Search Results

This paper details the development of an abdominal injury assessment device for loading due to belt restraint submarining in the Hybrid III family of dummies. The design concept and criteria, response criteria, choice of injury criterion, and validation are explained. Conclusions of this work are: 1) Abdominal injury assessment for belt loading due to submarining is now possible in the Hybrid III family of dummies. 2) The abdomen developed has biofidelity in its force deflection characteristics for belt loading, is capable of detecting the occurrence of submarining, and can be used to determine the probability of abdominal injury when submarining occurs. 3) Installation of the abdomen in the Hybrid III dummy does not change the dummy kinematics when submarining does not occur. 4) When submarining does occur, the dummy kinematics are very similar to baseline Hybrid III kinematics, except for torso angle.

The purpose of this study was to investigate approaches evaluating the performance of safety systems in crash tests and by analytical simulations. The study was motivated by the need to consider the adequacy of injury criteria and tolerance levels in FMVSS 208 measuring safety performance of restraint systems and supplements. The study also focused on additional biomechanical criteria and performance measures which may augment FMVSS 208 criteria and alternative ways to evaluate dummy responses rather than by comparison to a tolerance level. Additional analysis was conducted of dummy responses from barrier crash and sled tests to gain further information on the performance of restraint systems. The analysis resulted in a new computer program which determined several motion and velocity criteria from measurements made in crash tests.

Blunt impacts to the back of the torso can occur in vehicle crashes due to interaction with unrestrained occupants, or cargo in frontal crashes, or intrusion in rear crashes, for example. Six pendulum tests were conducted on the back of an instrumented 50th percentile male Hybrid III ATD (Anthropomorphic Test Device) to determine kinematic and biomechanical responses. The impact locations were centered with the top of a 15-cm diameter impactor at the T1 or at T6 level of the thoracic spine. The impact speed varied from 16 to 24 km/h. Two 24 km/h tests were conducted at the T1 level and showed repeatability of setup and ATD responses. The 16 and 24 km/h tests at T1 and T6 were compared. Results indicated greater head rotation, neck extension moments and neck shear forces at T1 level impacts. For example, lower neck extension was 2.6 times and 3.8 times greater at T1 versus T6 impacts at 16 and 24 km/h, respectively.

Side impact pendulum tests were conducted on Eurosid I and Biosid to assess the biofidelity of the thorax, abdomen and pelvis, and determine injury tolerance levels. Each body region was impacted at 4.5, 6.7, and 9.4 m/s using test conditions which duplicate cadaver impacts with a 15 cm flat-circular 23.4 kg rigid mass. The cadaver database establishes human response and injury risk assessment in side impact. Both dummies showed better biofidelity when compared to the lowest-speed cadaver response corridor. At higher speeds, peak force was substantially higher. The average peak contact force was 1.56 times greater in Biosid and 2.19 times greater in Eurosid 1 than the average cadaver response. The Eurosid I abdomen had the most dissimilar response and lacks biofidelity. Overall, Biosid has better biofidelity than Eurosid I with an average 21% lower peak load and a closer match to the duration of cadaver impact responses for the three body regions.

This paper contains a review of current information on biological structure, material properties and failure characteristics of bone, articular cartilage, ligament and tendon. The load-deformation response of biological tissues is presented with particular reference to the microstructure of the material. Although many of the tissues have been characterized as linear, elastic and isotropic materials, they actually have a more complicated response to load, which includes stiffening with increasing strain, inelastic yield, and strain rate sensitivity. Failure of compact and cancellous bone depends on the rate, type, and direction of loading. Soft biological tissues are vlscoelastie and exhibit a higher load tolerance with an increasing rate of loading. The paper includes a discussion on the basic principles of biomechanics and emphasizes material properties and failure characteristics of biological tissues subjected to impact loading.

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.

Knee bolsters on the lower instrument panel have been designed to control occupant kinematics during sudden deceleration. However, a wide variability in car occupant anthropometry and choice of seating posture indicates that lower-extremity contacts with the impingement bolster could predominantly load the flexed leg through the knee (acting through the femur) or through the tibia (acting through the knee joint). Potential injuries associated with these types of primary loading may vary significantly and an understanding of potential trauma mechanisms is important for proper occupant restraint.

In this study, U.S. crash data was analyzed to better understand bounce-over rollovers. Crash data was reviewed to evaluate the distribution of bounce-over crashes and injuries, initiation objects and impact locations. In passenger cars, bounce-over crashes account for 8.4% of rollovers but involve 36.2% of the seriously injured belted drivers. Most bounce-overs are initiated by contact with narrow objects such as a pole, tree or barrier, or large objects such as a ditch or embankment. Contact often occurs in the front of the vehicle. After contact, the vehicle yaws and rolls, and serious injuries are often sustained to the head. Based on field data, a laboratory test was developed to simulate a narrow object bounce-over. The test consists of towing a vehicle laterally on a fixture towards a stationary, angled barrier resting in gravel. The moving fixture is decelerated and the vehicle is released. The vehicle front impacts the edge of the barrier, simulating a narrow object impact.

