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。     

长窄型薄壁叶片的套料电解加工

为实现长窄型薄壁叶片的套料电解加工,设计了电解液沿叶片轮廓四周进液的流动方式,开展了导流式出液和开放式出液的仿真对比分析,结果表明,导流式出液可以明显改善加工区域内流场的均匀性。开展了薄壁叶片套料电解加工试验研究,在进给速度1.4 mm/min下实现了薄壁叶片的套型加工,轮毂表面粗糙度从0.532 μm 降低至0.307 μm,叶片型面粗糙度从0.816 μm 降低至0.583 μm。     

复合平面摆动展成电解加工整体构件异形面的成形分析及应用

各类新型航空发动机中大量采用整体结构件,其异形面加工一直是机械制造中的难点。提出整体构件异形面的复合平面摆动展成电解加工方法,用一次进给“电解”达到型面加工要求。分析复合平面摆动展成电解间隙动态过渡过程,进行成形规律分析;以整体涡轮大扭曲叶片型面为研究对象,优化复合摆动展成进给加工轨迹,设计有补液流场的薄片底板与阴极体的组合式阴极,进行复合摆动展成进给电解加工试验,一次进给电解同时去除叶片通道两面余量,达到精加工效果;验证此方法加工变断面整体构件在生产率、精度、成本等方面的技术优势,为复合平面摆动展成电解工艺的拓展应用建立基础条件。     

整体涡轮大扭曲叶片电解精加工方法与试验研究

材料为高温合金的整体涡轮盘,其大扭曲叶片加工一直是制造业中的难题。提出多轴联动复合平面摆动展成电解方法加工大扭曲叶片,用一次进给电解实现叶盆、叶背面加工;分析复合平面摆动展成电解加工叶片型面成形规律,优化复合摆动展成电解加工数控编程及阴极结构设计,解决叶背出气边电解过切、根部三角区过切、出口短路等关键工艺问题;进行摆动式展成进给电解试验与分析,一次电解可达叶盆、叶背型面精加工要求。     

航空发动机复杂扭曲叶片分步电解加工研究

为实现复杂扭曲叶片在较小间隙下的稳定加工,提出了一种分步式电解加工的工艺方法,建立了复杂扭曲叶片小间隙(0.2 mm)和大间隙下(0.5 mm)扭曲流道的流道模型,采用有限元法进行了流场仿真研究,结果表明增加流道间隙可以解决流道中涡流和流场紊乱的问题。开展了复杂扭曲叶片小间隙连续式加工和分步式加工的试验研究。结果表明,采用小间隙连续式加工,当阴极进给至3.8 mm位置时,在叶片排气边靠近叶根流道扭曲处出现短路打火情况;而采用分步式加工方式能够实现加工的顺利进行。     

大扭曲度整体涡轮叶片展成电解加工成形规律及试验研究

根据大扭曲度整体涡轮结构特点与加工难点，提出用展成电解方式实现其叶片加工；分析、研究大扭曲度整体涡轮展成电解加工叶片型面成形规律；根据其成形特点，进行多轴联动数控编程的优化；合理设计阴极及流场，对叶背二次腐蚀、出口短路及叶背余量去除等关键工艺问题进行分析讨论并提出有效解决措施；进行整体涡轮叶片展成电解加工试验，可稳定达到型面精度加工要求，为大扭曲度整体涡轮展成电解加工的应用创造了条件。     

超声电解复合加工小孔工艺试验研究

为了研究超声电解复合加工难加工材料上小孔工艺,在8 mm厚的不锈钢1Cr18Ni9Ti上进行通孔加工试验。通过正交试验研究了电压、初始间隙、阴极转速和进给速度对小孔直径和表面粗糙度的影响,运用综合平衡法得出最优组合是:电压7 V、初始间隙0.2 mm、阴极转速1 600 r/min、进给速度1.6 mm/min。     

薄壁回转体表面岛屿状高凸台结构旋印电解加工成形过程研究

以航空发动机机匣为代表的薄壁回转体表面分布有大量岛屿状的高凸台结构，此类零件普遍存在加工变形大、刀具损耗严重等制造难题。旋印电解加工采用回转体工具电极，通过工件与工具的同步对转实现阳极材料的逐层均匀溶解，对于机匣等薄壁回转体零件加工具有独特优势。开展了旋印电解凸台成形过程的仿真研究，建立了电极等效运动分析模型和阳极溶解数学模型，掌握岛屿状高凸台结构旋印电解加工成形规律。仿真结果表明，阴极进给深度和窗口宽度对凸台轮廓形状有着很大的影响。随着阴极工具的不断进给，阴极窗口运动轨迹的包络线逐渐由尖锥形变为纺锤形，凸台侧壁锥度不断减小，呈现从正锥形→垂直→倒锥的变化趋势。阴极窗口宽度的增加会导致窗口运动轨迹倾斜角度增大，有利于获得锥度较小的凸台侧壁轮廓。对于任意阴极窗口宽度的凸台侧壁轮廓均可以通过某一宽度的轮廓通过角度旋转偏置获得。此外，旋印电解加工间隙呈现出非平衡态变化趋势。在仿真分析的基础上，进一步开展了旋印电解加工试验研究，在镍基合金GH4169薄壁回转体表面加工出岛屿状高凸台结构。试验结果表明旋印电解加工技术对于具有较大高度复杂异形岛屿状凸台结构的薄壁回转体零件具有较好的加工能力。     

