Flow Field Simulation and Experimental Study of Ultrasonic Vibration Assisted Wire Electrochemical Discharge Machining

Due to the growing demand for high product performance in mould, medical equipment, and other manufacturing fields, more and more difficult-to-machine materials with unique properties were increasingly being used for research and application purposes. TiNi shape memory alloys (SMA) were a popular choice due to its excellent biocompatibility, corrosion resistance, and shape memory properties. However, this material was of great difficulty to machine by using traditional processes, as evidenced by significant tool wear and low-quality machined surfaces. Wire electrochemical discharge machining (WECDM) was a non-contact, specialized machining without macro cutting force, which has high machining accuracy and good machining quality when working with difficult-to-machine metal materials. In order to further enhance the processing efficiency, this paper presented a detailed study of a novel machining process called ultrasonic vibration assisted wire electrochemical discharge machining (USV WECDM), which combined ultrasonic vibration assisted process with wire electrochemical discharge machining process, and analyzed its effect on the machining process. The role of ultrasonic vibration on the machining process mechanism was studied in-depth to reveal its influence on the law. The impact of processing parameters on the machining performance was also analyzed through orthogonal and comparative experiments. The study investigated ultrasonic vibration assisted wire electrochemical discharge machining using nickel-titanium memory alloy as the processing material. The research included theoretical, simulation, and experimental aspects. Firstly, the influence of ultrasonic vibration on the radius of bubble detachment was investigated by theoretical analysis; secondly, the influence law on the flow field after the introduction of ultrasonic vibration was studied in depth by finite element simulation analysis; the optimum parameters of the ultrasonic vibration assisted wire electrochemical discharge machining process were analyzed by orthogonal tests; finally, the excellence of the ultrasonic vibration assisted wire electrochemical discharge machining process was analyzed by comparative tests. The mathematical model was based on the force of bubbles in the flow field. The introduction of ultrasonic vibration resulted in a lower bubble detachment radius, accelerating the detachment of bubbles from the electrode wire. The introduction of ultrasonic vibration significantly increased the velocity of the flow field between poles and improves the efficiency of gas exclusion, according to the results of finite element simulation. The orthogonal test revealed that the pulse width and peak current have a significant effect on the roughness of the machined surface, while the ultrasonic amplitude did not have much effect. Comparative experiments demonstrated that ultrasonic vibration could improve material removal rate by an average of 10%, and could prevent pitting phenomenon caused by over electrolysis on the machined surfaces. The paper proposes a new bubble detachment model and flow field simulation for studying the processing mechanism of ultrasonic vibration assisted wire electrochemical discharge machining process. The influence of processing parameters on the surface roughness (Ra) is as follows: Ip > Ton > Ausv. The optimal processing parameters are: Ton=12 μs, Ip=6 A, Ausv=8 μm. Combining ultrasonic vibration assisted processing with wire electrochemical discharge machining process can significantly improve machining efficiency and prevent pitting on the machined surface caused by over-electrolysis to improve surface quality. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.