Rollovers are an important vehicle safety issue. Various technologies have been developed to help prevent rollovers from occurring, but the evaluation of rollover resistance typically involves vehicle-handling tests that are conducted on flat road surfaces with a uniform or split coefficient of friction. The purpose of this study is to determine the precipitating events leading to rollovers by analyzing real-world rollover crashes. This is a first step in identifying and developing vehicle tests that are representative of the principal driving scenarios leading to rollovers. The sequence of events leading to rollovers was determined from 63 in-depth investigated cases in the NASS-CDS database from 1995-1999. The sequence was evaluated by vehicle maneuvers, vehicle stability, surface type, road and shoulder transition condition, posted and estimated speeds, vehicle type and driver injury severity.

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).

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.

A planar mathematical model was developed to provide means of studying factors which can influence the function of lower torso restraint via a padded lower instrument panel or knee bolster. The following factors were judged to play the most significant role: 1) initial fore-and-aft position of the seated occupant relative to the knee restraint; 2) location of the knee-to-bolster contact; 3) angular orientation of the bolster face; 4) primary axis of the bolster resisting force, 5) variations in vehicle crash parameters (e.g., toepan rotation and displacement and seat deflection); and 6) deformation characteristics of the bolster. The model of a seated occupant included radiographic and empirical data on the anatomy of the links and joints in the lower extremity.

Purpose: A better understanding of rear occupant fatality risks is needed to guide the development of safety improvements for 2nd and 3rd row occupants. This study investigates fatal accidents of 1st, 2nd and 3rd row occupants by principal direction of force (PDOF), irrespective of restraint use. It determined the number of fatalities, exposure and fatality risk. Methods: 1996-2005 FARS was analyzed for occupant fatalities by seating position (1st, 2nd and 3rd row) and principal direction of force (1-12 o'clock PDOF, rollover and other/unknown). Light vehicles were included with model year 1990+. 1996-2005 NASS-CDS was similarly analyzed for occupant exposure. Fatality risk was defined as the number of fatalities in FARS for a given category divided by the exposure from NASS-CDS. Results: Ten percent (9.6%) of fatalities were to 2nd row occupants in FARS. About 2,080 deaths occur to 2nd row occupants annually. 38.4% died in rollovers and 26.8% in frontal crashes.

Child safety is an important issue. The objective of this study was to analyze field accident data for 0-7 year old children in the 2nd row by vehicle and crash type, irrespective of restraint use. The data was obtained from NASS-CDS for calendar years 1991-2005. Accidents were selected based on 2nd row occupancy in towaway light vehicles with model year 1990 or newer. Side impacts caused 30.9% of serious-to-fatal injury (MAIS 3+F) to 2nd row children followed by frontal impacts (29.8%), rollovers (24.4%) and rear crashes (15.0%). The highest risk for MAIS 3+F was in rollovers (2.8 ± 0.7%) followed by rear (1.4 ± 0.4%), side (1.0 ± 0.2%) and frontal (0.46 ± 0.10%) crashes. The differences are statistically significant (p <0.01). Individual rear and frontal impact cases were also reviewed to better understand injury mechanisms of children in the 2nd row. The cases were obtained from the 1997-2005 NASS-CDS electronic database.

This paper covers the development of the General Motors Energy Absorbing Steering System beginning with the work of the early crash injury pioneers Hugh DeHaven and Colonel John P. Stapp through developments and introduction of the General Motors energy absorbing steering system in 1966. evaluations of crash performance of the system, and further improvement in protective function of the steering assembly. The contributions of GM Research Laboratories are highlighted, including its safety research program. Safety Car, Invertube, the biomechanic projects at Wayne State University, and the thoracic and abdominal tolerance studies that lead to the development of the Viscous Injury Criterion and self-aligning steering wheel.

The timing of liver laceration in swine during the course of a blunt impact was investigated. The swine were impacted on the upper abdomen by the lower segment of a steering wheel at 6, 9 and 12 m/s. The degree of compression in each impact was controlled independently from 10 to 50%. By varying when “the punch of an impact was pulled,” we reproduced progressive segments of a longer duration blunt impact. Autopsy of the subjects demonstrated that lacerations were initiated after 8 ms of loading at 9 m/s and 6 ms of loading at 12 m/s. The time of injury was concurrent with the time when the Viscous response exceeded a threshold of 1.2 m/s in our specimens. The Viscous injury criterion, defined as the peak Viscous response, was found to be the best predictor of liver laceration. We conclude that the Viscous response relates to the actual etiology of injury, in addition to being an excellent correlative measure.

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 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.

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.

Objective: This study analyzes rear sled tests with a 95th% male and 5th% female Hybrid III dummy in various seating positions on ABTS (All Belt to Seat) seats in severe rear impact tests. Dummy interactions with the deforming seatback and upper body extension around the seat frame are considered. Methods: The 1st series involved an open sled fixture with a Sebring ABTS seat at 30 mph rear delta V. A 95th% Hybrid III dummy was placed in four different seating positions: 1) normal, 2) leaning inboard, 3) leaning forward and inboard, and 4) leaning forward and outboard. The 2nd series used a 5th% female Hybrid III dummy in a Grand Voyager body buck at 25 mph rear delta V. The dummy was leaned forward and inboard on a LeSabre ABTS or Voyager seat. The 3rd series used a 5th% female Hybrid III dummy in an Explorer body buck at 26 mph rear delta V. The dummy was leaned forward and inboard on a Sebring ABTS or Explorer seat.