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The effects of high mean stresses on the fatigue behavior of nodular iron are studied in this paper. The high mean stresses are applied by two constant- minimum stress test sets and one constant- maximum stress test set. These constant maximum/minimum stress tests, together with standard fully reversed fatigue tests and overload tests, are specially designed not only to show mean stress effects on the fatigue behavior of materials but also to help determine material constants that can be used with a closure-based fatigue method to perform fatigue analysis. The ability of various fatigue methods in predicting mean stress effects on fatigue is also assessed.

Systems of alloys for liquid phase alloying during sintering were investigated. The solidification range of alloys of Mn-Ni-Cr-Mo-Fe and Mn-Cu-Ni was determined. Alloys with the lowest and narrowest melting range were prepared and atomized in nitrogen. Admixtures of master alloys to water-atomized, forging grade, pure iron powder were sintered at 1232°C (2250°F). After hot forging, these P/M steels exhibited hardenabilities which were 75%-90% of theoretical hardenability, as calculated from the factors for conventional steels. Alloying efficiency was further improved to 85%-100% of theoretical hardenability when additions of approximately 2% silicon and 1% rare earth misch-metal were made to the master alloys. The silicon and rare earth misch-metal additions were used to enhance diffusion and sintering.

This article describes three fatigue-life prediction methods for adhesive bonded sheet-aluminum joints. The methods are based on the concepts of containing a presumed damage, of tolerating a damage, and of potential development of a damage under cyclic loading, and thus referred to as damage-containment model, damage tolerant model and the total life model. The damage containment model can be applied in the regime where a fatigue crack, if developed, will not propagate because the applied strain energy release rate falls below the fatigue threshold. The damage tolerant model, on the other hand, predicts the potential growth of a crack. Finally, the total life model integrates the life-times for the initiation and subsequent propagation of a fatigue crack. The merit of each method is assessed by comparing the predicted lifetime with the experimental data for single lap shear specimens.

The ability to evaluate the bending fatigue behavior of carburized low alloy steels in a laboratory and relate these measurements to performance of high contact ratio helical gears is important to the design and development of transmissions. Typical methods of evaluating bending fatigue performance of carburized gear steels do not directly represent helical planetary gears because they lack the geometric and loading conditions of planetary pinions. The purpose of this study is twofold; 1) development of a lab fatigue test to represent the fatigue performance of planetary pinion gears tested in a dynamometer and 2) evaluation of the influence of alloy content on bending fatigue performance of two steel alloys. The steels under evaluation were modified 8620M and 4615M alloys machined into bend bars with a notch representing a gear root and carburized to a case depth of approximately 0.35 mm (using the same carburizing cycle as the planetary pinion gears).