Numerical Analysis of the Influence of Crack Growth Scheme on Plasticity Induced Crack Closure Results

Plasticity Induced Crack Closure (PICC) has been studied by means of finite element method for a long time. Most of previous work was developed considering bi-dimensional models. During last years, the use of three-dimensional models has been extended. Nevertheless, the methodology employed has been inherited from bi-dimensional analyses. Many previous bi-dimensional analyses studied different numerical parameters and optimized them. Present computational capabilities allow a comprehensive study of the influence of different modelling parameter in a similar way to those bi-dimensional analyses. Moreover, the influence of these parameters on the obtained results along the thickness can be taken into consideration. In particular, one of the key issues is related to the crack growth scheme. A fatigue analysis implies a crack growth. Each change in loading and boundary conditions implies solving a nonlinear problem. It is not feasible to consider all the cycles involved in a real fatigue problem when running a finite element analysis. The computational cost is not acceptable. In the present work, a CT aluminium specimen has been modelled three-dimensionally and several calculations have been made in order to evaluate the influence of the number of load cycles between node releases. The results are analysed in terms of crack closure and opening values.