Effect of heat source parameters in thermal and mechanical analysis of linear GTA welding process

Abstract

Double-ellipsoidal volumetric heat with Gaussian distribution of heat intensity is one of the most popular heat source model used in fusion welding process simulations. However, the major difficulty of this kind of heat source model is to define the parameters before start of simulation. It is common practice to define the heat source parameters from experimental measurement of weld dimensions for a particular welding condition that meet the demand of two parameters i.e. weld width and penetration. Till date, the definition of front and rear length of double ellipsoidal is to-some-extent arbitrary in linear welding. A sensitivity analysis shows that this ratio has significant effect on weld dimensions as well as thermal distortion and residual stress of final weld joint. This problem has been addressed in present work where the optimum value of the ratio of front and rear length of double ellipsoidal heat source model is designed within the kernel of an integrated optimization algorithm. The ratio is assumed as function of weld velocity and a suitable functional form is designed over a range of welding current and velocity. The proposed trend of ratio along with optimum values demonstrate fair agreement of experimentally measured weld dimensions for linear gas tungsten arc (GTA) welding process. 3D finite element model of thermal and mechanical analysis is developed and assuming elasto-plastic response of material. Temperature dependent material properties along with latent heat of melting and solidification are incorporated in numerical simulation. © 2012 ISIJ.