Table of Content

    10 February 2021, Volume 32 Issue 03
    Effects of Gravity Center Position of Sprags on Sprag Clutch Performance
    YAN Hongzhi1,2,3;WANG Zhibiao1,3;ZHU Chu2,3,4;CAI Mengkai2,3;LI Jia2,3;HU Xuan2,3
    2021, 32(03):  253-260.  DOI: 10.3969/j.issn.1004-132X.2021.03.001
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    In the working processes of the PCE type overrunning clutches, since the gravity center of the sprag did not coincide with its own rotation center, the centrifugal forces might generate a torque, which made the inertia torque of sprag change with the gravity center position, and might affect the working performance of the clutches. The gravity center position models of sprag were established by decomposition method and coordinate transformation herein. The dynamics model of the sprag clutches was established by ADAMS software. The sprag contact force, clutch engagement and disengagement performance at different gravity center were studied. The results show that when the gravity center is as 0.05 mm to the left of the rotation center, the contact force between the sprag and the inner-outer rings increases by 6% compared with that of 0.01 mm and the engagement time of the clutches raises 14%, which is beneficial to the engagement. When the gravity center position is as 0.05 mm to the right of the rotation center, the contact force between the sprag and the inner-outer rings reduces by 6% compared with that of 0.01 mm, the disengagement time of the clutches speeds up to 20%, and the disengagement performance may be better.
    Femtosecond Laser Processing Technology of Diamond Micro-channel Heat Sink Based on Radar Power Module
    JIANG Haitao1;CUI Jianlei2;YIN Dongping1;MEI Xuesong2
    2021, 32(03):  261-268.  DOI: 10.3969/j.issn.1004-132X.2021.03.002
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    In order to study the processing problems of the diamond micro-channel heat sinks of the radar power module, the femtosecond laser processing research of polycrystalline diamond micro-channel was carried out. The temperature field distribution and removal processes of diamond irradiated by femtosecond laser were simulated. The ablation threshold of the diamond was studied theoretically and experimentally. The influences of parameters such as laser energy, scanning speed, scanning times, focus position, and optimized parameter on the size of diamond microgrooves were investigated. The results show that the highest temperature of diamond may exceed the gasification temperature of material removal when the power of femtosecond laser is greater than 0.3 W. The highest temperature is in the center of the spot, and the power does not change the distribution of temperature field. The ablation threshold of femtosecond laser processing diamond is as 1.8 J/cm2. The depth of diamond microgrooves is positively correlated with laser power and scanning times, negatively correlated with scanning speed, and basically symmetrically distributed with positive and negative defocus. In addition, the surface width of diamond microgrooves does not change obviously. Under the optimized parameters of laser power of 5 W, scanning speed of 100 mm/s, scanning times of 30 and defocusing amount of -0.5 mm, the diamond micro-grooves have regular structure. The taper of side wall of sectional morphology is controlled within 3° and there are no defects such as residue, crack and edge collapse on the surfaces. There are no cracks in the inner part of micro-channels which have high consistency. The ‘cold’ machining of diamond material may realize, and the requirements of high-quality machining for micro-channels of diamond heat sinks in radar power components may be satisfied.
    Quantitative Research of Take-off Speeds and Wear of Graphite Water-lubricated Hydrodynamic Thrust Bearings
    WANG Rui1;JIA Qian1,2;YUAN Xiaoyang1
    2021, 32(03):  269-274.  DOI: 10.3969/j.issn.1004-132X.2021.03.003
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     Aiming at the problems that it was difficult to quantify the take-off speeds and wear of graphite water-lubricated hydrodynamic thrust bearings under the extreme conditions, the quantitative method was studied by using the half-size bearing of a nuclear reactor coolant pump. The model of a graphite water-lubricated tilting-pad thrust bearings was established. The theoretical take-off speed was calculated by using the surface roughness of friction pairs as the measurement index and compared with the experimental results by a bench test. Using the mass wear rate as the standard for measuring the wear, the small sample test and the start-stop bench test were both carried out to investigate the graphite-stainless steel friction pairs. The results show that the errors of take-off speeds between the theoretical and experimental results are as 20%, which proves the feasibility of the theoretical calculation method. The errors between the small sample test and the start-stop bench test are as 39.2%. The small sample test may be used to predict or evaluate the bench test results, and both of the two test results are comprehensively analyzed to guide the theoretical calculation.
