Abstract
In recent years, fatigue limit estimation based on energy dissipation has been attracting considerable attention. In this method, temperature change due to irreversible energy dissipation is measured by infrared thermography in various levels of stress amplitude, under cyclic loading. It is experimentally observed that dissipated energy increases with increasing stress levels, and that there is a certain stress level where the dissipated energy undergoes a sharp increase, which has been proven to coincide with the fatigue limit in certain BCC and FCC metals. In this study, this method was applied to an HCP metal, AZ31B magnesium alloy. Fatigue limit estimation based on dissipated energy and conventional fatigue test are conducted on two types of AZ31B magnesium alloy; rolled and extruded material. The estimated fatigue limit obtained for rolled AZ31B agrees well with results from conventional fatigue tests, with fatigue strength at N=10^7. The dissipated energy showed the two characterisitic changes for the plastic strain energy. It was considered that these changes imply twinning and slip deformation restated to fatigue damage, respectively.
