抄録
Fatigue crack propagation tests were carried out under two kinds of programmed random loadings to investigate the effects of variations of mean load and compressive peak load on fatigue crack propagation rate and crack closure. Crack length and crack closure were measured by using the unloading elastic compliance method with the aid of a mini-computer.
The crack opening point was affected by the variation of mean load and took a different value from that of stationary random loading without variation of mean load. This value was found to depend not only on the maximum range-pair of the stress intensity factor and its stress ratio but also on the block size of random loadings. It was also found that the periodic compressive peak load lowered the closure level and caused the acceleration of crack propagation.
The validity of the linear accumulation law of crack propagation in terms of the effective stress intensity range-pair was confirmed for the estimation of fatigue crack propagation rate under the programmed random loading conditions investigated in this study.
