基于电解液非线性特性的叶片电解加工阴极设计

叶片是航空发动机的关键零件,以某型航空发动机转子叶片为研究对象,针对叶片电解加工阴极设计这一工程问题,着重考察了采用非线性电解液进行加工时,电解液的非线性特性对阴极设计的影响.本文首先建立了模型叶片的三维实体造型,在此基础上探讨了电解液的非线性特性对电解加工过程和阴极设计产生影响的机理,通过半实验法与数据库技术相结合的方式有效的将这种非线性特性集成到阴极设计方法中.     

基于叶片电解加工电场和流场特性的阴极设计及工艺试验研究

针对航空发动机叶片电解加工阴极设计这一具体工程应用，在模型叶片三维实体建模的基础上，着重研究两种阴极设计方法，即基于叶片电解加工实际电场分布的阴极设计有限元数值解法以及同时考虑极间电场和电解液流场特性的阴极设计有限元数值解法。详细地对比了两种阴极设计方法对极间电势分布、间隙分布和阴极边界条件的影响，通过一系列的工艺试验验证了同时考虑电解加工电场和流场特性的阴极设计方法较单纯考虑电场特性的阴极设计方法更全面、更符合电解加工的实际物理过程，因而所设计的阴极更加精确合理。     

基于有限元数值方法的电解加工工件型面的预测

采用有限元数值算法求解加工间隙中的电场分布，考虑间隙内流场和非线性电解液的影响，对最终的阳极工件型面进行预测。对某型发动机叶片三维复杂曲面进行了预测计算，并与其工艺试验结果进行比较，证明预测模型具有较高的精度。     

发动机叶片电解加工阴极设计有限元数值解法研究

以某型航空发动机转子叶片为研究对象，讨论了加工区域内的电场分布模型和阴极、阳极需要满足的边界条件，利用有限元法对复杂边界曲面具有较强的适应能力的特性，将加工区域离散后逐层求解极间间隙内的电位分布，将有限元数值解法成功地运用到加工叶片的工具阴极的设计中，从而获得满足加工精度要求的阴极。     

基于六维力电解加工间隙在线检测试验研究

为了实时检测加工间隙,把流体作用在阴极上的六维力作为研究参数:设计通电解液不通电、通电加工两大类工况,从定性和定量两个角度分析六维力与加工间隙之间的关系;并以平面、斜面、叶片型面三种阴极进行试验加工,用最小二乘多变元线性拟合法,分别建立平面、斜面阴极加工的六维力与加工间隙之间的关系方程式,用叶片型面加工数据对建立的关系方程式进行检验与修正,得到最终的修正关系式:分析关系式各参量之间的关系,并得到结论:在15％的误差范围内,关系式可以用于在线检测加工间隙。     

涡轮叶片电解加工的流场仿真分析

涡轮叶片是航空发动机中的重要零件,主要加工方式是电解加工。基于电解加工流场理论,建立涡轮叶片的三维模型和电解加工的流场模型。应用COMSOL Multiphysics软件对涡轮叶片电解加工进行流场仿真分析,研究流场的分布及特性,分析不同加工间隙和不同电解液压力对流场的影响。通过分析,得出涡轮叶片电解加工时加工间隙、电解液压力与流场流速之间的关系。     

数控电解机械复合切割加工间隙研究

根据电解加工平衡间隙理论,建立了数控电解机械复合切割加工的物理和数学模型;基于FLUENT软件分析得到数控电解机械复合切割加工的间隙内流场分布规律,根据间隙内流场分布规律优化设计阴极,改善了流场分布。并以某一型号阴极为例进行试验研究,得到电压、主轴转速和电解液温度等加工参数与加工间隙的影响规律,求得对应条件下最快平衡进给速度,为实际加工提供依据。     