叶片电解加工三头柔性进给方向优化设计

以某型发动机叶片为研究对象,设计了新的三头柔性进给的电解加工方式,对毛坯装夹角度和阴极进给方向进行优化选择,提出了叶盆、叶背采用不同进给角度进行加工的方式来提高叶片的加工精度,以实现全方位叶片电解加工。进行了叶片电解加工实验,结果表明该进给方式可兼顾叶身和缘板的精度要求,实现叶片的全方位电解加工。     

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。     

电解加工工件成形过程仿真与预测系统研究

为提高电解加工自动化程度、更好地研究工件成形过程,在全面研究电解加工成形规律的基础上,结合UG软件平台开发了电解加工计算机辅助工件成形过程仿真与预测的软件系统.介绍系统的基本结构和组成,对加工间隙内实际电场分布进行分析,进而模拟出工件型面的形成过程.通过对某发动机叶片的工艺试验,验证了系统仿真预测的结果,试验结果表明开发的系统具有较高求解精度,对提高电解加工精度、实现电解加工自动化具有重要意义.     

无氧铜深孔套料加工工艺的试验研究

根据无氧铜的材料特性和切削加工性能,进行了无氧铜的大直径深孔套料加工试验,并设计了套料钻和加工工艺。试验结果证明,切削过程稳定可靠,通过套料加工可显著提高无氧铜的材料利用率。     

Experimental investigation on the electrochemical machining of 00Cr12Ni9Mo4Cu2 material and multi-objective parameters optimization

Special stainless steel 00Cr12Ni9Mo4Cu2 has multiple composition and inhomogeneous tissues; short circuiting will frequently occur when using conventional electrolyte processing. This article analyzes the reason why the process of machining is difficult from the material composition and structure. We used the NaNO₃ and NaClO₃ electrolyte composite to select the appropriate concentration, and then by using the orthogonal experiment and gray relational analysis method, we discussed how the voltage, feed speed, and electrolyte pressure solved the problem of the material removal rate (MRR), surface roughness (SR), and side gap. Under optimal conditions of 20 V, an electrolyte composite concentration of 178 g/l NaNO₃ and 41 g/l NaClO₃, a feed rate of 0.7 mm/min, and an electrolyte pressure of 0.8 MPa, a material removal rate of 100.8 mm3/min, a surface roughness of Ra 0.8 μm, and a side gap of 0.16 mm were produced. Given the same voltage, with an increasing cathode feed rate, the MRR was shown to increase while the surface roughness value and the side gap decreased. Under the same cathode feed rate, the MRR decreases, while the side gap and the surface roughness increase as the electrochemical machining application voltage increases. This study proves that using a certain concentration of electrolyte composite is a simple, low-cost, and feasible approach in improving efficiency and quality.     

叶片电化学加工过程多场耦合仿真

针对叶片电化学加工过程难以预测、实验参数修正周期长的问题,建立与温度相关的叶片多场耦合仿真模型,基于COMSOL Multiphysics平台对叶片电化学加工过程进行多场耦合仿真,仿真分析了不同加工电压和不同进液流量对法向平衡间隙的影响。结果表明：加工电压越大,间隙也相应增大,且间隙分布越不均匀;进液流量越大,间隙分布越均匀。采用其中一组仿真参数进行工艺实验,仿真与实验的对比结果表明,叶片轮廓曲率变化缓慢处的仿真结果和实验结果比较贴合,而轮廓曲率变化较快处的仿真值与实验值差别相对较大,但两者的变化趋势相同。     

Experiment and simulation study on concentrated magnetic field-assisted ECM S-03 special stainless steel complex cavity

