Fatigue fracture surface metrology of thin-walled tubular austenitic steel specimens after asynchronous loadings

This paper aims to study the effect of asynchronous axial-torsional strain-controlled loading histories on fracture surface behavior of thin-walled tubular X5CrNi18-10 (304/304L) austenitic steel specimens. Tests under pure axial loading and pure torsional loading are also conducted to better segregate the effect of multiaxiality. The fractures surface topographies were examined through the profiles over the entire surface with the support of an optical measurement system. Then, features of the post-failure fractures were related to the loading conditions and the fatigue life. The outcomes indicate that the multiaxial loading path significantly affects the surface topography. Overall, fracture surface parameters increase for higher fatigue lives. Based on the dialectic relationship, a fatigue damage model able to estimate the fatigue lifetime under asynchronous axial-torsional loading histories has been successfully developed. The fracture surface topology parameters collected from both sides of the same specimen lead to comparable results which reinforces the applicability of the proposed approach.