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A novel method for solving shortest tool length based on compressing 3D check surfaces relative to tool postures

Chinese Journal of aeronautics 2021年第2期34卷 641-658页

作者： Xiangyu LI Junxue REN Ximing LV Yuke ZHOU Congle LIU key laboratory of high performance manufacturing for aero engine(Northw estern Polytechnical University) Ministry of Industry and Information TechnologyXi'an 710072China

Solving the shortest tool length quickly under a known tool trajectory in multi-axis machining of complex channel parts is an urgent problem in industrial production. To solve this problem, a novel and efficient method is proposed which is featured by extracting only a few necessary curves from the check surface instead of sampling the entire surface. By rotating and compressing the 3 D check surface relative to all tool postures, the boundaries of the area occupied by the 2 D compressed surfaces are the essential elements for determining the shortest tool length. A tracking-based numerical algorithm is introduced to efficiently solve the silhouette curves which are formed in compressing. To define the multi-taper shaped tool holding system(THS) which is commonly used in production, a characterization model for THS profile is established. A model for solving the shortest tool length is finally constructed based on the critical interference relationship between the THS profile and all compressed boundary curves. For acceleration, the boundary splines are segmented according to their knot vectors. Then a new concept called the axis-aligned tool length box(AATB) is introduced,which can provide a conservative range of tool length for a spline segment. By scanning the AATBs of all spline segments, the very few effective spline segments that may ultimately determine the shortest tool length are filtered out. This acceleration method makes the solution for the shortest tool length more focused and efficient. The results of experimental examples are also reported to validate the efficiency and accuracy of the proposed algorithm.

关键词： CNC Compressed check surface Multi-axis machining Shortest tool length Silhouette curve Tool holding system

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Microstructure evolution of ATI718 plus alloy during high-speed machining:Experiments and a combined FE-CA approach

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Chinese Journal of aeronautics 2024年第12期37卷 498-521页

作者： Xuhang GAO Changfeng YAO Liang TAN Minchao CUI Wenhao TANG Guangyuan SHI Jikang ZHAO Jianxin LUO Ya ZHANG The key laboratory of high performance manufacturing for aero engine Ministry of Industry and Information TechnologyNorthwestern Polytechnical UniversityXi’an 710072China engineering Research Center of Advanced manufacturing Technology for aero engine Ministry of EducationNorthwestern Polytechnical UniversityXi’an 710072China

Excellent surface integrity is an eternal pursuit in high performance manufacturing,with microstructure being a crucial component of the surface integrity dataset and a key factor controlling surface properties such as fatigue and *** multi-physical fields generated by thermomechanical loads during high-speed machining act on the processed surface layer,influencing the evolution of *** investigate the microstructural evolution mechanisms of ATI718 plus during high-speed machining,cutting experiments and techniques such as Electron back scatter diffraction(EBSD),Transmission Kikuchi diffraction(TKD),and Precession electron diffraction(PED)is conducted to quantitatively analyze the microstructures in the chip shear zone and the machined ***,a combined finite element(FE)and cellular automata(CA)model is developed to simulate the microstructure evolution during the cutting *** discontinuous dynamic recrystallization(DDRX)mechanism is employed to demonstrate the nucleation and growth of grains under the influence of multiple physical *** simulation and experimental results show similar dynamic recrystallization(DRX)grain sizes,indicating acceptable accuracy of the CA model in terms of DRX grain *** comparison between experimental and simulation results confirms the occurrence of both continuous dynamic recrystallization(CDRX)and DDRX during the cutting *** synergistic competition between CDRX induced grain lamellar refinement and DDRX induced grain growth emerge as the primary mechanism driving microstructural evolution.A layer of ultrafine grains,with a thickness within 20 lm,is formed on the machined *** under different parameters demonstrate that the temperature has a more significant impact on the thickness of the ultrafine grain layer and the diameter of grains within the layer compared to the strain rate.

关键词： Surface integrity Dynamic recrystallization Microstructure evolution Finite element Cellular automata high-speed machining

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Machinability ofγ-TiAl:A review

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Chinese Journal of aeronautics 2023年第7期36卷 40-75页

作者： Ziwen XIA Chenwei SHAN Menghua ZHANG Minchao CUI Ming LUO key laboratory of high performance manufacturing for aero engine Ministry of Industry and Information TechnologyNorthwestern Polytechnical UniversityXi’an 710072China engineering Research Center of Advanced manufacturing Technology for aero engine Ministry of EducationNorthwestern Polytechnical UniversityXi’an 710072China State key laboratory of Cemented Carbide Zhuzhou 412000China

Owing to its outstanding mechanical properties,γ-TiAl is desirable materials for crossgeneration *** 70 years of exploration have made it into the initial ***,the intrinsic brittleness ofγ-TiAl is still a critical obstacle to its large-scale *** this context,researchers have made many attempts to study the machinability ofγ-*** present,existing relevant reviews have mostly discussed the processing methods ofγ-***,there is still a lack of a perspective on material properties to analyze the cutting ***,this paper provides the systematic review of such *** all,the developmental process,phase transformation,and microstructural evolution ofγ-TiAl are discussed,as well as its deformation mechanism at *** topics can provide a materials science foundation for the machining ofγ-*** then,the review focuses on the cutting mechanism and surface integrity ofγ-***,special attention is paid to the microscope deformation mechanism and surface defects evolution ofγ-TiAl during ***,the review indicates that the highperformance machining technology ofγ-TiAl faces challenges and proposes potential future research *** the difficulties during machiningγ-TiAl aero-engine components will accelerate the development of new aero-engines.

