The fabrication of film cooling holes on turbine blade of aero-engine is always a difficult problem. In this paper, the EDM & ECM hybrid machining method for small holes drilling is presented, in which electrical discharge machining (EDM) and electrochemical machining (ECM) occur simultaneously. According to experimental studies on the EDM & ECM hybrid machining method, machining process phenomenon, waveforms of voltage and current were observed. The composition of processed product was analyzed, and the ratio of material removal by electrochemical dissolution was also calculated. Effects of different working fluid conductivities on tool electrode wear performances were studied. Machining qualities of small holes by hybrid machining and pure EDM were compared. The results of experiments indicate that the EDM & ECM hybrid machining can effectively remove the recast layers on the side wall of the hole in the machining process. Thus, a novel way to machining the film cooling holes can be provided with high efficiency and free of recast layer. It also can be used for machining other small hole structures in aero-engine.
This paper introduces the electrochemical finishing of several components such as bearings, gears, hydraulic valves, metal pipes, free-form surfaces and so on. According to the requirements of aircraft performance, the application prospects of the electrochemical finishing technology in aircraft, especially in aeroengine, are discussed and the key technical problems to be solved are analyzed.
The large flange cover is one of the key components of centrifugal compressor and air separation compressor that is utilized in the aviation equipment , and the machining of the flow channel inside flange cover is a difficult problem. An electrical discharge machining method for machining an internally curved flow channel is proposed. The structure of a flexible transmission device used for EDM internal flow channel machining is studied. The bending avoidance technology, insulation & chip removal technology and EDM processing technics are prepared. Using this new method could solve the traditional mechanical processing problems, such as shorten parts service lives by drilling auxiliary holes, solve the high security risks that are caused by toxic liquid and gas leakage for easy cracking of the welding position, complex procedures and high costs. The method can achieve the high efficiency and high precision machining of the flow channel with various inclination angles. The experimental results show that this method can be used to process internal curved holes with diameter ranged from 15mm to 20mm, bending joint smooth transition and two hole docking at the accuracy of not less than 0.8 mm, surface roughness less than Ra3.2μm. This method of EDM provides an effective method for the manufacture of components with internally curved flow channel.
Aiming at the requirements in manufacturing cost and reliability of new generations of aero-engine, electrochemicalmachining technology has the advantage of efficiency and integrity in the manufacture of aero-engine integral thinwalled structure. This paper focuses on the current domestic machining technology for the complex surface of the thin-walledstructure and electrochemical machining technology for the aero-engine integral thin-walled structure of home and abroad, andpoints out the future problems and development prospects of the technology.
In order to solve the issue of the poor rigidity of cathode structure in the electrochemical machining (ECM) of titanium alloy with high length-width ratio, a hollow slice cathode with stiffeners was designed. The effects of the number of stiffeners and the angle between stiffener and sidewall on the overall rigidity of the cathode were studied by one-way fluid coupling analysis method. The simulation results show that the overall rigidity of the cathode is improved remarkably when three stiffeners are added to the cathode structure. In addition, the overall rigidity of the cathode decreases with the increase of the angle between stiffener and sidewall. Comprehensive cathode deformation and the maximum equivalent stress, the angle between stiffener and sidewall is 45°, the cathode structure has good rigidity, and can meet the rigid requirements. Finally, adopt self-developed experimental system to implement a ECM process test of deep narrow grooves with high length-width ratio. The optimized cathode structure can be used to process a deep narrow groove with lengthwidth ratio of 11 ∶ 1 and depth-width ratio of 9 ∶ 1.
This paper measured and studied the reaction force of blasting erosion arc machining (BEAM) of SiC/Al based on a piezoelectric sensor. The characteristics of the reaction force waveform was discussed, and the forces in different dielectric are compared. Then, the frequency characteristics and the relationship between reaction force and discharge parameters (pulse on time, current and open voltage) were researched. Furthermore, the influence of relationship between reaction force and the material removal mechanism of discharge processing was discussed. And finally, a method to reduce the reaction force during BEAM of thin-wall SiC/Al workpiece which is commonly used in aerospace industry was given.
