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Mechanistic identification of cutting force coefficients in bull-nose milling process

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Chinese Journal of Aeronautics 2013年第3期26卷 823-830页

作者： Gao Ge Wu Baohai Zhang Dinghua Luo Ming The key laboratory of contemporary design and integrated manufacturing technology Ministry of Education Northwestern Polytechnical University

An improved method to determine cutting force coefficients for bull-nose cutters is proposed based on the semi-mechanistic cutting force model. Due to variations of cutting speed along the tool axis in bull-nose milling, they affect coefficients significantly and may bring remarkable discrepancies in the prediction of cutting forces. Firstly, the bull-nose cutter is regarded as a finite number of axial discs piled up along the tool axis, and the rigid cutting force model is exerted. Then through discretization along cutting edges, the cutting force related to each element is recalculated, which equals to differential force value between the current and previous elements. In addition, coefficient identification adopts the cubic polynomial fitting method with the slice elevation as its horizontal axis. By calculating relations of cutting speed and cutting depth, the influences of speed variations on cutting force can be derived. Thereby, several tests are conducted to calibrate the coefficients using the improved method, which are applied to later force predictions. Eventually, experimental evaluations are discussed to verify the effectiveness. Compared to the conventional method, the results are more accurate and show satisfactory consistency with the simulations. For further applications, the method is instructive to predict the cutting forces in bull-nose milling with lead or tilt angles and can be extended to the selection of cutting parameters.

关键词： Bull-nose cutter Calibration Cutting force Cutting force coefficient Mechanistic model

Vibration suppression of thin-walled workpiece machining considering external damping properties based on magnetorheological fluids flexible fixture

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Chinese Journal of Aeronautics 2016年第4期29卷 1074-1083页

作者： Ma Junjin Zhang Dinghua Wu Baohai Luo Ming Chen Bing key laboratory of contemporary design and integrated manufacturing technology Ministry of EducationNorthwestern Polytechnical University

Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is designed to investigate the regenerative chatter suppression during the machining. Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular cantilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler-Bernoulli beam assumptions. Then, the displacement response function of the bending vibration of the beam is represented by the product of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equation of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests. (C) 2016 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

关键词： Chatter Machining vibration suppression Milling Stability lobe diagram Thin-walled workpiece

Chatter stability prediction in four-axis milling of aero-engine casings with bull-nose end mill

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Chinese Journal of Aeronautics 2015年第6期28卷 1766-1773页

作者： Zhou Xu Zhang Dinghua Luo Ming Wu Baohai key laboratory of contemporary design and integrated manufacturing technology Ministry of EducationNorthwestern Polytechnical University

An analytical model for chatter aero-engine casings is presented in this paper stability prediction in bull-nose end milling of And the mechanics and dynamics variations due to the complex cutter and workpiece geometry are considered by analyzing the effects of the lead angle on the milling process. Firstly, the tool-workpiece engagement region is obtained by using a previously developed method and divided into several disk elements along the tool-axis direction. Secondly, a 3D dynamic model for stability limit calculation is developed and simplified into a 1D model in normal direction considering only the dominant mode of the workpiece. Then the cutting force coefficients, the start and exit angles corresponding to each disk element are determined. And the total stability lobe diagram is calculated using an iterative algorithm. Finally, several experimental tests are carried out to validate the feasibility and effectiveness of the proposed ~rediction approach.

关键词： Aero-engine casings Bull-nose end mill Chatter Four-axis milling Stability lobe diagram

Adaptive sliding mode control of the A-axis used for blisk manufacturing

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Chinese Journal of Aeronautics 2014年第3期27卷 708-715页

作者： Zhao Pengbing Shi Yaoyao The key laboratory of contemporary design and integrated manufacturing technology Ministry of EducationNorthwestern Polytechnical University

As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.

关键词： A-axis Blisk processing Nonlinear compensation Positioning control Sliding mode control

Prediction of cutting forces in ball-end milling of 2.5D C/C composites

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Chinese Journal of Aeronautics 2016年第3期29卷 824-830页

作者： Shan Chenwei Wang Xiao Yang Xuanxuan Lyu Xiaobo key laboratory of contemporary design and integrated manufacturing technology Ministry of EducationNorthwestern Polytechnical University

Machining of carbon/carbon （C/C） composite materials is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous and low thermal conductivity, which can result in tear, burr, poor surface quality and rapid wear of cutters. Accurate and fast pre- diction of cutting forces is important for milling C/C composite materials with high quality. This paper presents an alternative cutting force model involving the influences of the directions of fiber. Based on the calculated and experimental results, the cutting forces＂ coefficients of 2.5D CC com- posites are evaluated using multiple linear regression method. Verification experiment has been car- ried out through a group of orthogonal tests. Results indicate that the proposed nmdel is reliable and can be used to predict the cutting forces in ball-end milling of 2.5D C/C composites.

