Stress Intensity Factor Solution for a Naturally Emanating Crack Out of a V-Notched Round Bar

Abstract

During the estimation of Stress Intensity Factor (SIF) of a notched round bar, standard crack geometries such as elliptical, semi-circular, and straight crack fronts are commonly considered at the notch root region. In the present work, the SIF solution for a naturally initiating crack out of a V-notched round bar has been estimated experimentally and the results are compared with data obtained from 3D finite element analysis. The fractographic investigation of the fractured surface suggested a non-symmetric crack propagation and the strong influence of stress concentration factor on SIF, especially in the early stages of crack growth (up to a/d ratio of 0.15, where “a’” is crack length and “d” is notch root diameter). Four aspect ratios (a/c = 0.4, 0.5, 0.75, and 0.85, where “c” is semi-major axis of elliptical crack) and seven crack depth (a/d) ratios in the radial directions were considered with and without offset of surface crack origin to match experimental observations. It was noted that a naturally formed crack had an elliptic shape with aspect ratio of 0.75, with its center offset by 0.5 mm in an upward direction from the notch root region.