Fatigue crack growth and closure behaviour of semicircular and semi-elliptical surface flaws

Abstract

The growth behaviour of semi-elliptical and semicircular cracks subjected to crack extensions due to tensile constant amplitude loading ( R = 0.1) was investigated using a three-dimensional elastic-plastic finite-element analysis of fatigue crack growth and closure. Based on this analysis, for both semicircular and semi-elliptical meshes, the crack first closed on the exterior (free) surface ( θ = 0°) and then closed towards the interior region upon further unloading of the cyclic loading. The closure and opening behaviour of crack surfaces for both semicircular and semi-elliptical geometries are investigated. An experimental investigation of semi-elliptical flaws under fin spectrum loading was conducted to simulate realistic growth rate behaviour for the semi-elliptical geometry.