Residual stresses are generated in engineering structures and components as a consequence of the welding process and are an important consideration in structural integrity assessment. Compressive residual stresses can have a beneficial effect on structural integrity, inhibiting crack propagation and enhancing fatigue life, but tensile residual stresses generally have an adverse effect on brittle fracture, corrosion properties and fatigue performance. The consequences of residual stress effects on structural integrity may be significant as residual stress levels can reach the yield strength of the material, particularly for offshore installations which are subject to severe loading arising from the harsh operating environment.
Published experimental data from residual stress measurements are generally limited and experimental data for offshore welded joints are rather scarce. Increased knowledge of the magnitude and the distribution of through-wall thickness residual stresses in offshore structures can help the offshore industry gain more understanding and confidence in the structural integrity of critical components.
TWI carried out a comprehensive study of residual stresses in offshore girth-welded joints. It included a brief literature review, through-wall thickness residual stress measurements in 16-inch and 20-inch diameter pipes, numerical modelling of residual stress profiles, determination of an upper bound expression for the throughthickness residual stress distribution for girth welds based on the revised database and assessment of the impact of the results on structural integrity assessment.
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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