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This paper describes the mathematical modeling of occupant kinematics in rollover accidents using the MVMA 2-D occupant motion simulation software. What little information is available on the kinematics of vehicle occupants during rollover accidents has been obtained either after the fact by accident reconstruction or by expensive experimentally-staged events. The paper describes the use of less expensive analytical techniques to graphically illustrate the applicability of occupant motion simulation computer models to this problem.

Life threatening chest injury can involve partial or full tears of the aorta. Investigations of fatal injuries in automobile accidents indicate that aortic trauma occurs in 10-20% of the cases. The major sites of aortic trauma include the aortic isthmus, the root, and the aortic insertion at the diaphragm - all of which are points of aortic tethering. The biomechanics of the injury process involve stretching of the vessel from points of tethering and hydrodynamic increases in blood pressure, which stretch the tissue to failure at a strain of about 150%. The non-isotropic stretch response of aortic tissue is discussed with reference to the frequent transverse orientation of the laceration. Congenital and pathophysiological conditions also influence the failure characteristics of the tissue. The significant factors associated with traumatic injury of the aorta are discussed in this review paper which is based on published technical information.

Current finite element models of head impact involve a geometrically simplified fluid-filled shell composed of homogeneous, linear and (visco) elastic materials as the primary surrogate of the human skull and brain. The numerical procedure, which solves the mechanical response to impact, requires and presumes continuity of stress and displacement between elements, a defined boundary condition simulating the neck attachment and a known forcing function. Our critical review of the models discussed, primarily, the technical aspects of the approximations made to simulate the head and the limitations of the proposed analytical tools in predicting the response of biological tissue. The following critical features were identified as major factors which compromised the accuracy and objectivity of the models: - The brain was approximated by a fluid contained in an elastic or rigid shell with no provision for relative motion between the shell and fluid.

The study was directed toward improving our understanding how postcrash column compression and steering wheel deformation relate to the driver interaction with an energy absorbing steering system during automotive collisions. Frontal sled tests conducted at 19–37 km/h investigated the Part 572 antropomorphic dummy interaction with a ball-sleeve column steering assembly over a range of column angles and surrogate postures. Neither column compression nor steering wheel deformation correlated with the mechanical severity of the test surrogate interaction with the steering system. The steering wheel deformed before the column compressed and the degree of wheel deformation strongly depended on the surrogate load distribution, the steering wheel being an important energy absorbing element.

As part of a continuing study of thoracic injury resulting from blunt frontal loading, the interrelationship of velocity and chest compression was investigated in a series of animal experiments. Anesthetized male swine were suspended in their natural posture and subjected to midsternal, ventrodorsad impact. Twelve animals were struck at a velocity of 14.5 ± 0.9 m/s and experienced a controlled thoracic compression of either 15, 19, or 24%. Six others were impacted at 9.7 ± 1.3 m/s with a greater mean compression of 27%. For the 14.5 m/s exposures the severity of trauma increased with increasing compression, ranging from minor to fatal. Injuries included skeletal fractures, pulmonary contusions, and cardiovascular ruptures leading to tamponade and hemothorax. Serious cardiac arrhythmias also occurred, including one case of lethal ventricular fibrillation. The 9.7 m/s exposures produced mainly pulmonary contusion, ranging in severity from moderate to critical.

Belt interaction with the dummy's chest or pelvis was investigated during simulated frontal decelerations to develop a better understanding of the mechanics of belt restraint. Hyge sled tests were conducted at acceleration levels of 6-16 g's with a Part 572 dummy forward facing on an automotive bucket seat. Dynamics were compared in similar tests where the dummy was restrained by a conventional shoulder belt or belt segments attached to a modified sternum - a steel sternum with extensions for fixed belt attachments. Tests were also conducted with a conventional lap belt or belt segments fixed to an extension of the H point. Deformation characteristics of the standard and modified thorax were determined for a lateral and superior point load or a belt yoke compression of the sternum. The pelvic structure was also compressed by a lap belt. Our evaluation of test dummy dynamics indicates the following sequence of events with a conventional shoulder belt: 1.)

