Table of Content

10 August 2020, Volume 31 Issue 15

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Model Predictive Control-based Starting Control Optimization Strategy for CVTs

HAN Ling, LIU Hongxiang, CAO Yue, REN Leilei

2020, 31(15):  1765-1771.  DOI: 10.3969/j.issn.1004-132X.2020.15.001

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In order to improve the starting performance of the vehicles, clutch and torque converter were usually used as starting devices for the new generation of high power CVT. The multi-objective characteristics of the cluth engagement process will cause problems such as vehicle starting shock. Therefore, the optimal control of drive-neutral-reverse(DNR) clutch engagement processes was studied. Firstly, a clutch pressure control system was designed so that the system had further optimization space. Then, the clutch engagement processes were analyzed to determine the starting evaluation index. Thirdly, the model predictive control strategy was proposed to achieve the consistency of clutch engagements. Finally, CVT powertrain simulation model was established by joint simulation and verified the system effectiveness by Lifan 520 auto for real vehicle tests. The results indicate that with the effects of the optimal control strategy, the clutch engagement processes may complete the oil filling processes at the target time, reduce the starting impacts and effectively improve the starting quality of the vehicles.

Milling Process Tests of Diamond Coated Micro-milling Cutters

ZHANG Yongbin, YAN Guanghe, LI Jianyuan, JIANG Chen

2020, 31(15):  1772-1777.  DOI: 10.3969/j.issn.1004-132X.2020.15.002

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In order to understand the effects of diamond coating on the milling performances of carbide micro-milling cutters with diameter of 50 μm, the micro-groove milling experiments of diamond coated and uncoated tools were carried out. Firstly, the D-shaped micro-milling cutter with diameter of 50 μm was prepared by using WEDG. Then, the micro-groove milling process experiments were carried out on pure copper workpieces with diamond coated and uncoated tools; Changes of the surface morphology and roughness of micro-grooves with milling distance were observed by white-light interferometer and ultra-depth-of-field microscope, and the effects of diamond coating on the milling processes of cemented carbide micro-milling cutters were analyzed. The results show that the micro-groove processed with diamond coating tools has less burr, the surface roughness value is twice lower than that milled with uncoated tools, and stable groove width, roughness value and side morphology may maintain within a certain distance.

Mechanism of Shock and Load Fluctuation of Variable Nozzle Turbines with Split Sliding Guide Vanes

YANG Dengfeng, PAN Yuzhou, WANG Guizhao, LAO Dazhong, HU Leon

2020, 31(15):  1778-1786.  DOI: 10.3969/j.issn.1004-132X.2020.15.003

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In view of the low efficiency and strong shock characteristics of the variable nozzle turbines in a diesel engine at low speed, a split sliding guide vane was proposed and designed, and the steady/unsteady numerical calculations were carried out under three typical nozzle openings of 10%, 40% and 100%. Results show that the split sliding guide vanes may effectively restrain the clearance leakage flows and greatly improve turbine efficiency under the small nozzle openings. Under the conditions of 10% opening, the turbine peak efficiency is improved by 10%, besides, turbine efficiency is also improved to different degrees under other openings. At the same time, the trailing edge shocks of the split sliding guide vanes are greatly weakened by the reasonable design of rotor-stator spacing. The weakening of guide blade clearance leakage flows and trailing edge shocks reduces the rotor-stator interference, thus weakens the intensity of load fluctuation on downstream rotor blades and increases the reliability of rotor blades.

Terminal Sliding Mode Control of Automatic Shell Magazine Based on Nonlinear Disturbance Observer

YAO Laipeng, HOU Baolin, LIU Xi, WANG Xi

2020, 31(15):  1787-1792,1797.  DOI: 10.3969/j.issn.1004-132X.2020.15.004

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To deal with the load change and uncertain disturbance in position control of a certain automatic shell magazine, a combined control strategy based on nonlinear disturbance observer and nonsingular fast terminal sliding mode was proposed. An uncertain dynamical model of the automatic shell magazine was established. The disturbance observer was used to observe the composite disturbance, and the observed value was compensated in the sliding mode controller which improved the robustness and anti-disturbance capability of system. Closed-loop stability of the system was proved by Lyapunov criterion. Compared experimental results of the proposed algorithm and PID control algorithm show that the designed combined control law realized precision position control of the automatic shell magazine, had good robustness, and effectively improved the positioning stability of the automatic shell magazine.

