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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 *** parameter design accuracy has an important impact on the spacecraft thermal balance but there are few studies focusing on the effect of film surface *** 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 *** film surface morphology of composite films is obtained by the atomic force *** present study creatively introduces surface roughness into modeling from the perspective of finite-difference time-domain(FDTD)*** 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 *** 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 *** has been found that the numerical accuracy is greatly improved and the numerical results agree well with the experimental data when surface roughness is *** 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

Improving profile accuracy and surface quality of blisk by electrochemical machining with a micro inter-electrode gap

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Chinese Journal of Aeronautics 2023年第4期36卷 523-537页

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

Electrochemical machining(ECM)has emerged as an important option for manufacturing the *** inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affects the process stability,profile accuracy and surface *** IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of *** achieve micro-IEG(<50 lm)blisk finishing machining,this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse *** modelling and simulation of the blisk micro-IEG machining have been carried *** experiments of variable-parameters blisk ECM were car-ried *** results illustrated that the IEG width reduced with the progress of variable parameter *** IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 lm and 21 lm,*** profile deviation for the blade’s concave surface and convex surface are 49 lm and 35 lm,while the surface roughness reaches R_(a)=0.149 lm and R_(a)=0.196 lm,*** profile accuracy of the blisk leading/trailing edges was limited to within 91 ***-pared with the currently-established process,the profile accuracy of the blade’s concave and convex profiles was improved by 50.5%and 53.3%,*** surface quality was improved by 53.2%and 50.9%,***,the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective *** electrolytic products were dispersed on the machined surface,and their components were mainly composed of the carbide and oxide products of Ti and Nb *** results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM,which can be used in engineering practice.

关键词： Electrochemical machining Blisk IEG Machining quality Surface quality

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 *** purpose of this study is to reveal the electrochemical behaviour and surface morphology in low-concentration *** 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

Breakthrough detection in electrochemical discharge drilling to enhance machining stability

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Chinese Journal of Aeronautics 2023年第6期36卷 460-475页

作者： Tianyu GENG zhengyang xu Chenxiang ZHANG Jin NING College of Mechanical&Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Film cooling holes are widely used in aero-engine turbine *** blades feature large numbers of holes with complex angles and require a high level of surface *** discharge drilling(ECDD)combines the high efficiency of electrical discharge drilling(EDD)with high quality of electrochemical drilling(ECD).However,due to the existence of a variety of energy for material removal,accurate and timely detection of breakthroughs is fraught with *** insufficient preset setting distance results in a tiny exit aperture,influencing the structure's *** addition,the electrode is prone to bending at a large overfeeding distance,causing secondary discharge damaging sidewall surface *** paper compares and analyzes the characteristics of processing waveforms using EDD and ECDD.A novel breakthrough detection method is proposed based on the variance signal of average voltage(VSAV)to increase machining stability and achieve fabrication without a recast *** method extracts the fluctuation transformation by calculating the variance of the *** signal detection,the overfeeding distance is *** experiment is used to validate the breakthrough detection with 100%accuracy in all *** optimum overfeeding distances for hole angles of 0°,30°,and 60° are obtained,and the stable removal of the recast layer is ***,the effectiveness of the method is verified on a typical workpiece with a double-wall structure and a nickel-based single crystal blade.

关键词： Change detection Electrochemical discharge drilling(ECDD) Electric discharge Film cooling holes Recast layer Variance signal of average voltage(VSAV)

Electrochemical machining on blisk channels with a variable feed rate mode

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Chinese Journal of Aeronautics 2021年第6期34卷 151-161页

作者： Jing WANG zhengyang xu Jingtao WANG Di ZHU National Key Laboratory of Science and Technology on Helicopter Transmission Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrochemical machining(ECM)is an economical and effective method for blisk manufacturing and includes two steps:channel machining and profile *** allowance distribution after the channel machining will directly affect the profile ***,to improve the uniformity of allowance distribution in the machining of channels,a method that incorporates a variable feed rate mode is *** the machining process,the feed rates are dynamically changed according to the needs of the side gap at the different feed *** a result,the side gaps at the different feed depths vary,contributing to a decrease in the allowance *** this study,the dissolution processes of a blisk channel are simulated using different feed rates,and prediction profiles are *** on the prediction profiles,the relationship among the feed rate,feed depth,and side gap is ***,the feed rates at different feed depths are adjusted according to the *** addition,contrast experiments are *** with blisk channel ECM using a constant feed rate of 1 mm/min,using the variable feed rate decreases the allowance differences in the convex and concave parts by 62.2%and 67.4%,*** indicates that using the variable feed rate in the ECM process for a blisk channel is feasible and efficient.

关键词： Allowance distribution Blisk channels Electrochemical machining Optimization strategy Variable feed rate

Improving surface integrity of micro-holes in ECDM using ultrahigh-speed rotary of tool cathode and non-water-based electrolyte

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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 *** on the magnitude of forces,controlling rotational speed changed the behavior and departure radius of bubbles on the cathode ***-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 *** 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/*** length loss and wear ratio of the cathode are only 9.75μm and 6.5%,***,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

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 *** work systematically investigates the effects of pulse current on the surface morphology,profile accuracy,and corrosion behavior of Inconel 718(IN718)in NaNO_(3)*** behavior reveals that IN718 in NaNO_(3)solution during pulse current machining exhibited significant passive,transpassive,and re-passive *** passive film generated at the re-passive state contained some oxides and had a loose porous *** 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 *** 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 *** dissolution mechanism of IN718 in NaNO_(3)solution was also investigated based on the effective pulse current ***,the leading-edge structure of a ruled blade with good dimensional accuracy and surface quality was successfully *** 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

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. (C) 2015 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

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. (C) 2016 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

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