Effect of the mean strength on the endurance limit or threshold value of the crack growth curve and two-dimensional joint probability distribution

Abstract

Two new phenomenological expressions for generalized constant-life curves are developed on the basis of a traditional fatigue constant-life curve. Parameter estimation formulae of the generalized constant-life curve are obtained from the standard procedure for regression analysis. From the generalized constant-life curves proposed, two-dimensional joint probability distributions of generalized strength are derived. Finally, the methods developed are used to analyse three sets of experimental data pertaining to the two-dimensional up-and-down tests for LY11 aluminium alloy and fracture threshold tests for aluminium alloy and alloyed steel in order to verify the practicability and validity of the new approaches. These matters have an important role in fatigue and fracture reliability analysis in ultra-long-life regions and need to be resolved.