Convergence Analysis of the Numerical Solution for Cathode Design of Aero-engine Blades in Electrochemical Machining

As a main difficult problem encountered in electrochemical machining （ECM）, the cathode design is tackled, at present, with various numerical analysis methods such as finite difference, finite element and boundary element methods. Among them, the finite element method presents more flexibility to deal with the irregularly shaped workpieces. However, it is very difficult to ensure the convergence of finite element numerical approach. This paper proposes an accurate model and a finite element numerical approach of cathode design based on the potential distribution in inter-electrode gap. In order to ensure the convergence of finite element numerical approach and increase the accuracy in cathode design, the cathode shape should be iterated to eliminate the design errors in computational process. Several experiments are conducted to verify the machining accuracy of the designed cathode. The experimental results have proven perfect convergence and good computing accuracy of the proposed finite element numerical approach by the high surface quality and dimensional accuracy of the machined blades.     

压气机叶片安装板内侧面自动化磨抛加工

针对压气机叶片安装板的自动化磨抛加工,基于北航提出的自动化磨抛加工工艺开展了应用研究。结合叶片安装板区域复杂曲面或结构特点,通过对磨抛轮的粒度优选、磨抛过程的优化以及接触压力的调整,实现了磨抛精度及表面粗糙度符合设计要求的攻关目标。试验结果表明:磨抛后表面粗糙度Ra在0.4μm以下,去除量在0.03mm以内,实现了替代手工磨抛的目的。在磨抛效率上也实现了与多台数控铣的节拍匹配,在200件叶片试制过程中磨抛工艺系统稳定,拟将该技术广泛推广应用于压气机叶片的研制和生产中。     

基于颗粒水射流的异型不锈钢元件确定性加工

基于颗粒水射流材料去除性能稳定、无刀具磨损、复杂面形适应能力强等优点,提出了基于确定性修形的异型不锈钢元件加工方法,确定了适用于不锈钢元件表面的测量方法,对其加工路线进行了规划.对于齿形"窄"环带表面经过3次确定性修形加工后,表面面形Rms由初始的9.774Wave(1Wave=632nm)收敛至2.009Wave,表面质量提升明显,表面粗糙度减少至63.303nm,达到加工要求.实验结果表明颗粒水射流加工对不锈钢件加工具有优良的确定性修形能力,具有广泛的应用前景.     

抛光参量对抛光光学元件亚表层的影响

研究了抛光粉的种类、抛光速度的大小以及抛光玻璃的性质等抛光参量对光学元件亚表层特征的影响,并结合抛光机理进行了分析。     

环形气囊抛光非均匀性的研究

针对环形气囊抛光光学元件表面时产生的抛光非均匀性现象,简要介绍了环形气囊抛光技术的运动方式和实验平台的主要组成部分。介绍了环形气囊的抛光机理,基于Preston方程,分析了抛光非均匀现象产生的原因和解决途径,通过调整环形气囊抛光头与工件之间的相对运动方式和调整环形气囊抛光头与工件之间的相对位置等两种方法,消除了工件中心抛光效果差的现象,实现了工件表面的均匀性抛光。     

熔石英元件纳米射流超光滑抛光流场仿真与实验

利用计算流体力学软件Fluent对纳米颗粒射流超光滑加工的流场分布特点进行了流体动力学分析。基于仿真结果对去除函数的变化规律进行了研究,通过具体实验来对流体动力学仿真结果进行了验证。搭建了纳米射流抛光装置,利用该装置对熔石英元件进行了加工。原子力显微镜观测结果表明熔石英元件表面粗糙度RMS值由初始的0.680nm减小到了0.307nm,实现了超光滑加工。     

Analysis and control of inter-electrode gap during leveling process in counter-rotating electrochemical machining

The inter-electrode gap (IEG) is an essential parameter for the anode shaping process in electrochemical machining (ECM) and directly affects the machining accuracy. In this paper, the IEG during the leveling process of an oval anode workpiece in counter-rotating ECM (CRECM) is investigated. The variation of the minimum IEG is analyzed theoretically, and the results indicate that rather than reaching equilibrium, the minimum IEG in CRECM expands constantly when a constant feed speed is used for the cathode tool. This IEG expansion leads to a poor localization effect and has an adverse influence on the roundness of the machined workpiece. To maintain a small constant IEG in CRECM, a variable feed speed is used for the cathode based on a fitted equation. The theoretical results show that the minimum IEG can be controlled at a small value by using an accelerated feed speed. Experiments have been conducted using a specific experimental apparatus in which the cathode tool is designed as a combined structure of two sectors and a thin sheet. By detecting the machining currents flowing through the minimum IEG, how the latter varies is obtained indirectly. The results indicate that using an accelerated feed speed is effective for controlling the IEG, thereby improving the roundness of the machined workpiece.     

纯钨材料环形微槽电解电火花加工特性研究

为解决氙灯钨阳极表面密集环形微槽加工的技术问题,提出了采用RC电源,在超低电导率下电解电火花加工纯钨表面微沟槽的方法。研究在RC电源下,不同电解液类型下的电解电火花加工特性。首先,通过电化学工作站测量纯钨材料在不同电解液类型下的极化曲线,分析不同电解液类型的初腐蚀电位。为研究加工过程形成的气泡对加工的影响规律,通过高速摄像仪对不同工艺条件下加工区域的气泡形成与分布进行观察。最后,采用自主研制的试验装置开展了纯钨棒材表面环形微沟槽电解电火花加工工艺试验,分析工作液成分、电导率、转速和电压不同参数对加工特性的影响规律。在极间电压60V,转速500r/min,电导率为50μS/cm的NaOH电解液下加工了槽宽为50.97μm,槽深为17.31μm的微沟槽结构。     

不锈钢中性复合盐溶液电解抛光新技术

主要介绍中性溶液电解抛光新技术及其对不锈钢焊接件氧化及去除的同步作用。     

激光陀螺超光滑反射镜基片的光学加工和检测技术

讨论了激光陀螺超光滑光学反射镜基片的加工和检测技术,并给出了超光滑光学基片的非接触光学测量仪和原子力显微镜的测试图。还论述了原子力显微镜测试的准确性以及超光滑光学表面的分形特征。