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A PC based interactive program was developed to simulate the unfolding and deploying process of a driver side airbag in the sagittal plane. The airbag was represented by a series of nodes. The maximum allowable stretch was less or equal to one between any two nodes. We assumed that the airbag unfolding was pivoted about folded points. After the completion of the unfolding process the airbag would begin to deploy. During the deploying process, two parameters were used to determine the nodal priority of the inflation. The first parameter was the distance between the instantaneous and final positions of a node. Nodes with longer distances to travel will have to move faster. We also considered the distance between the current nodal position and the gas inlet location. For a node closer to the gas inlet, we assumed that the deploying speed was faster. A graphical procedure was used to calculate the area of the airbag.

This study identified the mechanical properties of ten cadaveric lumbar spines and two Hybrid III lumbar spines. Eight tests were performed on each specimen: tension, compression, anterior shear, posterior shear, left lateral shear, flexion, extension and left lateral bending. Each test was run at a displacement rate of 100 mm/sec. The maximum displacements were selected to approximate the loading range of a 50 km/h Hybrid III dummy sled test and to be non-destructive to the specimens. Load, linear displacement and angular displacement data were collected. Bending moment was calculated from force data. Each mode of loading demonstrated consistent characteristics. The load-displacement curves of the Hybrid III lumbar spine demonstrated an initial region of high stiffness followed by a region of constant stiffness.

A three-dimensional finite element model of a human neck has been developed in an effort to study the mechanics of cervical spine while subjected to impacts. The neck geometry was obtained from MRI scans of a 50th percentile male volunteer. This model, consisting of the vertebrae from C1 through T1 including the intervertebral discs and posterior elements, was constructed primarily of 8-node brick elements. The vertebrae were modeled using linear elastic-plastic materials, while the intervertebral discs were modeled using linear viscoelastic materials. Sliding interfaces were defined to simulate the motion of synovial facet joints. Anterior and posterior longitudinal ligaments, facet joint capsular ligaments, alar ligaments, transverse ligaments, and anterior and posterior atlanto-occipital membranes were modeled as nonlinear bar elements or as tension-only membrane elements. A previously developed head and brain model was also incorporated.

Lower extremity injuries in frontal automotive crashes usually occur with footwell intrusion where both the knee and foot are constrained. In order to identify factors associated with tibial shaft injury, a series of numerical simulations were conducted using a finite element model of the whole human body. These simulations demonstrated that tibial mid-shaft injuries in frontal crashes could be caused by an abrupt change in velocity and a high rate of footwell intrusion.

A nonlinear foam was added to a previously created three-dimensional finite element model of the Hybrid III dummy chest which consisted of six steel ribs, rib damping material, the sternum, a spine box and a pendulum. Two standard calibration pendulum impact tests for a Hybrid III dummy chest were used to validate the new model. An explicit finite element analysis code PAM-CRASH was utilized to simulate the dynamic process. At impact velocities of 6.7 m/s and 4.3 m/s, the force and deflection time history as well as the force-deflection plots showed good agreement between model predictions and calibration data. Peak strains also agreed well with experimental data.

Auto racing has been in vogue from the time automobiles were first built. With the dawn of modern cars came higher engine capacities; the speeds involved in these races and crashes increased as well. However, the advent of passive restraint systems such as the helmet, HANS (Head and Neck Support device), multi-point harness system, roll cage, side and frontal crush zones, racing seats, fire retardant suits, and soft-wall technology, have greatly improved the survivability of the drivers in high-speed racing crashes. Three left lateral crashes from Begeman and Melvin (2002), Case #LAS12, #IND14 and #99TX were used as inputs to the Wayne State Human Body Model (WSHBM) in a simulated racing buck. Twelve simulations with delta-v, six-point harness and shoulder pad as design variables were analyzed for the average maximum principal strain (AMPS) in the aorta. The average AMPS for the high-speed crashes were 0.1551±0.0172 while the average maximum pressure was 110.50±4.25 kPa.

A three-dimensional finite element model of the Hybrid III dummy head-neck complex was created to simulate the Amended Part 572 Head-Neck Pendulum Compliance Test, of the Code of Federal Regulations. The model consisted of a rigid head and five circular aluminum disks joined together by butyl elastomer rubber. Contact surfaces were defined to allow the anterior neck to separate upon an application of extension moments. Two mounting positions, one for flexion and the other one for extension, were used to simulate the head-neck calibration tests. An explicit finite element code PAM-CRASH was utilized to simulate the model dynamic responses. Simulation results were compared to experimental data obtained from First Technology Safety Systems Inc. Model predictions agreed well in both flexion and extension. This model can be used to study the head-neck biomechanics of the existing dummy as well as in the development of new dummies.

