A Practical Procedure for Predicting the Remaining Fatigue Life at an Arbitrary Stress Ratio

A practical procedure for predicting the remaining fatigue life at an arbitrary stress ratio is developed and verified. The procedure was based on the validated damage function, in conjunction with the Kim and Zhang S-N curve model. The damage function was used for finding various iso-damage points dependent on three independent variables (i.e., stress level, number of fatigue cycles, and stress ratio). The verification was conducted using Alclad 24S-T aluminium alloy, available in the literature for fatigue loading varied under three different loading schemes. The first scheme was for two different stress ratios, the second was for three different stress ratios, and the last was for a single stress ratio as a special case. The prediction accuracies were found to be in an error range of −0.1 to 5.6%, −0.5 to −0.6, and 1.5 to 1.7% for the 1st, 2nd, and 3rd schemes, respectively.