A study on parameter optimization in the circumferential GTA welding of aluminium pipes using a semi-analytical finite-element method

Abstract

When an aluminium pipe is welded circumferentially under constant welding conditions, the width and depth of the weld bead increase gradually along the welding direction. Therefore, the welding parameters should be optimized continuously to obtain a uniform weld bead along the entire circumference of the pipe. In this study, a state equation governing the heat flow in circumferential pipe welding is analyzed using a semi-analytical finite-element method, and optimal welding parameters obtained using a state-space method. As the welding parameters to be optimized, the welding velocity, the effective radius of heat source and the heat input are considered. The sequences of welding parameters was optimized and compared with experimental results to verify the accuracy of the proposed model. The weld-pool geometry measured along the entire weld was found to be almost the same as the calculated results, a uniform weld bead around the pipe circumference being obtained. Three process parameters were optimized at the beginning of process optimization to obtain their proper initial values, and then only the heat input, which can be controled easily with a conventional welding machine, was considered as the optimization parameter, in order to reduce the amount of calculation involved.