Fatigue crack growth modelling by means of the strain energy density-based Huffman model considering the residual stress effect

Abstract

In this research work, the modelling of the fatigue crack growth behaviour of the 6061-T651 aluminium alloy through the Huffman fatigue crack growth approach, based on the strain energy density from dislocations and considering the residual stress effects was suggested. The Huffman fatigue crack growth model is based on the cyclic stress–strain behaviour of the material as well as the local elastoplastic stresses and strains obtained for a distance ahead of the crack tip (x), where those stresses are related to the fatigue damage of a crack increment Δa, as calibrator parameter. The calculations of the elastoplastic stresses and strains are done using Neuber's or Glinka's approach. Two approaches supported by the Noroozi and Huffman's suggestions to consider the residual stress effects were studied and discussed. Besides, in the modelling of the fatigue crack growth behaviour, the influence of the strain energy density calculated for values of critical dislocation density driven by the highest strain amplitude specimen and the mean value of the dislocation density for the available experimental fatigue results were also considered in this investigation. A comparison between the analytical solutions based on the Neuber and Glinka rules and numerical solutions from the finite element modelling of the CT geometry was done, where a satisfactory agreement for the elastoplastic stress distributions was found. The studied critical dislocation density values do not significantly influence the fatigue crack propagation behaviour. It is also concluded that the procedure for considering the residual stress effects influences the calibration parameter, Δa, being not possible to conclude which is the better method to describe the residual stress effects.