关键词： Ball-end milling C/C composites Culling force Fiber orientationOrthogonal test

Composite Adaptive Control of Belt Polishing Force for Aero-engine Blade

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Chinese Journal of Mechanical Engineering 2013年第5期26卷 988-996页

作者： ZHsAO Pengbing SHI Yaoyao key laboratory of contemporary design and integrated manufacturing technology of Ministry of Education Northwestern Polytechnical University

The existing methods for blade polishing mainly focus on robot polishing and manual *** to the difficulty in high-precision control of the polishing force,the blade surface precision is very low in robot polishing,in particular,quality of the inlet and exhaust edges can not satisfy the processing *** grinding has low efficiency,high labor intensity and unstable processing quality,moreover,the polished surface is vulnerable to burn,and the surface precision and integrity are difficult to *** order to further improve the profile accuracy and surface quality,a pneumatic flexible polishing force-exerting mechanism is designed and a dual-mode switching composite adaptive control(DSCAC) strategy is proposed,which combines Bang-Bang control and model reference adaptive control based on fuzzy neural network(MRACFNN) *** the mode decision-making mechanism,Bang-Bang control is used to track the control command signal quickly when the actual polishing force is far away from the target value,and MRACFNN is utilized in smaller error ranges to improve the system robustness and control *** on the mathematical model of the force-exerting mechanism,simulation analysis is implemented on *** results show that the output polishing force can better track the given ***,the blade polishing experiments are carried out on the designed polishing *** results show that DSCAC can effectively mitigate the influence of gas compressibility,valve dead-time effect,valve nonlinear flow,cylinder friction,measurement noise and other interference on the control precision of polishing force,which has high control precision,strong robustness,strong anti-interference ability and other advantages compared with *** proposed research achieves high-precision control of the polishing force,effectively improves the blade machining precision and surface consistency,and significantly reduces the surface roughness.

关键词： blade polishing force Bang-Bang control fuzzy neural network model reference adaptive control

Surface integrity and fatigue behavior when turning γ-TiAl alloy with optimized PVD-coated carbide inserts

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Chinese Journal of Aeronautics 2018年第4期31卷 826-836页

作者： Changfeng YAO Jiannan LIN Daoxia WU Junxue REN The key laboratory of contemporary design and integrated manufacturing technology Ministry of EducationNorthwestern Polytechnical University

This paper presents a comprehensive investigation on the effects of tool and turning parameters on surface integrity and fatigue behavior in turning c-Ti Al alloy. The wear of inserts surface, cutting forces, and surface roughness were studied to optimize PVD-coated carbide *** topography, residual stresses, microhardness, and microstructure were analyzed to characterize the surfaces layer under different turning parameters. Surface integrity and fatigue life tests of c-Ti Al alloy were conducted under turning and turning-polishing processes. The results show that compared to CNMG120412-MF4, CNMG120408-SM is more suitable because it obtained low cutting force, surface roughness, and tool wear. With increasing the cutting speed and depth, the depths of the compressive residual stress layer, hardening layer, and plastic deformation layer increased. For turning and turning-polishing specimens, the compressive residual stress was relaxed by less than 20%–30% after 10^7 cycles. The fatigue life of a turning-polishing specimen with Ra= 0.15 mm has increased 3 times from that of a turning specimen with Ra= 0.43 mm.

关键词： Fatigue behavior Microhardness Residual stress Surface roughness γ-TiAl alloy Tool wear

Topology Optimal design of Material Microstructures Using Strain Energy-based Method

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Chinese Journal of Aeronautics 2007年第4期20卷 320-326页

作者： Zhang Weihong Wang Fengwen Dai Gaoming Sun Shiping The key laboratory of contemporary design and integrated manufacturing technology Northwestern Polytechnical University Xi ＇an 710072 China

Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming. Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.

关键词： strain energy-based method homogenization method microstructure design topology optimization

Learning Bayesian network structure with immune algorithm

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Journal of Systems Engineering and Electronics 2015年第2期26卷 282-291页

作者： Zhiqiang Cai Shubin Si Shudong Sun Hongyan Dui Ministry of Education key laboratory of contemporary design and integrated manufacturing technology School of Mechatronics Northwestern Polytechnical University

Finding out reasonable structures from bulky data is one of the difficulties in modeling of Bayesian network （BN）, which is also necessary in promoting the application of BN. This pa- per proposes an immune algorithm based method （BN-IA） for the learning of the BN structure with the idea of vaccination. Further- more, the methods on how to extract the effective vaccines from local optimal structure and root nodes are also described in details. Finally, the simulation studies are implemented with the helicopter convertor BN model and the car start BN model. The comparison results show that the proposed vaccines and the BN-IA can learn the BN structure effectively and efficiently.

关键词： structure learning Bayesian network immune algorithm local optimal structure vaccination