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Precipitate Size and Distribution Effects on Fatigue Crack Initiation and Propagation in a High Strength Steel.
GEORGE WASHINGTON UNIV WASHINGTON D C INST FOR THE STUDY OF FATIGUE FRACTURE AND STRUCTURAL RELIABILITY
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It has been observed that high yield strength metals do not necessarily exhibit an equally high fatigue strength. Thus the dependence of fatigue failure on the precipitate size and distribution is investigated. Also, it is proposed that the permanent axial strain resulting from cyclic torsion is indicative of the metal response to cyclic loading. Microscopic observation of the failed specimens showed that failure at plus or minus 0.005 inin twist strain occurred by the propagation of a single shear macrocrack linking with shear microcracks. The initiation of the shear microcracks was found to depend upon the precipitate size and distribution. With fine particles localized deformation bands became microcracks, but with coarser particles crack initiation began at the particle-matrix interface. Author Modified Abstract
APPROVED FOR PUBLIC RELEASE