Elementary Modes Method for Evaluating SIFs Along Fronts ofSurface Cracks at Weld Toes

Lu Yanlin, Zhang Shujia, Yu Zhiqing
(College of Mechanical & Electrical Engineering, Zhejiang University of Technology, Hangzhou, Zhejinag 310014, P.R.China)

Abstract: A practical procedure, which is referred to as elementary modes method, was prop osed for evaluating stress intensity factors (SIF) along fronts of semi-elliptical surface cracks at weld toes in complex stress fields. Distributions of SIFs along crack fronts for 27 elementary geometries of semi-elliptical surface cracks at weld toes, which are combinations of parameters £Ô£±/£Ô£¬a/£Ô   and  a/c,   subjected to 8 kinds of selected elementary stress modes were analyzed by 3-D finite element method, and a database was thus built. SIF distributions for general geometries in complex stress fields can be calculated through interpolations and linear combinations of these elementary solutions. The surface effect of thickness ratio of fillet welded joints on SIF distributions can be taken into account. The procedure is very simple and fast. The method is especially suitable for fatigue analysis.
Keywords: stress intensity factor, semi-elliptical surface crack, welded joint, elementary modes method, fatigue.