整体叶盘叶栅通道电解加工流场仿真研究

电解加工是航空发动机整体叶盘制造的主要技术之一,加工间隙内电解液流动的均匀性是影响加工稳定性和表面粗糙度的核心因素。针对叶栅通道电解加工,对比分析电解液侧流式下的正向流动与反向流动加工间隙内流场状态,通过数值仿真对比分析可知,正流方式下加工间隙内电解液流速较高,流场均匀性较好,故正流方式有利于叶栅通道电解加工。开展了电解液正流电解加工试验,结果表明,采用正流方式进行叶栅通道电解加工,轮毂粗糙度可达0.316μm,叶盆、叶背余量重复误差分别为0.096 mm,0.103 mm,为下一步叶片型面精加工提供了良好的条件。     

双叶片套型电解加工流场设计及优化

具有大小双叶片的扩压器能够改善压气机的性能,在航空发动机中得到广泛应用。此类构件多采用高温合金等难切削材料制造,传统铣削加工存在刀具损耗等问题。电解加工技术具有无机械切削力、工具阴极无损耗等特点。提出一种双叶片套型电解加工的方法,基于法向流程等距的原则设计了叶间出液通道,建立了出液通道宽度递增的流道模型,开展了流场仿真研究,当出液通道的宽度为0.9 mm时,加工区域内电解液的流速分布最均匀。选择GH4169材料进行了双叶片套型电解加工的对比试验,试验结果表明,采用叶间出液的电解液流动方式,加工稳定性得到提高,阴极进给速度由0.6 mm/min提高至1.0 mm/min,材料去除速率达到1 396.5 mm³/min,叶片锥度降低至1：14.29以下,轮毂表面形貌得到改善。     

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。     

振动进给对微尺度群缝电解加工过程的影响

为精确控制振动进给运动,研制了多参数可调的电解加工振动进给装置系统。通过对工具阴极振动进给方式对电解加工间隙内电解产物排出、电解液流场稳定性影响的分析,以剃须刀网罩上的微尺度阵列群缝的电解加工为研究对象开展了系列工艺试验,研究了振动进给的运动参数对微尺度群缝的平均缝宽、侧壁锥度的影响,据此优选了工艺参数,并成功批量加工出了缝宽为0.26mm、侧壁锥度小于5%的微尺度阵列群缝。试验结果证明,振动进给能够有效提高微尺度群缝的电解加工精度和加工过程稳定性。     

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。     

电解光整加工齿轮齿面的试验研究

利用直线刃阴极进行电解光整加工齿轮齿面的试验和加工精度分析研究,试验结果表明,加工过程中电场和流场是影响加工精度的主要因素。基于ANSYS和CFD软件对加工过程中的电场和流场进行数值模拟,分析工具阴极与齿面的相对位置对电流密度、电解液流速和压力分布的影响,为后续试验的改进奠定了基础。     

采用非线性电解液的叶片电解加工阴极设计

工具阴极设计是航空发动机叶片电解加工工艺过程中的关键环节。本文采用有限元数值算法求解加工间隙内的电场分布,考虑非线性电解液对成型规律的影响,进行叶片的阴极设计计算。对加工间隙分布的分析表明,将非线性电解液的影响带入阴极求解中,能使所研究的问题更接近实际情况,从而能提高阴极设计的精度。     

微尺度弧形群缝电解加工试验研究

精密电解加工是剃须刀网罩上微尺度阵列弧形群缝的首选加工工艺,为提高电解加工精度和加工过程稳定性,基于电场分析,优化了工具阴极凸起宽度、凸起高度关键尺寸的设计;基于对流场的数值分析,优化设计了电解液流道结构,优选了电解液进出口压力参数,消除了流道内可能存在的缺液区和流线交叉区域,并据此研制了专用工装夹具。通过工艺试验,研究了端面初始间隙、平均电压,进给速度等关键工艺参数对群缝缝宽的影响。在研制的数控电解加工设备上加工出了缝宽0.24 mm的弧形群缝,且群缝的曲线形状精度高,加工过程稳定,已能够满足批量生产的需要。     

