Abstract
A study was carried out to investigate the influence of the weld toe radii on the fatigue strength of butt welded joints loaded in bending and tension. Fatigue analysis starting from weld toe cracks in marine and offshore welded pipe specimens were conducted using cut-out four-point bend fatigue test specimens. Fatigue life can be enhanced by reducing the local stress concentration generated by weld toe radius effects. This study investigated the effect of different weld toe radii on the stress intensity factor at the region of the weld toe through Finite Element Analysis (FEA). FEA was used to model a butt welded steel plate extracted from a pipe subject to tension and four-point bend loading. Semi-elliptical surface (SESC) cracks were modeled at the weld toe region with different SESC crack depth and surface crack length. Four weld toe radii and two modes of loading were investigated. The stress intensity factors, weald toe magnification factors, or Mkc and Mka are reported and used for fatigue life prediction.
Highlights
With the complex nature of dealing with welds in marine and offshore structures, it is essential to understand the fatigue life prediction research of welded joints better
2.1 Methodology XFEM was used in this study to produce a finite element model of the crack, to investigate the effect of different weld toe radii on the Mk factors
The fatigue life prediction is conducted through a C++ program developed called Fatigue Crack Growth Analysis (FCGA) software
Summary
With the complex nature of dealing with welds in marine and offshore structures, it is essential to understand the fatigue life prediction research of welded joints better. This study only allows for the assessment of stress intensity factors for the deepest point of the semielliptical crack, with no mention of the effect of the weld toe radius on the crack ends. Improving on Niu and Glinka’s weight function, Brennan et al [7] conducted a study to generate parametric equations for T-butt weld toe stress intensity factor, which took into account the weld toe radius effect, among other factors. The methodology employed the usage of twodimensional finite element analysis to evaluate the stress distribution caused by the opening of the crack, before using that as an input into a weight function solution for determining stress intensity factors. This work will investigate the influence of the weld toe radii on the Mkc and Mka factors for butt welded joints loaded in tension and bending. This allowed for a faster computational time and accuracy was calibrated with SIF solutions reported by Newman and Raju [12]
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