Numerical evaluation of plasticity induced crack closure in 3D structures

摘要

Fatigue growth of the crack may be retarded as a consequence of the fatigue crack closure occurrence. Complete understanding of the closure process and ability of its accurate assessment is in best interest of scientific and engineering community. In this paper, three-dimensional numerical model of M(T) specimen with straight crack front was created and subjected to loading at various load ratios from R = -1 to R = 0.1. Settings of input parameters such as element size, length of the crack growth, number of substeps and contact elements were adopted from two-dimensional analyses. Closure levels were determined by the method of first node behind the crack tip displacement monitoring. Closure level determination was performed locally for each node along the crack front, respecting the distribution of the stress intensity factor. Results were compared to experimental results and discussion on the reasons of fatigue crack front curvature was provided.