金属切削英文

Overview of the manufacturing technology of integralblisk of aero engineChen CanIntroductionIntegral blisk refers to a new type of monolithic structure, which made of a blade wheel and blades. Compared with the traditional structure, this new structure is able to reduce the connecting part of roulette and blade of rotor of engine, such as rabbet, mortise and fasteners. This new technology can greatly reduce the number of parts and the structural weight of the blade wheel. Therefore, it can not only improve the engine performance, such as thrust-weight ratio, but also improve the reliability of the engine. In addition, f rom the point of view of aerodynamics, the integral design can eliminate the clearance of the parts, so that avoid to the loss of pressure in the process of gas compression and improve the aerodynamic efficiency, which makes the structure of the engine greatly simplified. Therefore, all countries will increase research effort of integral blisk as a key technology of new engines. However, from the beginning of the integral blisk proposed, its manufacturing technology has been a very difficult challenge, especially，the high performance of a new generation of aircraft, and high thrust weight ratio and other technical characteristic have the new requirement. The application of new type of difficulty processing materials, the accuracy of the requirement to improve the manufacturing technology of blisk has put forward a new requirement. This paper gives a brief introduction to the development process and application status of the integral blisk, summarizes some pivotal problems and introduces the development trend of this technology.Structural featuresIntergral blisk is an aeroengine new structure proposed in the 1980s, and the structure have two different forms of overall structure and separating structure using welding technology. Compare with the traditional separation of blade discs, it have the following characteristics:1. It need not to connect the blades and the disk with the corbelled structure, that can enormously reduce the structural weight, simplifying the internal structure of the engine. Take R.R company in UK as an example, after adopted this structure of the blisk, the weight is reduced to 50%, compared with the traditional blade of separation structure.2. Compare with the traditional separation type blade and disc structure,the Figure 1: Integral bliskFigure 2: the difference between traditional blisk and integral bliskcharacteristic of integral blisk can eliminate the pressure loss which is caused by the leakage of air flow crossing the gap, thereby enabling to improve the efficiency of the engine, and affecting the whole entire engine thrust-weight radio.3. In traditional structure, the location of the installation side, bolts and other fastener installation is often the place of stress concentration of contact. Under extreme operating conditions of engine with the high temperature and pressure, it’s the key position, which often produces fatigue failure. The microscopic crack caused by the collision is also an important reason of the accident of the engine. However, the integral blisk is successful to avoid the above negative factors, so that the engine’s working life and the safety and reliability greatly is improved.Nevertheless, there are still many problems and shortcomings in the development of the integral blade.1. Compared with the traditional separation type blade and disc structure, the largest difficulty of the integral blisk is the difficulty of manufacture of processing. It put forward a very high demand for manufacturing technology and cost control.2. In the service process of engine, the impact or internal crack of rotor ofteb makes the blade damage or scrapped. The integral blisk is difficult to replace a single blade in the wheel flange which is different to the separation structure. So it lead to a serious problem is that the cost is huge when you must replace the whole blisk for just a separate damaged blade. For this reason, generally, in the engine design process, the designers will try to do not to use the integral blisk in the first or second fans which is easy to be destroyed.3. The integral blisk is complex and the precision demand is very high. The blade is a thin-walled part, so the deformation is large under the force causing by the mechanical processing of the deformation. Because It remove material from a piece of blank material, the amount of finish and the tool wear is greatly large. So generally speaking, the machining process of blade is not only the main process of the integral blade, but also the key part of the integral blisk technology.Development and application of the structure of the integralbliskIn 1980s, with the development of the third generation military fighter, the requirement of the engine have become higher and higher. After that, with the continuous development of the aviation manufacturing technology, the integral bliskis widely used in the new aero engine. A case study of the United States which is the largest aviation country, GE Corporation in the United States uses the integral blisk in the T700 series engine core largely. In the subsequent development model of GE, this technology is widely spread. The YF120 second fan and the 5stage high pressure compressor all adopt the integral blisk technology. the 2 and 3stage of the F414 engine use the “low aspect ratio blade and tandem rotor”as a whole vane wheel design. Two integral blisks are welded together to form an integral rotor. This weight of the fan is reduced by more than 20kg compared to the previous. Duo to the massive use of new technology, the whole engine parts of F414 have a decrease of 484, compared to conventional separate disc and the weight ratio increased to 9.1 from 7.5 at least. Because of its use of a number of integral blisk welding as a single structure, the F414 is superior to the European EJ2000 engine. Because it can further reduce the weight of the rotor, improve the durability of the engine.In the 1990s, GE also present a forward swept blade blisk fan, and in the experiment of the forward swept type have been tested successfully. The test result shows that the new structure can produce a higher flow rate. What is more, the weight is reduced, and the efficiency of the fan is improved by 4% compared with the conventional fan. The tip efficiency is increased by 8% and the stall margin is increased by 5%.GE has installed the technology to verify the machine for further evaluation, and plans to use to improve the active engine.Figure 3: F119 model of engineAnd the another P.W company of the United States have tried to the integral blisk structure of the fan engine in early 80s, and nowadays has been widely used in advanced F119 and F100 engine. Takes 119 as an example, this model of engine adopts 3 stage fan structure rotor, and all of them are the integral blisk, while the first and second blade of air-compressor using linear friction welding are connected into awhole, and three to six grade use the bonding