Thermo-Mechanical FE-Analysis of Heat Flow and Residual Stresses Distribution in Butt Welding

Abstract

In most of the Aerospace industries, welding play a vital role in joining process. Many of the structures presently built in space rockets, deep diving submarines and very heavy containment vessels for nuclear reactors could not have been constructed without the proper application of welding technology. It is well known fact that during welding the metal at the welding zone gets melted and then solidifies, which accompanies shrinkage in all directions. Residual strain and stress distributions coming from shrinking are largely influenced by the configuration of the welding process, metallurgical characteristics of weld and the geometrical shape of the welded joint. The material characteristics are mainly depends on the thermal history cycle through which the specimen undergoes. So these thermal history cycles have to be known in order to get a better knowledge of the phenomenon and to minimize the risks of failures. This work describes the detailed finite element simulation procedure for determination of heat flow pattern and residual stress for aluminium alloy during welding. In this Modified Double Ellipsoidal Distribution Pattern was modeled and considered for the weld pool design. Elasto-plastic material properties at various temperatures were also considered for the analysis. Transient thermal histories at various points were determined to obtain the cooling curve and cooling rate and compared with the theoretical values. From which metallurgical characteristic of the material at the weld zone and heat affected zone can be obtained during welding process. The problems of distortion and residual stress are also carried out. The transient stress and distortion plot were obtained from the FEM results. A customized programming was developed for the welding simulation.