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RESULTS of an investigation into the effect of shot-peening variables and the resulting residual stresses on fatigue life are reported in this paper. Leaf springs were the simple specimens heat-treated, cold worked, and tested in this study. Some of the conclusions reached are: 1. There is a minimum shot velocity for each shot size to obtain best fatigue life, and this value is much lower than that normally used. 2. Exposure time for this type of shot-peened specimen beyond some minimum value is wasteful and costly. 3. Shot size has little influence on fatigue life for these specimens. 4. Shot peening specimens while under tensile strain greatly increases fatigue life at 200,000 psi nominal stress over that of nonpeened or strain-free-peened specimens. 5. Shot peening these specimens gave residual compressive stresses 50% of yield strength, and these stresses can be increased to more than 50% by strain peening. 6.

EXPERIMENTAL analyses of residual stresses as related to fatigue properties and to the surface failure known as spalling are discussed in this paper. How those processing operations such as heat-treatment, machining, grinding and straightening contribute the factors causing residual stresses and what are the practical methods of measuring these stresses are also described here.

RELATIONSHIP of the factors of lubricant and engine design which affect wear of cams, lifters, rocker arms, and rocker shafts is discussed in this paper, which is part of the Symposium on Cam and Tappet Wear. To reproduce service failures of valve-train parts in the laboratory in a short time, special tests procedures and certain engine modifications were devised for this study. Results of these laboratory tests, which agree well with data obtained in actual service, are presented here.

STUDIES of cars on the road show that both fuel and lubricant characteristics affect the occurrence of autoignition. For instance it is indicated that autoignition can be eliminated by increasing the fuel antiknock quality, although the Research octane number required may vary slightly depending on fuel composition. Limited evidence is also presented to indicate that aromatic constituents of gasoline are somewhat less effective in suppressing autoignition than are paraffin hydrocarbons. In addition, it is shown that differences in autoignition tendency are observed when different fuels and lubricants are used during the deposit buildup period. In one series of tests a difference of seven octane numbers was observed between autoignition tendencies resulting from operation with different lubricants.