Table of Content

    10 September 2021, Volume 32 Issue 17
    Investigation of Influences of Stator Can Deformations on Axial Flow Resistance in Annular Gap Flow
    WANG Shengde, YAO Zhenqiang, SHEN Hong
    2021, 32(17):  2017-2024.  DOI: 10.3969/j.issn.1004-132X.2021.17.001
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    In order to predict the flow distribution between the upper and lower branches of the internal cooling circuit within a canned motor reactor coolant pump(RCP), the stator can deformations and the influences on axial resistance of the annular gap flow were studied. The deformed profile of stator cans under the high pressure was calculated with the finite element method and verified by experiments. The influences of stator can deformations on annular gap flow were studied by using computational fluid dynamics and a modified model for axial flow resistance evaluation was established by variable parameter analysis and mathematical fitting. Calculation result from the established model shows that, compared to ideal cylindrical state, 11% boundary deformation of the stator can under the rated working state of the RCP, will lead to 83% decrease of the axial flow pressure drop in the rotor and stator clearance.
    Research on Thermally Induced Preload of Machine Tool Spindle Bearings Based on FBG Sensor
    LU Tuanliang, QIU Ming, DONG Yanfang, ZHANG Yatao, DU Hui
    2021, 32(17):  2025-2031,2039.  DOI: 10.3969/j.issn.1004-132X.2021.17.002
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    Aiming at the difficult and inaccurate testing of the machine tool spindle bearing preloads, an online monitoring method was proposed herein based on FBG sensor. Firstly, the thermal analysis model of the spindle unit was established considering the heat generated by the spinning friction of the rolling elements, the contact thermal resistance between the inner/outer ring of the bearings and the spindle/housing. Secondly, a thermally induced preload test system for the spindle bearings was built. Through simulation and experimental comparison, the temperature distribution and thermally induced preloads of the key components of the spindle unit were analyzed at different speeds. The results show that the temperature measured by FBG sensor and thermal sensor is consistent with the simulation temperature prediction, which verifies the accuracy and reliability of the method proposed.
    Meta-action-oriented Reliability Allocation Method of Mechanical Transmission Systems
    CHEN Yifan, ZHANG Genbao, RAN Yan, LI Yulong, YU Hui,
    2021, 32(17):  2032-2039.  DOI: 10.3969/j.issn.1004-132X.2021.17.003
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    A reliability allocation method for mechanical transmission systems was proposed to quantify the uncertainty, aimed at the uncertainty in the reliability allocation of mechanical transmission systems. The minimum granularity of reliability allocation (i.e. meta-action) in transmission systems was extracted by the decomposition method of “function-motion-action (FMA)”. A method for calculating the sensitivity of the transmission systems was proposed based on the Sobol of LRA according to the reliability mathematical model of meta-action, which quantified the reliability sensitivity of meta-actions in the transmission systems, and the key meta-actions that affected the reliability of transmission systems were identified. The mapping relationship between the meta-action and the system reliability was established, and the mapping results were solved. The application results show that the method has high calculation accuracy and provides guidance for the reliability allocation of mechanical transmission systems.
    Research on Combined Transmission Performance of Magnetorheological Fluid and Electrothermal Shape Memory Alloys
    XIONG Yang, HUANGJin, SHU Ruizhi
    2021, 32(17):  2040-2046.  DOI: 10.3969/j.issn.1004-132X.2021.17.004
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    In order to solve the problems of small torque produced by magnetorheological fluid devices, a method of combined transmission of magnetorheological fluid and electrothermal shape memory alloys was proposed and the operating principle of the transmission devices was introduced. The relationship between temperature and friction torque was deduced based on the mechanics characteristics of electrothermal shape memory alloy springs, the magnetic fields of the devices were analyzed by finite element software, and the magnetic field strength and shear yield stress of magnetorheological fluid in working gaps of ring magnetorheological fluid were analyzed, and the transfer torque of magnetorheological fluid was calculated. The experimental results show that the friction torque caused by 8 shape memory alloy springs is as 1.798 N·m. When the current of the excitation coil is as 1A and the number of turns is as 380, the torque transmitted by magnetorheological fluid is as 1.41 N·m. Compared with the torque produced by a single magnetorheological fluid drives, the combined drives of magnetorheological fluid and electrothermal shape memory alloy generates a torque of 3.15 N·m, which improve the transmission performance by 1.2 times.
