Numerical Studies On The Crack Closure Effect In Fatigue Crack Propagation

This paper discusses the numerical analysis of plasticity-induced crack closureeffect for a middle-crack tension (MT) specimen made of 2024-T351 aluminum alloy, under plane-stress condition and constant amplitude cyclic loading.Elastic-plastic finite element method based on the plastic flow theory is adopted in analysis, with the assumption of bilinear elastic-plastic behavior and the kinematic hardening. The effect of the crack face contacting and the geometrically nonlinear are considered.The crack growth is simulated by separating the pre-defined coincident crack tip node pairs step by step. Emphasis is placed on the aspects of mesh refinement, crack length, and mean stresses.The simulating results have indicated that:The crack closure effect is obviously influenced by the fatigue crack length. The opening and closure stresses increase and then decline with the crack growth.Mesh refinement does not alter the maximum opening load level, but reduce the crack growth interval from the initial length to the length corresponding to the maximum opening load level.The crack opening load level increases with the increase of load ratio R for a constant maximum load.Some suggestions are given for the further improvement to the present research effort.