Abstract: There are two main shortcomings with the Miner cumulative damage theory. One is its linear cumulation of fatigue damage that the cumulative damage changes owing to loading series cannot be taken into account,and the other is its indeterminacy that the scatters caused by external scatter of loading and the inherent scatter of materials cannot be included. In this paper, the sources of scatters of Miner cumulative damage D i are discussed,and then an analytical method which attempts to overcome the two shortcomings is presented. Theoretical analysis and Monte Carlo numerical calculation show that Miner cumulative damage D i can be described by lognormal distribution.

Key words: Miner theory, stochastic loading, internal distribution, external distribution, MonteCarlo simulation.