Sled tests were conducted at farside oblique angles of 15°, 45°, and 75° with a Part 572 dummy restrained by a conventional driver lap/shoulder belt system or a preinflated driver inflatable restaint. Occupant dynamics were compared in similar tests where an inboard energy absorbing lateral restraint of the upper torso was or was not used. It can be concluded that the seat wing improves the control of the dummy's dynamics in oblique impacts by directing the occupant's motion more forward into the restraint system, thereby taking more advantage of the restraining potential of the shoulder belt or inflatable restraint in controlling the deceleration of the dummy and enhancing the benefit of the restraint system. However, additional factors associated with the use of a seat wing remain to be investigated including the effect of impact force on the occupant, interaction with out-of-position occupants and comfort/convenience.

The primary purpose of this parameter study was to carefully document occupant dynamics in well-controlled sled tests for comparison with simulated responses from the MVMA-2D analytical model. The test involved a Part 572 dummy exposed to a frontal deceleration while on a bucket seat and restrained by a lap-shoulder belt system. The length of belt webbing was incrementally increased from a snug configuration by as much as 30 cm. The addition of webbing increased the forward excursion, velocity, and acceleration of the head, chest, and hip without affecting the peak tension in the belt segments of the restraint system. Belt tension was identified as a poor measure of the horizontal load on the chest due to significant reaction forces in the lateral and vertical direction at the belt anchorages.

Barrier crash simulations with a torsobelted Part 572 dummy were conducted to determine the influence of knee bolster crush orientations of 0°–60° on lower extremity restraint. Responses from two sled velocity and mean deceleration severities were investigated: 6.6 m/s at 7.5 g and 13.5 m/s at 13.9 g. The dummy’s knees were prepositioned 10 cm from individual experimental bolsters, which crushed along a predetermined axis. Bolster orientation had only a minor effect on the level of peak dummy femur, and resultant knee bolster reaction load and on lower extremity kinematics of the torsobelted occupant; however, the local loading of the knee and level of tibial compression were significantly influenced.

The influence of body posture, and inherently support, on thoracic impact response was investigated in an animal model. Anesthetized and postmortem domestic swine were exposed to blunt, midsternal loading while supported in their natural quadrupedal posture, and the results were compared with previously reported data from similar tests involving an upright body orientation. Twelve male animals were tested, six while anesthetized and six postmortem. Each animal was impacted once by a 21 kg rigid mass with a flat contact interface moving at a nominal velocity of either 8 or 10 m/s. Measured mechanical responses included applied load, sternal and spinal accelerations, thoracic compression and aortic overpressure. Injury response was assessed from a thoracico-abdominal necropsy. In addition, ECG traces were recorded pre and postimpact to monitor electro-physiological response.

Previous pendulum impact tests have shown that knee joint injuries and tibial-fibular fractures may occur when loads are directed against the lower leg rather than directly against the femur in the knee. In order to further improve our understanding of lower extremity restraint mechanics, simulated frontal barrier crash experiments were conducted with unembalmed human cadavers and an anthropomorphic dummy restrained by a two-point shoulder belt. In the first test, an experimental bolster was specifically positioned so that the cadaver's lower leg would strike the bolster, thus inducing restraining loads entirely below the knee joint. The analysis of occupant kinematics showed that the flexed knee rode over and forward of the low-positioned bolster. Restraint induced considerable shearing load across the knee joint. Bolster measurements indicated a peak load of approximately 4.0 kN per leg which resulted in a contralateral central tear of the posterior cruciate ligaments.

Classical blunt thoracic impacts have involved midsternal anteroposterior loadings to an upright-positioned subject. Data on the sensitivity of human cadaver and/or animal model biomechanical and injury responses to blunt loadings at different sternal locations is needed to evaluate the efficacy of current injury-potential guidelines for nonsite-specific frontal impacts. In addition, the biomechanics and injury mechanisms associated with lateral impacts constitute a subject of increasing consideration for occupant protection. Twelve anesthetized pigs were subjected to various blunt frontal or a right-side impact to assess biomechanical and injury response differences in a living animal model.

A femur fracture injury criterion is presented that assesses the dependence of the permissible human knee load on the duration of the primary force exposure. Currently a constant allowable femur load limit of 7.6 kN (1700 lb) is specified in FMVSS 208, but recently the Federal Government proposed elevating the allowable limit to 10.0 kN (2250 lb), which is in excess of the limited experimental average static femur fracture force of 8.90 kN (2000 lb). A general analysis of all of the available biomechanics data and mathematical models on femoral impact response and fracture indicates a significant load time dependence for primary pulse durations below 20 ms that can elevate the permissible femur load above the Federally proposed allowable limit of 10.0 kN (2250 lb).