A novel concentrated magnetic field-assisted electrochemical machining (ECM) technology is proposed in this paper to machine contemporaneously seven workplaces’ complex cavity with high efficiency and good precision. An ECM clamping apparatus with concentrated magnetic field, periodic magnetic field, and no magnetic field was designed. The magnetic field simulation was carried out. Comparing the results of the concentrated magnetic field to the periodic magnetic field, the magnetic field intensity of the former is increased by 9.8 % than the latter. The ECM cathode with the same gap was designed and manufactured. Under the conditions of 12 % NaNO₃, 14-V voltage, 0.8-MPa electrolyte pressure, temperature 32 °C, cathode feed rate 0.9 mm/min, initial machining gap 0.1 mm, and the S-03 special stainless steel workpiece material, the experiments with concentrated magnetic field, periodic magnetic field, and no magnetic field were carried out. The results show that the gap magnetic field strength was increased by 16.7 % in the concentrated magnetic field than in the periodic magnetic field. Through a sectioning test, the precision in the concentrated magnetic field is increased by 33.3 % compared with no magnetic circuit and increased by 14.8 % compared with the periodic magnetic field. The concentrated magnetic field-assisted ECM technology cannot only reduce the cathode design cycle and cost but also increase the process accuracy.     

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。     

高速铣削铝合金叶片表面质量的试验研究

使用硬质合金球头铣刀对铝合金叶轮叶片进行了高速铣削试验。研究了切削速度和进给量对加工表面粗糙度的影响。试验结果表明:在高速加工中,每齿进给量比铣削行距对加工表面质量的影响更大;提高切削速度和减少每齿进给量有利于降低加工表面粗糙度。但当切削速度超过某一范围后,进一步提高速度对降低表面粗糙度的作用并不明显;每齿进给量减小到一定范围后,表面粗糙度反而会有所增加;对于铝合金叶片曲面的加工,合理选择切削速度、进给量和行距可获得较低的表面粗糙度值和较高的加工效率。     

An experimental investigation on machining parameters of AISI D2 steel using WEDM

The performance of the wire electrodischarge machining (WEDM) machining process largely depends upon the selection of the appropriate machining variables. Optimization is one of the techniques used in manufacturing sectors to arrive for the best manufacturing conditions, which are essential for industries toward manufacturing of quality products at lowest cost. As there are many process variables involved in the WEDM machining process, it is difficult to choose a proper combination of these process variables in order to maximize material removal rate and to minimize tool wear and surface roughness. The objective of the this work is to investigate the effects of process variables like pulse on time, pulse off time, peak current, servo voltage, and wire feed on material removal rate (MRR), surface roughness (SR), gap voltage, gap current, and cutting rate in the WEDM machining process. The experiment has been done using Taguchi’s orthogonal array L27 (3⁵). Each experiment was conducted under different conditions of input parameters and statistically evaluated the experimental data by analysis of variance (ANOVA) using MINITAB and Design Expert tools. The present work also aims to develop mathematical models for correlating the inter-relationships of various WEDM machining parameters and performance parameters of machining on AISI D2 steel material using response surface methodology (RSM).The significant machining parameters and the optimal combination levels of machining parameters associated with performance parameters were also drawn. The observed optimal process parameter settings based on composite desirability (61.4 %) are pulse on time 112.66 μs, pulse off time 45 μs, spark gap voltage 46.95 V, wire feed 2 mm/min, peak current of 99.99 A for achieving maximum MRR, gap current, gap voltage, cutting rate, and minimum SR; finally, the results were experimentally verified.     

航空发动机薄壁叶片精密数控加工技术研究

加工变形是影响薄壁零件数控加工效率、精度和表面质量的关键性制约因素。本文针对航空发动机薄壁叶片精密数控加工中的变形问题 ,在分析钛合金叶片结构和工艺特点基础上 ,提出了叶片的精确定位方案、以及支撑叶片并控制弹性变形和残余应力变形的有效方法。通过五坐标数控编程和加工试验对新方法进行了验证。测试结果表明 ,采用新方法加工出的叶片满足设计性能要求 ,不但质量上优于传统制造工艺 ,而且制造成本显著降低、周期缩短 6 0 %以上     

Shape control in micro borehole generation by EMM with the assistance of vibration of tool

Electrochemical micromachining (EMM) is gaining importance day by day due its advantages that include no tool wear, absence of stress/burr, high MRR, bright surface finish and ability to machine complex shapes regardless of hardness. Overcut and taper formation is the main problem during micro borehole machining. In this paper, an electrical circuit model of EMM is presented for better understanding of the process and experimental MRR is found to be in good agreement with theoretical MRR. In the present set up variation of overcut with voltage, pulsed frequency, vibration amplitude of tool and vibration frequency of tool are investigated. To reduce overcut and taper angle of micro borehole, machining zone is simulated with a reversed taper tool and verified by practical experiments for proper shape control during micro borehole generation. Variation of micro nozzle angle with different feed rates and different times of machining are also investigated for the shape control during micromachining with conical tool. Finally, it has been shown that both reversed taper and forward taper tool can be used for generation of taper less micro features i.e. boreholes.