Computational modelling for rapid creep life assessment and post-critical behaviour

摘要

In this paper a macroscopic modelling of creep behaviour is proposed. Back-stress models within unified formulation are used for numerical simulations of primary and secondary creep periods, associated with a scalar damage variable and nonlinear geometrical effects for tertiary creep description. These models have been implemented in finite element code. We will describe different modes of damage development and we will verify the very different early crack growth behaviour exhibited by different structures. For the numerical treatment, we propose to use the LATIN method in a version adapted to solve problems with geometrical nonlinearities. This method describes primary and secondary creep periods in a few large time increments to reach swiftly the tertiary creep period. If creep life assessment or creep strains evolution are the aims of a study, the LATIN method allows us to obtain a rapid solution to the problem in a few time increments with a reduction of the number of global resolutions. In this case we can stop the calculations when the beginning of the tertiary creep period is displayed, with a small error on the creep life assessment. If we want to know the post-critical behaviour, the calculations are possible because of the stability of the models which allow us to continue these calculations in order to describe the tertiary creep period and the patterns of damage evolution for a large range of components.