Table of Content

28 March 2019, Volume 53 Issue 3 Previous Issue    Next Issue

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Experimental Study of the Grain Size Effect on Scratching Behaviors of Pure Copper MAO Mengyun,PENG Linfa,LAI Xinmin 2019, 53 (3):  253-259.  doi: 10.16183/j.cnki.jsjtu.2019.03.001 Abstract ( 1253 )   PDF (977KB) ( 417 )   Save During the sheet metal forming process, the ploughing effect had an important influence on the magnitude of surface deformation due to the similar roughness of tool-workpiece. To have an in-depth understanding of the ploughing process, single cone scratching tests of different grain sized materials were conducted in this study. It was found that the location of cracks and the flow directions of materials in scratching process varied significantly with the change of cone angle. The increase of grain size can restrain the initiation of cracks and lower the entire strain caused by the moving of the rigid cone, which in a row decrease the scratching hardness and pileup height in scratching process. The results of this study can improve the understanding of the ploughing process and further help the optimization of the surface quality of the metal-deformed products. References | Related Articles | Metrics

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Assembly Deviation Simulation Considering Welding Deformation Applied on Electric Multiple Unit YAO Limin，ZHANG Daoliu，HOU Xiujuan，LIU Tao，LI Zhimin 2019, 53 (3):  260-268.  doi: 10.16183/j.cnki.jsjtu.2019.03.002 Abstract ( 859 )   PDF (1100KB) ( 291 )   Save Welding is the most widely used connection mode in the assembly process of the electric multiple unit (EMU) while the deformation induced by welding will have a great influence on the assembly precision. The influence of welding deformation on the assembly precision of the sidewall window module is discussed in this paper. Firstly, the inherent strain of three typical welded joints in the sidewall window module of the EMU is extracted by the thermal elastic-plastic finite element method. Then, the deformation of the sidewall window module is obtained by the finite element simulation based on the inherent strain method. The obtained deformation is considered as a mean shift to amend the 3D assembly variation simulation results of the window module. Finally, the amended simulation results are compared with the measured data. The simulation results of assembly variation considering welding deformation have a good agreement with the actual measured data which indicates that the proposed method is more accurate and feasible for predicting the assembly variation of the sidewall window module of the EMU. References | Related Articles | Metrics

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Error Analysis and Accuracy Synthesis for Linkage Mechanism of High-Precision Press QIAN Huanan,TAO Jing,YU Suiran 2019, 53 (3):  269-275.  doi: 10.16183/j.cnki.jsjtu.2019.03.003 Abstract ( 1077 )   PDF (884KB) ( 338 )   Save The development of high precision molding equipment is the key for near-net shape technology in our country. Research and development of parallel driven mechanical press with multi-link becomes important trends. How to determine the key error sources which influence the precision of servo press, thus to distribute the accuracy of the main parts economically and reasonably, is important for the design of high precision servo press. Based on the available research results, the definition, index and affecting factors of servo press’s precision are discussed. Then the structural characteristics of symmetry multi-linkage mechanism are analyzed, and precision analysis models of kinematics output are developed based on loop incremental theory; through sensitivity analysis, the key error sources are identified; considering the manufacturing cost and the constraints of mechanism reliability, the accuracy of the main parts is distributed. A case study of 4-RRPaR&PRPa R servo press is presented by using Monte Carlo method for demonstration of the proposed approaches. The result shows that the error factors which have relatively important influence on the servo press’s precision can be identified effectively, and the requirement of mechanism reliability can be satisfied by adjusting these factors’ tolerance. References | Related Articles | Metrics

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Capacity Balancing-Oriented Leasing Profit Optimization of Opportunistic Maintenance for Leased Series-Parallel Production System SUN Bowen,GUO Wenyu,XIA Tangbin,PAN Ershun,XI Lifeng 2019, 53 (3):  276-284.  doi: 10.16183/j.cnki.jsjtu.2019.03.004 Abstract ( 1080 )   PDF (970KB) ( 321 )   Save Aimed at service-oriented manufacturing model and outsourcing paradigm, an opportunistic maintenance strategy based on capacity balancing is proposed to meet the demand of complex series-parallel structure and multi-process, eventually maximizing the leasing profits. The series and parallel structures are taken as the research emphasis. And the capacity balancing of the whole system is also considered. Sequential maintenance scheduling for each machine with individual health evolution aims to minimize the maintenance cost rate. At the process layer and the system layer, these maintenance time points are taken as combined maintenance opportuuity. A capacity balancing-oriented leasing profit optimization (CB-LPO) policy is also developed by considering the capacity balancing to dynamically optimize maintenance decisions. In this study, by comparing with the global maintenance scheme during the lease contract period, it is verified that the proposed strategy has significant economic advantages in service outsourcing decision-making. References | Related Articles | Metrics

