John D. Horsch

MECHANISM OF INJURY FROM AIR BAG DEPLOYMENT LOADS

Loadings induced by deploying currently representative air bags were studied with driver surrogates (anesthetized swine) leaning against the system during inflation. Torso injury mechanisms were studied in a physiologic model, supported against a static steering wheel-mounted air bag system. Severe and extensive chest and abdominal injuries to the swine were observed in the tests. Loading caused by air bag deployment can occur in either of two phases. The first phase represents the initial punch out of the bag from the module; the second phase represents the membrane force of the inflating bag. Statistical analysis indicated that punch out induced injury because of the high rate of loading to the surrogate body region in direct contact with the air bag module. Membrane forces induced injury by high compression over a larger area. Punch-out loading might be reduced by allowing the bag to escape from other parts of the container not in contact with the driver during deployment. Loading by the inflating bag might be reduced by using a compliant steering system to support the module. The amount and rate of generated gas had only marginal effect on the cumulative injury. Even an inflator with inadequate gas output to protect a properly seated occupant had sufficient energy to induce severe injuries in a surrogate in contact with the inflating module. Analysis of the field relevance of the results must consider not only the injury potential given that a driver is in direct contact with the air bag module at the time of deployment, but also the expected field frequency of such an event. Analysis of the field relevance of the results must also consider the correlation of the laboratory test environment with real-world exposure.

Hybrid III sternal deflection associated with thoracic injury severities of occupants restrained with force-limiting shoulder belts

A relationship between the risk of significant thoracic injury (AIS is greater than or equal to 3) and Hybrid III dummy sternal deflection for shoulder belt loading is developed. This relationship is based on an analysis of the Association Peugeot-Renault accident data of 386 occupants who were restrained by three-point belt systems that used a shoulder belt with a force-limiting element. For 342 of these occupants, the magnitude of the shoulder belt force could be estimated with various degrees of certainty from the amount of force-limiting band ripping. Hyge sled tests were conducted with a Hybrid III dummy to reproduce the various degrees of band rearing. The resulting Hybrid III sternal deflections were correlated to the frequencies of AIS greater than or equal to 3 thoracic injury observed for similar and tearing in the field accident data. This analysis indicates that for shoulder belt loading a Hybrid III sternal deflection of 50 mm corresponds to a 40 to 50 percent risk of an AIS greater than or equal to 3 thoracic injury.

Biomechanics of Liver Injury by Steering Wheel Loading

Abdominal injury induced by steering wheel contact at a velocity of 32 km/hr was investigated using anesthetized swine as the surrogate on a Hyge sled. The lower rim of the wheel was positioned 5 cm below the xyphoid. By varying wheel stiffness, wheel orientation, and column angle, resultant abdominal injury ranged from fatal or critical to minor or none. Wheel stiffness was found to be the primary determinant of abdominal injury severity. The mechanism of abdominal injury was identified to be the rim impacting the abdomen and exceeding a combined velocity and compression sensitive tolerance limit. Abdominal injury occurred within the initial 15 ms of wheel contact before whole body movement of the surrogate of column compression, which were initiated by hub contact with the thorax. The severity of abdominal injury correlated with the peak viscous response which can be represented by the product of the instantaneous velocity of abdominal deformation and abdominal compression. It did not correlate with spinal acceleration.

Thoracic Injury Assessment of Belt Restraint Systems Based on Hybrid III Chest Compression

Chest compression is one of the vital responses for development of occupant restraint systems. This study conducted an analysis of two published crash reconstruction studies that involved belted occupants. The aim of the analysis was to provide a basis for comparing occupant injury risks with Hybrid III chest compression in similar exposures. Results from both studies were similar and indicate that belt loading resulting in 40 mm Hybrid III chest compression represents a 20-25% risk of an AIS 3 thoracic injury for car occupants. Additionally, the field experience of APR (Association Peugeot/Renault) and Volvo indicate that crashes severe enough to result in greater than 40 mm of Hybrid III chest compression are infrequent and that injuries in these classic field studies are mostly associated with crash severities which would result in less than 40 mm of hybrid III chest compression.

