8 - Mitigating welding residual stress and distortion

Abstract

This chapter discusses that residual stress is defined as any stress that would exist in a continuum body if all external loads were removed. Welding residual stresses occur in a structure because of the thermal stress developed by a non-uniform temperature distribution during welding, followed by plastic deformations. The corresponding distortions are in turn caused by the residual stresses. During arc welding, the welded piece undergoes complex temperature changes. The non-uniform temperature distribution along a continuum body causes thermal stresses and non-elastic strains. Many researchers and engineers have tried various techniques to quantify residual stresses analytically, numerically, and experimentally. The chapter discusses methods to control, or even to mitigate, weld-induced residual stresses and distortions. The chapter discusses welding-induced distortion control techniques, weld design optimization, pre-straining, optimum welding sequence and pre-cambering using simple examples. It is emphasized that computational fabrication models have emerged to the point that they are an important tool to the weld designer. By using the software, the optimum distortion control parameters could be obtained from the computer simulation. Therefore, the welding operation cost and prototype period can be reduced and the integrity of welded structures can be improved.