Three-dimensional finite element modeling of gas metal-arc welding
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I.
INTRODUCTION
ARC welding is one of the oldest and fastest growing metal-joining processes. It has applications ranging from joining thin sections, pipelines, e t c . to joining most large metal structures such as bridges, farm equipment, cars, trains, nuclear reactors, e t c . Yet, advanced arc welding has been developed mostly by experience rather than by understanding its science. The difficulty is caused by a rather complex, nonlinear conductive, convective, and radiative nature of heat flow in the workpiece caused by the localized intense heat input of the process. This gives rise to distortion, residual stress, and reduced strength of a structure in and around a welded joint. Thus, an accurate analysis of the weld thermal cycle is important for predicting soundness of welds. The mathematical theory of moving sources of heat seems to have been derived by Wilson ttl but was first applied by Rosenthal and co-worker ~2,3jto arc weld problems. Thereafter, many investigators tried to relax the assumptions taken by Rosenthal. I3l Tsai E41used a skewed Gaussian heat source. Ghent e t al. ~5~ considered heat of fusion, and Grosh e t al.[61 tried to incorporate temperature dependence of thermal conductivity and specific heat in their weld thermal models. These considerations were still too idealistic. With the advent and widespread use of computers, numerical methods have become strong tools in the hands of practicing engineers. Both finite difference fT-l~ and finite element r~M6J techniques have been applied for the solution of heat-transfer equations defining weld thermal cycle. Although many investigators have simulated the gas-tungsten arc welding process, t8,9,!1.13.t4,~61the literature on numerical treatment of the gas metal-arc (GMA) welding process is scarce. The foremost difficulty encountered in the simulation SUBODH KUMAR, Research Scholar, and S.C. BHADURI, Assistant Professor, are with the Department o f Mechanical Engineering, Indian Institute of Technology, Powai, 400 076, Bombay, India. Manuscript submitted December 9, 1992. METALLURGICAL AND MATERIALS TRANSACTIONS B
of the GMA welding process is related with various metal transfer mechanisms occurring at different welding parameters. For example, at lower values of current (
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