Microstructural Simulation of Damage and Crack Growth Due to Low Cycle Fatigue After Severe Plastic Deformation of 7075 Al Alloy

In this paper, the prospects of microstructural fatigue crack growth (FCG) simulation are investigated considering the elastic-plastic behavior of grains and boundaries. For this purpose, a finite element (FE) model incorporating the microstructure of the material is developed. Equal channel angular pressing is performed on 7075 Al alloy, and tensile tests are carried out. Besides macro-hardness tests, micro-indentation is also committed to assess the mechanical properties of grains and boundaries. In addition to relations between the hardness and the strength in macro mode, backward simulation of micro-indentation has been carried out to obtain stress-strain curves using hardness of grains and boundaries. The acquired microstructural behaviors have been used in microstructural modeling. The metallographic images are used to create a representing volume element, and then, the FE-predicted stress-strain behaviors for grains and boundaries are verified using microstructural simulation of the tensile test. Then, microstructural modeling of the FCG test has been performed using the approved FE model. Comparison of experimental and FE crack length indicates acceptable accordance of experimental, and FE results in predicting fatigue crack growth rate.