【作者】 解宝成；

【导师】 王振龙；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 微小孔和阵列孔加工一直是机械加工领域的难题之一。微细电火花加工技术的非接触式加工、无明显宏观作用力和“以柔克刚”等特点，使其在加工微小孔、阵列孔，尤其在加工难加工材料小孔时具有明显的优势。因此，微小孔和阵列孔的微细电火花加工技术已成为当前微细加工技术研究与应用的热点。然而在微小孔微细电火花加工过程中也存在着明显的局限性，如工具电极损耗大、放电状态不稳定、加工效率低等问题，阻碍了加工过程的顺利进行。通常采取电极旋转、电极削边、定时抬刀和超声复合加工等辅助策略来改善极间放电状态以降低电极损耗、提高加工效率和加工状态的稳定性。尽管如此，由于电火花放电过程的复杂性和随机性，对放电过程基础理论的研究，特别是对放电过程中材料蚀除过程和电蚀产物排出过程的研究尚存在诸多不足，已成为制约微小孔和阵列孔微细电火花加工技术发展与应用的瓶颈。为此，本文在分析国内外相关文献资料的基础上，对电火花单脉冲、有限次脉冲和连续脉冲放电过程的温度场分布和微小孔、阵列孔微细电火花加工过程的流场分布进行理论分析与实验研究，分析了放电过程中材料的蚀除过程和电蚀产物的排出过程的影响因素，为深入研究微细电火花加工技术提供了理论依据。单脉冲放电过程是认识和研究电火花放电过程的基础。本文基于热传导理论，对电火花单脉冲放电过程进行温度场研究。通过数值模拟单脉冲放电过程温度场分布，分析了峰值电流和脉宽对温度场分布和放电凹坑尺寸形貌的影响规律，并做相应的实验验证。通过数值模拟相同放电能量条件下单脉冲放电过程温度场分布，分析了不同的峰值电流和脉宽组合对放电凹坑尺寸的影响规律，为提高能量利用效率提供了理论依据。电火花连续脉冲放电过程可以看作是由无数次单脉冲放电过程重复叠加的结果。然而由于电火花放电过程的复杂性和随机性，很难将单脉冲放电过程的研究结果直接推广至连续脉冲放电过程。为此，在单脉冲放电过程温度场研究的基础上，通过数值模拟有限次脉冲放电过程温度场分布，分析了不同放电位置对后续脉冲放电过程温度场分布和蚀除凹坑的影响规律。根据有限次脉冲放电凹坑的分布情况和极间电场分布情况，确定了连续放电位置的随机分布原则，并依此建立了连续脉冲放电过程的温度场模型。通过数值模拟连续脉冲放电过程温度场分布，仿真了工件表面的动态蚀除过程；分析了单个脉冲放电过程的残留温度场和蚀除凹坑对后续脉冲放电过程温度场分布和蚀除凹坑的影响规律，并做了相应的实验验证。在微小孔微细电火花加工过程中，通常采用电极削边和定时抬刀等工艺来提高电蚀产物的排出效率以改善加工状态，这些改进措施都与间隙流场密切相关。因此，对微细电火花圆柱电极、削边电极旋转和抬刀加工过程中间隙流场进行了仿真，通过数值模拟间隙流场中速度场分布和电蚀产物的运动规律，分析了在电极旋转加工过程中电极形状差异对加工效率的影响规律、以及在抬刀加工过程中抬刀速度和高度对加工效率的影响规律，并做相应实验验证。在阵列孔微细电火花加工过程中，工具电极损耗严重、加工效率低、阵列孔一致性差和放电状态不稳定等问题一直限制着阵列孔微细电火花加工技术的快速发展，通常采取微细电火花超声复合加工方法来提高加工效率和放电状态的稳定性，但并没有从理论上合理的解释其作用机制。为此，结合微细电火花超声复合加工阵列孔实验，对阵列孔微细电火花超声复合加工过程间隙流场进行研究，通过数值模拟一个振动周期内间隙流场中电蚀产物的运动规律，分析了超声振动对微细电火花超声复合加工过程中电蚀产物排出过程的作用机制、以及超声的振幅和频率对加工效率的影响规律。综上所述，本文研究了电火花单脉冲、有限次和连续脉冲放电过程的温度场分布情况，并据此分析和探寻了电火花放电过程中材料的蚀除机理；研究了电火花加工微小孔和阵列孔过程的间隙流场分布情况，并据此分析和优化了电蚀产物的排出过程。上述研究为进一步挖掘微细电火花加工的技术潜能提供了一定的理论依据。更多还原

【Abstract】 The machining of micro-hole and array holes is always the difficult problem inthe field of mechanical processing. Micro-EDM technology has a feature of Non-contacting machining method, no obvious macroscopic applied force and goodcontrollability, and thus is an important means of machining micro-hole and arrayholes at present. So micro-EDM of micro-hole and array holes is one of theeffective approaches to solve the above processing problem.But micro-EDM of micro-hole and array holes has obvious limitations, forinstance, the heavy tool wear, the unstable discharge condition and low machiningefficiency, which hinder the machining process smoothly. In order to decrease toolwear and improve working efficiency and the discharge condition stability,processing strategies have been usually applied to improve discharge status, such astool electrode rotary, coated electrode, shaving electrode, shaking electrode, liftingelectrode, ultrasonic combined machining. However, there are still many problemsof the fundamental theory research in EDM process due to its complexity andrandomicity, especially material removal process and debris discharge processwhich have become bottleneck for EDM technology development and application.Therefore, according to numerous related literatures at home and abroad, theresearch on the temperature field distribution of single pulse discharge, finite pulsesdischarges and continuous pulse discharges and distribution of flow field of EDMof micro-hole and array holes was discussed by theoretical simulations andexperiments. Simultaneously the influencing factor on material removal process anddischarge process of debris has been analyzed to supplement and enrich the theoryof EDM technology.Single pulse discharge is the basis of knowledge and research of continuouspulse discharge processing. In this paper, the temperature field