The aero-engine nozzle is a key component that affects combustion performance. It has many components and complex structure, especially the difficulty of the processing of nozzle internal flow channel, resulting in long manufacturing cycle and high cost. However, the nozzle as a non-main load-bearing part is very suitable for laser selective melting manufacturing (SLM), which is due to the high precision of processing, strong free-form ability and high density of material of laser selection melting. In this paper, based on the technical advantages of SLM, the shell of the nozzle is integrally designed, and the mechanical analysis and topological optimization were analyzed. The molding part was printed by SLM and about 13.5% of its weight has been reduced. The printing error is less than 0.2mm, meeting the margin requirement of local finishing, and the mechanical properties of the furnace specimen reach the level of traditional casting and forging. SLM simplifies the processing of the nozzle, shortens the manufacturing cycle, and has high precision of flow path forming, which achieves the goal of reducing weight and improving performance.
In order to improve the service life and maintenance efficiency of electrical discharge machining (EDM) machine tools, reduce the process difficulty of EDM for difficult-to-machine materials and complex structural parts in the fields of aviation, aerospace and energy, and improve the sharing and convenience of processing technology services, key technology research on cloud service platform construction of EDM machine tools was carried out, including the system architecture design of platform, design and implementation of software and hardware. Based on the platform, the remote EDM process service test of turbine disk, which is the key component of aero-engine, and the cloud-base operation monitoring of EDM machine tools are carried out, and the validity of the platform is verified.
The micro-EDM in nitrogen plasma jet (NPJ) obtained better processing performance than that in gas. However, due to the small discharge gap and the difficult exfoliation of the molten material, the abnormal discharge phenomena such as short circuit and arcing still occurred frequently. These phenomena seriously affected the quality and stability of the processing. In this paper, a new method of applying ultrasonic vibration to the workpiece is proposed to improve the processing performance of micro-EDM in NPJ. The process experiments were carried out on process indexes such as discharge distance, material removal rate (MRR), surface roughness and tool electrode relative wear rate (TWR) of EDM. The experimental results show that after the ultrasonic vibration is applied to the workpiece, the molten material is more easily exfoliated from the surface of the workpiece. When the mixture of nitrogen plasma jet and high velocity air jet (NPJ+HVAJ) is used as the dielectric in the proposed method, the MRR increased by 13%, the surface roughness decreased by 19%, and the TWR decreased by 13%.
A processing method and equipment for achieving arc and milling combined machining was firstly introduced. Then, in order to further verify the feasibility of electrical arc machining (EAM) in the production of aerospace components and its friendliness to subsequent finishing processes, a combined machining of three-dimensional flow impeller sample with complex contour features by EAM Milling and CNC milling was conducted by utilizing a selfdeveloped special machine tool. The results show that the reasonable arrangement of the EAM process can achieve satisfying surface quality while obtaining efficient material removal. The maximum material removal rate (MRR) in EAM was 14500mm3/min. The surface roughness after small energy EAM was Ra12.5μm, and the hardness of the machined surface was 69.4HRB, which had no obvious change compared with the hardness of the substrate. Thus, the surface after the small energy EAM can be well adapted to the cutting requirements, which effectively confirms the friendliness of the EAM process. In the subsequent CNC milling process, the tool wear was small and the state during machining was stable. The surface roughness finally obtained was Ra1.2μm, and due to small cutting allowance, the machining deformation is effectively suppressed. Processing results of the sample flow channel met the design requirements, which fully demonstrates the feasibility of applying the combined processing method to the manufacturing of engine components with complex contour features.
In order to solve the technical problem of dense micro grooves on the surface of xenon lamp tungsten anode, a method of electrochemical discharge machining (ECDM) of micro grooves on pure tungsten at low conductivity electrolyte was proposed, and RC power supply was applied into the process. The characteristics of ECDM with different electrolyte under RC power supply were studied. Firstly, the polarization curves of pure tungsten materials under different electrolytes were measured by electrochemical workstation, and the open circuit potential at different electrolytes was analyzed. In order to study the influence of the bubbles distribution during the processing, the bubbles formation and distribution in the machining area under different experimental conditions were observed by high-speed camera. Finally, the process of ECDM of micro-groove on the surface of pure tungsten rod was carried out with self-developed test device. The effects of electrolyte type, conductivity, rotational speed and inter electrode voltage on the machining characteristics were analyzed. Under 50μS/cm NaOH solution with an inter electrode voltage of 60V and a rotating speed of 500r/min, the micro groove with width is 50.97μm and the depth is 17.31μm was obtained by ECDM.
