FATIGUE DAMAGE MODELLING AND FINITE ELEMENTS ANALYSIS METHODOLOGY: CONTINUUM BASIS AND APPLICATIONS

摘要

The mechanical phenomena known as fatigue produces a loss of material strength as a function of the number of cycles, load amplitude, reversion index, etc. This loss of strength induce the material to inelastic behaviour, micro-cracking followed by crack coalescence, leading to the final collapse of structural parts. In this paper, a mechanical constitutive model for the predictions of fatigue in structures using the finite element method is formulated. The model is based on the damage mechanics of the continuous medium and allows the treatment of coupled phenomena such as fatigue with damage and plasticity. The basis of the continuum mechanics formulation and the necessary modifications to include the fatigue phenomena are described. S-N functions are proposed depending on and capable of dealing with any value of the ratio between minimum and maximum stress. A two-stage time advancing strategy is proposed in order to allow a fast progress in the analysis. The efficiency and accuracy of the proposed model are validated through the fatigue analysis of industrial components. Numerical values from the analysis are compared with experimental testing results.