TWI Industrial Member Report Summary 641/1998
Distortion is a re-occurring and costly problem resulting from most industrial metalworking processes that employ heat, such as welding and cutting. Weld distortion, on which the focus of this report lies, is very apparent because of the concentrated nature of the heat source.
Distortion in a weldment is the result of the non-uniform expansion and contraction of the weld and surrounding base material caused by the heating and cooling cycle of the welding or cutting process. Because the expansion and subsequent contraction of the yielded material is restrained by the surrounding colder material, tensile stresses build-up around the weld combined with simultaneously generated compressive stresses in the rest of the plate. These stresses cause distortion if they exceed a certain level.
The quantification of the level of distortion that can be expected after welding has become very crucial to meet the increasingly stringent accuracy requirements for the design of any type of fabricated component or structure. Many research workers have formulated weld distortion prediction models in order to reduce the extent of practical trials required to determine actual distortion. However, none of the published models are universally applicable. This is not unreasonable, since distortion depends on too many factors to account for all of them within a simple prediction model. However, because of the large number of prediction models available, some guidance is required on the selection of appropriate models for a particular welding application. For this reason, this review of published weld prediction formulae has been carried out within the Core Research Programme of TWI. Whilst reviews have been carried out in the past, this summary differs in that it covers four types of distortion, ie longitudina
- To review simple models proposed for predicting distortion after welding.
- To provide guidance on the selection of appropriate predictive models for practical use.