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RESEARCH PAPER

Weld defect localization in friction stir welding process Debasish Mishra 1 & Sristi Shree 3 & Abhinav Gupta 4 & Ashok Priyadarshi 5 & Sarthak M. Das 6 & Surjya K. Pal 7 Debashish Chakravarty 8 & Srikanta Pal 4 & Tanushyam Chattopadhyay 2 & Arpan Pal 2

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Received: 4 October 2019 / Accepted: 6 November 2020 # International Institute of Welding 2020

Abstract The article attempts to detect the defects in friction stir welding (FSW) process by analyzing the signal acquired during welding. The said welding technique utilizes pressure and heat developed by the usage of a non-consumable tool. Thus, the axial force signal carries a lot of information about the physical process, and hence, it could be used to identify the weld defects. Signal analysis has been performed by using wavelet-based techniques. Before this analysis, a methodology has been followed to select the best mother wavelets suitable for the signal. The results of defect identification have been validated by mapping the processed signal with the actual weld quality. Keywords Mother wavelet selection . Friction stir welding . Force signals . Defect identification

1 Introduction The manufacturing sector has experienced a paradigm shift owing to globalization. They are now expected to cater to customer demands, i.e., being flexible about the varying product features each day. Demand for high precision products is on the rise as the traditional manufacturing style is getting obsolete. Integrating advanced manufacturing systems like sensory systems will help in achieving improved product quality at a low cost. Sensory systems integrated with mechanical components have been able to create a revolution in the manufacturing sector [1]. The manufacturing industries are under great thrust to reduce the cost of production, reduce the equipment downtime, and maintain the product quality.

As such, several advanced and innovative manufacturing methods are being adopted which are economically more effective and are environment friendly too. Friction stir welding (FSW) is one such manufacturing technique, and the details of the same have been discussed in the following paragraph. The principle of FSW is indicated by its title which reads friction and stirring [2, 3]. For the friction, a tool with a specific design is utilized, which plunges inside the base materials to be joined, and generates the frictional heat (schematic of the process depicted in Fig. 1). Thus, the material for the tool (schematically depicted in Fig. 2) is selected based on the base materials to be welded. Upon plunging, the base materials get plastically deformed and attain flowability [3]. The stirring action is then achieved via a combined action of rotating the

Recommended for publication by Commission V - NDT and Quality Assurance of Welded Products * Surjya K. Pal [email protected] 1

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Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur, India TCS Research and Innovation, Tata Consultancy Services, Kolkata, India Department