【作者】 王明环；

【导师】 朱荻；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 电解加工(electrochemical machining,ECM)是一种利用金属阳极电化学溶解原理将零件加工成型的特种加工方法。由于电解加工具有工具无损耗、加工材料范围广、加工后零件表面无变形和再铸层等优点,成为航空航天,兵器制造等国防工业生产中的关键技术之一。特别是电解加工以离子的形式对材料进行去除的特点,使得其在微细加工中具有一定的发展潜力。本论文结合制造业中大量存在的尺寸为几微米至几百微米的微细结构,对微细电解加工中关键技术进行研究,如微细工具电极的制备、微细电解加工过程的控制与检测、微细电解加工效率的提高、加工产物的排出、加工异型面等。本文采用了四轴联动的微细电解数控加工机床进行。针对微细电解加工的特点,开发出一套微细电解加工系统,该系统包括运动控制部分、实验数据采集与处理部分和电解液、电源系统等。系统充分考虑了微细电解加工中的间隙检测与短路保护。通过低电压短路对刀法可以准确测量出加工中的间隙;采用周期循环对刀加工的方法,可以稳定地将加工间隙控制在较小的范围内(二十微米以内),改善了微细电解加工的定域性,提高了加工的精度。实验过程中对加工中的电信号进行实时检测,同时控制系统根据采集到的信号作出快速反应,避免了加工过程中短路以及火花现象的发生,提高了加工过程的稳定性。针对微细电解加工中微细电极难以制备的问题,本文基于电化学原理进行了微细电极制备方法的工艺实验研究。选择具有较高热传导性、导电良好和较高硬度的钨为电极材料。通过对加工电压的控制,制备出探针形状和直径均匀的微圆柱体状的电极,并对电极的成形规律进行研究,得出其成形规律方程。论文同时分析了各加工工艺参数,如电解液浓度,电极浸入深度,通电方式等对微探针和微圆柱体电极成形的影响。加工出尖端尺寸微米级以下的探针和直径尺寸3μm～几十微米的微细圆柱体电极。针对微细电解加工效率低的问题,本文进行了微细群电极的制备研究。通过电极制备过程中工具阴极形状的优化,使阳极表面电流密度均匀,制备出直径一致的微细群电极结构。在微细电极制备成功的基础上,本文以微细孔和微细群孔加工为研究对象,对微孔电解加工的性能进行了研究,分析了不同的电极进给方式、电解液组成、加工电参数和电极形状等对微孔电解加工精度和加工稳定性的影响。结果显示,通过采用脉冲电解加工电源、带有排屑槽的微螺旋电极、低浓度的电解液、低加工电压等措施,可以改善微细电解加工的性能,加工精度、加工稳定性和加工速度等都得到了明显的提高。并根据分析优化后的参数,以制备出的群电极为工具阴极进行微细群孔的电解加工实验。本文还对涡轮叶片内具有环形肋的冷却通道(又名竹节孔)的加工方法进行研究,提出采用成形工具电极进行竹节孔电解加工的方法。工具电极为一管状成形电极,其外表面采用电解加工的方法加工呈凹槽状,经过绝缘处理后作为工具电极使用。同时,提出了计算机模拟电解加工的方法,以获得稳定的电解加工工艺参数和较好的尺寸精度,通过设定不同的参数,对竹节孔的电解加工过程进行模拟,并将模拟结果指导加工实验的进行,提高了加工精度和效率。论文中还对竹节孔对航空发动机叶片换热效果的影响进行了分析,结果表明将叶片内的冷却孔加工呈肋状,冷却效果比原来提高了2～3倍。更多还原

【Abstract】 Electrochemical machining (ECM) is a non-traditional machining technology based on electrochemical anodic dissolution of metal in electrolyte. ECM becomes an important technology in manufacturing of aviation and weapons because of hard material could be machined regardless of its property and there is no stress and recast on the machined workpiece. Furthermore, ECM could machine the material ion by ion and shows its potential in micro-machining system. In this dissertation the microstructures with size from a few microns to a few hundred microns in industry are researched. Some key technologies in electrochemical micromachining (EMM) are studied, including preparation of the micro-electrodes, gap control and detection between cathode and anode, increasing the efficiency for EMM, wipping off the sludge in the interelectrode gap and machining of complicated shape, etc.The four-feed CNC micro-ECM machine tool is used in the research. The numerical control system is developed on the basis of the characteristics of micro-ECM. It consists of motion control, detection and analysis of experimental date, electrolyte and power supply. Detection of the intereletrode gap and protection of the short circuit are also studied in this research. Low voltage is used to detect the tool contaction exactly. The machining gap could be measured and kept exactly as smaller as 20 micrometers by periodic tool positioning. The localization and the accuracy are improved. The electric signal in the experiment is detected in real time. The control system responds quickly to the signal gathered. Short-circuit and sparks could be avoided during the machining, the stability of the machining process is improved.The preparation of the micro-electrode in EMM is very important. The author studies the fabrication of the micro-pin on the basis of electrochemical principles. Tungsten is selected as the electrode material because of its good heat and electricity exchanger ability and rigidity. By controlling the applied voltage, the different shaped micro-pins could be obtained, including the STM tip and cylindrical micro-pin. Furthermore, the relationship between diameter of the micro-electrode and machine time is proposed. Various parameters affecting the formation of the micro-pin, such as electrolyte concentration, immerging depth, electrifying mode are discussed in detail. STM tips with size less than micrometers and the micro-pin electrode with size from 3 micrometers to several tens of micrometers are produced. The author also presents a method to process the multiple microelectrodes in order to improve the machining accuracy of EMM. Current density distribution on the anode becomes uniform by optimizing the shape of cathode in ECM. Finally, a row of multiple electrodes with cylindrical shape is machined.The author studies the performances of micro-ECM by processing the micro-hole and micro-holes array. The effects of various parameters on the machining accuracy and stability are investigated, including electrode feeding mode, electrolyte, electrical parameters and shape of electrode, etc. Results indicate that pulse current, low concentration electrolyte, low voltage and spiral microelectrode could attribute good performance of EMM. Machining accuracy, stability and machining velocity could be improved. By using the optimized parameters micro-holes array are produced by using the row of multiple micro-electrodes fabricated in advance.In this dissertation, the author also presents the machining method of a kind of cooling hole with ring ribs on the hole wall. These ribs are called turbulators. A shaped electrode is selected as cathode to machine the turbulators using ECM. The shaped cathode is a metal hollow tube with groove on the surface. These grooves are machined by electrochemical machining. After the insulated treatment, the shaped electrode could be used in preparation of the turbulated cooling duct. In order to obtain the good processing parameters and dimension accuracy, numerical simulation is applied. Different processing parameters are used to perform the simulation of the ECM process. Parameters with good accuracy and high efficiency are selected to machine the ribs in the experimentation. Finally, Computational Fluid Dynamics (CFD) model is used to analyse the heat transfer of this kind of cooling hole. Results indicate that the cooling duct with turbulators has a considerablely higher cooling efficiency than smooth cooling hole.更多还原