Reduction of residual stresses and distortion in girth welded pipes

Abstract

Conventionally, welding control has been used to assure that the quality of the weld itself is maintained. Residual stresses and distortion result from the non-uniform temperature distribution which form the weld process. In this thesis, an investigation into the reduction of residual stresses and distortion is performed. Potential benefits of reducing these include prevention of stress corrosion cracking, fatigue, brittle fracture and collapse strength. In an attempt to reduce residual stresses and distortion, a hydraulic restraining device was designed, constructed and tested. It was then compared to several other methods being investigated. This hydraulic restraining device is very effective in reducing the radial contraction. Although it also reduces the residual stresses, it does not change them from tensile to compressive as some of the other methods do.