Author(s)

P. Colombi & K. Dolinski

Abstract

Markov approach to fatigue crack growth under stochastic load P. Colombi," K. Dolinski* " Department of Structural Mechanics, University of Pavia, ^ Centre of Mechanics, Institute of Fundamental Technological Research, ul. Swietokrzyska 21, PL-00-049 Warsaw, Poland ABSTRACT Under variable amplitude loading the fatigue crack growth rate to the load cycles following an overload is reduced. Under stochastic loading the retardation phases occur randomly with random intensity and duration depending on the last ran- dom overload. In the paper the load process is assumed to be stationary and its extremes are modelled as a Markov sequence. The fatigue crack growth appears to form a random sequence of retardation and post- retardation phases. The drift and diffusion parameters of a Markov approximation for the whole crack growth process are evaluated from a numerical simulation within retardation and post-retardation blocks. This mixed, numerical and analytical, approach allows us

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