Simplified Method for Profiling Residual Stress Distributions in Plate and Pipe Components

A comprehensive review of through thickness transverse residual stress distributions in a range of as-welded and mechanically bent components made up of a range of steels has been carried out. The geometries consisted of welded pipe butt joints, pipe on plate joints, tubular Y-joints, tubular T-joints and T-plate joints as well as in cold bent tubes and pipes and the collected data cover a range of engineering steels including ferritic, austenitic, C-Mn and Cr-Mo steels. Measured residual stress data, normalised with respect to the parent material yield stress, have shown a good linear correlation versus the normalised crack depth (of upto half thickness) of the region containing the residual stress resulting from the welding or cold-bending operation. The proposed simplified generic residual stress profiling based on a family of linear distribution lines, derived from the mean statistical linear fit of all the analysed data, is shown to provide different levels of conservatism on the calculated stress intensity factors. Whereas the profiles in assessment procedures are fixed and case specific the proposed linear method can be varied by a combination of mean and bending shifts from the mean regression line to produce lower or higher safety factors on stress intensity factor values depending on the level of safety required.