A Study on Three-Dimensional Transient Heat Flow in Circumferential GTA Welding of Pipes Using Periodicity Conditions

Abstract

A transient three-dimensional finite difference mode (FDM) of the heat flow in the circumferential GTA welding of pipes was developed and applied to calculate the temperature distribution in the workpiece. In order to minimize the computing time required for solving the FDM equations as much as possible, the alternating direction implicit (ADI) scheme which makes use of the tridiagonal matrix algorithm efficiently was adopted. Based on the characteristics of the pipe welding process, the periodic boundary condition was applied to calculate the temperature distribution in the 8 direction. For treating the moving heat source effectively, the grid meshes with variable spacings were regenerated at each time step. In order to decrease the interpolating error by grid remeshing, the temperature values at new meshes were interpolated from those at old meshes by using the periodic spline function. The temperature-dependent thermal properties, the latent heat and the convective and radiative boundary conditions were included in the model. The calculated sizes of the fusion and heat-affected zone were compared with the observed values after experiments.

Characterization of welding arc and weld pool formation in vacuum gas hollow tungsten arc welding

“…(3), and the anode boundary is the edge of LTE. Gaussian model of arc heat flux, arc pressure and current density is adopted as many previous researches (Cho and Na, 2009;Lho and Na, 1991;Kim and Na, 1992;Lee and Na, 1996;Kim et al, 2003). The effective radius of arc, therefore, should be extracted accurately to conduct the Gaussian fitting.…”