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Abstract The aim of this thesis is improving of quality and efficiency of welding process. The friction stir welding (FSW) was chosen to be applied on AA6063 Aluminum alloy. The final results should demonstrate that the welding joints properties satisfy design requirements, determination of the best mechanical properties of the welding joints and develop a mathematical model to be more reliable as the main aim of this thesis. In this study, the welding parameters of FSW are traverse speed (B), tool rotational speed (A) and tool pin profile (Ḉ). The tool rotational speed values are (20, 40 & 60) mm/min. The welding tool rotational speed values are (800, 450 & 230) rpm. The last parameter to be considered is welding tool pin profile(Ḉ) with three different shapes of threaded taper profile, tapered profile & cylindrical profile. The target of this study is to find influence of these parameters on the FSW process, the mechanical properties (tensile strength, hardness & bending strength), and macromicrostructure (to discover the welding defects). Moreover, the genetic algorithm (GA) process conducted within the ranges of the welding parameters to optimize and increase the utility of welding process economics and for more quality of welding joints by maximizing the hardness, tensile strength and bending strength. The welding tool rational speed within (230 rpm A 800 rpm), welding traverse speed within (20 mm/min B 60 mm/min), and tool pin profile (Tapered, Cylindrical and Threaded Taper). Then, the finite element model was stablished to study structural analysis, heat transfer on the numerical designed model by using finite element method (FEM). The maximum contribution percentage for the welding pin profile equal to 39.13% for hardness model and the welding pin profile equal to 32.96% for tensile strength model. The maximum contribution percentage for traverse speed = 76.04% for bending strength model. The GA results giving the maximum hardness at A = 230 rpm and B = 20 mm/min as a following (threaded tapered profile = 32.66 HRB, cylindrical profile = 29.02 HRB and tapered profile = 27.46 HRB). The GA results was given the maximum tensile strength of 77.36 MPa at (A = 230 rpm, B = 20 mm/min and threaded tapered profile). The GA results giving the maximum bending strength at A = 563.8 rpm and B = 60 mm/min as a following (threaded tapered profile = 155.91 MPa, tapered profile = 155.31 MPa and cylindrical profile =140.95 MPa). The results of macro and microstructure study are helping to distribute the defects according to defect size discovered. Then, the analysis was shown that 63% of the defects are controlled by 50% of the root causes. The defects within (0.2 – 0.4) mm are caused by increasing in welding tool rotational speed with traverse speed and insufficient stirring surface. The defects within (> 1 mm) are caused due to low friction heat generation, excessive tool vibration and wrong setting of the joints. The defects within (0.8 – 1) mm are caused by pin profile type, pin depth and increasing in turbulence of the plasticized metal. The finite elements model identifies the temperature distribution along (X & Y) coordinates. The results providing that the temperature distribution depending on the welding tool pin profile. Whereas, the threaded taper profile giving regular temperature distribution. The reliability analysis results giving the reliability at high criticality (R) of 80%. The considered planned duration (Ṫ) is equal to 42 sec for the welding joints and 350s for the welding tool as an average value. |