Metallic glass is a new type alloy obtained by rapid cooling and solidification in molten state. Due to the extremely short solidification time, the atoms have no time to rearrange in order. Therefore, metallic glasses have no grains and grain boundaries, and their strength, hardness, elastic limit, wear resistance and other properties are superior to traditional metals. Electric discharge machining (EDM) can not only process metallic glasses, but also prepare metallic glass layers on the surface of metal materials in order to improve the mechanical properties, such as hardness and wear resistance. In this work, the applications of EDM in the processing of metallic glasses are reviewed from two aspects: the preparation of metallic glass layers on the metal surfaces and the processing of metallic glasses by EDM.
Whether the construction of aero-engine process research system is reasonable or not, which has an important influence on successful development of the model engine. Based on the analysis of the successful products process research system of world-renowned aerospace enterprises, this paper summarizes its logical structure and organizational characteristics, and then forms the constructing logic of the aero-engine process research system which is collaborative with design and manufacture. Finally, the general craftsman system of the commercial aircraft is constructed. A concept of process control is put forward, and the specific content of the control is expounded. It provides effective support for process capacity building and development of the commercial aircraft.
In order to complete the full-face automatic processing and production of the aero-engine’s whole leaf disc tip, blade body, edge, blade root and runner surface, it is necessary to integrate the aero-engine blisk grinding system. However, the processing equipment such as the robot grinding mechanism, the numerical control rotary table, the blue light detector, and the digital silo are isolated from each other to form an automated island phenomenon, which results in the data collected by each device cannot be uploaded and downlinked in time and effectively, and the integration of management and control cannot be realized. Therefore, this paper proposes a system integration scheme for the aero-engine blisk robot grinding method. Firstly, based on the analysis of the existing process, the integrated construction target and overall framework of the aeroplane blisk grinding system are proposed. Then, the integration of the whole system information is realized through the industrial Ethernet and OPC technology. Finally, the navigation is carried out. The leaf disc was experimentally verified by the system integration scheme. The experimental results show that the Blisk after the grinding by the robot has high surface integrity.
As the key hot end component of aero-engine, hollow turbine blades are usually made by near-net shape investment casting process, which has low molding quality and high rejection rate. Firstly, the research status of investment precision casting technology in “precise shape control” was introduced. It was found that the accuracy of shrinkage fraction assignment in mold design directly affects the dimensional accuracy of precision castings. Then, the influencing factors of casting shrinkage fraction during solidification process were summarized, and the research process of structural correlation of shrinkage fraction was analyzed emphatically. Finally, the research results of shrinkage fraction distribution of precision castings such as hollow turbine blades were summarized.
A new process using rotary swaging was introduced for the difficult machining of slender shafts for aero-engine. In order to process the square holes in the elongated shaft, the billet meeting the forming requirements were designed and optimized, and the forming parameters were determined. The 3D rotary swaging finite element model was used to simulate the swaging process using the obtained billet, and the internal square hole process was studied experimentally. The dimensions and microhardness after forming were measured and analyzed and the microstructure was observed. The results show that the forming of the square hole in the slender shaft of the aero-engine can be processed by the recessed rotary swaging method with the mandrel, the forming efficiency is high, the forming dimensions of the workpiece meets the requirements, and the influence on the hardness and the microstructure is minor.
A silicone polymer modified by epoxy resin was synthesized via the reaction of a liquid epoxy resin with a α,ω–dihydroxyl silicone under catalysis of dibutyltin dilaurate. Chemical structure of the modified silicone polymer was characterized by FT–IR, while heat-resistant of the polymer was tested by the thermogravimetry. The modified silicone polymer containing 70% (mass fraction) α, ω–dihydroxyl silicone shows excellent heat-resistant, which possesses residue of more than 30% (mass fraction) when heated at ≥ 500℃. A peelable heat-resistant coating cured at room temperature was used as anti-spatter coating under laser drilling, which was prepared with the modified silicone polymer as the film-former. The anti-spatter property of the coating on the engine blades was tested by exposing to laser drilling under air blowing conditions. The coating exhibits optimizing anti-spatter property which keeps adhered to the substrate after the laser drilling process. It has played a very good protective role and effectively improved the quality of laser drilling of engine blades.
The one-side pressed hole making process is a key technology for light automated holing system of aircraft. This article selects the typical position of the docking between aircraft fuselage and head section of a certain model as the research object, and mainly studies the influence of arrangement of the pre-tightening fixture on the quality of the hole during the unidirectional compression. Firstly, a simulation model was established to determine the influence parameters. On this basis, the simulation experiment was performed to obtain the discrete sample point data. Finally, the response surface methodology approximation model was established through Isight platform and an adaptive simulated annealing algorithm was used to analyze and optimize discrete data. Optimization results obtain the optimal pre-tightening arrangement parameters and corresponding layout scheme.
