液氮冷却实现电火花工具电极低损耗仿真研究
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摘要
工具电极损耗对工件的精度有较大影响.从电火花加工实质为热能加工着手,对常温和液氮冷却下工具电极单脉冲放电温度场进行对比、分析,通过传热理论得出常温下和液氮冷却时工具电极表面温度场及其变化曲线.结果表明:脉宽内,液氮冷却可降低放电点最高温度和温升;脉间内,液氮冷却可将放电点温度在极短时间内冷却至初始温度,从而减少因热量累积导致的工具电极损耗.因此,液氮冷却可有效降低工具电极损耗.
Tool wear obviously affect the accuracy of the workpiece in EDM.Thermal etching is the nature of EDM machining.Simulation comparisons between common and cryogenic cooling EDM were conducted,from which the temperature fields and temperature curves were obtained.Then,the simulation were studied and analyzed by using heat transfer theory.The analysis showed that,after the discharge pulse,liquid nitrogen could lower the maximum temperature and temperature range around the discharge point,and after the pulse interval,the temperature of the discharge point could be cooled to the initial temperature in an extreme short time,and avoided heat buildup caused by other discharge,which reduces tool wear caused by heat buildup.Thus,cryogenic cooling has obvious effect to reduce the tool wear in EDM.
Tool wear obviously affect the accuracy of the workpiece in EDM.Thermal etching is the nature of EDM machining.Simulation comparisons between common and cryogenic cooling EDM were conducted,from which the temperature fields and temperature curves were obtained.Then,the simulation were studied and analyzed by using heat transfer theory.The analysis showed that,after the discharge pulse,liquid nitrogen could lower the maximum temperature and temperature range around the discharge point,and after the pulse interval,the temperature of the discharge point could be cooled to the initial temperature in an extreme short time,and avoided heat buildup caused by other discharge,which reduces tool wear caused by heat buildup.Thus,cryogenic cooling has obvious effect to reduce the tool wear in EDM.
引文
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[2]李冬林,朱荻,曲宁松.电火花成型加工工具电极损耗的研究[J].电气技术与自动化,2005,34(4):108-111.
[3]李丽,殷凤仕,牛宗伟,等.电沉积Cu基SiC复合电极材料[J].功能材料,2013,44(8):1 188-1 190.
[4]明平美,朱荻,曾永彬,等.纳米氧化镧对电铸电极材料抗电蚀性的影响[J].稀土,2006,27(3):20-64.
[5]楚振斌.电火花加工中电极低损耗理论[C]//中国机械工程学会特种加工分会.第三届全国电加工学术会议论文选.庐山:中国机械工程学会特种加工分会,1979:1-12.
[6]Sidhu,Buta S.Influence of cryogenic treated electrode on EDM output parameters[C]//9th International Conference on Advances and Trends in Engineering Materials and their Applications.2011:219-225.
[7]Srivastava V,Pandey P M.Performance evaluation of electrical discharge machining(EDM)process using cryogenically cooled electrode[J].Materials and Manufacturing Processes,2012,27(6):683-688.
[8]Srivastava V,Pandey P M.Effect of process parameters on the performance of EDM process with ultrasonic assisted cryogenically cooled electrode[J].Journal of Manufacturing Processes,2012,14(3):393-402.
[9]Srivastava V,Pandey P M.Study of ultrasonic assisted cryogenically cooled EDM process using sintered(Cu–TiC)tooltip[J].Journal of Manufacturing Processes,2013,15(1):158-166.
[10]李建功,许加利,裴景玉.基于Fluent电火花深小孔加工间隙流场的研究[J].电加工与模具,2009(2):19-22.
[11]张朝晖.ANSYS14.0分析工程应用实战手册[M].北京:中国铁道出版社,2010.
[12]刘庆明,汪建平,李磊,等.火花放电能量及其损耗的计算[J].高压电技术,2014,40(4):1 255-1 260.
[13]刘志东,高长水.电火花加工工艺及应用[M].北京:国防工业出版社,2010
[14]Shao B,Rajurkar K P.Micro-EDM pulse energy distribution ratio determination[C]//University of Victoria.Symposium on Proceedings of the 8th International Conference on Micro-Manufacturing.Vitoria:University of Victoria,2013:318-323.