Study of the Thermal Profiles during Autogenous Arc Welding

摘要

The three dimensional transient temperature variations during autogenous Gas Tungsten Arc Welding are determined. The model employs a combination of un-equally spaced moving meshes 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 fourth order Runge-Kutta technique. The temperature dependent 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. Results are presented 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. A study of the startup and shutdown transients makes it possible to control the cooling rate during these transients. The potential use of this model in the development of an expert welding system using infrared imagery is indicated. In addition, a low cost infrared detector using an indium-arsenide diode is prototyped to determine its feasibility for production welding control. Keywords: Artificial intelligence; Welding; Computer; Modeling; Thermography; Heat transfer; Arc welding; Military thesis. (kt)