    Comprehensive Gear Shift Schedule of PELV Considering  Road Gradients and Vehicle Loads
    LI Congbo;ZHANG Chi;QU Shiyang;HU Zengming
    2021, 32(03):  275-283,289.  DOI: 10.3969/j.issn.1004-132X.2021.03.004
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    In order to improve the adaptability of the PELV to the dynamic driving conditions, a comprehensive gear shift schedule for three-speed powertrain was proposed with the consideration of road gradient and vehicle loads, as well as dynamic and economic performance of the vehicles. The influences of road gradients and vehicle loads on vehicle’s moment of resistance were analyzed. The dynamic and economic shift schedule with dynamic adaptability were established. Then an optimization model of comprehensive shift schedule under different driving conditions was formulated to take the minimum acceleration time of 0~50km/h and minimum energy consumption as optimization objectives, which was solved via a hierarchical gravitational search algorithm. With the proposed optimization model and algorithm, the comprehensive gear shift schedule was obtained. Finally, MATLAB/Simulink simulation platform was used for comparative analysis of three shift schedule. The results show that the energy consumption per kilometer of comprehensive gear shift schedule is close to economic shift schedule under CHTC-LT driving cycle and has better dynamic performance. Moreover, the comprehensive gear shift schedule eliminates the shifting cycle under different road gradients and vehicle loads, which shows great adaptability to driving conditions.
    Study on Dynamic Characteristics of Digital Hydraulic Transformers
    LIU Tao1,2;HAN Yan1,2;SUN Renfu1,2;ZHAO Dingxuan1,2
    2021, 32(03):  284-289.  DOI: 10.3969/j.issn.1004-132X.2021.03.005开放科学(资源服务)标识码(OSID):
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    The digital hydraulic transformer(DHT) combined several pump/motor flow units with binary displacement ratio to rotate synchronously, and realized different transformation ratio through the control of high-speed on-off valve group status. The structure and principle of DHT were introduced. The dynamic characteristics of DHT were simulated and analyzed through theoretical derivation and mathematical modeling. The prototype was manufactured and the dynamic characteristics were verified by experiments. DHT has a fast response and a wide range of pressure changes, and may be used as a secondary regulating element in the hydraulic constant pressure network systems to drive the linear loads, and may also recover the pressure energy at the load ends, which is of great significance to improve the efficiency of the hydraulic systems.
    Analysis of Cavitation Characteristics for Orifice Plates
    YU Kexin1;SHANG Qunli1;WU Xin2
    2021, 32(03):  290-296.  DOI: 10.3969/j.issn.1004-132X.2021.03.006
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    With the increase of system working pressure as well as before and after differential pressure, cavitation or blocking flow caused by vapor-liquid two-phase flow might occur in various valves, venturi tubes, orifice plates and other throttling parts in the piping systems, which might seriously affect the working performances and safety of the system. For the throttling parts represented by orifice plates of different specifications, with the applications of theoretical derivation as well as FLUENT fluid mechanics two-phase flow simulation, combined with cavitation flow characteristics of cavitation bench test, supplemented by the high-speed macrophotography results of local cavitation bubbles, and the flow curves of ramp ladder triangle were presented to express the whole processes of the development and change of blocking flow occurring in the orifice plates, which fully expressed the limitation and step characteristics of blocking flow in the development processes.
    Color Difference Detection of Polycrystalline Wafers Based on Multi-component Convolution Neural Network
    GUO Baosu;ZHUANG Jichao;ZHANG Qin;WU Fenghe
    2021, 32(03):  297-304.  DOI: 10.3969/j.issn.1004-132X.2021.03.007
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    Color difference detection of polycrystalline wafers with complex textures was a challenge in the manufacturing processes of solar cells. The traditional algorithm in color difference detection was not suitable for situations where the categories of color differences varied greatly, and the classification results were inaccurate. A detection algorithm of multi-component convolution neural network was proposed based on color features of different components. It is found that color features are different in H, S and V components by analyzing the feature distribution of polysilicon wafer images in HSV color spaces. The influences of model depth and convolution kernel size on detection results were evaluated to build the best convolution neural network structure based on full convolution neural network. A multi-component convolution neural network model was constructed based on the best network model to enhance the ability to distinguish different color difference features. The experimental results show that the accuracy, the values of MCC and F1Score of the multi-component convolution neural network are 92.28%, 95.45%, and 94.03% respectively, which has higher detection accuracy than that of other algorithms.
    A Flexible Position Selection Algorithm for Solving ECPP
    WANG Yingcong1;ZHANG Ling1;XIAO Renbin2
    2021, 32(03):  305-313.  DOI: 10.3969/j.issn.1004-132X.2021.03.008
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    A construction algorithm was proposed for ECPP based on position selection herein. The construction algorithms built solutions by placing circles one by one into a container. It is necessary to select an appropriate position from multiple feasible positions to place each circle. The key idea of the proposed algorithm was to regard this process as a position selection process, and to use the task selection in swarm intelligence labor division to achieve the position selection in ECPP. Based on the definition of configuration and feasible position, the position selection characteristics of the ECPP were analyzed. By introducing the stimulus-response principle of swarm intelligence labor division, the integrity of the unoccupied spaces was considered as stimulus and the tightness of the occupied space was treated as threshold. An adaptive threshold adjustment strategy was designed by combining with the change rules of threshold in swarm intelligence labor division. The results of 55 representative instances show that the proposed algorithm is feasible and efficient.
