State-of-the-art review on fatigue crack growth analysis under variable amplitude loading

Load bearing structural components of bridges, offshore platforms, aerospace and ships are subjected to variable amplitude loading (VAL). The remaining life prediction performed under constant amplitude loading differs significantly from VAL Load interaction or sequence effects under VAL influences the fatigue crack growth rate and consequently, the remaining life. This paper discusses the various load interaction effects on fatigue crack growth and remaining life. The available mechanisms/factors contributing to crack growth have been explained. It is observed from the literature that the compressive residual stresses ahead of the crack tip and the plasticity induced crack closure are the primary causes for retardation while other mechanisms are the secondary causes for retardation. A state-of-the-art review of available fatigue crack growth models under VAL has been presented highlighting the merits and limitations. It is further observed that most of the crack growth models under VAL require one or more calibration parameters or curve fitting constants to conduct crack growth analysis. It is felt that the models need to be more generalized in order to use them for the realistic loading situations straightaway.