    Effects of Lubrication and Loading Levels on POM Gear Durability Performance
    LU Zehua, LIU Huaiju, ZHU Caichao, YU Guoda, ZHONG Bingbing
    2021, 32(17):  2047-2054.  DOI: 10.3969/j.issn.1004-132X.2021.17.005
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    A series experimental work on the load capacity of POM-POM gear pairs was conducted based upon a gear durability test rig, together with the measuring examination of tooth temperature, wear volume, tooth profile deviation and surface morphology. Several loading levels were chosen under both of the dry contact and the lubrication conditions. Experimental results reveal that the failure modes of POM gears are related to the loading levels and lubrication modes. The wear modes of POM gears are identified as adhesive wear and abrasive wear through the characteristic analysis of tooth flank microtopography and debris. Meanwhile, the failure mode of POM gears under oil lubrication is contact fatigue failure. As the oil reduces the tooth surface friction and running temperature, the tooth surface deterioration is delayed and the load capacity of POM gears increases.
    Development of Belt Grinding Devices for Screw Rotor and Prediction of Material Removal Rates
    YANG Heran, HE Yuan, SUN Xingwei, DONG Zhixu, QIAO Heting
    2021, 32(17):  2055-2062.  DOI: 10.3969/j.issn.1004-132X.2021.17.006
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    In order to achieve the uniform removal of grinding materials on the surfaces of screw rotor, a new type of abrasive belt grinding device was developed, which was composed of contact wheel type and free type abrasive belt grinding tools. According to the contact characteristics of grinding tool and workpiece, the contact model was established by semi analytical method and geometric approximation method respectively, and the contact stress distribution laws in the contact areas were obtained. The material removal rate prediction model was proposed based on the ThunderGBM algorithm, the contact stress and grinding process parameters were used as inputs to predict the material removal rate of the screw rotors in belt grinding. The grinding experiment was designed and implemented for the five head screw rotor. The comparisons between experimental data and numerical results show that the proposed model has high accuracy and effectiveness. 
    Quality Analysis for Abrasive Flow Precision Machining of Special-shaped Holes
    LI Junye, ZHU Zhibao, ZHANG Xinming, SHI Guangfeng, ZHAO Weihong, SU Ningning
    2021, 32(17):  2063-2073.  DOI: 10.3969/j.issn.1004-132X.2021.17.007
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    The abrasive flow precision machining technology was used to carry out numerical simulation and experimental research for the special-shaped deep holes.A large-eddy simulation method was used to numerically analyze the titanium alloy shaped hole parts,and related experimental studies were conducted to reveal the creation mechanism of the surface of the abrasive flow machining special-shaped curved surfaces. The study finds that: the effects of dynamic pressure,velocity,the pressure of abrasive particles on wall surfaces and the effects wall shear force on wall surfaces were revealed through numerical analysis of precision machining of abrasive flow.The vortex position distribution and the cause of the vortex as well as the interaction relationship between the vortex and the abrasive particles in the flow directional sections of the special-shaped section holes were obtained;After precision machining by abrasive flow,the surface roughness of special-shaped curved surfaces improves from Ra=7.136 μm,Rz=40.103 μm to Ra=1.822 μm,Rz=8.964 μm respectively.The protrusions and spheroidization on the inner surfaces of the shaped holes are removed,and the surface quality is significantly improved.The vortex greatly improves the surface quality of the special-shaped curved surfaces.
    Contact States of Workpiece-Abrasive Particles-Polishing Pad in Cemented Carbide CMP Processes
    MAO Meijiao, XU Qing, LIU Jingli, YUAN Julong, LI Min, HU Zihua
    2021, 32(17):  2074-2081.  DOI: 10.3969/j.issn.1004-132X.2021.17.008
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    Theoretical analysis of the contact states among workpiece, abrasive particles and polishing pads was carried out based on the theory of elastoplastic mechanics, the depth of the abrasive particles pressed into the workpieces under each contact states was calculated, and the mathematical model of the critical conditions of the contact states was established, and the verification experiments were conducted. The research results show that in the cemented carbide CMP processes, there are three forms of non-contact state, partial contact state, and full contact state among workpiece, abrasive particles and polishing pads. The depth of the abrasive particles pressed into the cemented carbide workpieces in the three contact states is mainly affected by the polishing load, the size of the abrasive particles and the hardness of soft layer of workpiece, and the critical conditions of each contact states are determined by the characteristics of the polishing pad, the mass fraction of abrasive particles, and the polishing load. The experimental results show that the established mathematical model is credible. 
