Ultrasonic line source and its coupling with the tool induced heat generation and material flow in friction stir welding

To understand the synchronous interaction mechanism between the ultrasonic vibration exerted on the tool and the tool induced thermo-mechanical behavior in ultrasonic vibration-assisted friction stir welding (UVaFSW) process, the geometric shape of the contact surface between the horn and the tool was considered, and a previous point source of ultrasound was replaced by a line source which is more in line with the actual situation. With the established ultrasonic field model based on a line source of sound, the friction coefficient on the tool/workpiece interface was modified by considering the ultrasonic action from different directions. Combined with the computational fluid dynamics model, the UVaFSW process was numerically simulated. It was found that the line source of ultrasonic energy improved the computation accuracy of ultrasound pressure distribution, and ultrasonic antifriction effect greatly reduced the interfacial friction coefficient near the pin. The exerted ultrasonic vibration led to a slight overall decrease in total amount of heat generation in UVaFSW due to the dual effects of acoustic softening and ultrasonic antifriction. The model was validated by comparing the calculated thermal cycles and the thermo-mechanically affected zone with the experimental measurements. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study conducted numerical simulations and experimental validation on the ultrasonic vibration-assisted friction stir welding (UVaFSW) process by considering the synchronous interaction mechanism between ultrasonic vibration, tool, and thermo-mechanical behavior. The results showed that the use of a line source of ultrasonic energy improved the computation accuracy and reduced the interfacial friction coefficient.