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。     

电极平动式电解孔加工技术研究

从电解液流动角度对影响电解孔加工过程的主要原因进行了分析 ,提出利用电极平动来改善电解加工过程稳定性和提高加工精度 ,研制了电极平动系统 ,进行了加工试验。试验结果表明 ,电极的平动运动使得电解液分布变得均匀 ,消除了空穴和分离流等弊端 ,改进了过程稳定性 ,显著提高了加工精度。     

两步法电化学加工薄壁钼长管的数学建模与实验研究

针对某反应堆用高温燃料包壳加工难题,研究了钼合金薄壁长管部件的电化学加工技术,提出了固定阴极及移动阴极的两步电化学加工方法,建立了移动窄阴极电化学加工的数学模型,针对实施方式、工艺参数等进行了实验。实验结果表明：固定宽电极的电化学加工可大量去除材料,移动窄电极的电化学加工可进行表面精修,采用这两种工艺对直径25.4 mm、长度800 mm的钼管进行加工,获得的直径偏差在0.05 mm以内。     

Flow field design and experimental investigation of electrochemical machining on blisk cascade passage

Electrochemical machining (ECM) provides an economical and effective way for machining heat-resistant, high-strength materials into complex shapes that are difficult to machine using conventional methods. It has been applied in several industries, especially aerospace, to manufacture blisk. The electrolyte flow field is a critical factor in ECM process stability and precision. To improve the process stability and the efficiency of blisk cascade passages, ECM with a radial feeding electrode, a rational electrolyte flow mode for electrochemical machining called “Π shape flow mode”, is discussed in the paper. Three flow field models are described separately in this report: traditional lateral flow mode, positive flow mode and Π-shaped flow mode, and the electrolyte velocity and pressure distribution vectors for each flow mode are calculated by means of a finite element fluid analysis method. The simulation results show that the electrolyte flow is more uniform with the Π-shaped flow mode. The deformation of the cathode, which is caused by the pressure difference, is also analysed in this report. The cascade passage ECM with a radial feeding electrode was experimentally tested out to evaluate the rationality of the flow field, and the fluctuation of current during the process was less than 1 %, which means that the process that uses the Π-shaped flow mode is stable. The feeding velocity of the cathode with the Π-shaped flow mode is approximately 70 % higher than that with the other two flow modes, and the incidences of short circuiting are obviously decreased. The surface roughness of the blisk hub is only 0.15 μm, and the machining error of the hub is less than 0.1 mm. The results demonstrate that using the Π-shaped flow mode can enhance the quality, stability and efficiency of blisk cascade passage ECM.     

航天发动机叶片电解加工流场设计和试验研究

电解加工作为整体构件制造的主要技术之一,其流场设计的合理性将严重影响电解加工过程的稳定性、加工效率和质量。针对航天发动机叶片式扩压器设计了部分阻隔式反W型流场,并开展了与侧流式和反W型流场的仿真比较。仿真结果表明,该流场方式可以保证加工区电解液的高速流动,并能有效避免进/排气边漏液现象。最后,在部分阻隔式反W型流场中开展了叶片式扩压器电解加工试验,在阴极进给速度为0.5 mm/min时加工出了扩压器叶片,验证了流场设计的合理性。     

Cutting tool wear monitoring for reliability analysis using proportional hazards model

Electrochemical machining (ECM) is an important technology in machining difficult-to-cut materials and to shape free-form surfaces. In ECM, material is removed by electrochemical dissolution process, so part is machined without inducing residual stress and without tool wear. To improve technological factors in electrochemical machining, introduction of electrode tool ultrasonic vibration is justifiable. This method is called as ultrasonically assisted electrochemical machining (USAECM). In the first part of the paper, the analysis of electrolyte flow through the gap during USAECM has been presented. Based on computational fluid dynamic methods, multiphase, turbulent and unsteady electrolyte flow between anode and cathode (under assumption that cavitation phenomenon occurs) has been analysed. Discussion of the obtained solutions is the base to define optimal conditions of electrolyte flow in case of USAECM process. The second part of the paper is connected with experimental investigations of USAECM process. Classic experimental verification of obtained results in case of machining is extremely difficult, but influence of the ultrasonic vibration can be observed indirectly by changes in technological factors (in comparison to machining without ultrasonic intensification), whereas results of numerical simulation give possibility to understand reason and direction of technological factors changes. Investigations proved that ultrasonic vibrations change conditions of electrochemical dissolution and for optimal amplitude of vibration gives possibility to decrease the electrode polarisation.     

