Fatigue Damage Calculation Using the Critical Plane Approach

Abstract

The critical plane approach is applied to model material fatigue behavior under any constant amplitude proportional loading. The most critical plane and the largest damage parameter are determined in closed form for six damage criteria that have been proposed in the literature. The correct procedures of utilizing these closed-form solutions to construct the damage parameter versus fatigue life curve are outlined. It is shown that the common practice of characterizing the material’s fatigue behavior by plotting the damage parameter evaluated on the maximum shear plane against the observed fatigue life violates the principle of the critical plane approach, a problem which can arise during the calibration of any biaxial type of damage criterion. The study emphasizes that the critical plane approach should be consistently applied to both the initial calibration and the subsequent fatigue analysis.