Micromechanics of Crack Initiation in High-Cycle Fatigue

Abstract

Publisher Summary This chapter discusses micromechanics of crack initiation in high-cycle fatigue. Fatigue failures occur under loadings substantially lower than the yield strength of the material. Fatigue cracks occur in two stages that include crack initiation and crack propagation. A crystal subject to shearing stress deforms elastically until gliding starts in some region of the crystal. Part of the crystal slides with respect to the rest by unit atomic spacing. This slip can occur in a portion of a plane separating two parts of a crystal. The displacement gradient of an elastic-plastic body can be considered to consist of the elastic distortion and plastic slip. During plastic deformation, dislocation lines not only increase in number but also move within the crystal. The positive and negative dislocations move in opposite directions on the slip plane. The concentration of the positive dislocation on one side of the crystal and negative dislocations on the other side, referred to as the polarization of dislocations, facilitates the development of long-range internal stresses. The chapter also elaborates the analogy between inelastic strain and applied force.