Friction Stir Welding of High-Density Polyethylene

Abstract Friction stir welding (FSW) presents a strong competing alternative for adhesive and riveted joining in a wide range of applications. Among the benefits are lower energy consumption, lower product weight, increased joint strength, and versatility across diverse materials. In the case of thermoplastics, particularly high-density polyethylene (HDPE), FSW holds a promising approach as it can create excellent welds with minimal defects and superior strength. In this experimental study, the use of a custom-designed bobbin tool (BT) for Butt welding 4 mm thick HDPE carbon black sheets is explored. In this research, the impact of two critical FSW process parameters: tool rotation speed (800, 1000, and 1200 rpm) and welding speed (33, 42, and 50 mm/min) has been considered. In a systematic variation of these parameters, the research investigates the potential for refinement of FSW for HDPE using a bobbin tool. The overarching goal of this work is to identify the critical FSW process parameters that exert the most significant influence on joint strength and overall welding quality. This investigation revealed that tensile strength is maximized at a lower rotation speed (800 rpm) with moderate welding speed (33 mm/min) due to optimal heat input and material mixing at these settings, which is 16.137 MPa, which is approximately 55% of the base metal strength (29.0667 MPa). Lower rotational speed, because of increasing time and pressure for material interaction, leads to higher tensile strength. The study aims to establish optimal process conditions for achieving high-performance HDPE welds using the bobbin tool FSW technique. This investigation will contribute valuable insights to the development and optimization of FSW for joining thermoplastics, leading the way for its greater application in various industrial applications.