Analysis of Long Life Lubrication Characteristics for Space Hydrocarbon Lubricating Oils

XU Zengchuang, CUI Weixin, HAO Lichun, LIANG Yuxiang, ZHENG Weibo

2020, 31(15):  1793-1797.  DOI: 10.3969/j.issn.1004-132X.2020.15.005

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The friction and wear and long-life lubrication performances of space lubricants in space environments were investignted. The hydrocarbon lubricant RP4752 was used as the research object, and the vacuum spiral orbit tribometer (SOT) and sliding friction test system were used to test the lubricating oils. Nominal lubrication life, wear spot diameter and sliding friction coefficient were combined with scanning electron microscopy and X-ray energy dispersive spectrometer for microscopic analysis. The results show that RP4752 has a small sliding friction factor and a long wear life in a vacuum environments, and has good vacuum boundary lubrication performance. The lubricating infrared transmittance has no significant change in 14~16.25μm band. In the vacuum life verification tests, the numbers of rotations of two scanning motors lubricated with RP4752 reach 3.02×10⁸, which meets the 8-year on-orbit operating life requirements of the moving mechanisms. The results form a comparison relationship with a nominal life of 1 615 rotations by SOT tests, which provides a test basis for the selection of lubricants for other space motion mechanisms and long-life lubrication design.

Two-layer Contact Nonlinear Mechanics Analysis of Controllable Universal Joint Flexible Structure in the Tubes

XU Tingting, LUO Min, JIANG Jiajun, WANG Jing, ZHANG Jiahe

2020, 31(15):  1798-1807,1814.  DOI: 10.3969/j.issn.1004-132X.2020.15.006

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The controllable universal joint flexible slender structure in the tubes was an unique structure of the ultra-short radius horizontal wells. Considering the mechanism problems of controllable universal joint structures where the three-body two-layer contact problems of structural discontinuity and slotted incomplete structure, the 3-D beam elements, universal joint elements, rigid beam elements and the beam-beam contact elements were combined. A two-layer contact nonlinear finite element model of a controllable universal joint flexible structure in the tubes was established and a numerical calculation method was carried out. It was compared with an analytical solution by an example. The calculation results are in good agreement. The mechanics analysis of the flexible drilling tools in oblique drilling of ultra-short radius horizontal wells was carried out. The deformation state, the law of load transmission of the flexible drilling tools and the distribution law of the contact forces with the borehole walls were obtained.

Analysis on Vibration Characteristics of High-speed Helical Gear Transmission for Pure Electric Vehicles

DU Jinfu, WANG Zhengrong, LIU Kai, WEN Jianshuang, MAO Jin

2020, 31(15):  1808-1814.  DOI: 10.3969/j.issn.1004-132X.2020.15.007

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In order to study the influences of time-varying meshing stiffness and meshing impacts on the dynamic characteristics of the helical gear transmissions, a high-speed helical gear transmission was taken as the research object. The bending-torsion-axis coupling dynamics model was established. The computing method based on the improved loaded tooth contact analysis (LTCA) was applied to calculate the time-varying meshing stiffness. The meshing impact time and the size of the meshing impact forces were calculated. The vibration characteristics of the helical gear systems were analyzed under three excitation conditions: the time-varying meshing stiffness, the meshing impacts, and their combination. The results show that, the effects of rotation speed changes on system vibration are unsignificant in nonresonant regions under the time-varying meshing stiffness excitations, but the system vibration increases with the increase of the rotation speed under the meshing impact excitations and comprehensive excitations, and the amplifications of the vibration are relatively small compared with that of the meshing impact excitations. This research may provide a reference for the design and applications of high speed helical gear transmissions in PEVs.

