Residual Stress Predictive Model of TIG Welding Process Using Finite Element Analysis

Abstract

Residual stress occured in welding process generally causes reduction in the strength of welded joints, shortens the fatigue life, and brings about the distortion of the workpiece. In this research, finite element analysis (FEA) model of the butt-joint tungsten inert gas (TIG) welding process with the application of birth-death technique was presented. The material used in this research was AISI 304 stainless steel. The FEA model was constructed on a simulation software, ANSYS. The predictive residual stress from a welding condition obtained from the FEA model was verified by the value measured from X-ray diffraction (XRD) machine. Effects of four welding process parameters: efficiency, welding speed, arc current, and arc voltage on residual stress at the center of the welded joint and at the heated affected zone (HAZ) were investigated. The welding conditions were generated by varying these four main effects according to the Taguchi design of experiment technique (L8 orthogonal array). In general, compressive residual stress is beneficial to the strength and fatigue life of welded joints. For the Taguchi method the larger is better constraint was used; larger means higher magnitude of compressive residual stress. The predictive residual stress results obtained from the FEA model were consistent with the values obtained from the XRD measurement. The result suggested that the most significant effect was the arc current, followed by the arc voltage, welding speed, and the efficiency. The response optimizer in MINITAB software showed the optimal magnitude of compressive residual stress values of about 52 MPa obtained at the arc current of 126 Ampere, arc voltage of 17 Volts, welding speed of 110 mm/min, and the efficiency of 80%.