    Selective Assembly for Coordinator Parts by RNGRU Based on Comprehensive Grey Relational Order Model
    ZHONG Baihong;WANG Lin;ZHONG Shisheng
    2021, 32(03):  314-320,356.  DOI: 10.3969/j.issn.1004-132X.2021.03.009
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    The drift performance of coordinator, one of the key factors that determined the tracking ability and guidance accuracy of the precision-guided weapon directly, might be improved by the selective assembly for coordinator parts. In view of the low success rate of the first selective assembly for coordinator parts, a CGRO model was proposed to perform the relevancy on assembly parameters affecting the selective assembly for coordinator parts, and key assembly parameters affecting the selective assembly for coordinator parts were obtained. The RNGRU model was established to realize the selective assembly for coordinator parts. Taking the selective assembly between the gyro rotor and drift-adjusting screw which affected the drift performance of the coordinator as an example, CGRO was used to analyze the assembly parameters of the gyro rotor, and the key assembly parameters that affected the selective assembly of the two were obtained. Based on RNGRU, the regression prediction of the mass of the drift-adjusting screw was realized. The experimental results show that the proposed method may achieve the selective assembly for coordinator parts, and the prediction accuracy is superior to the traditional GRU network.
    Drilling Forces and Temperature Rises in Axial Low-frequency Vibration-assisted Cortical Bone Drilling
    BAI Xiaofan;HOU Shujun;LI Kai;QU Yunxia
    2021, 32(03):  321-330.  DOI: 10.3969/j.issn.1004-132X.2021.03.010
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     In order to study the influences of axial LFVAD method on drilling forces and temperature rises in cortical bone drilling processes, experiments of the drilling forces and temperature rises in conventional drilling and axial low-frequency vibration-assisted cortical bone drilling were conducted based on a self-developed LFVAD equipment. Drilling forces and heat generation rate models were presented. Experimental results show that the feed force and torque in axial LFVAD are obviously reduced, and the temperature rises are reduced by 3~5 ℃. It is found that the spindle speed is the most significant influence factor of drilling forces and temperature rises. Double objective optimizations were performed by statistics. Results from the model are consistent with experimental data. It may be regarded that periodic separation of drill bit and bone tissue generated by axial LFVAD is the main reason for the reductions of drilling forces and temperature rises.
    Functional Occlusal Surface Morphology Design Method for Missing Teeth Based on CGAN
    TIAN Sukun1;DAI Ning1;YUAN Fulai1;SUN Yuchun2;YU Qing3;CHENG Xiaosheng1
    2021, 32(03):  331-340.  DOI: 10.3969/j.issn.1004-132X.2021.03.011
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    In view of the problems that the distribution of tooth wear facets was not taken into account in the dental restoration and that the standard crown was difficult to express the diversity of natural tooth morphology, an automatic design method was proposed for the missing tooth functional occlusal surface morphology based on occlusion spatial constraint and tooth wear facet guidance. The wear facets of the crown were semi-automatically extracted by using the heuristic search algorithm, and an adaptive visual distance orthogonal projection method was used to calculate the depth image of the crown and its wear facets in the front view direction. By grading the expression of the functional occlusal surfaces of the missing teeth, a generation network was used to obtain the overall structure of the tooth occlusal surfaces based on the occlusion spatial constraint, and then the functional occlusal surfaces with real crown details were synthesized by using the wear facets as constraints. Finally, the mesh reconstruction algorithm and the skinning method were used to design full crown restoration that satisfied the normal chewing function. Experimental results demonstrate that the full crown restorations designed by the proposed method have sufficient natural tooth anatomical features and higher clinical applicability.
    Dynamic Mechanics Behaviors of 1Cr12 Weld Cooling Based on Coupling of Phase Transformation and Contraction
    XU Qian1,2;HU Guangxu3;DONG Zhibo4;REN Xinxing4;FANG Hongyuan4
    2021, 32(03):  341-347.  DOI: 10.3969/j.issn.1004-132X.2021.03.012
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    Considering the following hardening and transformation plasticity, the solid-state transformation model of volume strain and mixed-phase mechanics properties was established. The effects of various factors on the dynamic mechanics behavior of 1Cr12 steel weld cooling were studied.  The experiments of welding longitudinal residual stress were carried out, the results of tests are in good agreement with the simulation ones. It is shown that the volume expansions of martensitic transformation, the changes of mechanics properties and the plastic mechanism have influences on the dynamic mechanics behaviors of weld shrinkages, and the longitudinal stress of weld joint changes from contraction tensile states to compression states under the action of various factors.
