Fatigue Crack Growth Model for Part-Through Flaws in Plates and Pipes

A fatigue crack growth model is developed to evaluate the behavior of planar elliptic flaws in structural components under cyclic loadings. The model is applied to plates with cyclic tensile load and nuclear piping under cyclic pressure loading. It is found that small flaws in plates tend to grow to a fixed aspect ratio, b/a≃0.9 (b is the through thickness direction). The trend checks well with available experimental data. For an axial part-through flaw in piping there is no fixed aspect ratio for growth. However, the flaws in piping are found to grow to a definite axial length. An evaluation is made of the applicability of the model to nuclear primary piping.