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Elastodynamics Analysis of Pure Torsional Model of Spur Gear ZHENG Yuxin,XI Ying,YUAN Lang,BU Wanghui 2019, 53 (3):  285-296.  doi: 10.16183/j.cnki.jsjtu.2019.03.005 Abstract ( 1156 )   PDF (1584KB) ( 407 )   Save In order to study the influence of nonlinear factors on the elastodynamics of spur gear’s pure torsional model, a pure torsional dynamic model of four-degree-of-freedom spur gear is established by using the principle of D’Alembert and the method of micro-displacement. Firstly, a time-varying equation set is solved by Runge-Kutta and time-dispersion methods with the consideration of the nonlinear factors such as gear meshing error, time-varying meshing stiffness and meshing gap, and the dynamic response and the corresponding spectrum of the system are obtained. Next, combined with the nonlinear analysis theory, the global bifurcation diagram and the maximum Lyapunov exponent are obtained by changing the meshing stiffness, the excitation frequency and the tooth side clearance of the system. Then, the periodic motion, quasi-periodic motion and chaos of the system are analyzed from the quantitative and qualitative point of view respectively by using the time history plot, phase space trajectory, Poincáre map and power spectrum. Finally, the coupling influence of nonlinear factors on the system are considered, which provides a complete method for the nonlinear characteristic analysis of gear transmission system. References | Related Articles | Metrics

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The Effect and Construction Control of Large Diameter Shield Tunneling Under Railway Culvert YANG Junlong,MEN Yanqing,LIAO Shaoming,GAO Dongqi,SU Fengbin 2019, 53 (3):  297-304.  doi: 10.16183/j.cnki.jsjtu.2019.03.006 Abstract ( 1012 )   PDF (1230KB) ( 225 )   Save In order to reveal the effect of large diameter shield tunneling under railway culvert, the mechanical behavior of the operating railway bridge and culvert caused by shield crossing were predicted by numerical method, based on the practice of large diameter slurry balance shield for boring North Huancheng Road underground expressway tunnel in Hangzhou. Then the implementation effects such as shield construction parameters, controlling technology and bridge deformation were verified by field testing. The numerical analysis shows that the maximum settlement will reach 21.6mm at the bottom of the bridge and culvert, while the maximum tensile stress will reach 1.60MPa at the top and bottom of the middle wall of the bridge during the shield tunneling machine passing without the underneath soil strengthened. On the contrary, the maximum settlement and tensile stress will reduce to 9.3mm and 1.46MPa respectively when the underneath soil is reinforced. In the actual practice, the pressure at the cutting face is 15kPa larger than the static earth pressure. However, to ensure the operating bridge and culvert structure in the state of security during shield machine passing, the cutting face pressure increases to 25kPa larger than the static earth pressure, the total thrust and torque reduces by 10% approximately respectively considering the upper load decrease 13%. Furthermore, the tail grouting volume is parameterized between 150% and 200%. The field testing shows that the deformation of bridge and culvert will upheaval 3-4mm before the shield crossing, then translate into settlement about 4mm after the shield crossing. After 3 days since crossing completed, the differential settlement will decrease and tend to be stable gradually, and the final stability value is about 0.01%. References | Related Articles | Metrics

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Roll Damping of Damaged Ship Based on OpenFOAM OU Shan，MAO Xiaofei，LIU Zuyuan，HUANG Tianqi，YU Zeshuang 2019, 53 (3):  305-314.  doi: 10.16183/j.cnki.jsjtu.2019.03.007 Abstract ( 1199 )   PDF (1491KB) ( 300 )   Save Based on OpenFOAM, the linear and nonlinear roll damping coefficients of the intact and damaged ship are obtained through the simulation of ship free roll decay motion in calm water. The detailed comparison and discussion of various perspectives such as initial roll angle, bilge keel, damage forms and damage process reveal the characteristics of damaged ship roll damping. And then the damaged model tests are carried out to verify the reliability of numerical method. For numerical simulation, the second and the third forms of damage models are built. Both the damage process and the coupled problems of inside/outside fluid are successfully resolved. These studies lay a foundation for roll motion and capsize research of damaged ship, and also provide technical reference for study of damaged ship stability criteria. References | Related Articles | Metrics

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Crack Life Evaluation of Flywheel for Canned Main Pump LIU Bingyi，ZHANG Jige，WANG Dezhong，LI Bin 2019, 53 (3):  315-320.  doi: 10.16183/j.cnki.jsjtu.2019.03.008 Abstract ( 960 )   PDF (828KB) ( 168 )   Save A new crack life assessment method is proposed for the bimetal shielded nuclear main pump flywheel with complex structure and force. This paper establishes a three-dimensional model of canned main pump flywheel with crack and uses the finite element software ANSYS Workbench to analyze the fracture mechanics. Then we find the relationship between the stress intensity factor of flywheel crack with the rotational speed, crack depth and crack length, which is used to fix the formula of stress intensity factor. Moreover, we use the Paris formula to evaluate the life of flywheel crack. The stress distribution of the flywheel and the stress intensity factor of the crack are obtained, and the relationship between crack size and the stress intensity factor is found to calculate the crack life, which is within safety limits. The revised calculation method is adopted to bimetallic flywheel for canned main pump under complex situations and with complex structures. References | Related Articles | Metrics