    Short Term Wind Speed Prediction of Wind Turbine Hubs Based on Combined Neural Network
    MA Junyan, YUAN Yiping, CHAI Tong, ZHAO Qin
    2021, 32(17):  2082-2089.  DOI: 10.3969/j.issn.1004-132X.2021.17.009
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    The wind speed less than 6 hours at the wind turbine hubs was predicted by comprehensively considering the historical wind speed rules and wind speed changes in recent numerical weather forecasts. In order to improve the accuracy of short-term wind speed prediction under the condition of sudden changes of wind speeds, a new combined neural network was proposed. According to the characteristics of different frequency subsequences obtained by signal decomposition, the deep convolution neural network and the gated cyclic recursive unit were used to predict the low-frequency subsequence, and Elman recurrent neural network was established to predict the high-frequency sequence. The downscaling numerical weather prediction wind speed was used to identify inflection points, and the generalized autoregressive conditional heteroscedasticity model was used to modify the non inflection point of wind speed. Finally, the actual wind speed data of a wind farm in Xinjiang were used for the experiments. The mean absolute errors, mean square errors and mean absolute percentage errors were used to calculate the deterministic prediction accuracy, and the coverage rate and interval width were used to calculate the uncertainty prediction accuracy, which verified the effectiveness of the proposed algorithm. 
    A Novel Fault Early Warning Method for Centrifugal Blowers Based on Transfer Learning
    LI Congbo, WANG Rui, ZHANG You, JIANG Lijun , SUN Hao
    2021, 32(17):  2090-2099,2107.  DOI: 10.3969/j.issn.1004-132X.2021.17.010
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    The fault early warning model for centrifugal blowers established by laboratory data become invalid when used in factories. And data collecting there was difficult to build high-precision model. To address this problem, this paper proposed a transfer learning method based on AE, which had ability to build the fault early warning model suitable for factory environments quickly. Firstly, the monitoring data of centrifugal blowers collected in the laboratory was windowed resampled to establish an AE model with sparse constraints. Secondly, the factory and laboratory data were input into the AE network to obtain low-dimensional features, and  the maximum mean discrepancy(MMD)between the two low-dimensional features was minimized, then  the AE model with small learning rate was fine-tuned to complete the transfer of AE model. Finally, based on the trained AE model and early warning in dicator, the fault early warning strategy was formulated to realize fault early warning for centrifugal blowers under the actual environments of the factories. The experimental results on a centrifugal blower show that the proposed method has higher accuracy compared with other three methods. 
    Design and Experiments of Rotary-cutting Forming Devices for Tapered End Blanks
    ZHANG Xinyan, WANG Ying, HU Pengke, WANG Rui, SHU Xuedao
    2021, 32(17):  2100-2107.  DOI: 10.3969/j.issn.1004-132X.2021.17.011
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    Aiming at designing the tapered end blank rotary-cutting forming device and getting cross wedge rolling without concave, the influences of parameters were analyzed, and the main structure of the device was designed. The best combination was obtained by analyzing the influences of baffle gap, base circle diameter, widening angle during the forming processes. Furthermore, a differential gear train transmission mechanism of the rotary-cutting tool was proposed. And according to the requirements of the processes, a reasonable transmission ratio distribution of the differential gears was determined. The device was designed and manufactured, and the experiments were carried out. The results show that the quality of the tapered end obtained by rotary-cutting forming is good, and the size of the tapered end of test is the same as the simulated ones. The feasibility of the rotary-cutting forming processes of the tapered end blanks and the rationality of the structure design of the rotary-cutting forming are verified. 