This paper aims to study the machinability of carbon fiber reinforced Mg-matrix composite (Cf/Mg), the ultrasonic assisted cutting experiments of carbide milling cutters and carbide drill bits are carried out. Through orthogonal test, it is found that the milling force of ultrasound-assisted milling Cf/Mg composite increases with the increase of feed and milling depth of each tooth, and decreases with the increase of spindle speed. In the test, when ultrasonic assisted milling is carried out, the feed per tooth is 0.025mm, the milling depth is 0.2mm, and the milling force is the minimum under the processing parameters of 6000r/min. The feed per tooth is 0.025mm, the milling depth is 0.2mm, and the surface quality under the processing parameters of 4000r/min is relatively good. When single factor drilling test is carried out with carbide bit, the axial drilling force decreases with the increase of spindle speed. Compared with traditional drilling, ultrasonic assisted drilling can reduce the axial drilling force. Compared with traditional drilling, ultrasonic assisted drilling can reduce the axial drilling force by about 36% when the machine speed is 6000r/min and the feed speed of the machine is 100mm/min. Compared with traditional drilling, ultrasonic assisted drilling can decrease burr and stratification at the drilling exit.
According to a typical structure of non-resonant elliptical vibration cutting (EVC) device, the dynamic hysteresis characteristics of piezoelectric stack in non-resonant EVC device are considered, the static PI hysteresis model is segmented into dynamic weights, and the dynamic PI hysteresis model is constructed to describe the relationship between the axial input voltage and the output displacement of the non-resonant EVC device. The feed-forward controller of the non-resonant EVC device is established by inversion of the hysteresis model, and in order to further improve the accuracy and stability of the control system, the PID feedback link is introduced and the feed-forward is used. The compound control method of inverse controller and PID feedback is used to control the sinusoidal displacement of the specified frequency and amplitude of each axial output of the non-resonant EVC device, so that the motion frequency, shaft length and inclination of the elliptical vibration track can meet the requirements, and the non-resonant EVC device can be controlled. The experimental results show that the non-resonant EVC device can output an elliptical vibration trajectory with an adjustable amplitude and dip angle below 100Hz under compound control, and the motion error is less than 3.5%.
Based on the engineering experience that subarea–scanning can effectively reduce the residual stress of large-scale structure formed by laser deposition forming, a finite element model based on thermo–elastic–plastic finite element theory was established to simulate the temperature and stress fields in the forming process. And the effects of different subarea–scanning on temperature and stress evolution, thermal cycling curve and residual stress of T–joint formed by laser deposition forming were studied. The results showed that the maximum values of thermal stress and residual stress occurred at the four outer corners of the contact between the upper edge strip and base metal, which is independent of the zoning method; The subarea–scanning has little effect on the outer corner points and the short outer midpoints of T–joint, but has certain influence on the thermal cycle curve and thermal stress curve of the inner corner points, the inner points and the long outer midpoints; Subarea–scanning has a great influence on the distribution of residual stress, especially on the distribution law and amplitude of residual stress along the specified section.
In order to improve the grinding and polishing precision of aero-engine blades and reduce the trajectory deviation of complex curved blades, the hybrid force/position control strategy was adopted to realize on-line correction of grinding and polishing trajectory. A blade grinding and polishing verification platform was built which based on Staubli robot and ATI six-axis force/torque sensor. The upper computer was developed by C++ to collect the information of force sensor and preform Kalman filter. Through the trajectory teaching, the robot trajectory and force/torque information were collected and analyzed. It is turn out that the trajectory of the robot can be corrected online based on the force/position hybrid control, which provides a solution for the trajectory control of blade grinding and polishing on complex curved surfaces.
Fatigue tests of the specimen designed according to the typical interconnected structures of a certain airplane’s wing box were carried out to analyze the effects of different assembly processes of high locked bolts on fatigue performance. The results show that the fatigue performance of interconnected structures can be improved effectively by exerting an appropriate second–tightening torque to high locked bolts after the current assembling processes. A three–dimensional finite element model was established to investigate the effects of tightening torque of bolts, friction coefficient between plates as well as elastic modules of bolts on the stress concentration factor of the hole edge in basic plates. The study indicates that all the three factors have great influence on the stress concentration factor of the hole edge. Furthermore, tightening torque of bolts has the most significant impact. It also shows that exerting a second–tightening torque is an effective mean to improve the fatigue performance of interconnected structures.
Aiming at the process characteristics of integral forming and cementing connection of light composite material aircraft, the overall design of the process scheme was carried out. It included the determination of assembly order, the choice of assembly tooling benchmarks. Then, the integration of the tooling structure is designed, refinement of the mold forming and positioning and clamping of the structural parts are also studied. Finallly, small parts like tail, drag plate are manufactured again. The practical use of integrated tooling is verified, meanwhile the feasibility and advancement of integrated tooling design on light composite material aircraft fuselage is verified by analogy analysis. The study can provide reference for design of composite material aircraft.
