No abstract

This study focuses on optimization of process parameters, which may result in improved mechanical properties of the friction stir weldments of AA2014-T651. Plain taper and threaded taper cylindrical tool pin profiles were used for the study. A set of experiments was conducted at different levels of tool rotational and weld speeds using two tool pin profiles. Mechanical properties such as tensile strength, yield strength, impact strength, percentage of elongation, and hardness were measured. Objective functions are developed for the five mechanical properties in terms of input parameters. The input parameters were optimized using teaching–learning-based optimization algorithm technique to improve mechanical properties. The teaching–learning-based optimization algorithm suggested three best combinations such as combination-I (940 r/min and 32 mm/min), combination-II (1100 r/min and 40 mm/min), and combination-III (1205 r/min and 45 mm/min). The optimization is also validated with experimental results.

Joining of Al-Cu based alloys such as AA2014-T651 is very difficult by fusion welding techniques due to liquefaction and solidification cracks. Therefore, solid state welding namely Friction Stir Welding (FSW) is most suitable to join these alloys. The main objective of this work is to identify the most influenced process parameters such as rotation speed of the tool, and tool traverse speed and their levels for fabricating the weldments by FSW process with using ultrasonic vibrations (UAFSW). A set of experiments were carried out using the plain cylindrical and taper threaded cylindrical tool pin profile at different levels of process parameters and experimental results were collected. A graph theory and utility concept was proposed and found an optimal working condition for better weldment properties. The UAFSW process enhanced the AA2014-T651 weldment mechanical characteristics at 1100 rev/min of tool rotation speed, and 40 mm/min of tool traverse speed. The tensile strength, yield strength, percentage of elongation, impact strength and micro hardness were found to be 431.69 MPa, 307.47 MPa, 11.66 %, 8.32 J, and 139 HV respectively at optimal working condition. The weld joint obtained using a taper threaded tool pin profiled with ultrasonic vibration exhibits 95% joint efficiency compared to the weldments made by plain cylindrical taper tool pin profile with ultrasonic vibration. The measured characteristics have been correlated with microstructure and fracture features. The optimized responses were verified by the validation test.

This work focused on the optimization of process parameters, which may result in increasing mechanical properties of copper weldments. The different tool pin profiles such as plain taper cylindrical, taper cylindrical with threaded, triangular, square, pentagonal and hexagonal having constant shoulder diameters were used to fabricate the weldments. The experiments were conducted at different levels of tool rotational speed and weld speeds using six different tool pin profiles. The experimental results revealed that the defect free weldments could be obtained by using different tool pin profiles. From the investigation, it was found the weldments made by using a square (SQ) tool pin profile resulted in better mechanical properties compared to other tool pin profiles. Objective functions are developed for the mechanical properties in terms of input parameters. The input parameters of an SQ tool pin profile were optimized using a metaheuristic optimization based algorithm named teaching learning based optimization (TLBO) technique to improve mechanical properties. The TLBO suggests a combination of 900 rpm of tool rotation speed and 40 mm/min weld speed for better properties.

Joining of Al-Cu based alloys such as AA2014-T651 is very difficult by fusion welding techniques due to liquefaction and solidification cracks. Therefore, solid state welding namely Friction Stir Welding (FSW) is most suitable to join these alloys. The main objective of this work is to identify the most influenced process parameters such as rotation speed of the tool, and tool traverse speed and their levels for fabricating the weldments by FSW process with using ultrasonic vibrations (UAFSW). A set of experiments were carried out using the plain cylindrical and taper threaded cylindrical tool pin profile at different levels of process parameters and experimental results were collected. A graph theory and utility concept was proposed and found an optimal working condition for better weldment properties. The UAFSW process enhanced the AA2014-T651 weldment mechanical characteristics at 1100 rev/min of tool rotation speed, and 40 mm/min of tool traverse speed. The tensile strength, yield strength, percentage of elongation, impact strength and micro hardness were found to be 431.69 MPa, 307.47 MPa, 11.66%, 8.32 J, and 139 HV respectively at optimal working condition. The weld joint obtained using a taper threaded tool pin profiled with ultrasonic vibration exhibits 95% joint efficiency compared to the weldments made by plain cylindrical taper tool pin profile with ultrasonic vibration. The measured characteristics have been correlated with microstructure and fracture features. The optimized responses were verified by the validation test.