الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 163 |  |  |
| | | from | 163 | | |
Abstract
The effect of smooth tool pin eccentricity on mechanical properties and microstructure of 5 mm thick friction stir welded aluminum alloys AA1050-H12 and AA5754-H24 were investigated. Three different tools were used, cylindrical tool pin without eccentricity (T0), two cylindrical tool pin with eccentricity of 0.2 mm, and 0.8 mm (T2, T8). The friction stir welding FSW was performed using tool rotation speed of 600 rpm and different welding speeds of 100, 300, and 500 mm/min. The joints were investigated using tensile testing, hardness testing and optical microscopy. The use of FSW tool pin eccentricity 0.2 mm produces a friction stir weld joint with higher mechanical properties and finer precipitates. The tensile strength increases with increasing welding speed with maximum at 500 mm/min. However, the case is reversed in case of FSW tool pin eccentricity of 0.8 mm, the tensile strength decreases with increasing welding speed. The ratio between pin surface area and effective frictional area affects the cooling rate at the contact area. The peak temperature for AA1050-H12 and AA5754-H24 decreases with the tool pin eccentricity and welding speed, and the energy per unit length increases with tool pin eccentricity. As a measure of the wear of the tool shoulder, it is found that, the variations in tool shoulder size after FSW are almost the same for the three different tools because the three tools have the same shoulder profile and size. Using the three different tools with pin eccentricities of 0, 0.2 and 0.8 mm, the radial wear rates of the pin are 0.03, 0.04 and 0.09 mm/m, respectively. The values of torque during friction stir welding process at 600 rpm rotational speed and 500 mm/min welding speed using T0, T2, and T8 tools are almost the same for the three different tools. An artificial neural network (ANN) model was developed for the simulation and analysis of the effect of FSW tool pin eccentricity (TPE) and weld speed on the mechanical properties of FSW AA5754-H24. The input parameters for the model in this work are welding speed (WS) 50, 100, 150, 200, 300 and 500 mm/min, and tool pin eccentricity (TPE) 0, 0.2 and 0.8 mm. The outputs of the ANN developed model include the mechanical properties of FSW AA5754-H24 (ultimate tensile strength, elongation, hardness of thermo mechanical affected zone (THAZ), and hardness of weld nugget zone (WNZ). The ANN model showed a good performance. It can be used to calculate mechanical properties of FSW AA5754 aluminum alloy as functions of TPE and WS. The predicted results were in good agreement with measured data. It could be stated that smooth tool pin eccentricity is becoming one of the main technical parameters of friction stir welding. Wear rate of tool pin is not affected by pin eccentricity less than or equal to 0.2 mm.