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A single-cylinder engine was used to study the effect of engine operating parameters on the early stage of deposit formation (first 8 hours). Deposit samples were collected from the engine cylinder using removable sampling probes. Among the engine operating parameters studied, coolant temperature had the greatest influence on deposit formation. Equivalence ratio of the air-fuel mixture was also important. Other variables such as compression ratio and intake air temperature had minimal effects. Investigations using a temperature controlled probe revealed that surface temperature is a dominant factor in the deposit forming process. Within a temperature range from 98°C to 256°C, there is an inverse relationship between the amount of deposit accumulated and the surface temperature. Extrapolating the experimental data showed that the critical surface temperature for deposit formation is near 310°C, above which no deposit is expected to form.

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.

A NEW BARRIER to higher compression ratios has recently become apparent — engine rumble! This phenomenon will prevent further increases in compression ratio unless corrective measures are taken. This paper describes the phenomena of engine rumble not only in terms of the noise and vibrations that emanate from the engine but also in terms of the pressure development inside the cylinder. Rumble is the result of abnormally rapid pressure buildup in the combustion chamber due to multiple ignition of the fuel-air mixture by glowing deposits. Since deposits are responsible for the occurrence of engine rumble, studies have been made to determine the contribution of various gasolines and oils to the rumble tendency of the deposits formed. Results from dynamometer and road tests show that combustion-chamber deposits formed by the use of some oils and fuels are considerably less likely to cause rumble than deposits from others.

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.