Tool/Workpiece Interface Temperature Measurement and Prediction

In the process of friction stir welding(FSW), the peak temperature at the interface between tool and workpiece has critical influence on the microstructure and properties of the weld joints. In this study, the interface temperature measuring system is established. Two thermocouples are inserted into the bottom surface of shoulder and the side surface of pin to monitor the temperature at the contact interface. Signal acquisition, amplification and processing units are integrated with the tool, and the temperature signal is wirelessly transmitted to the computer via Bluetooth. Butt FSWelding tests of AA6061-T6 aluminum alloy are carried out to analyze the influence of different process parameters on the interface temperature. The interface temperature increases with the increase of rotation rate or the decrease of welding speed. The influence of rotation rate on interface peak temperature is higher than welding speed. And the increase of interface peak temperature gradually slow down with the increase of rotation rate. The tilted tool can make the interface temperature go up at some extent. When the plunge depth of shoulder are different, the measured interface temperature curves look different, so that the weld quality can be judged by the interface dynamic temperature curves to some extent. The measured data were used to modify the prediction empirical formula of peak temperature in FSW. Compared to the computational fluid dynamics based numerical analysis method, the modified prediction formula is more convenient and efficient in calculating the peak temperature in FSW, which is beneficial to application in engineering. © 2021 Journal of Mechanical Engineering.