International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 04 | Apr-2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 3062 Experimental Investigation on Influences of Tool Shoulder Diameter (D) to Plate Thickness (T) ratio on Friction Stir Welding of Dissimilar Aluminium Alloys Srirangam Adithya Vamshi 1 , M. S. Srinivasa Rao 2 , S. N. S. Sai Hari 3 1 P. G. Student, Department of Mechanical Engineering, VNR VJIET, Hyderabad, India, 500090 2,3 Assistant Professor, Department of Mechanical Engineering, VNR VJIET, Hyderabad, India, 500090. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Friction Stir Welding is a novel solid-state welding technique ideal for joining metals in similar and dissimilar joint configurations, that generally yield a low efficient joint, when fabricated with conventional welding techniques. The dissimilar joint configuration welded joint of aluminium alloys of 5xxx series and 6xxx series is of greater importance in many industrial applications. In this present research work, an attempt has been made to identify the influences of tool shoulder diameter to plate thickness ratio on the quality of the weldments fabricated. The fabricated weldments are analyzed by various tests like Liquid Penetrant Test, Bending test, Macro and Micro structures of weldments, Vickers hardness test. Results revealed that the joints fabricated with tool shoulder diameter to plate thickness ratio as 3.5 yielded optimum results, indicating effective plasticizing of the material, better flow of the plasticized material along the length of the joint. Key Words: Friction Stir Welding, Dissimilar butt joint configuration, Liquid Penetrant Test, Bending test, Macro and Micro structure, Vickers hardness test. 1. INTRODUCTION Joining of dissimilar metals with a higher joint efficiency is of greater importance in various engineering domains like electrical, electronic, aerospace, petrochemical, defense etc. which generally strive for low weight structures with desired amount of strength. Welding of dissimilar metals is carried over a large basis as benefits from both the materials can be derived from within a single structure. Conventional welding techniques like Gas welding, Arc welding; High energy welding techniques like Laser Beam Welding, Electron Beam Welding, Plasma Arc Welding etc. causes a high heat density in the joint interface. These welding techniques normally use an under matched filler metal during welding, resulting in a lower efficient joint, residual stresses in the weldments, distortion in the welding; making a post processing operation like annealing necessary for the weldments. Moreover, the use of conventional welding techniques results in the evaporation of lower melting point elements in the weldments and formation of Inter Metallic Compounds which tend to lower the strength of the weldments [1,2]. Friction Stir Welding is an emerging solid- state welding technique invented in 1991 at TWI [3] and is proved to be successful for joining metals in both similar and dissimilar joint configurations. This process does not involve in high operating temperature as in case of conventional welding techniques, do not require any use of filler metal, no or little distortion to the welded plates, no emission of harmful gases during welding and is practically possible to weld any metal. Fig.1 Schematic diagram of Friction Stir Welding [20] During the process of Friction Stir Welding as in Figure 1, a rotating tool consisting of shoulder and pin is inserted till the surface of the shoulder contacts the surface of the plates to be joined at the joint interface and is traversed along the length of the joint. As the tool traverses along the length of the joint, the frictional heat generated between the tool and workpiece helps in plastically deforming the material. The plasticized material is then travelled from the front face of the tool from the advancing side of the joint and is deposited to the retreating side of the joint by back face of the tool [4]. Local heat generation due to friction [5] between tool and work piece is given by equation 1 as: De f = δ ȋωr-Usinϴ) µ f p dA (1) Where, δ = Extent of slip; δ = ͳ when no sticking of the material occurs and all the heat generated is due to friction and δ = Ͳ indicates complete sticking of the material and heat generation is due to plastic deformation.