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EVALUATING THE INFLUENCE OF PLASTIC DEFORMATION TO THE DAMAGE SUSCEPTIBILITY OF MATERIALS FROM THE NATURE OF FATIGUE-STRENGTH CHANGE,
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
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The effect of preliminary tensile deformation on the fatigue strength of ferrous and nonferrous materials is examined. Samples were fatigue tested in pure shear at a frequency of 3000 cyclesmin. The endurance limit was arbitrarily selected as 5,000,000 cycles. After undergoing plastic deformation in tension, some samples had their surfaces machined off to a depth of 0.2-0.3 mm. Before fatigue testing, all surfaces were polished with a rubber wheel. Microhardness tests along the cross section and near the surface showed no change in hardness after machining. The ratio of endurance limit at any tensile strain to that at zero strain was used to determine the effect of plastic deformation. The fatigue strength of type 35 steel in the normalized and tempered 650C condition is given as a function of the number of cycles to failure. Author
APPROVED FOR PUBLIC RELEASE