Predicting the Weld Bead Geometry of GTA Welding on AISI 202 Stainless Steel M. S. Mohammed Musthaq 1 , M. Mohaideen Batcha 2 1 Professor of Mechanical Engineering, Al-Ameen engineering college, Erode 2 Professor of Mechanical Engineering, Al-Ameen engineering college, Erode Abstract— The prediction of the optimal bead geometry is an important aspect in welding process. Therefore, the mathematical models that predict and control the bead geometry require to be developed. This paper focuses on investigation of the development of the simple and accuracy interaction model for prediction of bead geometry in TUNGSTEN INERT GAS (TIG) welding process. The independently controllable parameters affecting weld pool geometry and the quality of the weld pool V, I, F and G were selected as input control variables. The experimental designed and constructed to control the linear movement of the torch along the weld pad center line. Weld pools were laid on the joint to join thin stainless steel plate with the experimental setup. AISI type 202 stainless steel plates of 3mm thicknesses are going to be used as a work piece material. The specimens joined using a single pass welding. The quality parameters are measured. The suitable mathematical relationship is going to be generated. This developed systematic approach can also be adopted for other type of arc welding processes. Keywords— GTAW, Bead geometry, Mathematical model. I. INTRODUCTION TIG welding is an arc-welding process that produces coalescence of metals by heating them with an arc between a non-consumable tungsten electrode and the base metal. Many delicate components in aircraft and nuclear reactors are TIG welded due to its reliability. Basically, TIG weld quality is strongly characterized by the weld pool geometry as shown in Figure 1. This is because the weld pool geometry plays an important role in determining the mechanical properties of the weld. TIG welding is a highly non-linear, strongly coupled, multivariable process. The weld pool geometry and, hence, the quality of TIG welded joints are greatly dependent on the selection of input control variables such as welding speed (V), welding current (I), shielding gas flow rate (F) and gap distance (G). Therefore, in the TIG welding, engineers often face with the problem of selecting appropriate and optimum combinations of input control variables for the required weld pool quality. In this work, nonlinear and multi-objective mathematical models are developed for the selection of the optimum processes parameters. First, the upper and lower limits of the input control variables are obtained and the effect of the input control variables on the weld pool quality parameters is determined. Then, the mathematical relationships between the input control variables and weld pool quality parameters are obtained. These relationships are considered as objective functions in the mathematical models. To the best of our knowledge the optimization problem of the TIG welding using nonlinear and multi-objective mathematical models has not been investigated previously and applied on real life case study like in this work. Fig.1 Weld bead dimensions II. A SYSTEMATIC APPROACH Development of a systematic approach is required to obtain optimum combinations of input control variables for the required weld pool quality system. This approach includes the following steps. I) Identify the process control variables and their Upper and lower limits II) Identify the quality parameters, III) Construct mathematical models, IV) Develop a design matrix, V) Conduct experiments, VI) Obtain mathematical relationships, VII) Apply the constructed models. A. INPUT PROCESS CONTROL VARIABLES The independently controllable parameters affecting weld pool geometry and the quality of the weld pool V, I, F and G were selected as input control variables. 2463 International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 2, February - 2014 ISSN: 2278-0181 www.ijert.org IJERTV3IS21229