Received by the editors and in revised form December 21, 2007 462 INTERNATIONAL JOURNAL INFORMATION AND SYSTEMS SCIENC Volume 4, Number 3, Pages 44 OF ES 9-461 INTERNATIONAL JOURNAL INFORMATION AND SYSTEMS SCIENC Volume 1, Number 1, Pages 1-22 OF E INTERNATIONAL JOURNAL OF INFORMATION AND SYSTEMS SCIENCES Volume 4, Number 3, Pages 462-477 ©2008 Institute for Scientific Computing and Information MULTI INPUT SINGLE OUTPUT FUZZY MODEL TO PREDICT TENSILE STRENGTH OF RADIAL FRICTION WELDED GI PIPES JAGDEV SINGH AND SIMRANPREET SINGH GILL Abstract In this paper an effort has been made to design and demonstrate the use of fuzzy logic based model to predict the tensile strength of tubular joints of GI pipes which are welded with the technique of radial friction welding. The model is based on two inputs signals; rotational speed (RPM) and forge load. The Adaptive Neuro-Fuzzy Inference System (ANFIS) technique of fuzzy based systems for modeling and simulation of the complex systems has been employed. The performance of the model is validated by comparing the predicted results with the actual practical results obtained by conducting the confirmation experiments. Key Words Fuzzy logic, ANFIS, Friction welding, Tensile strength, Forge load. 1. Introduction There is a strong trend for increases in natural gas consumption worldwide, which implies continued growth of gas pipeline installation. World gas use is projected to almost double over 24 years, from 90 trillion cubic feet in 2000 to 176 trillion cubic feet in 2025 [1]. The need to construct pipelines over long distances has led to an increased demand to improve the productivity of pipeline girth welding. Many novel techniques have been tried in the past to achieve productivity gains, including laser welding, flash butt welding, homopolar welding, and radial friction welding. Radial friction welding is pioneering pipe girth welding technique, and has been optimised in the past to produce the maximum productivity possible with this process. The advantages of the process are high reproducibility, short production time and low energy input. An important area of application for friction welding is the joining of similar material and dissimilar material. The friction welding is a process in which the heat for welding is produced by direct conversion of mechanical energy to thermal energy at the interface of the work pieces without the application of electrical energy or heat from other sources, to the work pieces. The friction welds are made by holding a non-rotating work piece in contact with rotating work piece [2]. The basic principle of friction welding involves the simultaneous applications of pressure and relative motions, generally in a rotational mode between the components to be joined. The friction heat thus generated raises the interface temperature of the components to nearly their melting points, while the applied pressure perpendicular to the plane of motion serves to extrude the heated material including any dirt and oxide films from the interface, bringing the components to be joined into intimate contact. Termination of the relative motion while maintaining or even increasing the applied forge pressure then serves to produce a sound metallurgical bond