The significance of weld imperfections and surface peening on fatigue crack propagation life of butt-welded joints

This study describes the influence of various weld imperfections (solidification crack, undercut and porosity) on fatigue crack propagation life due to combined axial and torsional fatigue loading. The stress intensity factors for different weld imperfections have been calculated by finite element method. The fatigue crack propagation life has been calculated using fracture mechanics approaches. It has been found that the weld imperfections significantly reduce the fatigue crack propagation life of welded joints and the torsional loading accelerates the initiation of fatigue crack significantly. The tensile residual stress, bending stress, torsional shear stress and dissimilar mechanical properties of base, weld and heat-affected zone (HAZ) metals also decrease the fatigue crack propagation life. However, the surface peening produces limited improvement in the fatigue strength of welded joints and the torsional load eliminates the greater pan of the benefit. For the validation of the prediction, the results have been compared with available experimental data from the literature. A good comparison has been found between predictions and experimental results. (C) 2004 Elsevier B. V. All rights reserved.