关键词： Cutting mechanism Deformation Machinability Surface integrity γ-TiAl

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Position-varying surface roughness prediction method considering compensated acceleration in milling of thin-walled workpiece

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Frontiers of Mechanical engineering 2021年第4期16卷 855-867页

作者： Zequan YAO Chang FAN Zhao ZHANG Dinghua ZHANG Ming LUO key laboratory of high performance manufacturing for aero engine(Ministry of Industry and Information Technology) Northwestern Polytechnical UniversityXi'an 710072China engineering Research Center of Advanced manufacturing Technology for aero engine(Ministry of Education) Northwestern Polytechnical UniversityXi'an 710072China

Machined surface roughness will affect parts?service ***,predicting it in the machining is important to avoid *** roughness will be affected by system position dependent vibration even under constant parameter with certain toolpath processing in the *** at surface roughness prediction in the machining process,this paper proposes a position-varying surface roughness prediction method based on compensated acceleration by using regression *** reduce the stochastic error of measuring the machined surface profile height,the surface area is repeatedly measured three times,and Pauta criterion is adopted to eliminate abnormal *** actual vibration state at any processing position is obtained through the single-point monitoring acceleration compensation *** acceleration features are extracted,and valley,which has the highest/^-square proving the effectiveness of the filtering features,is selected as the input of the prediction model by mutual information ***,by comparing the measured and predicted surface roughness curves,they have the same trends,with the average error of 16.28%and the minimum error of 0.16%.Moreover,the prediction curve matches and agrees well with the actual surface state,which verifies the accuracy and reliability of the model.

关键词： surface roughness prediction compensated acceleration milling thin-walled workpiece

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Effect of void nucleation on microstructure and stress state in aluminum alloy tailor-welded blank

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Progress in Natural Science:Materials International 2021年第1期31卷 77-85页

作者： L.Xing M.Zhan P.F.Gao M.Li Y.D.Dong T.Y.Wang State key laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University Shaanxi key laboratory of high-performance Precision Forming Technology and Equipment key laboratory of high performance manufacturing for aero engine (Northwestern Polytechnical University) Ministry of Industry and Information Technology

The microscopic damage initiation characteristic in welded joint greatly determines the subsequent damage evolution and fracture behavior of aluminum alloy tailor-welded blank(TWB) during plastic forming. In this study, the interactive dependence of void nucleation on microstructure and stress state in the welded joint of a2219 aluminum alloy TWB was quantitatively explored by in-situ SEM testing. Moreover, a micromechanical model based on actual microstructure was adopted to reveal the underlying mechanisms from the perspective of microscopic heterogeneous deformation. The results showed that three void nucleation mechanisms, including particle-cracking, interface-debonding and matrix-cracking, coexisted in the deformation at different microstructure regions and stress states. The nucleation strain of each mechanism mainly depended on the particle volume fraction, grain size and stress triaxiality. Besides, the proportions of particle-cracking and interfacedebonding greatly varied with the grain size and particle volume fraction, and the variation law changed with the stress state. The proportion of matrix-cracking had a weak dependence on the microstructure, while increased with the stress triaxiality decreasing. It made the damage initiation in aluminum alloy welded joint transit from particle-cracking dominance to matrix-cracking dominance with the stress triaxiality *** micromechanical modeling results suggested that the changes of evolutions and distributions of Mises stress in particle, hydrostatic stress at interface and plastic strain in matrix with microstructure and stress state were responsible for the above effects.

关键词： Aluminum alloy Welded joint Void nucleation Microstructure Stress state Micromechanical model

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Optimizing circumferential assembly angle of rotor parts connected by curvic couplings based on acquired tooth surface error data

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Chinese Journal of aeronautics 2024年第3期37卷 404-416页

作者： Huibin SUN Meng LIU Yingzhi ZHANG Chenle WEI key laboratory of high performance manufacturing for aero engine Ministry of Industry and Information TechnologyNorthwestern Polytechnical UniversityXi’an 710072China AECC South Industry Company Limited Zhuzhou 412002China

Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine ***,curvic tooth surface errors lead to poor assembly *** physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak *** unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and ***,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic *** origin of curvic tooth surface error is deeply *** 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired *** on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly *** results show that the assembly precision can be predicted accurately and improved *** uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.

