Analysis of probabilistic low cycle fatigue design curves at strain cycling

Abstract

In this investigation, low cycle fatigue tests were carried out and mechanical characteristics of three materials (steel of grades 15X2MFA and 45 and aluminium alloy D16T1), representing all possible variations of cyclic properties (fatigue, quasi-static and intermediate mode of fracture) were determined experimentally. Based on the data obtained, design curves of equal fracture probability for steels 15X2MFA and 45 and aluminium alloy D16T1 at low cycle strain-controlled loading were generated and the design curves were compared with experimental data. Analysis of calculated and experimental low cycle fatigue curves constructed according to the fracture probability parameter, revealed that the use of analytical relationships for lifetime assessment of structures may lead to an error and decreasing safety margin. It is recommended to use experimental 50% fracture probabilistic curves in lifetime assessment of power equipment structures.