Experimental Study on Effects of Debris on Electrode Shape Wear in Micro-EDM

LI Xiaopeng, WANG Yuangang, LIU Yu, WANG Hui, ZHAO Fuling

2020, 31(15):  1815-1822,1889.  DOI: 10.3969/j.issn.1004-132X.2020.15.008

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The formation mechanism of electrode shape wear was studied based on the characteristics of micro-EDM technology, where the experimental method of open-state micro-EDM was designed to change the concentration of debris. Through experiments, the influence laws of electrode shape wear under different debris concentrations were systemically investigated by comparing the changes of electrode shape wear, the surface micromorphology and the recast layers of workpieces in micro-EDM under different machining conditions. The influence mechanism of the shape wear of the microelectrodes was analyzed and the intrinsic relationship between the shape change of the craters and the debris was summarized. The results provide an experimental and theoretical basis for the shape control of microelectrodes and achieve the goal of improving the quality and stability of micro-EDM.

SOC Estimation of Lithium-ion Battery Based on Ampere Hour Integral and Unscented Kalman Filter

DING Zhentao, DENG Tao, LI Zhifei, YIN Yanli

2020, 31(15):  1823-1830.  DOI: 10.3969/j.issn.1004-132X.2020.15.009

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Based on Thevenin equivalent model, the second-order RC equivalent circuit model was established. The pulse discharge data of battery were obtained by the tests of hybrid pulse power characteristics, and the parameters of battery equivalent circuit were identified. In order to make up the fitting errors of battery model parameter identification when the SOC of lithium-ion batteries was in the range of 90% to 100%, ampere hour integral and UKF were used comprehensively to estimate battery's SOC. Battery management system was designed by using HIL test platform and environmental simulation test platform. The results of SOC estimation of batteries under different operating conditions show that the estimation errors of SOC are from -1.5% to 1.0%. This method has relatively high accuracy and good effectiveness.

Surface Micro-texture Characteristics of 7075 Aluminum Alloys by Elliptical Vibration Assisted Turning

YUAN Lusheng, ZHAO Bo, WANG Yi, ZHAO Chongyang

2020, 31(15):  1831-1838.  DOI: 10.3969/j.issn.1004-132X.2020.15.010

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To study the fabrication processes of micro-texture for the elliptical vibration assisted turning technique and the characteristics of machined micro-surfaces, the change rules of surface micro-texture was analyzed with vibration principle of ellipse and the micro-texture formation under different speeds and feed rates. The vibration track, surface topography, single micro-texture geometry size and surface roughness were analyzed under the elliptic vibration track measurement tests and elliptic vibration turning tests. The analysis results show that in the turning test processes, compared to the common turning, due to the space elliptic movement of the tool, the surface of ultrasonic elliptical vibration turning presents micro-texture grooves similar to ellipse. With the changes of rotation speed and feed rate, it indicates that the geometric size, profile height and surface roughness of micro-texture grooves will change regularly based on the theoretical analyses and experimental results.

Experimental Study of SLS Processes for Artificial Graphite Powders

WU Haihua, ZHANG Cheng, LI Yafeng, LIU Li, XU Lijie

2020, 31(15):  1838-1845.  DOI: 10.3969/j.issn.1004-132X.2020.15.011

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SLS process was applied to artificial graphite powders, the possibility of recycling and reutilization was explored. Firstly, effects of different mass fractions of spherical graphite powders on the fluidity and bulk density of mixed powders were studied, thus the reasonable composition of graphites for 3D printing materials was determined. Secondly, effects of different process parameters of laser power, scanning speed, scanning spacing and layer thickness on directional dimensions and bending strength of samples were studied, the ranges of parameters were decised. Finally, the optimum process parameters were determined by orthogonal experiments, the complex graphite functional parts were fabricated quickly, and feasibility was verified.

Electric-field-driven μ-3D Printing Wax-based Molds for Microfluidic

PENG Zilong, WEI Zilong, LIU Mingyang, LI Yinan, LAN Hongbo

2020, 31(15):  1846-1851.  DOI: 10.3969/j.issn.1004-132X.2020.15.012

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A new process for preparing wax-based microstructures using electric-field-driven μ-3D printing was proposed. The self-excited electrostatic field provided by pulsed direct currents driven the wax droplets deposition with the volume of picoliter degrees. The effects of printing parameters such as gas pressure, electrical field strength, pulse frequency and duty cycle on wax printing were investigated. A wax mold with 61.25 μm in line width of and 44.13 μm in height was fabricated, by optimized experimental parameters which may be used for PDMS transfer processes. Combining the micro-transfer technique and plasma modification, a microfluidic chip sample with the feature size of tens of microns was achieved. And the basic characteristics of microfluidic chip were verified by experiments.

