石墨电极电火花高效低损耗加工仿真与实验研究
发布时间：2018-12-18 20:39
【摘要】：电火花加工作为特种加工的重要组成部分,凭借其无宏观切削力、可加工异形型腔、材料适应范围广等优点,在航空航天、能源动力、模具制造等领域得到了长足的发展。在电火花加工的过程中,工具电极是加工效果的关键决定因素。不同材料的电极对加工效率、电极损耗、工件表面粗糙度等都有较大的影响。石墨电极具有放电效率高、损耗小、重量轻、膨胀率极低、易加工修整、不易拉弧放电等优点,在电火花加工领域受到广泛应用。探究石墨电极电火花加工机理与工艺规律,是提高电火花加工效率、减小电极损耗、改善工件表面质量的关键,也是电火花行业的追求目标。本文为探寻石墨电极电火花高效率低损耗加工的机理与最佳参数,进行了深入的理论分析与大量的实验研究。首先为探究电火花加工的微观过程与原理,进行了基于单脉冲放电实验的石墨电极电火花加工温度场仿真。根据单脉冲放电实验结果,对放电过程中的能量分配进行总结分析,拟合出放电通道半径。结合目前电火花领域主流的高斯热源模型建立起石墨电极电火花单脉冲放电的热传导模型。在该模型的基础上进行温度场有限元仿真,得到温度场仿真模型并进行实验验证,利用该仿真模型对加工效率与电极损耗进行了预测与验证。为探索各加工参数对石墨电极电火花加工效果的影响,进行了单因素实验研究。进行实验方案设计与实验误差排除,分别研究了电极极性、脉冲占空比、脉冲宽度、峰值电流与伺服参考电压等因素对加工效率、电极损耗、表面粗糙度的影响规律,结合温度场仿真模型对实验现象与成因进行理论分析,给出了实际加工过程中参数选取的建议。在总结单因素实验结果的基础上,开展石墨电极电火花加工中心复合实验,建立加工效率与电极损耗的回归方程并进行了实验验证。通过多目标优化求解出高效率低损耗加工的最佳参数。对实验过程中出现的电极负损耗现象进行了探究。通过观察石墨电极表面微观结构、分析积碳层的组成成分,发现电极表面生成了类金刚石物质,利用仿真确定了其保护作用。通过表面形貌与实验测量推断出电极表面积碳不定期生长与脱落的现象。
[Abstract]:As an important part of special machining, EDM has made great progress in the fields of aerospace, energy power, mould manufacturing and so on, because of its advantages such as no macroscopic cutting force, machining special-shaped cavity and wide range of materials. In the process of EDM, tool electrode is the key determinant of machining effect. The electrode of different materials has great influence on machining efficiency, electrode loss, workpiece surface roughness and so on. Graphite electrode is widely used in the field of EDM because of its advantages such as high discharge efficiency, low loss, light weight, low expansion rate, easy to be machined and trimmed, and not easy to pull arc discharge. It is the key to improve the efficiency of EDM, reduce the electrode loss and improve the surface quality of the workpiece to explore the mechanism and process law of EDM with graphite electrode, and is also the pursuit goal of EDM industry. In order to find out the mechanism and optimum parameters of graphite electrode EDM with high efficiency and low loss, the theoretical analysis and a large number of experimental studies have been carried out in this paper. In order to explore the micro process and principle of EDM, the temperature field of EDM based on single pulse discharge experiment was simulated. According to the experimental results of monopulse discharge, the energy distribution during discharge is summarized and analyzed, and the discharge channel radius is fitted. The heat conduction model of single pulse discharge of graphite electrode EDM is established by combining Gao Si heat source model which is the mainstream in the field of EDM at present. Based on this model, the temperature field is simulated by finite element method, and the simulation model of temperature field is obtained and verified by experiments. The machining efficiency and electrode loss are predicted and verified by the simulation model. In order to explore the effect of machining parameters on the effect of graphite electrode EDM, a single factor experiment was carried out. The effects of electrode polarity, pulse duty cycle, pulse width, peak current and servo reference voltage on machining efficiency, electrode loss and surface roughness were studied. Based on the simulation model of temperature field, the experimental phenomenon and cause of formation are analyzed theoretically, and some suggestions on the selection of parameters in the process of practical processing are given. On the basis of summing up the results of single factor experiments, the composite experiment of graphite electrode EDM center was carried out, and the regression equation of machining efficiency and electrode loss was established and verified by experiments. The optimum parameters of high efficiency and low loss machining are solved by multi-objective optimization. The phenomenon of negative electrode loss in the process of experiment was investigated. By observing the microstructure of graphite electrode surface and analyzing the composition of carbon deposition layer, it was found that diamond-like carbon was formed on the electrode surface, and its protective effect was determined by simulation. The phenomenon of irregular growth and falling off of carbon deposition on the electrode surface was inferred by surface morphology and experimental measurement.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG661
本文编号：2386468
[Abstract]:As an important part of special machining, EDM has made great progress in the fields of aerospace, energy power, mould manufacturing and so on, because of its advantages such as no macroscopic cutting force, machining special-shaped cavity and wide range of materials. In the process of EDM, tool electrode is the key determinant of machining effect. The electrode of different materials has great influence on machining efficiency, electrode loss, workpiece surface roughness and so on. Graphite electrode is widely used in the field of EDM because of its advantages such as high discharge efficiency, low loss, light weight, low expansion rate, easy to be machined and trimmed, and not easy to pull arc discharge. It is the key to improve the efficiency of EDM, reduce the electrode loss and improve the surface quality of the workpiece to explore the mechanism and process law of EDM with graphite electrode, and is also the pursuit goal of EDM industry. In order to find out the mechanism and optimum parameters of graphite electrode EDM with high efficiency and low loss, the theoretical analysis and a large number of experimental studies have been carried out in this paper. In order to explore the micro process and principle of EDM, the temperature field of EDM based on single pulse discharge experiment was simulated. According to the experimental results of monopulse discharge, the energy distribution during discharge is summarized and analyzed, and the discharge channel radius is fitted. The heat conduction model of single pulse discharge of graphite electrode EDM is established by combining Gao Si heat source model which is the mainstream in the field of EDM at present. Based on this model, the temperature field is simulated by finite element method, and the simulation model of temperature field is obtained and verified by experiments. The machining efficiency and electrode loss are predicted and verified by the simulation model. In order to explore the effect of machining parameters on the effect of graphite electrode EDM, a single factor experiment was carried out. The effects of electrode polarity, pulse duty cycle, pulse width, peak current and servo reference voltage on machining efficiency, electrode loss and surface roughness were studied. Based on the simulation model of temperature field, the experimental phenomenon and cause of formation are analyzed theoretically, and some suggestions on the selection of parameters in the process of practical processing are given. On the basis of summing up the results of single factor experiments, the composite experiment of graphite electrode EDM center was carried out, and the regression equation of machining efficiency and electrode loss was established and verified by experiments. The optimum parameters of high efficiency and low loss machining are solved by multi-objective optimization. The phenomenon of negative electrode loss in the process of experiment was investigated. By observing the microstructure of graphite electrode surface and analyzing the composition of carbon deposition layer, it was found that diamond-like carbon was formed on the electrode surface, and its protective effect was determined by simulation. The phenomenon of irregular growth and falling off of carbon deposition on the electrode surface was inferred by surface morphology and experimental measurement.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG661
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