Design of Experiment for Predicting Residual Stresses in Gas Tungsten Arc Welding Process

Abstract

Gas Tungsten Arc Welding (GTAW) requires high heat input for welding. After welding, the workpiece cools down non-uniformly which creates residual stresses. Generally tensile residual stress weaken the strength of the welded joints and shorten the fatigue life of the material. It is very important to identify appropriate welding conditions in order to prevent negative effects from the residual stresses. In this research, the full factorial design of experiment technique was constructed for predicting residual stress occurred after the GTAW welding process. The values of the residual stresses were obtained from the results from the Finite Element Analysis (FEA) model, which had been verified by the residual stress measurement from the X-ray diffraction (XRD) machine. Effects of four welding process parameters: efficiency, arc voltage, arc current, and welding speed on residual stresses at the center of the welded joint and at the heated affected zone (HAZ) were investigated. Each factor had 2 levels (24 Full Factorial Design). The regression equation for predicting the residual stress from significant factors was constructed. The results showed that the arc voltage, arc current, welding speed and interaction effects between efficiency and welding speed were significant factors, with the most compressive residual stress value of about -50.97 MPa.