    Influences of Pulse Frequency on Microstructure and Properties in Laser Cladding Layers
    LI Yunfeng, SHI Yan,
    2021, 32(17):  2108-2117,2124.  DOI: 10.3969/j.issn.1004-132X.2021.17.012
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     The coarse grains and hard precipitates in the laser cladding layers had adverse effects on the corrosion resistance and impact resistance. The effects of pulse frequency on microstructure and properties of the coating were studied by pulse laser cladding technology. The microstructure of the coating was characterized by scanning electron microscope (SEM)morphology. High speed camera and numerical simulation method were used to analyze the shapes and temperature changes of molten pools. The hardness, wear resistance, impact resistance and corrosion resistance of the coating were tested by microhardness tester, wear tester, charpy impact tester and electrochemical corrosion tester respectively. The results show that the microstructure of the coating coarsens with the increase of pulse frequency. At the same time, the numbers of precipitates in the coating decrease first and then increase. The wear resistance of the coating decreases with the increase of pulse frequency. The wear resistance of the coating is the best because the microstructure of the coating is refined and there are fine hard precipitates at 20 Hz. The impact resistance and corrosion resistance of the coating increase first and then decrease with the increase of pulse frequency. Because the amount of hard phase in the coating decreases obviously at 80 Hz, the coating has the best impact resistance and corrosion resistance. 
    Research on Hysteresis Compensation Method of MEMS Piezoelectric Vibratory Platforms
    HAO Rui, PENG Bei, ZHOW Wu
    2021, 32(17):  2118-2124.  DOI: 10.3969/j.issn.1004-132X.2021.17.013
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    The MEMS piezoelectric vibratory platforms, as the new candidate for recalibration platforms, could provide the on-chip physical impulse environment to recalibrate the accelerometers by providing a continuous and stable acceleration signals. However, the piezoelectric material used for actuation exhibited clear hysteresis characteristics which seriously affected the stability and the continuity of the harmonic vibration signals. According to the vibratory platform vibration performance, a piezoelectric hysteresis model was established based on polynomial fitting, and the control of platform and compensation of acceleration were realized by combining the feedforward controller and feedback controller. The experimental results show that the maximum acceleration error is reduced from 1. 3g to 0. 05g under the driving conditions of 10 V(317 Hz)sinusoidal voltage. 
    Recognition Method of Braking Intention of Electric Vehicles Based on ABC-SVM Algorithm
    LI Xiangjie, ZHANG Xiangwen,
    2021, 32(17):  2125-2135.  DOI: 10.3969/j.issn.1004-132X.2021.17.014
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    For the regenerative braking systems of electric vehicles, the corresponding regenerative braking control strategy might be designed according to the different braking intentions of the driver, so as to improve the safety, comfort and economy effectively during the vehicle braking processes. Accurate and fast recognition of drivers braking intentions was the basis of designing control strategy. An on-line recognition method of driver braking intentions was designed based on ABC-SVM algorithm  and implemented to identify the drivers braking intentions accurately and quickly for the electric vehicles with brake-by-wire. Firstly, the braking data were preprocessed, and the effective features were selected by NCA feature selection algorithm, and then the braking intention recognition model was established by the ABC-SVM algorithm, and on-line recognition was carried out finally. Offline verification and online test results show that the NCA algorithm may effectively filter out irrelevant features caused by signal noise. Compared with the fuzzy reasoning, back propagation(BP), particle swarm optimization support vector machine(PSO-SVM)and genetic algorithm support vector machine (GA-SVM) recognition algorithms, the ABC-SVM algorithm may identify drivers braking intentions more accurately and quickly.
    Optimization of Gear Grinding Parameters with Worm Grinding Wheel
    WANG Liting, ZHAO Xiuxu, LI Jiao
    2021, 32(17):  2136-2141.  DOI: 10.3969/j.issn.1004-132X.2021.17.015
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    Taking the 20CrMnTi gear grinding processes with worm grinding wheels as the research object, the uniform design test method was selected to study influences of the grinding parameters(i. e. grinding wheel linear speed vs, grinding wheel along the gear axial feed speed vw, grinding thickness ap)on the tooth surface roughness. The regression model of grinding parameters and tooth surface roughness was established by using two-level stepwise regression method, and the optimization model with multiple goals was established with the machining efficiency and tooth surface roughness as the optimization objectives. The particle swarm optimization algorithm was used to optimize the grinding parameters. The experimental results show that the optimized grinding parameters may improve the machining efficiency and reduce the tooth surface roughness.