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1、南京航空航天大学博士学位论文发动机叶片高精度电解加工阴极设计系统及实验研究姓名：王蕾申请学位级别：博士专业：机械制造及其自动化指导教师：朱荻20061201南京航空航天大学博士学位论文 I摘 要 叶片是航空发动机中重要的零件，对发动机的性能起着关键作用，其主要加工方法之一是电解加工。阴极设计是电解加工首先要解决的问题，也是电解加工中难以解决的问题。本文对叶片电解加工阴极设计系统的关键技术进行研究，主要目的是方便快捷地设计、制造出高精度的阴极工具，提高叶片电解加工精度和质量。同时，本文对叶片电解加工成型过程进行的分析研究，也为实现加工过程实时控制做了理论铺垫。 本文以某型航空发动机叶片为研究对象
2、，根据其结构特点和加工精度的要求，结合对阴极设计有直接影响的阴极进给方向与叶片型面法线夹角的分布情况，首先对叶片阴极的进给方向进行了优化。 以电解加工成型规律为理论基础，分别采用基于简化电场模型的阴极设计方法和基于实际电场分布模型的有限元阴极设计方法，求解出阴极工具的三维型面。为了提高阴极型面的设计精度和效率，本文探索研究并提出了一种把叶片试件的形状测量结果代入阴极工具设计的数字化修正模型，这种修正方法以线性闭环控制系统、空间 Fourier 变换和频域传递函数为理论基础，结合工艺实验和对叶片试件形状测量结果对阴极工具进行了完善，大大提高了阴极型面的设计精度。 根据流体力学基本理论研究电解液在
3、加工间隙内的流动模型，求解了三维加工间隙内电解液电导率的变化，并将流场因素影响代入到阴极设计中。同时，采用半实验法与数据库技术相结合的方法有效地解决了非线性电解液对工具阴极设计的影响，使阴极设计模型更全面地反映电解加工的实际物理过程。 除了电解加工阴极工具设计，还进行了关于叶片电解加工成型过程的分析研究，探讨了考虑流场和非线性电解液因素的影响，叶片由初始毛坯型面变化到最终型面的过程仿真和最终型面预测问题。在此基础上，针对新型三头进给叶片电解加工机床的特点，对加工过程中阴极工具进给路径的优化进行了研究探索，得出初步的优化结果。采用 BP 神经网络技术，将电解加工参数与试件的形状误差建立起映射关系
4、，对加工出的叶片试件的形状误差进行预测。 结合上述关键技术的研究，本文在 Unigraphics（UG）软件平台上开发了用于发动机叶片电解加工阴极设计的系统软件（NHECM1.0） ，该软件具有从发动机叶片零件图纸开始精确地设计出工具阴极型面的 CAD 功能、模拟阴极工具制造生成相应加工代码的 CAM 功能，和优化工具进给方式、叶片成型仿真预测及叶片试件形状误差预测等一系列 CAE 功能。 发动机叶片高精度电解加工阴极设计系统及实验研究 II最后，本文在新型三头进给叶片电解加工机床上对阴极设计的各种方法和叶片成型的仿真结果进行了一系列的工艺实验，结果证明了设计出的阴极工具具有较高的精度，叶片型
5、面预测分析结果具有较好的可靠性，试件形状误差预测的 BP 网络能较精确地映射实际加工时输入加工参数与输出工件型面的形状误差之间的关系，具有较高预测的精度。 本文对电解加工阴极设计若干关键技术问题进行了较深入的研究，将研究结果与高性能的计算机辅助设计制造软件结合起来，初步开发出用于发动机叶片电解加工阴极设计的 CAD/CAE/CAM 系统，这对提高电解加工阴极设计精度、实现阴极设计的自动化，以及提高叶片电解加工效率和精度有重要的意义。 关键词： 叶片， 电解加工， 阴极设计， 有限元， 数据库， 流场， UG ， CAD/CAE/CAM 南京航空航天大学博士学位论文 IIIABSTRACT Bl
6、ades are the most essential parts in aero-engines and play important roles in aero-engines in the national defense industry. One of the main manufacturing methods of blades is the electrochemical machining (ECM). The problem of cathode design is the key and difficult one should be solved first. The
7、aim of the researches in the thesis is to design the blades cathode efficiently and precisely, and to improve the precision of blades which are manufactured in ECM. And the study of the shape evolution and prediction in the thesis emphasizes on the theoretical analysis, it will be helpful to the ECM
8、 process control in the future. Using the compressor rotor blade of some type aero-engine as research object, according to the structure requirements and the precision requirements of the blade, the thesis has proposed the optimization criterions and optimized the feeding direction of cathode. Furth
9、ermore the distribution of space angle between the cathodes feeding direction and the normal direction of the blade shape has been analyzed, which can directly influence to cathode design. Based on the ECM shaping theories, two kinds of methods have been demonstrated in the paper: the cathode design
10、 method established on the basis of mathematics model of simplified electric field and the finite element cathode design method on the basis of mathematics model of actual electric field distribution. To improve the precision of the cathode design, a new method to remedy the cathode is proposed, whi
11、ch is a closed-loop control system constructed by transmiting the shape errors of the blade in experiments to the cathode. In the thesis the distribution of variable flow factors has been studied based on the hydrodynamics theories in detail for the special three-dimension inter-electrode gap space
12、during the all-round ECM process. The thesis has used the database technology to solve the influence of variable electric current efficiency on tool cathode design, which is brought by non-linear electrolyte. All of the above studies make the cathode design be accord with the actual physics course o
13、f ECM. In the thesis the ECM process of the blade has been analysed. The analysis includes the blade shaping simulation and prediction considering of the influences of flow field factors and non-linear electrolyte, and the optimization of the cathodes feeding route during the ECM process that is pri
14、mitively analyzed. Besides these researches, the 发动机叶片高精度电解加工阴极设计系统及实验研究 IVprediction of the blades shape accuracy using BP neural network has been constructed. The CAD/CAE/CAM system for cathode design of blades in ECM is developed on the UG software in this thesis. In the system a precise tool cat
15、hode according to a blades sketch can be designed by using the CAD model, and the NC code of the cathode can be acquired in the CAM part. Furthermore the system also includes the optimization of the cathodes feeding direction, the simulation of the blades evolution in the ECM process and the predict
16、ion of the experimental blades accuracy. Finally a serial of experiments have been carried on the new designed three-direction feeding electrochemical machine. The experimental results are used to prove the cathode design precision and the reliability of the whole system. And the BP model trained by using the experimental results is of good accuracy and practical worth too. The cathode design system for ECM aero-engine blades combines the key technologies in the thesis with the
