TWI Industrial Member Report Summary 942/2010
By L Wei and W He
Welding residual stresses are generated by the complex interaction between the transient heat flow during welding and the mechanical restraints of the material around the weld. It is known that welding residual stresses can reach the yield strength of the surrounding material, so engineering critical assessments (ECAs) often have to assume that residual stresses are of yield magnitude. Residual stresses parallel to the welding direction can be very high, but the values transverse to the weld are often much lower. It has also been demonstrated that the residual stresses due to welding vary with plate thickness. Hence, for many industries (eg oil and gas, nuclear, construction) it is important to develop methods for determining residual stresses through the plate thickness as well as on the plate surfaces so that realistic values may be used in ECAs, reducing the conservatism arising from the assumption of a residual stress of yield strength. It is also important to quantify the effects of various parameters on residual stress distribution (eg geometric variations, external loading and crack growth) so that appropriate considerations of welding residual stress can be given to corresponding conditions in ECAs. Clearly, as far as ECAs are concerned, all the efforts for quantification of welding residual stresses are aimed at achieving a more realistic evaluation of crack driving forces.
- Develop finite element analysis (FEA) procedures for modelling welding residual stresses and validate against measurements.
- Examine the effects on welding residual stress of geometric variations, restraints, and external static and cyclic loadings.
- Evaluate fracture mechanics parameters (K and J) characterising a crack in a welding residual stress field.