Evaluation of low-cycle fatigue strength of structural metals

Better understanding of the multiaxial low-cycle fatigue strength of structures and/or components is important for the design of structures under severe repeated loading. Significant discrepancies exist between experimental results and currently available analytical predictions. This paper presents a method to evaluate the low-cycle fatigue strength of structural metals based on a plastic work concept. The maximum principal tensile stress is incorporated into the evaluation as a second parameter to account for the progressive failure characteristics. This proposed approach narrows the scatter band of low-cycle fatigue life predictions, and is convenient for engineering applications. The two necessary parameters in this evaluation method, the plastic work per cycle and the maximum tensile principal stress, can be obtained by experiments or by using theoretical constitutive modeling. In this study, they have been obtained through theoretical calculations and validated by experimental data. Also illustrated in this paper is a relatively simple design procedure using the proposed method.