human thorax was merged with a rigid body finite element implementation of the Hybrid III dummy (after removal of the Hybrid III thorax) and the combined model is used in simulations of an out of position driver during airbag deployment. Parameters related to injury, such as A-P thorax deformation, Viscous Criterion, rib stress distribution and strain in the thoracic contents are used to quantify the thoracic injury response. Initial driver position is varied to examine the relationship between distance from the airbag module and thoracic injury risk. The potential for injury mitigation through modulation of airbag inflation after initiation is also investigated. The utility of the combined model as an effective tool for the analysis of occupant kinematics and dynamics, examination of injury mechanisms, and optimization of restraint system design parameters is demonstrated.

The present study investigated the effects of the structural stiffness of the head restraint and its attachment rigidity on the biomechanical responses and related injury measures of the neck in a rear impact vehicular collision. A series of simulated rear impacts were conducted using a mid-sized male test dummy seated in a modified late-model front passenger seat on a deceleration crash sled with a FMVSS 202 pulse. Preliminary results demonstrated that a more rigid head restraint in its design and attachment produced lesser values in most biomechanical injury measures such as neck shear force, neck extension bending moment, tension-extension neck injury criterion (Nij), shear-moment neck injury criterion (Nkm), and head-torso relative extension angular displacement. This is true for a wide range of seatback recliner stiffness. This suggests that a more rigid head restraint may have a protective advantage over a more pliant one for the neck in a rear impact.

A detailed finite element model of the human pelvis and lower extremities was developed based on anatomic data from the NIH-sponsored Visible Human Project. Anatomic slices were digitized and converted through a multi-step process into a fully hexahedral element finite element mesh. A procedure was also developed to rotate the femur about the center of rotation of its head to provide various degrees of hip flexion/extension and abduction/adduction. A preliminary series of simulations was conducted using LSDYNA to investigate the effects of hip position on the contact area within the joint and the associated stress levels in the surrounding bony structures. Results suggest that the risk of femoral neck fracture increases as the amount of hip abduction increases.

A three-dimensional finite element model of a human ligamentous cervical spine was developed to study the mechanics of cervical injuries related to automotive crashes. Patran and LS-DYNA3D were used to create this preliminary model consisting of the cervical vertebrae, intervertebral discs, and biomechanically relevant spinal ligaments. Material properties were obtained from published experimental data. A rigid head was included to provide proper application of non-contact inertial loading. Model development began with the generation of a single cervical motion segment. This model was subjected to a variety of loading conditions to provide a qualitative check of material properties and tissue interface conditions. Based on this motion segment model, a complete cervical model was developed including an attached rigid head. Simulations were run for axial compression and frontal flexion.

Three different measurement methods for angular displacement (rotation) of a dummy head and torso were evaluated in a rear impact crash environment. The data were collected using a Hybrid III 50th percentile male dummy in rear impact sled tests tuned to the FMVSS 202 deceleration pulse. Angular rate sensors yielded rotation data closely matching the results from high-speed digital video images to within 3 degrees with a total displacement range up to 110 degrees. Linear acceleration data generally yield less accurate angular displacement results, in addition to being cumbersome in data processing.

This study explores the dynamics of head and cervical spine impact with the specific goals of determining the effects of head inertia and impact surface on injury risk. Head impact experiments were performed using unembalmed head and neck specimens from 22 cadavers. These included impacts onto compliant and a rigid surfaces with the surface oriented to produce both flexion and extension attitudes. Tests were conducted using a drop track system to produce impact velocities on the order of 3.2 m/s. Multiaxis transduction recorded the head impact forces, head accelerations, and the reactions at T1. The tests were also imaged at 1000 frames/sec. Injuries occurred 2 to 30 msec following head impact and prior to significant head motion. Head motions were not found to correlate with injury classification. Decoupling was observed between the head and T1, resulting in a lag in the force histories.

Lower extremity injuries caused by floor plate impacts through the axis of the lower leg are a major source of injury and disability for civilian and military vehicle occupants. A collection of PMHS pendulum impacts was revisited to obtain data for paired booted/unbooted test on the same leg. Five sets of paired pendulum impacts (10 experiments in total) were found using four lower legs from two PMHS. The PMHS size and age was representative of an average young adult male. In these tests, a PMHS leg was impacted by a 3.4 or 5.8 kg pendulum with an initial velocity of 5, 7, or 10 m/s (42-288 J). A matching LS-DYNA finite element model was developed to replicate the experiments and provide additional energy, strain, and stress data. Simulation results matched the PMHS data using peak values and CORA curve correlations. Experimental forces ranged between 1.9 and 12.1 kN experimentally and 2.0 and 11.7 kN in simulation.

A new anthropomorphic test device (ATD) is being developed by the US Army to be responsive to vertical loading during a vehicle underbody blast event. To obtain design parameters for the new ATD, a series of non-injurious tests were conducted to derive biofidelity response corridors for the foot-ankle complex under vertical loading. Isolated post mortem human surrogate (PMHS) lower leg specimens were tested with and without military boot and in different initial foot-ankle positions. Instrumentation included a six-axis load cell at the proximal end, three-axis accelerometers at proximal and distal tibia, and calcaneus, and strain gages. Average proximal tibia axial forces for a neutral-positioned foot were about 2 kN for a 4 m/s test, 4 kN for 6 m/s test and 6 kN for an 8 m/s test. The force time-to-peak values were from 3 to 5 msec and calcaneus acceleration rise times were 2 to 8 msec.