Two and three dimensional finite element simulation and experimental correlation of fatigue crack closure

A review is made of different experimental techniques and numerical methods used in the estimation of plasticity-induced fatigue crack closure under cyclic loading. Load interaction effects and temperature exposure on closure levels are highlighted. Some of the recent experimental works on estimation of closure levels with part through cracks are discussed. With the advent of large and fast computing power, it is possible to adopt numerical methods such as elastic-plastic finite element analysis to carry out parametric study from the viewpoint of design estimates. Researchers worldwide have carried out both two and three dimensional numerical simulation of crack closure phenomenon. The effect of constraint variation across the thickness on crack closure levels are better appreciated with three dimensional analysis. The authors have also contributed in this direction by carrying out both two and three dimensional numerical studies. The results of numerical analysis are compared with fractographic data obtained from a series of specially designed experiments. The load interaction effects on crack closure levels are numerically simulated and compared with the earlier experimental results reported in literature. For the first time, crack closure levels are estimated across the crack front under part through crack situations using three dimensional elastic-plastic finite element software. These configurations are very important in the present day, where damage tolerance concepts are used in the design of high performance aerospace and automobile components. This paper presents an overall picture of the work done in the area of fatigue crack closure and the different experimental techniques employed in the estimation of closure levels and the numerical procedures adopted in the estimation of crack closure levels