FATIGUE CRACK INITIAITON AND PROPAGATION LIFE OF STEELS PREDICTED BY LOCAL ELASTOPLASTICITY RESPONCE

Abstract

Fatigue damage process is generally divided into two stages, fatigue crack initiation and propagation. Stress intensity factor or J-integral are usually used for driving force of fatigue crack propagation. Various assessment methods for fatigue crack initiation life have been proposed, and the authors have recently proposed an assessment method for fatigue crack initiation life utilizing elasto-plasticity FEM analysis adopting the material model which can describe cyclic hardening or softening. If it is possible to assess the fatigue crack initiation and subsequent propagation which strongly depend on elasto-plastic response of material under the same numerical analysis framework, it is useful to understand the detailed mechanism of fatigue damage process. The purpose of present study is to propose a method which can evaluate the fatigue crack propagation behavior by extending the assessment method for fatigue crack initiation life, and consider the accuracy of its evaluation.