航空叶片电加工多物理场耦合仿真及实验研究

针对涡轮转子叶片电解加工过程参数分布复杂、型面难以预测的问题,分析电解加工过程中电场、流场、温度场特性,建立多场耦合数学模型并利用Matlab ode45函数求解多物理场耦合数值解;利用COMSOL软件对叶片电解加工过程多物理场进行数值模拟,得到加工间隙内电解液流速、温度、电解质电流密度的分布规律;选择合适的工艺参数完成了Inconel 718叶片电解加工试验,用三坐标测量机得到叶片轮廓曲线的实测值,与单电场仿真的理论值与多物理场耦合后仿真的理论值进行对比。结果表明,多物理场耦合仿真的理论值更接近于试验检测的实测值,能够准确模拟实际电解加工过程,可以为实际加工过程阴极工具设计、参数优化等提供理论依据,对提高电解加工质量和效率有重要意义。     

旋转超声电解复合加工三维流场仿真

单因素试验表明在相同加工条件下旋转超声电解复合加工小孔效率优于旋转电解加工小孔,为研究阴极旋转和高频振动对旋转超声电解复合加工流场的影响,基于有限元ANSYS CFX软件建立了旋转超声电解复合加工流场仿真模型,分析了阴极旋转和阴极高频振动下加工间隙内的流场变化。分析结果表明:阴极旋转使得电解液绕流,对电解液速度、压力影响较小,而阴极高频振动使得加工区发生抽吸,加速了电解液的流动,使得加工区内电解液压力波动变化,有利于电解液的更新与电解产物的排出。     

圆形出液口悬浮阴极平面电化学加工间隙建模及实验研究

提出利用极间电解液液膜支撑阴极悬浮形成加工间隙,通过调节流量和电流实现极间间隙的调节和控制的新方法。以圆形出液口悬浮阴极平面电化学加工为例,基于流体力学和电极过程动力学理论建立加工间隙的数学模型,得到间隙与流量、压差及电流之间的关系。利用Fluent软件对间隙模型流场特性进行分析,得到间隙中电解液的压力场和速度场的分布情况,进而得到进出口压差和出口流速;实验获得不同流量、电流条件下的加工间隙。理论模型计算结果和实验数据结果相近,变化规律基本一致。     

采用BP神经网络的叶片电解加工精度预测

工件成型精度的预测是实际电解加工的重要研究课题,快速、准确地选取加工参数并预测出工件的形状精度可以减少试验次数,缩短试制周期,降低生产成本。本文以某型发动机叶片为研究对象,对影响电解加工精度的主要加工参数进行了分析,结合工艺试验的数据建立了BP网络模型,并采用该模型进行了不同加工参数组合下叶片型面的预测。结果表明,该模型的预测精度比较高,具有一定的工程实用性。     

发动机叶片电解加工夹具结构设计与密封性能分析

探讨了叶片全方位电解加工时,夹具的总体结构设计、电解液流道布局、夹具体防腐蚀、导电和绝缘等影响叶片成型精度的若干关键问题;分析了夹具的密封性能对电解液压力、流速和加工稳定性的影响;通过叶片加工试验验证了所设计夹具的精度和可靠性。试验结果表明所设计的夹具定位准确,能加工出符合精度要求的发动机叶片;夹具的密封性能得到极大改善,在相同的进口压力下,加工腔及流道内的压力损失急剧减小,出口压力提高。     

发动机叶片电解加工工具进给方向分析和系统设计

超薄扭曲叶片因叶型薄、型面复杂、精度高 ,目前主要以电解加工作为首选加工工艺。本文以某型发动机叶片为研究对象 ,对电解加工中阴极进给方向和毛坯装夹位置作了优化选择 ,同时采用开放式控制系统、模块化设计思想开发可重构电解机床系统以满足不同叶片型面加工的要求。     

Electrochemical machining of the spiral internal turbulator

Electrochemical machining (ECM) is promising to machine the complex surface due to the advantages of no tool wear, stress free, and good machining accuracy. In this study, a machining method of the spiral internal ribs by ECM is presented. Firstly, the ECM experimental system is developed, which consists of electrolyte supply module, power supply unit, and workpiece-holding device. Then, a shaped cathode was used to process the spiral-turbulated hole on the built system. The shaped cathode was prepared by means of ultraviolet-curing mask method considering the expected spiral turbulator’s shape. Furthermore, parameters affecting the machining accuracy in shape duplication and machining efficiency are analyzed and discussed, especially the voltage and electrolyte concentration which have the main effect on the processed results.     