distribution of thesingle pulse discharge process was firstly discussed. Based on heat transfer theory,the time-varying radius, time-varying heat flow density of the temperature fieldmodel of electric spark single pulse discharge process has been established. Basedon temperature field simulation of the model, the influence law of the peak current and pulse width on the temperature field distribution and discharge crater size, andthe corresponding experiment has been carried out.Continuous pulse discharges process can be regarded as the superpositionprocess of countless times single pulse discharge process. But it is difficult to makesingle pulse discharge process results directly applied to continuous pulse dischargeprocess because of the complexity of continuous pulse discharge process. Therefore,the model of finite pulses discharge has been established based on the temperaturefield of single pulse discharge process. Through the temperature field simulation offinite pulses discharge model, the influence law of discharge position far and nearon the temperature field distribution of subsequent pulse discharge has been carriedout. According to the finite pulses discharge crater position distribution and thesimulation distribution of electric field, the random distribution principle of thecontinuous discharge position has been established. The temperature field model ofcontinuous pulse discharge process has been established, the temperature fieldmodel of continuous pulse discharge and the dynamic process of surface corrosionprocess and the formation process of surface topography has been simulated. Theinfluence laws of the each pulse discharge removal of crater and the highesttemperature and the pulse width and peak current on the material removal inprocess and processing surface morphology formation have been analyzed.In micro-EDM of micro-hole process, chamfered edge electrode and electrodelifting usually adopt to improve the discharge efficiency, which are closely relatedwith gap flow field. So gap flow field simulation model of micro-EDM has beenestablished. Through the numerical simulation of the particle movement rule in gapflow field, the influence of electrode shape differences and height of electrodelifting on machining efficiency have been analyzed, and the correspondingexperiment has been carried out.In micro-EDM of array holes process, the wear of tool electrode, the low ofworking efficiency, the difference consistency of array holes and the instability ofdischarge status has been limit micro-EDM of array holes technology. Micro EDMcompound ultrasonic processing method has been usually adopt to improve workingefficiency and the stability of the machining process. Therefore, combined withmicro-EDM compound ultrasonic processing experiment results, the flow fieldsimulation model of micro-EDM of array holes compound ultrasonic machiningprocess has been established. Through the numerical simulation of the particle movement of flow field, the influence law of ultrasonic amplitude and frequency onmachining efficiency has been analyzed, and the corresponding experiment hasbeen carried out.Sum up, the temperature field distribution of single pulse discharge, finitepulses discharge and continuous pulse discharge process has been carried out toexplore the mechanism material removal of EDM process. The flow fielddistribution of micro-EDM of micro-hole and array holes has been carried out tooptimize EDM process. The above research for further micro-EDM technologypotential laid a certain theoretical basis.更多还原