||In this study, a friction model is developed to investigate the behavior of material plastic flow and the temperature rise during the friction stir welding process using a pin tool, while solving the continuity, momentum and energy conservation equations. The results obtained by this model is verified by comparing with the theoretical results using another model and the experimental results. Finally, the influences of rotation speed, downward force, and feed rate on the interface temperature rise between the tool and the workpieces and the speed of plastic flow are investigated.|
The interface temperatures between the butt workpieces were measured using the thermocouples during the friction stir welding process. Numerical results were in very good agreement with the measured temperatures. Numerical results showed that the temperature in front of the tool was lower than that behind the tool. The temperature at the advancing side is about 40℃~50℃ higher than that at the retreating side. The results showed that the temperature was achieved to the maximum at the interface between the tool and the workpieces close to the pin, so that the speed of plastic flow in this area is higher with lower viscosity. The temperature and speed of plastic flow increased with increasing rotation speed under a certain of downward force and feed rate; they increased with increasing downward force under a certain of rotation speed and feed speed. With increasing feeding rate, the interface temperature decreases, the accumulation of heat to the rear of the tool phenomenon became obvious. Empirical formulas for the maximum temperature rise in terms of tool rotation speed, downward force, and feed rate is derived by least square method.