Measurement of Head Dynamics and Facial Contact Forces In the Hybrid III Dummy

Injury and disability associated with head (brain), neck (spinal cord) and facial injury account for 61.7% of the total societal harm in the most recent estimate of motor-vehicle related crash injuries. This paper discusses the need for accurate information on translational and rotational acceleration of the head as the first step in critiquing the Head Injury Criterion (HIC) and other injury predictive methods, and developing a fuller understanding of brain and spinal cord injury mechanisms. A measurement system has been developed using linear accelerometers to accurately determine the 3D translational and rotational acceleration of the Hybrid III dummy head. Our concept has been to use the conventional triaxial accelerometer in the dummys head to assess translational acceleration, and three rows of in-line linear accelerometers and a least squares analysis to compute statistical best-fits for the rotational acceleration about three orthogonal axes. For the covering abstract see IRRD 864472.

Response of belt restrained subjects in simulated lateral impact

Far-side lateral impacts were simulated using a Part 572 dummy and human cadavers to compare responses for several belt restraint configurations. Sled tests were conducted having a velocity change of 35 km/hr at a 10 g deceleration level. Subjects restrained by a three-point belt system with an outboard anchored diagonal shoulder belt rotated out of the shoulder belt and onto the seat. The subject received some lateral restraint due to interaction with the shoulder belt and seatback. The subjects restrained by a three-point belt system with an inboard anchored diagonal shoulder belt remained essentially upright due to shoulder belt interaction with the neck and/or head. Kinematic responses of the Part 572 dummy were generally similar to those of the cadaver subjects. Injuries were found in cadavers restrained by both shoulder belt configurations, but were more extensive to the cervical region for those subjects receiving direct neck and/or head loading from the belt.

A Study of Driver Interactions with an Inflating Air Cushion

Conceptually, a steering wheel mounted air cushion is inflated before the upper torso of the driver significantly interacts with the cushion. However, this might not be the case for some seating postures or vehicle crash environments which could cause the driver to significantly interact with an inflating cushion. These experiments utilized several environments to study the interaction between an inflating driver air cushion and mechanical surrogates. In these laboratory environments, the measured responses of mechanical surrogates increased with diminishing distance between the surrogates sternum and the steering wheel mounted air cushion. For the covering abstract see IRRD 810752. (Author/TRRL)

Assessment of lap-shoulder belt restraint performance in laboratory testing

Hyge sled tests were conducted using a rear-seat sled fixture to evaluate submarining responses (the lap belt of a lap-shoulder belt restraing loads the abdominal region instead of the pelvis). Objectives of these test included: an evaluation of methods to determine the occurrence of submarining; an investigation into the influence of restraint system parameters, test severity, and type of anthropomorphic test device on submarining response; and an exploration of the mechanics of submarining. The results of of the laboratory tests are presented in this paper.

Influence of the surrogate in laboratory evaluation of energy-absorbing steering system

Various surrogates and responses are available for study of the impact performance of energy absorbing steering systems in the laboratory. The relative influence of the SAE J-944 body block, the part 572 dummy, and the GM hybrid III dummy and of the associated thoracic responses were investigated for steering assembly impact in a series of sled tests. Not only did response amplitudes differ among the surrogates but more importantly trends in impact performance associated with modifications of the steering assembly depended on the choice of surrogate response. They Hybrid III dummy was judged the best of the tested surrogates for study of the steering system impact performance in the laboratory, based on its more humanlike construction, impact response and expanded measurement capacity. For the covering abstract of the conference see TRIS 399532. (Author/TRRL)

THE ROLE OF STEERING WHEEL STRUCTURE IN THE PERFORMANCE OF ENERGY ABSORBING STEERING SYSTEMS

This study identifies important parameters that influence the basic response mechanics of a compressible column steering assembly. Energy can be absorbed either by column compression and/or steering wheel deformation, depending on relative deformation force. Neither column compressive force nor steering wheel deformation force are uniquely defined but depend on several parameters. Steering wheel deformation force is dependent on occupant load distribution. The force necessary to compress the column differs from the column EA element compressive force due to inertial and geometric considerations. For our test conditions and the components we studied, off axis impact resulted in initial steering wheel deformation with the wheel and column sharing energy absorption. Axial impact resulted in almost negligible wheel deformation and the column was the energy absorbing component. For the covering abstract of the conference see HS-036 716. (Author/TRRL)