It is extremely difficult to measure the strain energy dissipated in each loading cycle, especially when the material suffers from low cycle fatigue under plastic strain. This paper attempts to simulate the dissipated strain energy of aluminum alloy 6061-T6 induced by the low cycle fatigue under an imposed plastic strain. Hence, an ANSYS numerical simulation was performed on the low cycle fatigue permitting to generate the hysteresis loops at failure of each cyclic plastic strain imposed on aluminum alloy 6061-T6. The area of the hysteresis loops was adopted to measure the dissipated strain energy. The simulation results show that the energy dissipated during loading gives a good measure of a material's residual strength, stiffness and capacity to resist further loading.

The residual stresses which result from the manufacture are present in the mechanical part with absence of any external force, but also they can be generated by various procedures. These stresses are the result of incompatibilities of deformation related to the heterogeneity of the plastic strain. Therefore, as the crack propagated in the residual stress field, the distribution of residual stresses is changed. The purpose of this work is to generate the thermomechanical residual stresses on along direction of crack propagation using a numerical simulation by Ansys software. This numerical approach allows us to evaluate the thermomechanical relaxation of the compressive residual stresses induced by plastic strain at crack tip.