Effect of high-power ultrasonic vibration on the flexible bending process of thin-walled circular tubes: Numerical and experimental research.

Thin-walled bent tubes are a significant component utilized in the aerospace, shipbuilding, and chemical industries, as well as considering that they are employed as fluid and gas transporters, the quality of their manufacturing and production is critical. In recent years, new technologies for the manufacture of these structures have been developed, the most promising of which is the flexible bending process. Nevertheless, during tube bending, defects like an increase in contact stress and friction force in the bending area, thinning of the bent tube in the extrados zone, ovalization, and spring-back are some of the issues that arise. So, based on the softening and surface effects induced by ultrasonic energy in metal forming, this paper is suggested a novel method to fabricate the bent components by adding ultrasonic vibrations into the static motion of the tube. Therefore, experimental tests and finite element (FE) simulations are employed to assess the impact of ultrasonic vibrations on the forming quality of the bent tubes. Initially, an experimental setup was designed and built to guarantee the transmission of ultrasonic vibrations with a frequency of 20 kHz to the bending area. Afterward, based on the experimental test and its geometrical parameters, a 3D finite element model of the ultrasonic-assisted flexible bending (UAFB) process was developed and validated. According to the findings, forming forces were significantly reduced when the ultrasonic energy was superimposed, and thickness distribution in the extrados zone was significantly enhanced as a result of the acoustoplastic effect. In the meantime, the UV field's application effectively diminishes the contact stress between the bending die and tube, as well as greatly reduces the material flow stress. In the end, it was found that applying UV at the appropriate vibration amplitude can effectively improve ovalization and spring-back. The current study will assist researchers in better understanding the role of ultrasonic vibrations in performing the flexible bending process and achieving improved tube formability.