Analysis of welding conditions based on induced thermal irreversibilities in welded structures: Cases of welding sequences and preheating treatment

Preheating treatment and employing a proper welding sequence are introduced as two efficient approaches for reducing residual stresses in welding processes. Selecting a right welding sequence and a proper preheating temperature for a weld system are crucial tasks, since welding residual stresses are inevitably produced in a welded structure. However, obtaining residual stresses is very complex, and much time is needed in some cases, particularly for the modeling and prediction of residual stresses in welded structures. So in this work, we attempt to show that these stresses depend on generated entropy during the arc welding process. Thus by obtaining thermal irreversibility effects from temperature distribution, due to a variation of different welding parameters, selection of optimum factors to achieve minimum residual stress is not only possible, but easier to undertake. In the proposed method, it is not a necessity to obtain residual stress values, and one can predict the behavior of residual stress qualitatively. To do so, 3D numerical models are employed to study the similar behavior of created residual stresses and entropy due to a variation of different preheating temperatures and three common welding sequences.