Prediction of High Cycle Fatigue Life with Variable Loading Amplitude using Thermography Method

In this article, the life of metals under fatigue loading with variable amplitude has been investigated. For this purpose, the continuum damage mechanics method is used to model the damage parameter, in which the amount of dissipated energy in each cycle per volume is known as the damage index. The damage model introduced in this article has the ability to be used in problems with variable amplitude, therefore, in this study, a specimen of Q235 steel was simulated in Abaqus software and from two subroutines UMAT and UMATHT to simultaneously extract dissipated energy in Each cycle and its corresponding temperature were used. In order to investigate the fatigue life under variable amplitude loading, Two blocks with different amplitudes have been considered. Different types have been considered for these two blocks, and their results show that the introduced damage model has a high sensitivity to the loading history and sequence; Also, there is a good agreement between the results of this research and the experimental results.