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Couplant Effect and Evaluation of FSW AA6061-T6 Butt Welded Joint

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Couplant Effect and Evaluation of FSW AA6061-T6 Butt Welded Joint COPYRIGHT AND CITATION CONSIDERATIONS FOR THIS THESIS/ DISSERTATION o Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. o NonCommercial — You may not use the material for commercial purposes. o ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original. How to cite this thesis Surname, Initial(s). (2012) Title of the thesis or dissertation. PhD. (Chemistry)/ M.Sc. (Physics)/ M.A. (Philosophy)/M.Com. (Finance) etc. [Unpublished]: University of Johannesburg. Retrieved from: https://ujcontent.uj.ac.za/vital/access/manager/Index?site_name=Research%20Output (Accessed: Date). Couplant Effect and Evaluation of FSW AA6061-T6 Butt Welded Joint By Itai Mumvenge 217093863 Submitted in partial fulfilment of the requirements for the degree of Master of Engineering in Mechanical Engineering In the Department of Mechanical Engineering Science Of the Faculty of Engineering and the Built Environment At the University of Johannesburg, South Africa Supervisor: Dr Stephen A. Akinlabi Co-Supervisor: Dr Peter M. Mashinini November, 2017 i 1. DEDICATION This dissertation is dedicated to my late grandmother Esnath Mvenge ii 2. COPYRIGHT STATEMENT The copyright of this dissertation is owned by the University of Johannesburg, South Africa. No information derived from this publication may be published without the author’s prior consent, unless correctly referenced. ………………………………….. 25 November 2017 Author’s Signature Date: iii 3. AUTHOR DECLARATION I, Mumvenge Itai hereby declare that the research work documented in this dissertation is my own, and no portion of the work has been submitted in support of an application for another degree or qualification at this or any other university or institute of learning. All sources used or cited are documented and recognised. ………………………………….. 25 November 2017 Author’s Signature Date: iv 4. ACKNOWLEDGMENT I would like to acknowledge the following people for their help and support: Dr Stephen A. Akinlabi, for introducing me to the Friction Stir Welded process and his immense guidance in the early structuring of this study. His supervision and assistance with interpretation of results made this study a success. Dr Peter Madindwa Mashinini, for his utmost guidance during this study. I am extremely grateful for his input and feedback. Without his valuable contribution, the study would never have been a success. Prof Satish (India), for the preparation of the 9 friction stir welded AA6061 samples and clearly marking the process parameters on the samples. Without these samples the study would not have been conducted. Mr. Shawn Crous and Ms. Ntombi Mthimunye, for helping me with performing the NDT test on the samples. Mr. Brian Bakkes and Mikateko Shuma, for providing the training on Metallographic sample preparations. Prof Esther T. Akinlabi and Phd Candidate Oladije, for their invaluable contribution during the laboratory testing on the samples and assistance in producing the experiment results. Special thanks due to: The University of Johannesburg, Mechanical Engineering Material Science Department, for granting me this wonderful opportunity to further my studies. Ms B.S. Mathobela for being there on every step providing emotional support and encouragement to overcome study challenges and assisting in creating a balance between my work, personal life and studies. Personal thanks due to: My late grandmother Ms. Esnath Mvenge, to whom I dedicate this dissertation. Grandmother, thank you for taking care of me and showing me the direction to become independent no-matter what challenges arose during my upbringing. v 5. ABSTRACT Couplant Effect and Evaluation of FSW AA6061-T6 butt welded joint Mumvenge I. Aluminium is an alloy material vastly used for manufacturing components in aviation, transport and a host of commercial use. Friction stir welding is a novelty solid state welding technique that was invented at The Welding Institute (TWI) of UK in 1991. This study presents the effects of process parameters on achieving sound welds of the friction stir butt welded joint of similar AA6061-T6 Aluminium alloys. The only parameters used and varied for this study were rotational speed and feed rate. The geometry of the tool was kept constant and the material used was tool steel, W302. Friction stir welds were evaluated both by visual inspection and non-destructive testing methods. Evaluation allowed for assessment of the weld integrity by examining for the presence of weld defects. The results indicated that the welds do not have any defects. The weld macrostructure and microstructure were examined and mechanical properties evaluated. The microhardness was also evaluated which showed that optimum speeds are required to achieve uniform hardness value across the weld traverse. The base metal showed higher hardness values when compared to the weld region. However, higher rotational speeds and higher feed rates result in increased hardness values, with the highest values recorded in the weld nugget and the least values recorded in the HAZ/TMAZ interfaces with a W-shaped hardness distribution. Couplant attenuation effect was investigated using four different types of couplants, employing Ultrasonic Testing contact pulse-echo longitudinal wave to detect weld defects. The attenuation effect was minimal when the Ultrasonic gel, oil and water were used. This was attributed to the coupling conditions such as the acoustic impedance values and the viscous properties of the couplants. Conversely, grease provided poorer frequency gain than all the couplants though it had comparable acoustic impedance values. This was attributed to its poor wetting properties and development of air pockets on contact with weld sample to be examined. vi 6. TABLE OF CONTENTS Copyright Statement................................................................................................... iii Author Declaration...................................................................................................... iv Acknowledgment ........................................................................................................ v Abstract ...................................................................................................................... vi Table of Contents ...................................................................................................... vii Abbreviations ............................................................................................................. x Nomenclature ........................................................................................................... xiii Units ......................................................................................................................... xiv LIST Of Figures ......................................................................................................... xv List Of Tables ........................................................................................................... xxi Glossary of Terms ................................................................................................... xxii 1. Background........................................................................................................... 1 1.1 Introduction ................................................................................................... 1 1.2 Problem Statement ....................................................................................... 4 1.3 Aim ................................................................................................................ 5 1.4 hypothesis ..................................................................................................... 5 1.5 Scope of research ......................................................................................... 5 1.7 Research Methods ........................................................................................ 6 1.8 Delimitations .................................................................................................. 9 1.9 Significance of the Research......................................................................... 9 1.10 Study Layout ................................................................................................. 9 2. Literature Review ................................................................................................ 11 2 Introduction ................................................................................................. 11 2.1 Welding ....................................................................................................... 11 2.1.1 Fusion Welding ..................................................................................... 12 2.1.2 Solid-state Welding ............................................................................... 13 2.2 Friction Stir Welding .................................................................................... 13 2.3 Application of FSW ...................................................................................... 16 vii 2.4 Friction Stir Weld Process Parameters ....................................................... 18 2.5 Tool Design and Geometry ......................................................................... 19 2.6 Tool Tilt and Plunge
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