Simplified method to predict fatigue crack growth life by combining finite element method and Willenborg’s model

Abstract

Among various cold expansion methods, Split Sleeve Cold Expansion technique is widely used. This method induces a zone of compressive residual stresses by pulling an oversized mandrel followed by removal through the hole. An appropriate amount of compressive residual stress reduces the severity of tensile stresses acting on the components there by retarding the fatigue crack growth rate or extending the service life of the components. It has been observed that either extensive testing or special computer codes (AFGROW) are required to determine fatigue crack growth life around residual stress fields. There was no generalized procedure to predict fatigue crack growth life around residual stress fields of cold expanded holes. An attempt has been made in this work to develop a systematic, simplified method to predict fatigue crack growth life around cold expanded holes by combining finite element method and Willenborg’s model. This method was in very good agreement to the classical approach and the variation of predication of fatigue crack growth was about 5.77% compared to the classical approach. The outcome of this work is the development of a systematic and simple procedure for predicting fatigue crack growth life around cold expanded fastener holes. This procedure helps in recommending appropriate inspection intervals and extending the service life of fatigue prone fastener holes.