Investigation of Fatigue Crack Propagation in Line Pipes Containing an Angled Surface Flaw

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In the present paper, an investigation of fatigue crack initiation and propagation in line pipes containing an inclined surface crack is presented. The inclined angle of the surface crack with respect to the axis of loading varies between $0deg$ and $90deg$⁠. Based on the concept of the effective stress intensity factor range $Δkeff$⁠, the rate of fatigue crack propagation $db∕dN$ is postulated to be a function of the effective strain energy density factor range $ΔSeff$⁠. This concept is applied to predict the crack growth due to fatigue loading. Furthermore, the threshold condition for nongrowth of the initial crack was established and assessed based on the experimental data.