Crack growth and closure mechanisms of shear cracks under constant amplitude biaxial straining and periodic compressive overstraining in 1045 steel

摘要

Crack growth and roughness induced closure mechanisms of shear cracks under 180° out-of-phase strain histories having constant amplitude straining and periodic compressive overstrains (PCOs) were investi- gated. The results revealed that shear cracks initially nucleated on a slip band at 45° to the axis of the specimen which coincides with the plane of maximum shear strain. Growth on the shear planes (microcracks) into the specimen surface occupied up to 90-95/100 of fatigue life during which time the surface length of the microcracks remained nearly constant. Failure then occurred by a rapid linking of microcracks at the end of a test.