Thoracic impact response and injuries of living and postmortem porcine siblings were investigated to quantify comparative differences. Thirteen male animals, averaging 61.4 kg, from five different porcine litters comprised the two animal samples. Porcine brothers were subjected to similar impact exposures for which at least one brother was tested live, anesthetized and another dead, post rigor with vascular repressurization. Statistically significant differences in biomechanical responses and injuries were observed between live and postmortem siblings. On the average the anesthetized live animals demonstrated a greater thoracic compliance, as measured by increased normalized total deflections (21% Hi), and reduced overall injuries (AIS 14% Lo and rib fractures 26% Lo) at lower peak force levels (13% Lo) than did the postmortem subjects. However, individual comparisons of “match-tested” siblings demonstrated very similar responses in some cases.

Five anesthetized porcine subjects were exposed to blunt thoracic impact using a 21 kg mass with a flat contact surface traveling at 3.0 to 12.2 m/s. The experiments were conducted to assess the appropriateness of studying in vivo mechanical and physiological response to thoracic impact in a porcine animal model. A comprehensive review of comparative anatomy between the pig and man indicates that the cardiovascular, respiratory and thoracic skeletal systems of the pig are anatomically and functionally a good parallel of similar structures in man. Thoracic anthropometry measurements document that the chest of a 50 to 60 kg pig is similar to the 50th percentile adult male human, but is narrower and deeper. Peak applied force and chest deflection are in good agreement between the animal's responses and similar impact severity data on fresh cadavers.

Currently used criteria based on functions of spinal acceleration obtained from crash test dummies are shown to be invalid indicators of chest injuries in blunt frontal impacts. Cadaver impact data are analyzed; and injury is found to be a statistically significant function of chest deflection, chest depth, and cadaver age at death. Based on the resulting regression equations, injury-limiting chest deflections are recommended for various size test dummies. The recommendations apply only to test dummies that have significant thoracic biofidelity for blunt frontal impact. They are valid for environments which include signigicant blunt frontal impact. Their extension to other environments has not been validated.

The concept of rate of onset as an injury potential index is critically discussed through the analysis of a wide range of noninjurious whole body decelerations and localized impacts. Examination of the physical data shows that extremely high rates of onset are tolerable without injury and that these levels of rate of onset are reciprocally dependent on the pulse rise time. The physical data is next discussed with reference to existing acceleration injury criteria, specifically the GSI and HIC indices. This work substantiates the conclusions that a single rate of onset tolerance level is not warranted and that rate of onset is not a proven injury potential index.

Two Highway Safety Research Institute (HSRI) dummies were tested and evaluated. Based on the analysis given, the HSI dummy should not be used for vehicle qualification testing. However, many of its components offer viable alternatives for future dummy development. The dummy was found to have inadequate biomechanical fidelity in the head, neck, and chest, although its characteristics were very promising and, as a whole, biomechanically superior to the Hybrid II. Its repeatability and reproducibility in dynamic component tests were better than the Hybrid II dummy. In particular, the HSRI friction joints were outstanding in repeatability and had a significant advantage in usability in that they do not require resetting between tests. In three-point harness and ACRS systems tests, the values of injury criteria produced by the HSRI dummy were generally lower than those obtained with the Hybrid II, especially the femur loads in the ACRS tests.

Details of a new crash simulator and preliminary results from a series of cadaver knee impact experiments were presented at the Eighth Stapp Conference. During the past year additional data concerning injury to the knee-thigh-hip complex have been obtained, and the studies have been extended to consider impact to the chest. Results to date indicate that for knee impacts against a moderately padded surface it is not possible to predict whether failure of the patella, femur or pelvis will occur first, although in these studies femoral fractures occurred most frequently. A force of 1400 lb. is recommended at this time as a reasonably conservative value for the over-all injury threshold level. Volunteers tolerated impact loads to the knee of 800-1000 lb. For loads applied over the sternum through a 25-30 padded surface, static and dynamic thoracic stiffness characteristics were determined for a limited number of cadavers.