TOOL DESIGN OF ELECTROCHEMICAL MACHINING WITH PASSIVATED ELECTROLYTE

ＴＯＯＬＤＥＳＩＧＮＯＦＥＬＥＣＴＲＯＣＨＥＭＩＣＡＬＭＡＣＨＩＮＩＮＧＷＩＴＨＰＡＳＳＩＶＡＴＥＤＥＬＥＣＴＲＯＬＹＴＥＺｈｕＤｉＮａｎｊｉｎｇＵｎｉｖｅｒｓｉｔｙｏｆＡｅｒｏｎａｕｔｉｃｓａｎｄＡｓｔｒｏｎａｕｔｉｃｓＡｂｓｔｒａｃｔＢａｓｅｄｏ...     

Investigation into the blade-formation process in electrochemical trepanning of diffusers

Abstract

Electrochemical trepanning process is an advanced manufacturing technology suitable for the machining of aero-engine components such as blades and diffusers. Tool-electrode (cathode) with special electrical isolation is adopted in the experimental investigations of this article using the electrochemical trepanning to produce a flow mode in which the electrolyte is supplied evenly to the blade being machined. The material removal model for these experiments is built based on the main technical principles of the ECM. For a better understanding of the electrochemical trepanning process during the machining of a blade, computer simulations were previously conducted aiming to observe the geometric shaping of the inter-electrode gap. The shaping process dynamic was analyzed and the distribution of electrical field intensity within the gap has been obtained under different feed rates of the tool-electrode relative to the blade. The profile of the cross-section of the blade was evaluated through the simulation, thus indicating that the blade’s taper angler decrease by increasing the feed rate. Also, practical experiments have been carried out, where the corresponding experimental results proved the simulation was effective. The best taper angle (0.70°) resulted from a machining condition in setting up a feed rate of 4?mm/min, whereas 3.72° was produced using 1?mm/min. Furthermore, a sector with multiple blades was electrochemically manufactured with the optimal set up of experimental parameters, being that the machining accuracy was about 0.12?mm. The application reflected that the method proposed in this article is appropriate and can be used for other complex structures in electrochemical trepanning.     

Effects of shielding coatings on the anode shaping process during counter-rotating electrochemical machining

Electrochemical machining (ECM) has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is to a great extent limited by the stray corrosion of the unwanted material removal. Many attempts have been made to improve the ECM accuracy, such as the use of a pulse power, passivating electrolytes and auxiliary electrodes. However, they are sometimes insufficient for the reduction of the stray removal and have their limitations in many cases. To solve the stray corrosion problem in CRECM, insulating and conductive coatings are respectively used. The different implement processes of the two kinds of coatings are introduced. The effects of the two kinds of shielding coatings on the anode shaping process are investigated. Numerical simulations and experiments are conducted for the comparison of the two coatings. The simulation and experimental results show that both the two kinds of coatings are valid for the reduction of stray corrosion on the top surface of the convex structure. However, for insulating coating, the convex sidewall becomes concave when the height of the convex structure is over 1.26 mm. In addition, it is easy to peel off by the high-speed electrolyte. In contrast, the conductive coating has a strong adhesion, and can be well reserved during the whole machining process. The convex structure fabricated by using a conductive iron coating layer presents a favorable sidewall profile. It is concluded that the conductive coating is more effective for the improvement of the machining quality in CRECM. The proposed shielding coatings can also be employed to reduce the stray corrosion in other schemes of ECM.