Applied modelling techniques for welding induced distortions and residual stresses

Abstract

Prediction of residual stresses and distortion induced by welding is relevant to many industries involved with the manufacture and assembly of thin plate structures. The ability to predict these unwanted effects on such structures subjected to welding processes is important to minimise costs associated with rework and other corrective actions. The main challenge is to model the complex and at times indeterminate nature of the welding process, preferably in a simple and transparent manner. The present work dealt with the development, validation and application of advanced simulation techniques for the prediction of welding induced residual stresses and distortions. Current literature presents a wide-ranging number of approaches, which vary in complexity and purpose, but at times fail to present a clear methodology for numerical based analysis. In the current work a commercial finite element software package was used to develop thermo-elasto-plastic models suited for this application. The proposed methodology was developed by initially analysing simple set-ups, validated through the use of experimental measurement techniques for both residual stresses and distortions predictions. This provided confidence in the application of the numerical models, which were then used to investigate more complex cases of particular interest to the shipbuilding industry. This part of the project dealt with ancillary operations, namely the initial application of tack welds and restraints on the structure, for which little attention is usually given due to their apparent insignificance compared to the final welding process. Their effects are in fact substantial and were investigated by using the thermo-elasto-plastic models together with experimental trials. A better understanding of their influence was hence illustrated, providing a basis for the establishment of a best industrial practice.