一种整体叶盘加工预变形控制方法

为解决钛合金整体叶盘薄壁弯扭跨音速叶片叶型制造过程中存在的加工变形大、铣削稳定性差等问题,本文提出了一种整体叶盘加工预变形控制方法。采用叶型三维检测技术获取叶型位置度和扭转角,利用叶型铣削变形误差反向补偿方法控制叶片弯曲及扭转变形。在整体叶盘上进行了实验验证,结果表明该方法可有效提高叶型加工精度和成品合格率,具有技术借鉴价值。     

涡轮叶片竹节孔冷却通道电解加工实验研究

为了改善发动机的性能,提出了在发动机叶片上加工竹节状冷却孔的方法,以提高冷却效果.针对竹节孔加工的特点,构建了竹节孔电解加工实验系统,该系统包括工具阴极制作模块、夹具模块、电解液模块、运动控制模块和电源模块等.采用电解反拷法制作竹节孔加工工具阴极,并将其应用于竹节孔加工中,加工效率明显提高.同时对实验过程中的各种工艺参数,如加工电压、实验材料、电解液种类对竹节孔成形的影响进行分析,实现竹节孔稳定加工.     

毛坯开槽方式中零件加工变形的演变机理与控制方法

广泛用作飞机薄壁整体结构件毛坯的铝合金厚板,在制造过程中出现的塑性变形不均匀性将导致残余应力的产生。高速铣削过程中残余应力的释放将引起飞机薄壁整体结构件的加工变形,这严重影响加工质量。因此,建立了毛坯释放变形后零件铣削的有限元仿真方法,挠度解析法的计算结果和实验测量的数据均验证了有限元仿真值无论是在趋势上还是变形量上均高度吻合。利用有限元方法揭示了开槽方式对毛坯释放变形的影响规律,分析了零件加工变形与毛坯释放变形之间的关系。结果表明:毛坯释放多大变形量,零件就能减小多大的变形量。在建立毛坯释放变形预测模型的基础上,提出了开槽方式的遗传算法优化方法,随机测试集表明神经网络的预测精度高达95%左右,而三框件在最佳开槽方式下能减小34.5%的变形。     

基于超纯水电化学加工的扫描直写技术

为了充分发挥电化学加工以离子状态去除材料的加工机理,实现其在微细、精密,甚至是纳米加工领域中的应用,针对绿色制造和微细加工的需求,提出以超纯水为电解液的微细电化学加工方法．采用阳离子交换膜促进超纯水解离,提高电化学加工过程中电流密度;利用微探针作为工具电极,通过数控机床控制运动轨迹保持与阳极表面的间距恒定,以不同路径横向扫描工件,即可在工件阳极表面加工出2D／3D几何结构．并通过试验加工字母“PW-ECM”,验证了超纯水作为电解液进行电化学扫描直写加工技术的可行性．     

300M超高强度钢车削加工性能仿真模拟分析研究

目的研究不同切削参数对300M超高强度钢切削性能的影响。方法通过单因素试验法,采用Advant Edge切削仿真软件,建立300M钢三维有限元模型,对不同切削参数下车削300M钢的切削力、刀片温度、刀片应力及切屑形状进行分析。结果在300M钢车削过程中,刀片温度随着切削速度增大而增大,但切削力和刀片应力反之;背吃刀量和进给量越小,切削力、刀片应力及刀片温度越小;切削刃半径越小,切削力越小,但小的切削刃半径使得刀片应力变大,容易导致刀片磨损。车削300M钢的切屑呈锯齿螺旋状,切屑温度为带状分布,切削速度越高,进给量、背吃刀量越大,切削刃半径越小,切屑温度越高。结论在300M钢车削加工中,应选用较高的切削速度,适中的切削刃半径,较小的进给量和背吃刀量。     

Tool path generation for five-axis machining of blisks with barrel cutters

A barrel cutter has a cutting segment with a large radius on its profile, and this arc segment allows the cutter to tilt away from the part surface, avoiding the collisions of the tool with the part. Therefore, barrel cutters are suitable for five-axis blisk machining. However, the barrel cutters are more challenging for CAM software to generate paths. A method of generating collision-free and large-machining width flank milling paths with smooth axes movements for blisk machining with barrel cutters is proposed. Local gouge between the tool flute surface and the blade to be machined is considered, and the collisions of the blisk with the non-cutting parts of the tool, i.e. tool shank and holder, are also detected. The machined part geometry is the complement of the cutter’s swept envelope from the stock. Accordingly, the swept profile of the cutter at each cutter contact point is employed to evaluate the machining width naturally. Thereafter, a multi-criteria tool path generation model is established, and it is converted into a single-objective optimization with the weighted sum method. An algorithm based on the Differential Evolution algorithm is developed to solve this model. The numerical example illustrates the effectiveness of the proposed method.     

