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Chinese Journal of Aeronautics 2024年第5期37卷 506-519页

作者： Jiwen SHEN Weijing KONG zhengyang xu Yongbin ZENG Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The surface integrity of metal micro-hole structures produced by electrochemical discharge machining is unsatisfactory owing to the insufficient reaction area and strength of electrolysis action.A novel ultrahigh-speed Rotary Electrochemical Discharge Machining(R-ECDM)using non-water-based electrolyte is proposed to improve surface integrity by changing the breakdown medium of spark discharge and increasing the reaction area and strength of electrolysis.A mathematical model was developed to establish the relationship between rotational speed and forces acting on the bubble.Based on the magnitude of forces,controlling rotational speed changed the behavior and departure radius of bubbles on the cathode surface.High-speed photographs validate that,in the mathematical model,the number and departure radius of bubbles on the cathode surface gradually decrease with the increase of rotational speed.The experimental results show that the roughness(Ra)of the micro-hole sidewall decreases from 2.54μm to 0.20μm when the rotational speed increases from 500 r/min to 40000 r/min.The length loss and wear ratio of the cathode are only 9.75μm and 6.5%,respectively.Finally,the micro-holes array with recast-free and surface roughness of 0.20μm is fabricated,demonstrating that the proposed approach contributes to improving surface integrity of metal micro-holes.

关键词： Electrochemical discharge machining Micro-holes Recast layer Ultrahigh-speed rotary Bubbles Force analysis Non-water-based solution

Numerical and Experimental Investigation on Photothermal Performance of Polyimide/High-Electrical-Performance-Coating Composite Films Considering Surface Roughness

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Journal of Thermal Science 2022年第4期31卷 1206-1219页

作者： JING Peng ZHOU Xiao xu zhengyang xu Zhiguo School of Mechanical Engineering Shanghai Jiao Tong University Shanghai 200240 China Sunman(Zhenjiang)Co. LtdZhenjiang 212000China

Polyimide(PI)films are the common and important components on spacecraft for thermal control.Their parameter design accuracy has an important impact on the spacecraft thermal balance but there are few studies focusing on the effect of film surface defects.In the present study,photothermal properties of composite films made of PI films and germanium/indium tin oxide/aluminum coatings are obtained by UV-VIS-NIR spectrophotometer.The film surface morphology of composite films is obtained by the atomic force microscope.The present study creatively introduces surface roughness into modeling from the perspective of finite-difference time-domain(FDTD)model.The FDTD method considering surface roughness is used to present a comprehensive investigation on the coating effect on the photothermal properties including transmittance and reflectance of composite films.Based on the random rough surface generated by root-mean-square(RMS)roughness and correlation length,the FDTD method is applied to characterize the electromagnetic field of composite films.It has been found that the numerical accuracy is greatly improved and the numerical results agree well with the experimental data when surface roughness is considered.The results also show that coating material and thickness have remarkable impacts on photothermal properties of the composite films.

关键词： FDTD composite film surface roughness photothermal property coating material

Dependency of the pulsed electrochemical machining characteristics of Inconel 718 in NaNO_(3)solution on the pulse current

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Science China(Technological Sciences) 2022年第10期65卷 2485-2502页

作者： WANG JingTao xu zhengyang GENG TianYu ZHU Di College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Pulsed electrochemical machining(PECM)has attracted increasing interest as a technique to improve material dissolution localization and surface quality.This work systematically investigates the effects of pulse current on the surface morphology,profile accuracy,and corrosion behavior of Inconel 718(IN718)in NaNO_(3)solution.Polarization behavior reveals that IN718 in NaNO_(3)solution during pulse current machining exhibited significant passive,transpassive,and re-passive characteristics.The passive film generated at the re-passive state contained some oxides and had a loose porous structure.The critical value for the quantity of electric charge to rupture the passive film was determined to be 26.88℃cm^(−2).The current efficiency indicates that the material removal rate of IN718 in NaNO_(3)solution during pulse current machining was nonlinear.The PECM experiments indicate that the loading process of the electrical double layer was prolonged with an increased workpiece scale,i.e.,the loading process of the electrical double layer lasted for the entire pulse-on time when the workpiece scale was 100 mm^(2)at a frequency of more than 10 kHz regardless of the duty cycle.A pulse current with a short pulse length and short pulse period improved the profile accuracy,as did the low applied voltage and small workpiece scale.The dissolution mechanism of IN718 in NaNO_(3)solution was also investigated based on the effective pulse current time.Finally,the leading-edge structure of a ruled blade with good dimensional accuracy and surface quality was successfully fabricated.The maximum deviations of the machined profile were effectively restricted within 0.057 mm,and the surface roughness was Ra=0.358μm.

