Fatigue damage and crack growth under variable amplitude loading with reference to the counting methods of stress-strain ranges

Experimental studies, carried out by the author and colleagues in order to gain a fundamental understanding of the effects of load variations on fatigue damage and crack growth, are extensively reviewed. Plastic strain cycling and the effective stress intensity factor range were monitored; these being the most important parameters for fatigue damage accumulation and fatigue crack growth, respectively. The behaviour of both these parameters is discussed in detail. It was confirmed that the range-pair counting or the rain-flow counting method should be employed when estimating fatigue lives under variable amplitude loading.