    Research on Springback Defects in Incremental Forming of Cu-Al Bimetal
    QIN Qin1,2 ;HE Liu1;LI Cheng2;ZANG Yong1
    2021, 32(03):  348-356.  DOI: 10.3969/j.issn.1004-132X.2021.03.013
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    In order to discuss the influences of different processing parameters on springback in incremental forming of bimetals, a three-dimensional model was established including the tool head, laminated sheet and composite interface. The parameters of the interface cohesion elements were obtained by comparing the results of T-peeling, and the reliability of the finite element model was verified through experiments. The experimental results show that the forming angle is the most critical factor affecting the springback, and tool diameter is least sensitive to springback. In addition, the cohesive element may effectively simulate the interface of the laminated sheets, and the simulation error is only 7.9%. The analysis shows that the step-down size, sheet thickness and tool diameter are positively related to the springback values, the forming angle is negatively related to the springback ones. And the springback value decreases by 21% as the forming angle increases from 30° to 60°.
    Experimental Study of Impact Resistance of 2A12 Aluminum Alloy Circular Corrugated Sandwich Plates to Blunt-nosed Projectile
    DENG Yunfei;JIA Huiru;LU Mingjian;ZHANG Yinbo
    2021, 32(03):  357-362,367.  DOI: 10.3969/j.issn.1004-132X.2021.03.014
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    In order to study the impact resistance of aluminum alloy circular corrugated sandwich plates to blunt-nosed projectile, the impact tests of aluminum alloy circular corrugated sandwich plates and monolithic homogeneous plates with equal area density were carried out by the one stage gun system. Based on the test data, the protection performance, failure mode and energy absorption of the circular corrugated sandwich plates against the impacts of projectile were analyzed, and sandwich plates were compared with the monolithic plates to obtain the difference and reason of the impact resistance of the two kinds of plates. The results show that the ballistic limit velocity of the circular corrugated sandwich plates is lower than that of monolithic plates. The impact position of the circular corrugated sandwich plates has an effect on its impact resistance, the ballistic limit of the node of the circular corrugated sandwich plates is higher than that of pedestal. The front plate of circular corrugated sandwich plates is mainly damaged by shear punching, while the core is damaged by shear and crushing, and the back plate is mainly damaged by tensile tearing. For the monolithic plates, the shear plug is localized. In addition, the failure mode and energy consumption of the plates are affected by the impact velocity of projectile.
    Delay Locking Buckle Technology in Hot Rolled Steel Coil Bundling
    GAO Yankai;CHEN Dong;XIA Huichao;WU Guangtao
    2021, 32(03):  363-367.  DOI: 10.3969/j.issn.1004-132X.2021.03.015
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    The loose coil problem was a common problem in hot steel coil bundling, which seriously affected the transportation safety and product quality of steel coils. The detailed processes of hot steel coil bundling were analyzed, and the temperature difference between steel coils and steel strap was pointed out as the main reason for the problem of loose coil. Therefor a delay locking buckle technology was proposed. The pre-heating of the steel straps was achieved through the delay locking buckle. The steel coil were no longer loose in cold state by controlling the minimum bundling force for secondary tightening. The pre-heating time was calculated, and the calculation formula of the delay locking buckle time was deduced. Based on the analysis of the relative deformation of the steel coil and the steel strap, the minimum bundling force for secondary tightening was determined on the premise of ensuring the standard residual bundling force. Experiments were performed on the automatic bundling machine using the delay locking buckle technology, and the results show that the technology may effectively solve the problem of loose strap and improve the quality of steel coil bundling.
    Analysis Method and Experimental Research on Cooling System of High Power Submersible Motor
    ZHANG Qi1;LI Zengliang1;DONG Xiangwei1;LIU Yanxin1;WANG Yuting2
    2021, 32(03):  368-377.  DOI: 10.3969/j.issn.1004-132X.2021.03.016
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    In order to study the temperature distribution of high power submersible motors, a 580 kW submersible motor was calculated. The temperature field calculation model was established according to the working conditions. The automatic heat transfer was realized through configuring the fluid-structure interaction and the flows of internal and external cooling medium were simulated. The fixed values of iron loss of stator and rotor, the variable of oil friction loss and copper loss were used as heat source. Based on the influences of cooling system parameters, the bidirectional coupling relationship between temperature field and flow field was obtained. A cooling system analysis method was proposed. The proposed method was used to study the influence laws of cooling system structural parameters on temperature distribution. The optimal impeller parameters were obtained by comparing the cooling system calculation results under different impeller working characteristics. Finally, through the indoor no-load test and sea load test, the results show that the relative errors between test values and simulation ones of iron loss and temperature are less than 5%. The designed cooling system may operate stably under different loads.