The system resonance is difficult to maintain in the machining process of ultrasonic combined electrochemical machining, because a manual adjustment of ultrasonic frequency generates test error. This problem can be solved by constructing and perfecting the online parameter detection and control system of ultrasonic combined electrochemical machining. This study build the data acquisition system of the signal parameters by selecting a variety of high speed and high precision sensor, vibration displacement of tool electrode in the process of ultrasonic power and pulse power output voltage, EDM electrode current of online detection, and the use of PCI-1706U data acquisition card; designs the vibration displacement signal of laser displacement sensor detection as the chopper voltage control signal of pulse power supply; uses digital potentiometer to replace the original mechanical potentiometer, ultrasonic power supply, the output resistance of the digital potentiometer controlled by MCU STM32 communication. By the tools of Visual C++ 6.0 design of compound ultrasonic EDM detection and control system software, through the data acquisition card library programming, data acquisition, processing, display functions including the signal detection module design parameters; design the control software module through the serial port. Compared with the manual control parameters, the control system of ultrasonic combined electrochemical machining test can guarantee precision, improve the process stability and machining efficiency.
Recently, laser keyhole welding technique has brought it widespread attention due to its good quality and high productivity in joining dissimilar alloys. The laser keyhole welding technique used in joining dissimilar alloys can be classified as keyhole welding-brazing and keyhole welding according to whether the steel base materials are melted or not at the interface of steel/Al joints. The research status of laser keyhole welding-brazed steel/Al joints is discussed in terms of different laser beam sources in details. In considering laser keyhole welding of steel/Al joints, the research progress in abroad and at home is described by means of different joint configurations. Finally, a very import research direction of dissimilar joining steel/Al joints using laser keyhole welding technique is proposed.
Light-weight integrated large components with high properties in aviation and aerospace industry are required to be manufactured efficiently and cheaply. Low cost and high deposition rate make wire and arc additive manufacturing (WAAM) a more suitable candidate for manufacturing the large scale and medium complexity parts, comparing with other 3D printing technologies. The development including the existing problems and feasible solution methods of aluminum and titanium WAAM technology is reviewed in this paper. The key technologies in the manufacturing large WAAM components, such as control of internal stress and strain, path planning and online monitoring, are also discussed.
The precision of traditional mass and gravity center measure method is relatively low and the system fault tolerance is not high. This paper presents a high precision redundant measure method for mass and gravity center. The method could make on-line calibration for the measurement unit, and the software could automatically select the calibration coefficient with respect to the measurement value of sensors to correct the mass and gravity center value, so as to eliminate the nonlinear error of the sensors. The software can automatically compensate the measurement result of the gravity center according to the installation error of the payload so that the misalignment and deflection effect of installation can be reduced and the measurement accuracy of the mass and gravity center can be improved. The system reliability is enhanced based on the realization of cross redundancy through the hardware system’s redundant design and the software system data sharing. The method has passed the actual tests, its mass measurement error is better than 0.05%, and its gravity center measurement error is less than ±1mm, at the same time the mass and gravity center redundancy switching function of the system has been verified.
In this article, with the demand of composite sandwich NDT, the tap force time criterion theory of digital tap test was introduced. The portable tap test imaging system was designed. To different type and damage dimension sandwich structure, the tap test validate experiment was studied, and the NDT experiment results were discussed and analyzed. The experiment proves that the digital tap test technique can effectively detect the delamination and debonding defects of honeycomb and foam sandwich structures.
For the condition that composite stringer cannot connect the titanium joints properly due to the manufacturing defect, three kinds of connecting type comparison tests are designed and the test conditions are normal connection, stringer vertical edge with failure and stringer free edge with failure, respectively. FEM is used to study the changes of the failure mode and failure load of the structure under the out-of-tolerance condition. The results show that the three connection type structures have the same failure mode which fails along the 45° fiber of the skin precast crack; three different conditions almost have no influence on connection stiffness; the condition that stringer vertical edge with failure has less effect on connection strength, the failure loads decrease 5.31%; the condition that stringer free edge with failure has greater effect on connection strength, the failure loads decrease 22.13%. The condition that stringer free edge with failure is the most severe failure condition.
