超声辅助电解电火花线切割流场仿真及试验研究

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

目的将超声振动工艺引入电解电火花线切割加工,研究分析超声振动对加工过程的影响规律,并分析加工参数对加工性能的影响。方法以镍钛记忆合金为加工材料,对超声振动辅助电解电火花线切割加工进行仿真及试验研究。通过理论分析和有限元仿真分析,对超声振动引入后对流场的影响规律进行深入研究;通过正交试验,分析了超声振动辅助电解电火花线切割的最佳工艺参数。结果基于气泡在流场内的受力情况构建了数学模型,超声振动引入后气泡脱离半径变小,加速了气泡从电极丝上脱离。根据有限元仿真结果可知,附加超声振动能使极间流场速度明显上升,气体排除效率显著升高。正交试验结果表明,脉冲宽度以及峰值电流对加工表面粗糙度值的影响显著,超声振幅对加工表面粗糙度值的影响较小。对比试验结果表明,超声振动能显著提高材料去除率,平均增幅达10%,加工表面可以避免由过电解引起的点蚀现象。结论提出的气泡脱离模型以及流场仿真为超声振动辅助电解电火花线切割加工机理研究提供了新的思路。加工参数对加工表面粗糙度值的影响程度依次为峰值电流(I_(p))>脉冲宽度(T_(on))>超声振幅(A_(usv)),最优加工参数为T_(on)=12μs、I_(p)=6 A、A_(usv)=8μm。将超声振动工艺与电解电火花线切割相结合,在提高材料去除率的同时提高加工表面质量。

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:I_(p)>T_(on)>A_(usv).The optimal processing parameters are:T_(on)=12μs,I_(p)=6 A,A_(usv)=8μm.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.