Extraction of milling know-how from NC programs through reverse engineering

To automate machining process planning, the acquisition and representation of machining knowledge or know-how in a reusable way is needed. The machining know-how is implied in NC programs made by experienced workers. In this paper, the methodology and system for extracting machining know-how in milling operations have been developed. With the system, machining features, operations and their associated cutting conditions (depth of cut, feed rate and spindle speed, etc.) and machining method can be extracted by analysing NC programs in conjunction with the tools used and workpiece blank model. The milling know-how is represented as a collection of these extracted data that can be used in future machining operations. To verify the system, actual NC programs for milling have been analysed and the milling know-how has been extracted successfully.     

Friction Drilling of IN-713LC Cast Superalloy

Friction drilling utilizes the heat generated from the friction between the rotating conical tool and the workpiece for hole-making. The process produces no chips and incurs less tool wear, thus lengthening the service life of the drill. In this study, IN-713LC, a nickel-based superalloy, was friction-drilled under different rotation speeds and feed rates. Material properties including hardness, roundness, and surface roughness (Ra) were examined after machining. Experimental results reveal that hardness is greater near the hole's wall and decreases with increasing distance from hole's edge. Moreover, higher rotation speed and faster feed rate can yield better roundness and smoother Ra.     

陶瓷基复合材料涡轮叶盘设计、制备与考核验证

涡轮转子是燃气涡轮发动机的核心部件。针对SiC/SiC涡轮叶盘设计、制备与考核验证开展研究,采用蛛网仿形(SWS)SiC纤维预制体作为涡轮叶盘的增强体,预制体表面分别沉积BN界面相与SiC基体,通“在线加工”方式对SiC/SiC涡轮叶盘分别进行粗加工和精加工,采用大气等离子喷涂方法制备环境障碍涂层,形成满足设计要求的涡轮叶盘。采用CT对SiC/SiC涡轮叶盘进行无损检测,表征叶盘内部缺陷分布。针对制备的SiC/SiC涡轮叶盘开展性能评价、超转试验、台架试验等考核验证,研究表明：SiC/SiC涡轮叶盘最大破坏强度达到300 MPa;在室温超转试验中,当转速达到n=104 166 r/min时,叶片发生断裂,当转速达到n=108 072 r/min时,轮体发生破裂;在发动机台架试验中,累积完成了N=994次最高转速n_max=60 000 r/min的循环载荷及N=100次最高转速n_max=70 000 r/min的循环载荷试车考核。2022年1月1日,SiC/SiC涡轮叶盘在株洲成功完成了首次飞行试验验证,这也是国内陶瓷基复合材料转子首次配装平台...     

Parametric relationship between hypoid gear teeth and accurate face-milling cutter

The cutter systems of hypoid gear cutting machines contain groups of inside and outside blades. In these cutter systems, the side cutting edges of the blades machine the convex and concave gear teeth while rotating about the cutter rotation axis. The side cutting edges lay on the rake face formed through the blade, rake, and relief angles; hence, the normal cross-section of the cutter swept surface forms hyperboloid gear teeth. Using the accurate geometry of the cutter system, a relationship between the pressure and spiral angles of the gear tooth and the parameters of the cutter system is developed for the FORMAT machining of a hypoid gear. A new parameterization of the gear tooth surfaces is introduced to determine these angles for the accurate gear tooth by the accurate cutter system. A numerical example with different cutter systems and blade parameters is presented, demonstrating the effects of rake and relief angles over the pressure and spiral angles on mean point projections and gear tooth surface. Finally, the change in pressure and spiral angles with respect to the rake and relief angles are plotted, and the results are analyzed. Finally, it is concluded that the pressure and spiral angles are changed up to a few seconds of a degree in the operating area of the tooth with the change in the back and side rake angles. The side relief angle exhibited little or no effect over the geometry of the gear tooth.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-019-00286-x     

A Study of the Movement Path for NC-Electrochemical Machining of an Integral Impeller

Aiming at machining an integral impeller used by an aero-engine by NC-Electrochemical Machining (NC-ECM),we first describe the fitting of a distorted blade surface with a ruled surface. Then a four-axis NC-electrochemical machining process is analyzed and the movement of the impeller is studied by using an equivalent open-loop plane motion link,and every program segment's feed displacement of three axes is calculated by analytical solution. Through comparing two results which are obtained,respectively,from analytical solution and experimental result,the comparative effectiveness has proved that the analytical solution is useful in calculating the feed displacement. The study is helpful for the programming of the machining process.     

