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Previous studies of human thoracic injury tolerance and mechanical response to blunt, midsternal, anteroposterior impact loading were reported by the authors at the 1970 SAE International Automobile Safety Conference and at the Fifteenth Stapp Car Crash Conference. The present paper documents additional studies from this continuing research program and provides an expansion and refinement of the data base established by the earlier work. Twenty-three additional unembalmed cadavers were tested using basically the same equipment and procedures reported previously, but for which new combinations of impactor mass and velocity were used in addition to supplementing other data already presented. Specifically, the 43 lb/11 mph (19.5 kg/4.9m/s) and 51 lb/16 mph (23.1 kg/7.2 m/s) conditions were intercrossed and data obtained at 43 lb/16 mph (19.5 kg/7.2 m/s) and 51 lb/11 mph (23.1 kg/4.9 m/s).

In order to understand better the head injury mechanism and to clarify the unsettled question as to whether the shear strain or the reduced pressure is the primary injury etiology during a given impact, a realistic model capable of predicting both the shear strain and the reduced pressure effects should be devised. The approach to such a realistic but complicated boundary value problem in biomechanics is achieved through the application of the finite element method. By use of the finite element displacement formulation, the human head is modeled as a viscoelastic core bonded to a thin viscoelastic shell, which simulates the brain and the skull, respectively. For purpose of comparison, two configurations-a spherical shape and a prolate ellipsoid-have been used to describe the geometry of the human head.

Dual-phase steels have been used primarily for reducing weight of complex shaped automotive parts which could not be made with less formable, conventional high strength steels. Recently, a microalloyed dual-phase steel was found also to possess superior machining characteristics. This paper describes laboratory data which compare machinability of dual-phase steel with that of conventional steels. The effects of material strength, tensile prestrain, and cutting depth on machined surface quality are elucidated. The improved machinability of dual-phase steel was explained on the basis of its unique micro-structure. In addition, two applications of dual-phase steel are discussed. In one application, broaching is the critical machining step, and dual-phase steel is currently used in production. In the other, turning is the critical step, and further studies are under way.

SAE 1046 steel axle I-beam forgings produced by the direct quench method and the conventional reheat and quench method were examined. Impact and tensile specimens obtained from sections of two direct quench and one conventional reheat and quench axle I-beams were tested. These data were correlated with hardness and microstructure to determine the relationship between microstructure and properties. The microstructure of direct quenched beams is coarse grained with a martensite case and bainite core. In contrast, the microstructure of conventionally heat treated beams is fine grained with a martensite and/or bainite case and pearlite core. Tensile and impact properties indicate that direct quenching is an acceptable alternative to the conventional reheat and quench process. Fatigue testing of direct quenched beams is currently being performed.

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