After a rear end impact, various clinical symptoms are often seen in car occupants (e.g. neck stiffness, strain, headache). Although many different injury mechanisms of the cervical spine have been identified thus far, the extent to which a single mechanism of injury is responsible remains uncertain. Apart from hyperextension or excessive shearing, a compression of the cervical spine can also be seen in the first phase of the impact due to ramping or other mechanical interactions between the seat back and the spine. It is hypothesized that this axial compression, together with the shear force, are responsible for the higher observed frequency of neck injuries in rear end impacts versus frontal impacts of comparable severity. The axial compression first causes loosening of cervical ligaments making it easier for shear type soft tissue injuries to occur.

The mechanisms of knee fracture were studied experimentally using cadaveric knees and analytically by computer simulation. Ten 90 degree flexed knees were impacted frontally by a 20 kg pendulum with a rigid surface, a 450 psi (3.103 MPa) crush strength and a 100 psi (0.689 MPa) crush strength aluminum honeycomb padding and a 50 psi (0.345 MPa) crush strength paper honeycomb padding at a velocity of about five m/s. During rigid surface impact, a patella fracture and a split condylar fracture were observed. The split condylar fracture was generated by the patella pushing the condyles apart, based on a finite element model using the maximum principal stress as the injury criterion. In the case of the 450 psi aluminum honeycomb padding, the split condylar fracture still occurred, but no patella fractures were observed because the honeycomb provided a more uniform distribution of patella load. No bony fractures in the knee area occurred for impacts with a 50 psi paper honeycomb padding.

Previously, a 10-year-old (YO) pediatric thorax finite element model (FEM) was developed and verified against child chest stiffness data measured from clinical cardiopulmonary resuscitation (CPR). However, the CPR experiments were performed at relatively low speeds, with a maximum loading rate of 250 mm/s. Studies showed that the biomechanical responses of human thorax exhibited rate sensitive characteristics. As such, the studies of dynamic responses of the pediatric thorax FEM are needed. Experimental pediatric cadaver data in frontal pendulum impacts and diagonal belt dynamic loading tests were used for dynamic validation. Thoracic force-deflection curves between test and simulation were compared. Strains predicted by the FEM and the injuries observed in the cadaver tests were also compared for injury assessment and analysis. This study helped to further improve the 10 YO pediatric thorax FEM.

One of the leading causes of death in automotive crashes is traumatic rupture of the aorta (TRA) or blunt aortic injury (BAI). The risk of fatality is high if an aortic injury is not detected and treated promptly. The objective of this study is to investigate TRA mechanisms using finite element (FE) simulations of reconstructed real-world accidents involving aortic injury. For this application, a case was obtained from the William Lehman Injury Research Center (WLIRC), which is a Crash Injury Research and Engineering Network (CIREN) center. In this selected crash, the case vehicle was struck on the left side with a Principal Direction of Force (PDoF) of 290 degrees. The side structure of the case vehicle crushed a maximum of 0.33 m. The total delta-V was estimated to be 6.2 m/s. The occupant, a 62-year old mid-sized male, was fatally injured. The occupant sustained multiple rib fractures, laceration of the right ventricle, and TRA, among other injuries.

The program objective was to develop an effective inflatable occupant restraint system for unbelted rear seat occupants of motor vehicles. An extensive series of developmental and evaluative impact sled tests included variations in occupant position and size using a standard-size American sedan as the basic vehicle for incorporation of the passive restraint. The restraint system includes a crushable honeycomb knee bar to limit femur loads and to control the head and upper torso trajectory of the unbelted occupants. At speeds below which the airbag deploys, protection is provided by energy-absorbing padding on a head bar as well as on the knee bar. For high-speed crashes, the airbag deploys, and the bag loads are carried out through the head bar and the knee bar support plate. Nondeployed protection is provided for crash speed pulses up to approximately 20 mph in order to satisfy multiple impact considerations, and nonvented side bags are used for oblique impact protection.