关键词： pulsed electrochemical machining corrosion behavior current efficiency blade leading edge machining quality

Evaluation of embedded modular branched stent graft in treating aortic arch aneurysm using imaging-based computational flow analysis

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Medicine in Novel Technology and Devices 2024年第1期21卷 80-87页

作者： xuehuan Zhang Jiang Xiong Wei Ma Lijuan xue zhengyang xu Hongpeng Zhang Yongsheng Wang Duanduan Chen Wei Guo School of Medical Technology Beijing Institute of TechnologyBeijingChina Department of Vascular and Endovascular Surgery The First Medical Center of Chinese PLA General HospitalBeijingChina Department of Vascular and Endovascular Surgery Hainan HospitalChinese PLA General HospitalHainanChina Department of Radiology The First Medical Center of Chinese PLA General HospitalBeijingChina Hangzhou Endonom Medtech Co. LtdZhejiangChina

Embedded modular branched stent graft(EMBSG)was a new option for aortic arch aneurysm.However,the therapeutic effect of this innovative stenting technique has not been fully assessed.Computational fluid dynamics and three-dimensional structural analyses were performed on three patients(Patient Ⅰ,Patient Ⅱ and Patient Ⅲ)with aortic arch aneurysm,both before and after EMBSG implantation.Patient-specific alterations from preoperative to postoperative were analyzed via morphological and functional metrics.Patient Ⅰ and Patient Ⅱ showed notable curvature changes and area reduction after intervention procedure.Three patients showed an increase in flow velocity after EMBSG implantation,while the pressure drop from ascending aorta to the aortic arch was remarkable in Patient I and Patient Ⅱ with the value of 7.09mmHg,and 10.95mmHg,respectively.Patient I and Patient Ⅱ also showed elevated time-averaged wall shear stress(TAWSS)in the stenting region,while Patient Ⅲ showed a trivial change in TAWSS after intervention procedure.Three patients showed low relative residence time after EMBSG insertion.The short-term results of EMBSG in treating aortic arch aneurysm were promising.Hemodynamic parameters have the potential to assist in the outcome evaluation and might be used to guide the stent graft design and wise selection,thereby improving the long-term therapeutic effect in managing complex vascular disease.

关键词： Aortic archaneurysm Embedded modular branched stent graft Endovascul araorti carch repair Computational fluid dynamics Functional evaluation

Surface morphology and electrochemical behaviour of Ti-48Al-2Cr-2Nb alloy in low-concentration salt solution

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Science China(Technological Sciences) 2021年第2期64卷 283-296页

