Clearance a 05 mm R25 mm L50 mm 15 L M10g P246 SolutionWher

Clearance a = 0.5 mm R=25 mm L-50 mm 1.5 L M=10g P2.46

Solution

Where V nor is the normalized value, V i is the value of a given variable, and V max and V min are the maximum and minimum values of the independent variable. The rotary speed of tool and welding speed were provided by milling machine, which is equipped with gear boxes to generate various levels of rotary speed of spindle and linear feed rate for machine table. Also, welding axial forces have been provided by axial motion of tool into plates and measured by a Kistler multicomponent milling force dynamometer. For measuring of tensile and yield strengths, the tensile test specimens, which is cut from the welded joint, have been gripped by grippers of 100 KN servo-controlled universal testing machine, and the values of tensile strength and yield strength have been measured. The schematic diagram of tensile specimen is visible in Fig. 4. Also, the Vickers hardness of welded joints have been measured by Vickers\'s microhardness testing machine (Make: Shimadzu and Mod- el: HMV-2 T), with 0.05 kg load at 15 s. In order to decrease experimental error, each experiment has been replicated for three times, and average of each response has been reported as main response value.

In this research, an attempt has been made to develop mathematical models for predicting mechanical properties including ultimate tensile strength, impact toughness, and hardness of the friction stir-welded AA6061-T6 joints at 95 % confidence level. Response surface methodology with central composite design having four parameters and five levels has been used. The four parameters considered were tool pin profile, rotational speed, welding speed, and tool tilt angle. Three confirmation tests were performed to validate the empirical relations. In addition, the influence of the process parameters on ultimate tensile strength, impact toughness, and hardness were investigated. The results indicated that tool pin profile is the most significant parameter in terms of mechanical properties; tool with simple cylindrical pin profile produced weld with high ultimate tensile strength, impact toughness, and hardness. In addition to tool pin profile, rotational speed was more significant compared to welding speed for ultimate tensile strength and impact toughness, whereas welding speed showed dominancy over rotational speed in case of hardness. Optimum conditions of process parameters have been found at which tensile strength of 92 %, impact toughness of 87 %, and hardness of 95 % was achieved in comparison to the base metal. This research will contribute to expand the scientific foundation of friction stir welding of aluminum alloys with emphasis on AA6061-T6. The results will aid the practitioners to develop a clear understanding of the influence of process parameters on mechanical properties and will allow the selection of best combinations of parameters to achieve desired mechanical properties.