关键词： Curvic couplings Tooth surface error Assembly precision Axial and radial runouts Circumferential assembly angle

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Three-dimensional modeling and reconstructive change of residual stress during machining process of milling, polishing, heat treatment, vibratory finishing, and shot peening of fan blade

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Advances in manufacturing 2021年第3期9卷 430-445页

作者： Ji-Yin Zhang Chang-Feng Yao Min-Chao Cui Liang Tan Yun-Qi Sun key laboratory of high performance manufacturing for aero engine Northwestern Polytechnical UniversityMinistry of Industry and Information TechnologyXi’an710072People’s Republic of China engineering Research Center of Advanced manufacturing Technology for aero engine Northwestern Polytechnical UniversityMinistry of EducationXi’an710072People’s Republic of China

Residual stress during the machining process has always been a research hotspot,especially for aero-engine *** three-dimensional modeling and reconstructive laws of residual stress among various processes in the machining process of the fan blade is studied in this *** fan blades of Ti-6Al-4V are targeted for milling,polishing,heat treatment,vibratory finishing,and shot *** surface and subsurface residual stress after each process is measured by the X-ray diffraction *** distribution of the surface and subsurface residual stress is *** Rational Taylor surface function and cosine decay function are used to fit the characteristic function of the residual stress distribution,and the empirical formula with high fitting accuracy is *** value and distribution of surface and subsurface residual stress vary greatly due to different processing *** reconstructive change of the surface and subsurface residual stress of the blade in each process intuitively shows the change of the residual stress between the processes,which has a high reference significance for the research on the residual stress of the blade processing and the optimization of the entire blade process.

关键词： Fan blade Machining process Surface residual stress Subsurface residual stress Three-dimensional modeling Reconstructive change

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A tip clearance prediction model for multistage rotors and stators in aero-engines

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Chinese Journal of aeronautics 2021年第2期34卷 343-357页

作者： Huibin SUN Jing WANG Kai CHEN Huateng XIA Xin FENG Zhiyong CHANG key laboratory of high performance manufacturing for aero engine Ministry of Industry and Information TechnologyNorthwestern Poly technical UniversityXi'an 710072China AECC South Industry Company Limited Zhuzhou 412002China

Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3 D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program,and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.

关键词： Tip clearance Prediction Error propagation model Rotor and stator aero-engine Assembly

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Research on Cooling Effectiveness in Stepped Slot Film Cooling Vane

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Journal of Thermal Science 2016年第3期25卷 273-279页

作者： LI Yulong WU Hong ZHOU Feng RONG Chengjun National key laboratory of Science and Technology on aero-engine aero-Thermodynamics Beihang University

As one of the most important developments in air cooling technology for hot parts of the aero-engine, film cool- ing technology has been widely used. Film cooling hole structure exists mainly in areas that have high temperature, uneven cooling effectiveness issues when in actual use. The first stage turbine vanes of the aero-engine consume the largest portion of cooling air, thereby the research on reducing the amount of cooling air has the greatest potential. A new stopped slot film cooling vane with a high cooling effectiveness and a high cooling uniformity was researched initially. Through numerical methods, the affecting factors of the cooling effectiveness of a vane with the stepped slot film cooling structure were researched. This paper focuses on the cooling effectiveness and the pressure loss in different blowing ratio conditions, then the most reasonable and scientific structure parameter can be obtained by analyzing the results. The results show that 1.0 mm is the optimum slot width and 10.0 is the most reasonable blowing ratio. Under this condition, the vane achieved the best cooling result and the highest cooling effectiveness, and also retained a low pressure loss.

关键词： Film cooling Cooling effectiveness Blowing ratio Pressure loss

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Effect of ultrasonic impact treatment on the surface integrity of nickel alloy 718

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Advances in manufacturing 2021年第1期9卷 160-171页

作者： Zheng Zhou Chang-Feng Yao Yu Zhao Yang Wang Liang Tan key laboratory of high performance manufacturing for aero engine Ministry of Industry and Information TechnologySchool of Mechanical EngineeringNorthwestern Polytechnical UniversityXi'an 710072People's Republic of China engineering Research Center of Advanced manufacturing Technology for aero engine Ministry of EducationSchool of Mechanical EngineeringNorthwestern Polytechnical UniversityXi'an 710072People's Republic of China

Ultrasonic impact treatment(UIT)is a type of surface strengthening technology that can improve the fatigue properties of materials by improving the surface quality,residual stress,and other *** this study,the influence of ultrasonic impact parameters on the surface integrity of nickel alloy 718 was *** micro stress concentration caused by the surface morphology was also *** cosine and exponential decay functions were used to fit and characterize the distribution of residual stress and work hardening in the surface *** results showed that the feed rate had the greatest influence on surface roughness,stress concentration,and surface residual *** was not appropriate to evaluate the surface hardening effect only by the number of impacts per unit area,the ultrasonic impact parameters such as feed speed and pre extrusion depth should also be *** grain refinement was obvious after *** multiobjective optimization of machining parameters was performed with the objective of surface stress concentration and residual stress.A surface with a smaller surface stress concentration factor and larger compressive residual stress can be obtained simultaneously using medium linear velocity,medium pre extrusion depth,and smaller feed rate.

关键词： Nickel alloy 718 Ultrasonic impact Surface stress concentration Surface integrity Grain refinement

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