The role of crack tip deformation in fatigue crack growth

This paper is a synopsis of some of the authors' work on the role of crack tip deformation in the behaviour of mode I fatigue cracks under cyclic loading. That problem was investigated both numerically and experimentally. A dynamic elastic-plastic finite element technique was developed and utilised to simulate cyclic crack tip plastic deformation. Cracks with bath stationary and artificially advancing tips were analysed. Different idealisations were investigated. Based on the numerical analyses, a crack tip deformation parameter was devised to correlate fatigue crack growth rates. This parameter can correlate and predict some experimentally observed phenomena relevant to physically long and short cracks under both constant and variable amplitude loading of simple patterns with different cycle parameters. Some three-dimensional experimental data of the growth behaviour of a long crack in a thick plate were also predicted.