作者： WANG YuDi xu zhengyang ZHANG An xu GuangChao ZHANG ChenXiang National Key Laboratory of Science and Technology on Helicopter Transmission Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrochemical machining(ECM) is becoming increasingly important for the efficient machining of parts with a large machining area. This is an addition challenge for ECM because of the very high machining current. To overcome this difficulty, a direct and effective strategy is to adopt the machining mode that uses a low-concentration electrolyte with a low current density.The purpose of this study is to reveal the electrochemical behaviour and surface morphology in low-concentration electrolyte.The polarization behavior of Ti-48Al-2Cr-2Nb is measured by linear sweep voltammetry and cyclic voltammetry curves. The ηω-j curves demonstrate the special dissolution behaviour of Ti-48Al-2Cr-2Nb at low current densities. The surface morphology,surface quality, and dissolution mechanism are analysed in three low-concentration electrolytes at different current densities after the ECM dissolution experiments. The results demonstrate that Ti-48Al-2Cr-2Nb exhibits three unique dissolution morphologies in the three solutions, and we found that the γ-TiAl phase dissolves faster than the α2-Ti3Al phase. These results also show that 1% NaCl solution is more suitable for Ti-48Al-2Cr-2Nb in ECM compared with the other two solutions, considering its good surface quality, low breakdown potential, and high material removal rate. Later, the dissolution process of the sample in 1% NaCl solution at different corrosion times is revealed. Moreover, a dissolution model is proposed for the electrochemical dissolution behaviour of Ti-48Al-2Cr-2Nb in 1% NaCl solution.

关键词： electrochemical machining γ-TiAl alloy low-concentration salt solution surface morphology electrochemical behaviour

Effect of tube-electrode inner diameter on electrochemical discharge machining of nickel-based superalloy

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Chinese Journal of Aeronautics 2016年第4期29卷 1103-1110页

作者： Zhang Yan xu zhengyang Xing Jun Zhu Di College of Mechanical and Electrical Engineering Nanjing University of Aeronautics & Astronautics

Nickel-based superalloys are widely employed in modern aircraft engines because of their excellent material characteristics, particularly in the fabrication of film cooling holes. However, the high machining requirement of a large number of film cooling holes can be extremely challenging. The hybrid machining technique of tube electrode high-speed electrochemical discharge drilling(TEHECDD) has been considered as a promising method for the production of film cooling holes. Compared with any single machining process, this hybrid technique requires the removal of more complex machining by-products, including debris produced in the electrical discharge machining process and hydroxide and bubbles generated in the electrochemical machining process. These by-products significantly affect the machining efficiency and surface quality of the machined products. In this study, tube electrodes in different inner diameters are designed and fabricated, and the effects of inner diameter on the machining efficiency and surface quality of TEHECDD are investigated. The results show that larger inner diameters could effectively improve the flushing condition and facilitate the removal of machining by-products. Therefore, higher material removal efficiency, surface quality, and electrode wear rate could be achieved by increasing the inner diameter of the tube electrode.

关键词： Electrical discharge machining Electrochemical machining Film-cooling hole Inner diameter Nickel-based superalloys Tube electrode

Cathode design investigation based on iterative correction of predicted profile errors in electrochemical machining of compressor blades

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Chinese Journal of Aeronautics 2016年第4期29卷 1111-1118页

作者： Zhu Dong Liu Cheng xu zhengyang Liu Jia College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

Electrochemical machining(ECM) is an effective and economical manufacturing method for machining hard-to-cut metal materials that are often used in the aerospace field. Cathode design is very complicated in ECM and is a core problem influencing machining accuracy, especially for complex profiles such as compressor blades in aero engines. A new cathode design method based on iterative correction of predicted profile errors in blade ECM is proposed in this paper. A mathematical model is first built according to the ECM shaping law, and a simulation is then carried out using ANSYS software. A dynamic forming process is obtained and machining gap distributions at different stages are analyzed. Additionally, the simulation deviation between the prediction profile and model is improved by the new method through correcting the initial cathode profile. Furthermore, validation experiments are conducted using cathodes designed before and after the simulation correction. Machining accuracy for the optimal cathode is improved markedly compared with that for the initial cathode. The experimental results illustrate the suitability of the new method and that it can also be applied to other complex engine components such as diffusers.