Analysis and compensation of workpiece errors in turning

A new method for workpiece error analysis and compensation in turning is introduced. It is known that the workpiece error consists of two parts: machine tool error (including the geometric error and thermal-induced error) and cutting-induced error. The geometric error of the machine tool is independent on machining operation and, hence, can be measured off-line using a fine-touch sensor with a Q-setter (FTS-Q) (also called quick touch setter). The thermal error of the machine tool is dependent on cutting speed, feed, machining time and environmental temperature. It can be estimated using a radius basis function (RBF) artificial neural network (ANN). The cutting-induced error plays a dominant role and can be estimated based on the cutting condition (speed, feed and depth of cut) and the motor currents (main spindle motor current and feed spindle motor current) using a two-stage RBF ANN. Based on the estimated error, the compensation can be done by overwriting the CNC code on-line. Experimental results indicate that the new method can reduce the workpiece error by as much as 75% (average workpiece error is reduced to 8 µm from 14 µm). The new method is also easy to implement in the shop floor.     

Experimental Investigations of Abrasive Mixed Electro Discharge Diamond Grinding of Nimonic 80A

This paper presents a novel hybrid machining process (HMP) called abrasive mixed electro discharge diamond grinding (AMEDDG) in which abrasive powder is mixed in dielectric fluid to perform electro discharge diamond grinding (EDDG) action on a workpiece. In-house-fabricated AMEDDG setup was used to experimentally evaluate the performance of the process during the machining of Nimonic 80A. The effects of wheel speed, powder concentration, current, and pulse-on-time (POT) were investigated on the material removal rate (MRR). The surface morphological properties of the machined workpiece were investigated based on some quality surface indicators. The experimental results show that MRR of the workpiece was influenced by wheel speed, current, and powder concentration, and optimum MRR can be achieved at a wheel speed of 1400 RPM, a powder concentration of 4 g/L, a current of 10 A, and a POT of 26 µs.     

Effect of Tool Rotation on MRR,TWR, and Surface Integrity of AISI-D3 Steel using the Rotary EDM Process

Electric discharge machining (EDM) is an acclaimed non-conventional machining process that is used for machining of hard or geometrically complex and electrically conductive materials which are extremely difficult to machine by conventional methods. One of the foremost demerits of this process is its very low material removal rate (MRR). For this, researchers have proposed some modifications like; providing rotational motion to the tool or workpiece, mixing of conducting fine powders (such as SiC, Cr, Al, graphite etc.) in the dielectric, providing vibrations to either the tool or the workpiece etc.

The present research examines how the MRR and tool wear rates (TWR) vary with the variation in the tool rotation speed and their effects on the surface integrity of the workpiece. The results obtained clearly indicate that the tool rotation significantly improves the average MRR up to 49%. Moreover, the average surface finish also gets improved by around 9–10% while using the rotational tool EDM. Due to the tool rotation, the recast layer thickness is less for the rotary EDM as compared with the stationary tool EDM process. Furthermore, the micro-cracking on the recast surface of the workpiece is also less for the rotary tool EDM as compared with the stationary tool EDM.     

Rotary ultrasonic machining— a new cutting process and its performance

In conventional ultrasonic machining (USM), brittle materials are machined by using ultrasonic impacts on the workpiece, through a medium of abrasive slurry. In this paper a new cutting process that resulted due to introduction of an additional parameter, namely the rotation of the workpiece during the machining, is presented. This may be called ‘rotary ultrasonic machining’. The material removal rates (MRR) in rotary USM are up to four times those in conventional USM. The MRR increases with increase in speed of rotation of workpiece. An explanation for the superior performance of rotary USM is presented. The performance of rotary USM as a function of static load, abrasive grain size, concentration of abrasive slurry, diameter of tool and ratio of diameters of hollow tools, is studied and the parameters are optimized for minimum machining time or maximum material removal rate. Comparisons are made with conventional USM.     

