Examination of asperity-induced crack closure

The crack closure effects on fatigue crack growth are evaluated by both theoretical and experimental approaches. The theoretical approach is based,asperity with finite width near a crack. The analysis indicates that asperity-induced crack closure cannot be ignored even though it is less than conventional estimation. The experimental results of fatigue crack growth in sintered steel show that the crack closure however cannot be fully responsible for observed increase of fatigue resistance with low stress ratio, R. Experimental results support that both K-max and DeltaK control near threshold crack growth.