A new technique for three-dimensional transient heat transfer computations of autogenous arc welding

Three-dimensional (3-D) transient temperature variations during autogenous gas tungsten arc welding are determined. The heat diffusion equation is solved using an efficient semidiscrete technique. The model employs a combination of unequally spaced grids concentrated near the moving torch in order to minimize the total number of nodes. Finite differencing is used for the spatial terms. The resulting ordinary differential equations for the transient evolution of thermal transport are solved using the fourth-order Runge-Kutta technique. The temperaturedependent thermal properties and latent heats of phase transformations are accounted for. Computations are carried out for a rectangular parallelepiped with convective and radiative surface thermal conditions. Sample results are presented first for the evolution of thermal profiles during ideal welding conditions. These are next compared with variations obtained due to defects, such as weld track misalignment and inclusions. The potential use of this model in the development of an expert welding system using infrared imagery is indicated.