Vol.:(0123456789) 1 3 Journal of the Brazilian Society of Mechanical Sciences and Engineering (2019) 41:553 https://doi.org/10.1007/s40430-019-2059-2 TECHNICAL PAPER Development of a Self‑Heated Friction Stir Welding tool for welding of polypropylene sheets Rahul Kanti Nath 1  · Pabitra Maji 1  · John Deb Barma 1 Received: 28 March 2019 / Accepted: 28 October 2019 / Published online: 9 November 2019 © The Brazilian Society of Mechanical Sciences and Engineering 2019 Abstract The present investigation is focused on the development of a new FSW tool for polymer welding. The newly developed Self- Heated Friction Stir Welding (FSW) tool as well as a conventional FSW tool was employed to join 3-mm polypropylene sheets at diferent traverse speeds. The spindle torque and various forces exerted on the tool pin during welding were stud- ied. The weldments obtained from both the tools were tested in order to analyse the weld morphology and tensile strength. SEM analysis of the stir zone revealed that the Self-Heated FSW tool had signifcant infuence on the material fow and consequently resulted in defect-free welded joints. Also, the relationship between weld quality and tool axial and transverse forces on tool pin was established. The Self-Heated FSW tool was able to produce durable weld with superior mechanical property in terms of tensile strength compared to the conventional FSW tool. Keywords Friction stir welding · Self-Heated FSW tool · Polypropylene · Axial and transverse force · Microstructure · Joint strength 1 Introduction Thermoplastic polymers have huge applications in industries and manufacturing sectors such as automobile, railways, aerospace and shipbuilding as they ofer excellent physical properties with a good solvent, corrosion and high impact resistance and good fatigue life [1–6]. The conventional polymer joining technology includes adhesives bonding, ultrasonic joining, hot plate joining, hot gas joining, extru- sion joining, friction welding, etc. [7]. FSW was proposed for welding of soft metallic materials such as aluminium alloys which are strenuous to weld by traditional techniques [8–10]. Since the last few decades, this technique is used as an efcient method for joining of diferent thermoplastic materials. It is observed that in the case of polypropylene (PP) welding, FSW gives better joint efciency compared to the existing joining techniques used in plastics [11]. Figure 1 shows a typical schematic diagram of the con- ventional FSW process. In FSW technique, the tool is the heart of the process which consists of shoulder and pin. The rotating tool which creates frictional heat between tool and workpiece leads to softening of the material around the pin and simultaneously mechanical deformation takes place. The combination of the pin rotation and translation results in producing a welded joint. Being a solid-state joining process [12], the generation of heat in FSW is low as compared to the fusion welding process. Due to the low heat, this tech- nique produces components with high mechanical properties with low energy consumption, low distortion and residual stresses. Moreover, FSW is a pollution-free process due to the absence of toxic gases [13]. The tool is one of the most important components in the FSW process [14]. Generally, H13 tool steel is used as a tool material in FSW due to its low thermal conductivity, high temperature strength and wear resistance [15–17]. In recent years, signifcant researches are focused on the geometry of tool during the welding of thermoplastic [18]. Bilici and Yükler [19, 20] used six diferent tool pin profles (straight cylindrical, threaded cylindrical, tapered cylindrical, trian- gular, square and hexagonal) to perform FSW spot welding of thermoplastics and evaluated the efect of the pin profle on weld quality. They observed that the tapered cylindrical Technical Editor: Lincoln Cardoso Brandao. * Rahul Kanti Nath riserrahul@gmail.com 1 Department of Mechanical Engineering, NIT Agartala, Agartala, Tripura (W) 799046, India