Analysis of weld toe radius effects on fatigue weld toe cracks

Abstract

Stress analysis of as-welded and weld toe ground fillet welded joints was carried out for four different weld toe radii (0·5, 1·0, 2·5 and 5·0 mm). This provided the stress distributions through the thickness of the plate and the stress concentration factor was determined by extrapolation to the weld toe surface. Closed form stress distribution equations were curve-fitted to the finite element results. Stress intensity factor computations for weld toe cracks were carried out using a weight function method and finite element techniques. Short weld toe cracks with crack depth to plate thickness ratios between a T = 0·001 and a T = 0·1 , were modelled and analysed for the weld toe radii of 0·5, 1·0, 2·5 and 5·0 mm. For the finite element analysis a virtual crack extension method was employed in computing the linear elastic J-integral and the average value for three contours was used to calculate the stress intensity factor. The stress intensity factor is presented as a stress concentration magnification factor (Mk) multiplied by the basic crack geometry for a single edge cracked plate (SECP). This was employed in a fatigue crack propagation analysis where the fatigue endurance curves were evaluated.