technology. In the use of the integral new technology, the temperature of the turbine inlet decline 49 degree celsius, while the engine reliability and life expectancy has been greatly improved.Entering into the new century, the United States developed a new joint attack aircraft JSF ,which lift fan also used the integral blisk. However, its integral blisk is the largest one so far in the worlds, which the outer diameter is 1.27m, and the weight is 100kg.Manufacturing technology of integral bliskThe manufacture technology and the maintenance difficulty of the engine is the main reason which restricts the application and extension of the structure. Due to the increasing difficulty of the mechanical manufacturing of the integral blisk, the traditional mechanical processing methods have been unable to do it. What’s worse, the extensive use advanced materials of titanium alloy and powder of high temperature alloy, greatly affect the machinability of the material. Therefore, we must develop advanced special processing technology, seeking and exploring a more efficient and reliable processing technology. Because the integral blisk is divided into two types, the integral type and the welding separation type, so the manufacturing method is also different. The methods of manufacturing integral type are Precision blank making technology, non-traditional machining and CNC milling. On the other hands, the important process of the welding separated type is the welding performance between the blade and the disc. The wielding processes are electron beam welding, linear friction welding and solid state diffusion bonding. The following are the key technologies to be introduced.Precision blank making technologyPrecision blank making technology is being developed and perfected continuously. This technology is generally used CATIA software to simulate the modeling, and improve the quality of metal filling by using the computer aided design technology, as well as improve the production efficiency of the product and reduce the cost of production at the same time. Nowadays the precision blank making technology has exceeded the stage of blank production, which was able to produce quality closed to finished part. The precision blank making technology, which is widely used in the integral blade, can greatly reduce the workload of machining, and improve the utilization efficiency of the material. In the United States, the utilization efficiency ofthe material is increased by 4 times and the surface roughness of the precision forging parts can reach the R0.4um level by using the technology. At the meantime, with the development of this technology, the fatigue resistance and the stress of the blade are increasing continuously.Electrochemical MachiningAs a kind of non-traditional processing method, electrochemical machining is one of the high precision and efficiency machining method which can be applied to the integral blisk made of the high temperature alloy. Compare with CNC milling, it has the advantages of high efficiency, and less deformation of the thin wall parts without tool wears. As early as 80s, the United States used the technology for the processing of F414. Electrochemical machining processing time reduced by 50%~80%, compare to traditional method. At present, the technology of the electrochemical machining has been able `to meet the` requirements of the processing precision of the integral blisk.Linear friction welding methodLinear friction welding is a solid state bonding technique, similar to that of diffusion welding. The strength and flexibility of the weld seam is stronger than the body, without the weld in the welded structure. The different between linear welding and diffusion welding is that the method to reach to the welding temperature. Linear friction welding is welding by a high temperatureheating zone which is produced by the high frequencyoscillation of the two workpiece diameters. It firstclamping the blade on the rim of the surface of the disc,then the disc vibrates at a high speed. So the bottom ofthe blade and disk interface produced a local narrowfrictional heating area, when the temperature reachedFigure 4: Electrochemical MachiningFigure 5: the fundamentals ofLinear friction welding methoddistrict heating blade and the disk are fixed together. Compare to other manufacturing methods, one of the most important advantages of linear friction welding is the repair of a single damage balde. Because the blade is welded on the disc, when a blade is damaged, the damaged one is able to remove and weld a new one. In addition, because welding can make different two kinds of materials together, this technology can maximize the performance of the material by using different material according to the different conditions of blade and the wheel.The development status of the integral blisk technology in ChinaAt present, the domestic research of the integral blisk technology is still constant development, some of which have made outstanding achievements in scientific research. For example, the Northwestern Polytechnical University and the Beijing Research Institute of Aviation Engineering have do the research of friction welding technology to carry out a lot of research work. Since 90s, Beijing aeronautical manufacturing research institute has carried out the research on the process of linear friction welding process and microstructure mechanism of the TC4, TC17, TC 11 and so on, which has accumulated rich experience. In the special processing direction of the integral blade, the research on the new technology of the electromechanical machining and the pulse electrochemical machining technology has been studied.Nanjing University of Aeronautics & Astronautics studied the numerical control of the electrochemical machining method since 1980s. The technique is based on the simple linear edge cathode to carry out the numerical control of the movement, and based on the principle of electrochemical anodic dissolution, the rough and the finishing of the blade disk is realized. Subsequently, the Nanjing University of Aeronautics and Astronautics studied a forming or near net shape forming flexible Figure 6: sample of integralcasting Figure 7: numerical control of the electrochemical machining methodcathode electrolysis processing technology. this technology can be used to achieve non developable ruled surface NC profile machining.SummaryWith the extensive application of new technology in the aviation engine, the technology of the engine components becomes the overall, lightweight development. And the integral blisk is also changing to make new demands on the manufacturing technology. Therefore, our country must follow the international trend of development, vigorously put into the development of the integral blisk manufacturing technology. in order to solve the short board of china’s aviation engine, and promote the continuous progress of China’ s national defense aviation industry.References[1]. Shiyaoyao duanjihao zhang feng dong ting . 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