Effect of cryogenic CO2 and LN2 coolants in milling of aluminum alloy

The research work was carried out on the end milling of Al 6082-T6 alloy with cryogenic CO₂, LN₂ and wet conditions. The highest axial force (F_z), normal force (F_y) and feed force (F_x) values were recorded on cryogenic LN₂ machining. Use of cryogenic LN₂ helped to reduce the cutting temperatures up to 38.29% and 32.8% when compared with wet and cryogenic CO₂ conditions, respectively. The conventional fluid coolant offered a better surface roughness value (R_a) over cryogenic coolants at a feed rate of 0.015 and 0.02 mm/tooth and cutting speed of 100 m/min. The workpiece surface quality degraded in cryogenic machining conditions during the slot end milling operation of aluminum alloy under the given machining parameters.     

采用疏水材料侧壁绝缘电极的微细电解加工实验

微细电解加工中工具电极和工件之间的加工间隙是影响加工效果的核心因素.工具电极侧壁施加绝缘膜的工艺方法,可显著改变侧面加工间隙内的电场分布,提高加工精度,同时保持原有的加工效率,有着良好的应用前景.本文基于仿真方法,分析了绝缘膜对端面加工间隙和侧面加工间隙的影响规律,研究了绝缘膜疏水性质对电解加工中产生的氢气泡运动的吸附作用对微细电解加工的影响.在直径为数十到数百微米的钨丝侧壁制备出可用于微细电解加工的几微米厚的硅胶疏水材料侧壁绝缘薄膜.在硝酸钠电解液中,实现了不锈钢材料上将微气泡附着于电极前端与绝缘膜结合处、保护绝缘膜和约束杂散腐蚀的微细电解端面分层扫描加工效果.     

Excimer laser micromachining of oblique microchannels on thin metal films using square laser spot

Excimer laser micromachining of thin metal films with a sacrificial polymer coating is a novel technique that produces features with smooth edges. Using this technique, oblique microchannels are fabricated by workpiece dragging and using a square laser spot, where the axis of traverse of the workpiece is not parallel to the edges of the square laser spot. The microchannels have serrated edges that are particular to the shape of the mask producing the spot. The edge roughness of the channels, machined with a square laser spot of side 100 μm, is found to be most affected by the fluence–spot overlap interaction, and the channel width by spot-overlap and the angle of tilt of the traversed path. Polymer coated metal films underwent close to ideal machining, aided by the clamping action of the polymer layer. Through this technique of machining post polymer coating, the edge roughnesses of the microchannels have been curtailed to less than 10 μm, and channel widths to 150 μm. This technique may be used in fabrication of oblique and circular patterns using excimer laser micromachining with rectangular and square laser spots.     

轴对称非球面镜超精密加工新方法的几何模型

介绍了轴对称光学非球面镜超精密加工的新方法．超精密金刚石切削加工机床的刀具进给机构通常由直线导轨实现．由于旋转轴与同等精度的直线导轨相比,具有制造难度小、成本低及结构紧凑等优点,所以采用具有快速伺服机构的金刚石刀架摆臂代替直线导轨进给运动方式．根据非球面方程,快速伺服机构的微进给量根据车刀摆角实时计算．快速伺服机构、工件以及金刚石刀具的同时运动,可以实现轴对称非球面的超精密加工．构建了回转进给工具路径、快速伺服机构运动以及相关的几何模型．通过计算机模拟验证了该加工方法的简便与可靠性,可以降低非球面反射镜加工的设备投入,提高生产效率．     

基于双电层电容的微细电解加工间隙的在线检测

根据微细电解加工中工具电极下端面面积远小于工件表面的非对称特征,在水基中性盐钝性电解液侧流冲入和金属电极处于钝化状态的条件下,提出了一种基于双电层电容的微细电解加工间隙的在线检测方法．在微细工具电极和／或工件上不外加传感器的前提下,利用工具电彬溶液界面上双电层电容值随加工间隙增大而单调递增的变化关系,精确、快速地实现加工间隙的在线检测．在冲液速度为1．058m／s的条件下,当加工间隙在O．100μm时,可在数毫秒内在线检测出微细电解加工间隙的大小,数值仿真与实验测量值之间的最大相对误差小于10％．为实现高精度、高质量、稳定的微细电解加工提供必要条件．