Analytical and computational investigation into the influence of the compressive stress cycles on crack growth under variable amplitude loading using CTOD. (17th January 2014) - Iranpour, M.
ABSTRACT Fatigue crack growth rate of 6061 T651 aluminum alloy centre‐cracked plates, subject to a variable amplitude loading (VAL), is established using a coupled analytical/computational approach. The method utilises the generalised Willenborg retardation model in conjunction with the Walker model, with several of the models parameters obtained through nonlinear finite element analyses. A two‐parameter approach is also used in this study to explore the influence of compressive stress cycles in a VAL scenario on the crack tip opening displacement, and in turn, on the resulting fatigue crack growth rate of the material. The work includes the evaluation of the crack tip opening displacement and residual stresses in the vicinity of a crack by nonlinear finite element analysis, and application of the Generalised Willenborg model to evaluate the fatigue crack growth; particularly, under the influence of the compressive stress cycles, tensile overloads and underloads have been investigated. The finite element analysis results are compared with the experimental results reported in earlier studies by the authors. The results further demonstrate two important phenomena, that is, (i) the influence of FCG retardation effects due to the tensile overloads and (ii) the acceleration effect due to the applied compressive underloads of a VAL stress–time history.