CI Literature Review and Its Application Exploration in Social Manufacturing

JIANG Pingyu, YANG Maolin, LI Weidong, LIU Jiajun, GUO Wei, LI Pulin

2020, 31(15):  1852-1865.  DOI: 10.3969/j.issn.1004-132X.2020.15.013

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To support systematically understanding and development of CI, and to further explore the applications of CI in the field of manufacturing (especially in the field of social manufacturing), related works on CI from 2000 were reviewed and the related concepts were discussed. Then, CI was classified into human social system CI, natural social system CI, and artificial social system CI according to different individual categories in a collective system. Research advancements and application status of the three kinds of CI theories from the perspectives of system architecture, enabling techniques, and engineering applications were reviewed, and the results show that CI has great application potentials in the field of social manufacturing. Thus, integrated CI architecture was established, preliminary application scheme of CI on social manufacturing was proposed, and the problems to be solved were discussed.

Review Data Driven Customer Need Model Research Based on Product Performance Lexicon

ZHANG Wenxu, XIAO Renbin, LIN Wenguang

2020, 31(15):  1866-1876.  DOI: 10.3969/j.issn.1004-132X.2020.15.014

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It was an urgent problem in product development to quickly and accurately obtain customer need informations from customer behavior data by means of data-driven method. Therefore, the customer need model was studied, and the customer need modeling method driven by review data was proposed. Firstly, aiming at the problem that the number of topics was not easy to determine in the review analysis based on topic clustering, a product performance lexicon was put forward to determine the clustering topics. The TF-IDF method was improved to be used for lexicon creation, and the customer need mining was completed based on the product performance lexicon. Secondly, in view of the lack of customer need analysis processes in current product review research, the product review data based Kano analysis method was proposed. On the basis of above metioned, matter-element theory was introduced to quantitatively express the customer need model. At last, the feasibility and effectiveness of the proposed methods were verified by a case study.

Numerical Simulation of Stainless Steel Tube Shearing Based on Johnson-Cook Model

XIONG Jiangming, ZHOU Jie, WANG Shilong, YANG Bo, WANG Sibao, DONG Jianpeng

2020, 31(15):  1877-1884.  DOI: 10.3969/j.issn.1004-132X.2020.15.015

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Shearing was a key part of the spent fuel reprocessing processes. Due to the strong irradiation constraints, there were few studies on the shearing processes. The parameters of shearing processes needed to be optimized by a large number of experiments. But the high cost, the long experimental cycle and complex shear mechanism made it unaccessible. The stainless steel tubes, the main support structures of spent fuel assemblies, were introduced as the research object and based on Johnson-Cook model the finite element numerical simulation method was used to analyze the shearing processes. The shear test was designed to verify the correctness of the previous model, and the effects of process parameters such as shear clearance, tool angle and tool edge width on shearing processes. The results show that the shear test and the simulation of model have good fitting performance, which proves the correctness of the model. The maximum shear forces and shear forces during fracturing are positively related with the augment of shear clearance and edge width, and the decreases of tool angle. The shear clearance has a great influence on the fracture morphology of the compression sections, and the tool angle and the edge width have a great influence on the opening width of the separation sections.

Study on Effects of Drawbead on Deformation Characteristics and Mechanics Properties of Sheet Metals

LI Qiaomin, KE Junyi, LIU Yuqi, LI Hongjun

2020, 31(15):  1885-1889.  DOI: 10.3969/j.issn.1004-132X.2020.15.016

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Taking experiments where sheet metal samples were pulled through drawbead inserts with different geometrical parameters, the effects of the height and the radius of the drawbead, as well as the number of times passing through the drawbead, on the deformation characteristics of the sheet metal samples, were analyzed. Besides, the influences of the pre-strain on the subsequent mechanics properties of the sheet metals were also studied. The results show that, after passing through the drawbead, the sheet metal samples were uniformly stretched in the flow direction, and the pre-strain caused by the drawbead increases with the height of the drawbead, decreases with the radius of the drawbead and increases almost linearly with the times of passing through the drawbead. The larger the pre-strain(is), the higher the subsequent yield strength and tensile strength of the material(is), but the smaller the subsequent elongation(is). With the increase of the pre-strain, the total elongation first decreases and then increases.