关键词： Cathode design Compressor blade Correction Electric field Electrochemical machining

Trajectory control strategy of cathodes in blisk electrochemical machining

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Chinese Journal of Aeronautics 2013年第4期26卷 1064-1070页

作者： Zhu Dong Zhu Di xu zhengyang Zhou Laishui College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University

A turbine blisk, which combines blades and a disk together, is one of the most important components of an aero engine. In the process of blisk electrochemical machining （ECM）, the sheet cathode, which is usually used as a tool electrode, has a complicated structure. In addition to that, the channel between the adjacent blades is narrow and twisted, so interference is apt to happen when the sheet cathode feeds into the channel. Therefore, it is important to choose suitable trajectory control strategy. In this paper, a new trajectory control strategy of the sheet cathode is presented and corresponding simulation analysis is conducted on the basis of an actual blisk model. The simulation results demonstrate that the sheet cathode can feed into the channel by a spatial line trajectory without interference. Moreover, the verification experiments are carried out according to the simulation. The experimental results show that the cathode can move into the channel without interference. It is verified that the new trajectory control strategy is correct and can be used in the blisk ECM process successfully.

关键词： Blisk Cathodes Electrochemical machining Feed Trajectory control

Machining of a film-cooling hole in a single-crystal superalloy by high-speed electrochemical discharge drilling

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Chinese Journal of Aeronautics 2016年第2期29卷 560-570页

作者： Zhang Yan xu zhengyang Zhu Yun Zhu Di College of Mechanical and Electrical Engineering Nanjing University of Aeronautics & Astronautics

Single-crystal superalloys are typical advanced materials used for manufacturing aero- engine turbine blades. Their unique characteristics of high hardness and strength make them exceedingly difficult to machine. However, a key structure of a turbine blade, the film-cooling hole, needs to be machined in a single-crystal superalloy; such machining is challenging, especially considering the increasing levels of machining efficiency and quality demanded by the aeroengine industry. Tube electrode high-speed electrochemical discharge drilling （TSECDD）, a hybrid technique of high-speed electrical discharge drilling and electrochemical machining, provides high machining efficiency and accuracy, as well as eliminating the recast layer. In this study, TSECDD is used to machine a film-cooling hole in a nickel-based single-crystal superalloy （DD6）. The Tagu- chi methods of experiment are used to optimise the machining parameters. Experimental results show that TSECDD can effectively drill the film-cooling hole; the optimum parameters that give the best performance are as follows： pulse duration： 12μs, pulse interval： 30 gs, peak current： 6 A, and salt solution conductivity： 3 mS/cm. Finally, a hole is machined by TSECDD, and the results are compared with those obtained by electrical discharge machining. TSECDD is found to be promising for improving the surface quality and eliminating the recast layer.

关键词： Electrical discharge machin-ing （EDM） Electrochemical machining（ECM） Film-cooling hole Hybrid technique Single crystal Taguchi methods

Experimental research on electrochemical machining of titanium alloy Ti60 for a blisk

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Chinese Journal of Aeronautics 2016年第1期29卷 274-282页

作者： Chen xuezhen xu zhengyang Zhu Dong Fang Zhongdong Zhu Di College of Mechanical and Electrical Engineering Nanjing University of Aeronautics & Astronautics

Ti60 （Ti-5.6A1-4.8Sn2Zr-1Mo-0.35Si-0.7Nd） is a high-temperature titanium alloy that is now used for important components of aircraft engines. Electrochemical machining （ECM） is a promising technique that has several advantages, such as a high machining rate, and can be used on a wide range of difficult-to-process materials. In this paper, orthogonal experiments are conducted to investigate ECM of Ti60, with the aim of determining the influences of some electrochemical pro- cess parameters on the surface roughness. The most important parameter is found to be the frequency of the pulsed power supply. It is found that using suitably optimized parameters for ECM can greatly decrease the surface roughness ofa workpiece. A surface roughness of approximately 0.912 μm can be obtained with the following optimal parameters： NaC1 electrolyte concentration 13wt%, voltage 20 V, pulse frequency 0.4 kHz, duty cycle 0.3, temperature 23 ℃, and anode feed rate 0.5 mm/min. Furthermore, blisk blades have been successfully processed using these optimized parameters

关键词： Blisk Electrochemical machining（ECM） Surface roughness Titanium alloy Ti60