Local strain computation of crack initiation life of an unstiffened steel tubular T-joint

Abstract

This paper presents the results of the fatigue crack initiation life estimation for offshore tubular welded joints. The results are obtained by using the fatigue strength exponent, b, and fatigue ductility exponent, c, computed by a backcalculation procedure from an extensive experimental crack initiation estimation of both small scale and medium scale welded steel tubular joints. A general purpose finite element package, ABAQUS, was used for the stress analysis. This allows for the accurate determination of the critical location where the crack/cracks is/are likely to initiate. From the stress analysis, the stress and strain concentration factors (SCF and SNCF) along the intersection of the tube were obtained. The peak SCF and SNCF were used in modified Neuber's rule and the result introduced into a Manson-Coffin model for crack initiation life computation. The results obtained were compared with the experimental results previously obtained at the Canadian Cooperative Fatigue Studies Program.