LARGE-SAMPLE SIZE EXPERIMENTAL INVESTIGATION ON THE STATISTICAL NATURE OF FATIGUE-CRACK INITIATION AND GROWTH

A statistical investigation of the fatigue crack initiation and growth process is conducted in this paper. A total of 102 replicate constant -amplitude crack initiation and growth tests were designed and carried out on Ly12-CZ aluminium alloy. According to the post-mortem fractogr aphic examination by scanning electron microscopy (SEM), some qualitat ive observations of the spatial correlation between fatigue striations are developed to reveal the statistical nature of the intrinsic mater ial inhomogeneity during the crack growth process. From the experiment al data, the distributions of crack initiation life Ni and growth life N-g are found to be accepted as log-normal distributions, and the sta tistical characteristics of crack growth rate da/dN are also investiga ted. All of these results would be able to provide solid test foundati on for the study of probabilistic fatigue, probabilistic fracture mech anics, fatigue reliability and its engineering applications.