Stochastic fatigue limits and fatigue life variability for unplasticised PVC pipes

This paper uses the random fatigue limit (RFL) model of Pascual and Meeker to address fatigue limits for PVC pressure pipes. This model differs from previous ways of describing fatigue data for PVC by recognising that the fatigue limit is a stochastic quantity rather than a single valued stress amplitude below which fatigue failures will not occur. By analysing published fatigue data, it is demonstrated that the RFL model is capable of quantifying fatigue limit variability and its influence on fatigue life variability. Moreover, the RFL model was used to illustrate the risks associated with defining fatigue limits based on small quantities of high-cycle fatigue data. In particular, it is shown that fatigue failure can occur below the mean fatigue limit and that the RFL model is capable of quantifying the probability of failure at a given level of stress amplitude.