Parameter C lifetime calculation for the high cycle regime

Abstract

ABSTRACTAn analytical fatigue lifetime prediction using the nominal stress concept and the Palmgren‐Miner‐Rule is performed. A comparison of prediction and experiment shows a large uncertainty. Miner‐Rule modifications have been developed to improve the fatigue lifetime prediction. Stress amplitudes below the fatigue limit are assumed to contribute to the damage at different ratings.The modifications have a significant influence on the predicted fatigue lifetime especially in the high cycle regime. When the maximum stress value is just above the fatigue limit, this influence is most significant. Because there are not many test results of variable amplitude loads available for the high cycle regime, a verification is difficult.In the present paper a new modification for the lifetime prediction is applied. The modification was introduced in 1988 by Hück and suggests a variable slope of a reference S–N‐curve for the damage accumulation. A parameter C and the relation between the maximum stress value of the load spectrum distribution and the fatigue limit determine the slope of the reference S–N curve.The aim is to characterize the influence factors of the parameter C using test results for the high cycle regime achieved on a new test facility and from published test data. This would lead to an improvement of the lifetime prediction in the high cycle regime.