Porous metal-bonded cubic boron nitride (CBN) grinding wheels are fabricated by employing ammonium hydrogen carbonate (NH4HCO3) as pore-forming agents to avoid workpiece burn, improve ground surface quality and service life during grinding Ti–6Al–4V titanium alloys. The graphite particle concentrations are optimised with the flexural strength and interface morphology between the metallic matrix and grains. The grinding performance, including grinding temperature, material removal rate, grinding ratio, grains wear and ground surface quality of the porous CBN wheels and silicon-carbide abrasive wheels is evaluated during grinding Ti–6Al–4V titanium alloys without cooling lubricants. Results indicate that porous CBN wheels with 10% (mass fraction) graphite particles are optimized in terms of the wettability between the metallic matrix and abrasive grains as well as the flexural strength. In addition, porous CBN wheels exhibit high porosity and promising comprehensive grinding performance. In comparison with the silicon-carbide abrasive wheels, a lower grinding temperature (approximate 250℃) and better ground surface quality can be achieved by porous CBN wheels. Moreover, the material removal rate and grinding ratio of porous CBN wheels reach about 4 and 2 times than that of the silicon-carbide abrasive wheels under the same conditions.
Involute gear is a key part of mechanical equipment. In the process of gear measurement or mapping, the base circle center needs to be obtained by inverse calculation of the measuring points, and the precision of inverse calculation will directly affect the accuracy of gear measurement or mapping. In this paper, under the condition of known radius of base circle, the method of establishing the non-linear least squares equation for inverse calculation of the center of base circle was studied and solved by Newton method, and the coordinates of the center of base circle were obtained. The main factors affecting the accuracy of inverse calculation were discussed: the number of measuring points of single involute, the number and position distribution of the measured involute, the selection range of the initial value of the center of base circle. The experimental design of the influence of the above factors on the accuracy was carried out. Taking the involute cylindrical gears with modulus 3.5 and tooth number 36 as an example, the method proposed in this paper was verified and the influence of main factors on the accuracy of reverse calculation was quantitatively analyzed. It is found that at least 100 measuring points should be selected for each measured involute profile, and four involute profiles should be selected in the circumferential uniform distribution direction for the reverse calculation of the base circle center. The research in this paper has certain guiding significance and reference value for the inversion of the base circle center in the measurement and mapping of involute gears.
The difficulty of surface defect detection of silicon steel strip under oil pollution is that the images obtained contain a variety of interference. In order to remove the interference while detecting defects, a nondestructive detection method based on image processing technology was proposed. Median filter and Wiener filter were employed to suppress the texture interference on the surface of silicon steel strip. Then the disconnected oil contour edge was connected and completed, after which oil pollution area mask was made to remove the interference of oil pollution edges. Bright spot mask was made to remove the interference of bright spot edge on oil surface. Finally, only the edge of the defect was left. Upon test, the method can effectively detect the surface defects of silicon steel strip under oil pollution interference, such as small defects, surface scratches and cracks.
The paper introduces tolerance analysis technology and its basic theory. The research uses tolerance analysis software VSA to study the process of civil aircraft pylon assembly. The process one: connecting rod is installed at last. The process two: diagonal bracing rod is installed at last. Comparing process one with process two, the following results can be obtained. Both of two assembly programs are required to set the process compensation. According to the weights of influencing factors, some measures should be applied on the greatest effects for control target. Therefore, improve the design of connecting rod structure to make upper and lower nodal hole position in a certain range to meet the coordination requirements of pylon assembly.
The pitot tubes’ material is 2A12 aluminum alloy, belongs to Al–Mg–Cu–Si–series wrought aluminum alloy. The alloy has good corrosion resistance, weld ability and cold working ability. It is mainly made of aluminum alloy with copper as the strengthening term. Because the main alloy elements contain Mg, Si, and form Mg2Si, they have better processing properties and higher tensile strength, yield strength and hardness. Strengthened copper content is relatively high, hardness is moderate, thermal conductivity is large, beneficial to cutting. At the same time, it is easy to cause hot deformation in cutting. Therefore, it is difficult to control the dimensional accuracy. In this paper, the robot belt grinding method and adaptive machining technology was used to grind the pitot tubes of aluminum alloy. The point position in formation of parts was identified by blue light and added into Polyworks software based on standardized model. According to the point position information extracted from the web welded airspeed tube parts, the fourth-order homogeneous matrix was established to inversely calculate the motion trajectory of the robot to ensure the grinding posture and grinding param eters. Finally, the adaptive processing method is adopted, according to the surface allowance information of the web welded pitot tube parts. Then, the material removal of web welded pitot tube parts is quantitatively carried out to ensure the processing accuracy.
When milling large diameter internal thread parts, it is often due to the selection of improper milling cutter diameter and cutting parameters, resulting in after cutting, the surface shape error of the workpiece is large and the machining accuracy is low and other situations. Tool diameter and cutting parameters affect tool path to different degrees. Thus the theoretical roughness of the machined surface is further affected. Therefore, it is of great importance to study and theoretically analyze the influence of tool diameter and cutting parameters on tool path. On the one hand, the tool path matrix equation is set up by using the homogeneous coordinate transformation method. According to different reference objects, the matrix equations of two kinds of point trajectories on cutting edges are established. On the other hand, single factor test method is used to select different tool diameters and cutting parameters for machining trajectory simulation. The results show that with the increase of milling cutter diameter, milling cutter speed and the number of milling cutter teeth, the theoretical roughness decreases, making the machined surface close to the ideal smooth surface.
