In the experimental study of fatigue crack closure and growth behavior under random loading, the history length of random loading should be long enough that any closure effect from randomly occurring tensile peaks dies out before the block repeats itself. So, in this study fatigue crack growth tests under random loading of long history length are performed and the behavior of crack closure and growth is investigated. In particular, the effect of band-width characteristics and history length of random loading on the behavior of crack closure and growth is discussed.
Results show that the crack opening point under random loading of long history length is also nearly constant within a block of random loading and the fatigue crack growth under random loading of long history length can also be well explained in the crack closure phenomenon. The effect of band-width characteristics and history length of random loading is not observed clearly. But, in case of narrow-band Gaussian loading when it's history length is longer, the possibility of non-conservative prediction in prediction using the measured crack opening point may exist.
