Investigation on Mechanical Behavior of Friction Stir Welded Nylon-6 Using Temperature Signatures
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JMEPEG https://doi.org/10.1007/s11665-020-05030-2
Investigation on Mechanical Behavior of Friction Stir Welded Nylon-6 Using Temperature Signatures Santosh K. Sahu, Raju P. Mahto, and Kamal Pal (Submitted November 22, 2019; in revised form June 10, 2020) The present investigation focused on parametric optimization for improving joint efficiency of friction stir welded nylon-6 sheets using particle swarm optimization algorithm using a response surface method-based regression model. Initially, parametric effects on weld quality characteristics such as weld bead profile, bead shape and its microstructure along with micro-hardness variation and stress–elongation behavior of the butt weld have been studied considering cylindrical, square and triangular pin contours. The thermal cycles along advancing and retreating side of tool rotation have also been acquired during welding which was further used in the response surface models for the improvement in weld quality prediction capability. The joint efficiency was found to be maximum (49.68%) at intermediate value of each parameter using square pin. The material scooping action and undercut defects along with non-uniform grain morphology with micro-cavities were primary reasons for weld failure at weld interface. The response surface-based regression model of joint strength of the weld was significant, whereas weld hardness and percent elongation were found to be insignificant. However, weld peak temperature with associated cooling rate-based regression models was found to be highly adequate as per substantial improvement for the prediction of each weld quality-based features. Finally, response surface-based regression model of joint strength was further used for parametric optimization using response surface method as well as evolutionary particle swarm optimization tools. The particle swarm optimization was found to be more precise with better optimization capability than response surface methodology. Keywords
friction stir welding, joint strength, nylon-6, particle swarm optimization, pin profile, response surface method, thermal cycle
1. Introduction In recent years, manufacturing-based industries are often faced with quality-based problems associated with joining or welding. The weld quality specified the working efficiency in the service lifespan in different engineering applications (Ref 1). Now a days, polymeric materials like acrylonitrile butadiene styrene (ABS), polypropylene (PP), polycarbonate (PC) and nylon-6 are found to be hugely popular in expanded industrial applications due to low weight, high specific strength and design flexibility with low handling cost (Ref 2). However, the joining of polymers is an interesting task due to its poor thermal properties such as low thermal conductivity as well as low melting temperature which is responsible for poor weldability. Hence, traditional fusion welding methods are found to be unsatisfactory in thermoplastic joining, which specifies the necessity of solid-state welding without melting the base materials (Ref 3). Therefo
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