The air bag restraint system or automatic restraint system is specifically designed to control forces and deceleration to the human body during an automobile accident. The three basic components comprising the air bag restraint system include: 1) the crash sensor(s), the diagnostic package for determining operability status, and the driver and front passenger air bag assemblies. The information presented is limited to a description and the operational features of the driver and passenger unit assemblies; parts which are located in the steering wheel and instrument panel respectively. Both assemblies consist of three basic components: 1) the inflator, 2) the module, and 3) the air bag.

The objective of this program was to design, test, evaluate, manufacture and install in 500 state highway patrol vehicles, a driver air bag retrofit system. Air bag system benefits are universally accepted. However, the costs, complexities and availabilities of these systems are widely misunderstood. This program takes much of the “mystery” out of the air bag and demonstrates to fleet operators and to the public at large that air bag technology, components and systems do presently exist and can be acquired at a reasonable cost. The following paper provides a description of the system, the tests which were conducted, the installation procedures and field experience with the 500 car fleet.

Development of an aspirator air bag has been completed at Calspan Corporation. The aspirator air bag has been developed through computer simulations and sled tests, and has been evaluated in a 41.6 MPH crash of a standard Volvo into a flat barrier. This evaluation included both out-of-position and normally seated occupants. This paper describes the aspirator system and presents results of the sled tests and the car crash. This research was conducted under U. S. Department of Transportation, National Highway Traffic Safety Administration, Contract No. DOT-HS-5-01254.

An experimental program is discussed wherein fresh, unembalmed cadavers and anthropomorphic test dummies (ATD's) were exposed to identical crash situations. Results include tests conducted on the Calspan HYGE acceleration sled and full-scale car crash tests using belt restraint systems and air bag systems. Cadaver test data obtained include head and chest triaxial accelerations from externally mounted sensors, chest deflections and belt loads. Cadaver test data also include arterial and lung pressure measurements as well as X-ray and gross necropsy evaluations. Dummy test data include normally measured internal triaxial head and chest accelerations. High-speed movie coverage produced cadaver and dummy kinematic results. AT THIS TIME there exists some question in the automotive safety community as to the proper role cadaver experiments can play in the design, development and evaluation of safety related vehicle systems.

A front passenger passive restraint system has been developed which provides frontal impact protection under small car, high speed crash conditions. The system consists of an extended crushable dashpanel, a knee bar and a relatively small volume air bag. Computer simulations, static tests and sled tests have been used to develop this system for the range of occupant sizes from 6 yr. child to 95th percentile adult for crash speeds to 50 mph. This paper reviews these efforts and presents observations regarding not only the performance of the system but those concerned with production feasibility and consumer acceptance as well. This research was conducted under contract to the U. S. Department of Transportation, NHTSA, under Contract DOT-HS-4-00972.

The objective of this program is to design, test, evaluate, manufacture, and install in 500 state highway patrol vehicles a driver airbag retrofit system. Airbag system benefits are universally accepted. However, the costs, complexities, and availabilities of these systems are widely misunderstood. This program takes much of the mystery out of the airbag and demonstrates to fleet operators and the public at large that airbag technology, components, and systems do presently exist and can be acquired at a reasonable cost. Detailed information on system design, selection of vehicles and states to participate, as well as sled testing and full-scale crash testing are presented as SAE Paper 841216, "Driver Airbag Police Fleet Demonstration Program--A 15-Month Progress Report" by the same authors.

A test program was conducted in which 12 full-scale automobiles were crashed under controlled conditions to provide detailed performance data on inflatable occupant restraint systems (IORS). Head, chest, and pelvis, three component acceleration data are presented. Femur and tibia forces, and vehicle acceleration and crush data are also shown. Several different methods of analyzing the IORS are discussed. From these analyses, it is possible to identify reasons for marked deviations from normal IORS performance as well as to rate tentatively the more normally performing systems. The conclusions reached are founded on quantitative data analysis and are of considerable scope for the small data sample available from this program.

Investigations were performed to determine for oblique impacts the occupant kinematic protection limits afforded by full front seat air bags installed in a subcompact car. Techniques used in this investigation included three-dimensional crash victim simulation modeling (CAL-3D model), the use of the NHTSA developed passenger air cushion (DJPAC) simulation program, and the design, installation and testing of production component driver and passenger air bag systems in a compact car. The results of this program demonstrate that occupants of the subject small car can be protected by air bag restraints in 45° oblique principal direction of force (PDOF) impacts up to 30 mph barrier equivalent velocity.