Temperature change and fatigue crack initiation associated with local cyclic slip deformation in a single crystal material

Abstract

Evaluating the fatigue limit by measuring temperature changes via infrared thermography has attracted significant interest because of its potential for rapid assessments. However, the physical background and validity of this technique are not yet fully understood. In this study, notched specimens of a single crystal Ni‐base superalloy with different crystallographic orientations are subjected to cyclic loading to investigate crack initiation and temperature change. Local slip deformation is quantified using crystal plasticity finite element analyses. It is found from the experimental and analytical results that the distribution of the temperature change and the local slip deformation (a plastic shear strain on the most active slip system) are affected by the crystallographic orientation. However, the correlation between the plastic shear strain and the second harmonic amplitude, as well as the threshold values of these parameters for crack initiation, is independent of the crystallographic orientation.