【作者】 宋涛；

【导师】 余祖元；

【作者基本信息】 大连理工大学 ， 机械工程（专业学位）， 2021， 硕士

【摘要】 叶片是航空发动机关键零部件,广泛采用镍基高温合金、钛合金等高强度、高硬度材料。国内外常采用电解加工(Electrochemical Machining,ECM)进行发动机叶片的加工制造,但由于ECM中间隙的存在使叶片边缘成型阶段的流场与电场十分复杂、难以控制,导致加工后的边缘存在与设计不符的形状尺寸误差,严重影响航空发动机的使用性能和寿命。电火花加工(Electrical Discharge Machining,EDM)具有适用于难切削材料加工、可加工复杂形状零件等特点,因此本文用EDM对叶片进排气边缘进行修整加工。加工可大致分为粗加工去除余量和成型精加工两个阶段。本文主要针对粗精加工工艺参数及电火花机床控制系统进行了优化与设计。粗加工阶段对叶片边缘进行切断以去除较大的加工余量。实验采用立式振动辅助电火花机床,以石墨电极和TC4钛合金与GH4169镍基合金薄片为加工对象,进行了边缘2mm系列切断实验。由于影响电火花加工特性的因素较多,采用正交试验的方法探究了电火花加工过程中脉冲宽度、峰值电流、振动电极的幅值和频率对工件材料去除率的影响,通过极差分析和验证实验得到了TC4钛合金最优电加工参数为峰值电流30A、脉冲宽度4μs、振动幅值1.8μm、振动频率700Hz,最大材料去除率为11.18mm~3/min。GH4169合金的最优电加工参数为峰值电流30A、脉冲宽度4μs、振动幅值1.2μm、振动频率1200Hz,最大材料去除率为10.86mm~3/min。通过与前期实验比较发现,不同材料在其最优电加工参数下材料去除率存在较大差异,为了比较不同材料对实验结果的影响,在同一加工参数下对比研究了不同工件材料对实验结果的影响,并分析了产生差异的原因。在粗加工完成的基础上进行了精加工参数优化实验。利用控制变量法得到了石墨电极精加工TC4钛合金的最优电加工参数为脉冲宽度0.5μs、峰值电流5A、开路电压90V,工件表面粗糙度平均值为1.356μm。石墨电极精加工GH4169镍基高温合金最优电加工参数为脉冲宽度0.5μs、峰值电流10A、开路电压120V,工件表面粗糙度平均值为1.43μm。由于叶片边缘形状高度扭曲,现有的三轴联动电火花机床难以满足加工要求,因此设计搭建了六轴电火花机床。设计了机床运动控制系统的结构并对相关硬件设备进行选型。基于Lab VIEW编写了机床运动控制程序手动控制模块、粗加工切断模块和成型精加工模块等,经上机调试,机床控制程序能够精确稳定运行,实现加工所需要的各种功能。基于生成的刀具轨迹源文件编写了机床后处理程序,采用Lab VIEW在平面两轴插补的基础上通过复合插补的思想构建了六轴电火花机床插补程序。最后通过PID调节对控制系统进行了优化。更多还原

【Abstract】 Blade is one of the key parts of aeroengine,made of titanium alloy,nickel-based superalloy and other high strength,high hardness materials.Electrochemical Machining(ECM)is often used in blade machining,but due to the existence of clearance in ECM,the flow field and electric field of blade edge machining by ECM are very complex and difficult to control,resulting in the shape and dimensional error of the machined edge,which seriously affect the aeroengine performance.Electrical Discharge Machining(EDM)is suitable for the processing of difficult cutting materials and complex shape parts.This paper adopts EDM to trim the blade edge.The machining process can be divided into two stages: rough and finishing machining.In this paper,the process parameters of rough and finish machining are optimized and the motion control system of EDM is designed.In the rough machining stage,the blade edge was removed a large amount of material.The vertical vibration assisted EDM machine was used in the experiment.Graphite as electrode material and TC4 titanium alloy and GH4169 nickel-based superalloy sheet with a size of(29×29×0.5)mm3 as workpiece material were used.A series of cutting experiments with a edge of 2mm were carried out.Based on primary experimental results,orthogonal experimental design was used to study the effects of peak current,pulse width,amplitude and frequency of vibration on material removal rate(MRR).Based on range analysis and verification experiments,the optimum processing parameters of TC4 titanium alloy are peak current of 30 A,pulse on-time of 4μs,vibration amplitude of 1.8μm,vibration frequency of 700 Hz,and MRR is up to 11.18mm3/min,The optimum processing parameters of GH4169 nickel base alloy are pulse on-time of 4μs,peak current of 30 A,vibration amplitude of 1.2μm,vibration frequency of 1200 Hz,and MRR is up to 10.86mm3/min.Compared with the previous experiment,it is found that the MRR of different materials is obviously different under their optimal electromachining parameters.In order to compare the influence of different materials on the experimental results,the investigation is carried out under the same processing parameters,and the reasons for the differences were analyzed.After rough cutting,the finishing parameter optimization experiment was carried out.Using the control variable method,the optimal machining parameters of TC4 titanium alloy were obtained as pulse on-time of 0.5 μs,peak current of 5A,open circuit voltage of 90 V,and average surface roughness 1.356μm.The optimal machining parameters of GH4169 nickelbased superalloy are pulse on-time of 0.5μs,peak current of 10 A,open-circuit voltage of 120 V,and average surface roughness 1.43μm.A set of six-axis EDM machine was designed and developed to trim complex blade edge shape.The structure of EDM motion control system was designed and the related hardware equipment was selected.Based on Lab VIEW,the rapid positioning module,single step moving module,rough machining cutting module and forming finishing module of machine tool motion control program were programmed.After debugging on the machine,the control program of the machine tool can run accurately and stably,and realize various functions needed for machining.A post-processing program was written based on the generated tool path source file,and based on planar two-axis interpolation,a six-axis EDM interpolation program was constructed with the idea of compound interpolation based on Lab VIEW.Finally,the control system is optimized by PID adjustment.更多还原