Optimize the flow field during counter-rotating electrochemical machining of grid structures through an auxiliary internal fluid flow pattern

Flow field distribution plays a vital role in electrochemical machining (ECM) because it can directly affect the machining stability and accuracy of ECM. In counter-rotating electrochemical machining (CRECM), the uniformity of the flow field is difficult to control due to the complicated and changeable flow channel shape. Through the simulation of the conventional lateral fluid flow pattern, it is found that the complexity of the flow channel with grid structures makes the flow field of machining area strongly disordered, which leads to the low velocity zones and dead zones. Based on the simulation results, a new electrolyte flow pattern with an auxiliary internal fluid is proposed, which can remarkably improve the uniformity of flow field by apply supplementary electrolyte to the machining area. Experimental results show that the new flow pattern effectively improves the machining stability of CRECM, and enhances the machining precision of grid structures, the sidewall taper angle is reduced from 29.3° to 7.7°.     

窄缝精密电解加工的实验研究

通过在理论上分析窄缝电解加工中片状电极和丝状电极对加工间隙和流场分布的影响,提出了采用小直径丝状电极提高加工精度和改善加工稳定性的方法。文中分别进行了片状电极和丝状电极之间、不同直径丝状电极之间的窄缝电解加工对比试验。结果表明,小直径丝状电极可以减小电解液流过电极丝产生的涡流死水区,改善加工区内的电解液更新和电解产物的排除,提高加工精度和加工过程的稳定性。     

Research on the cathode design and experiments of electrochemical machining a closed impeller internal flow channel

In order to improve the electrochemical machining (ECM) precision and efficiency of a closed impeller internal flow channel, the internal flow channel cathode shape and structure were optimized by gap flow field simulation. Firstly, the theoretical model and three-dimensional gap flow field simulation geometric model were set up. Next, the inter-electrode gap flow field simulation results were draw from the streamline, velocity, and pressure cloud picture. Secondly, the cathode and the frock clamp were designed according to the simulation results. Finally, the verification experiment was carried out to evaluate the cathode structure and the ECM process parameters, and the experimental results were consistent with the simulation results. The whole process is stable and no short-circuit phenomenon with the forward flow field machining pattern. The results show that the method of gap flow field simulation-assisted ECM cathode design is useful and economical for machining closed impeller internal flow channel.     

旋转超声电解复合加工小孔流场仿真

为解决电解加工深小孔中电解液难以进入加工区和电解产物难以排出的问题,构建了内喷式旋转超声电解复合加工装置,进行了电解加工、旋转电解加工和旋转超声电解复合加工小孔的对比试验。试验结果表明,阴极旋转能明显提高孔的圆度,旋转超声电解复合加工具有最大的平均加工电流,所加工孔的直径、深度都为三者中最大,表明其材料去除率是最大的。在此基础上,利用有限元ANSYS CFX软件,建立了气液两相流三维气穴模型,分析了阴极旋转和阴极高频振动对电解加工流场、电场的影响。仿真结果表明：阴极旋转使得气泡在阴极表面聚集,不利于气泡的排出,阴极振动加速了电解液的运动,有利于气泡的排出,因此具有最大的材料去除率。     

Wire electrochemical machining using reciprocated traveling wire

Wire electrochemical machining (WECM) is a cutting process in which the workpiece acts as an anode and the wire as a cathode. WECM is typically used to cut plates and exhibits a great advantage over wire electro-discharge machining, namely, the absence of a heat-affected zone around the cutting area. The enhancement of WECM accuracy is a research topic of great interest. In WECM, the homogeneity of the machined slit has a decisive influence on the machining accuracy. This is the first study in which the integration of pulse electrochemical machining (ECM) and a reciprocated traveling wire electrode was used to improve the homogeneity of this slit. The experimental results show that the combination of pulse ECM and a reciprocated traveling wire electrode could enhance the accuracy of WECM and that generally a low applied voltage, pulse duty cycle, and electrolyte concentration; an appropriate traveling wire velocity; and a high pulse frequency and feeding rate enhance the accuracy and stability of WECM. Finally, a microstructure with a slit width of 177 μm, with a standard deviation of 1.5 μm, and with an aspect ratio of 113 was fabricated on a stainless steel substrate measuring 20 mm in thickness.