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Automatic Sleep Scoring Based on Refined Composite Multi-Scale Entropy and Support Vector Machine YE Xian,HU Jie,TIAN Pan,QI Jin,CHE Datian,DING Ying 2019, 53 (3):  321-326.  doi: 10.16183/j.cnki.jsjtu.2019.03.009 Abstract ( 1137 )   PDF (770KB) ( 249 )   Save Sleep scoring is an important research direction in medical research and clinical medicine. Traditional visual scoring method is based on scoring rules, which is a time consuming and subjective procedure. Therefore an automatic sleep staging method based on refined composite multi-scale entropy (CMSE) and multi-level support vector machine is proposed. Firstly, to ensure the reliability of the input characteristics, refined CMSE is extracted as the feature input and two channels of electroencephalogram (EEG) and electrooculogram (EOG) are used. Then a three-layer support vector machine classification scheme is applied to classify sleep stages. Specifically, the inputs of each layer are obtained according to the trend of the entropy curves. The overall accuracy of the proposed method is 85.3%. Compared with traditional methods, the classification accuracy of the proposed method is more balanced and the global performance is much better. References | Related Articles | Metrics

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Pilot Allocation Based on Matched Game for Massive Multiple-Input Multiple-Output Systems FENG Wenjiang，LI Le，DAI Caili 2019, 53 (3):  327-333.  doi: 10.16183/j.cnki.jsjtu.2019.03.010 Abstract ( 1019 )   PDF (820KB) ( 189 )   Save In order to maximize the uplink achievable sum rate of the multi-cell and multi-user massive multiple-input multiple-output (MIMO) system, a pilot allocation algorithm based on matched game (PA-MG) between users and pilots is proposed. Firstly, on the user side, a preference list of pilots is generated according to the user utility function, and an application is made to the pilots with the best arrangement for all users. Then, on the base station side, the preference list of the requesting users is generated according to the pilot utility function, and the pilots are assigned to the users with the best arrangement in turn until all users are assigned with the pilot. Simulation results show that the PA-MG algorithm supports larger cellular and less time complexity than the pilot allocation based on potential game (PG-PA) algorithm. Compared with the weighted graph coloring based pilot decontamination (WGC-PD) algorithm, the PA-MG algorithm can achieve greater uplink achievable sum rate, making the distribution of signal to interference plus noise ratio (SINR) of each user be more uniform, and the robustness to shadow fading is stronger. References | Related Articles | Metrics

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Detection of Double Compression with the Same Quantization Parameter Based on Dual Encoding Parameter Model SHEN Ting，SUN Tanfeng，JIANG Xinghao 2019, 53 (3):  334-340.  doi: 10.16183/j.cnki.jsjtu.2019.03.011 Abstract ( 982 )   PDF (838KB) ( 216 )   Save A novel method was proposed to detect double H.264 compression with the same quantization parameter, based on the dual encoding parameter model composed of Intra Prediction MacroBlock Modes (IPMBM) and the quantized discrete cosine transform (DCT) coefficients of I frames. The method designed the classfication feature based on the property that coding parameters of single compressed videos and double compressed videos have different convergencies. Firstly, the input video was recompressed repeatedly with the same quantization parameter. Then, the IPMBMs and the quantized DCT coefficients were extracted from I frames. The numbers of altered IPMBMs and quantized DCT cofficients between adjacent recompressions were used to calculate the classification feature. Finally, the extracted feature was fed to the trained support vector machine to detect double H.264 compression. Experimental results show that the proposed method can detect double H.264 compression correctly and efficiently. References | Related Articles | Metrics

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Adaptive Impedance Control for Underwater Manipulator Intelligent Grasping in Unknown Environment ZHANG Jianjun,LIU Weidong,LI Le,CHENG Ruifeng,ZHENG Haifeng 2019, 53 (3):  341-347.  doi: 10.16183/j.cnki.jsjtu.2019.03.012 Abstract ( 1115 )   PDF (812KB) ( 291 )   Save In order to realize the diversity of the unknown environment target capture of underwater manipulator, the adaptive impedance control method is proposed to ensure grasping, holding and minimizing the damage of the target. A force tracking control system based on position impedance model is established, and the target impedance parameter is identified by recursive least square method, and the expected value of grasping force is adjusted online according to the impedance parameter and the manipulator motion characteristic with fuzzy inference. According to the expectation force and grasping force error, the adaptive PID controller adjusts the desired position, realizes the tracking of different expected force signals while tracking the target position, and realizes the simulation verification on the MATLAB/Simulink platform. The results show that the adaptive impedance control has good force and displacement tracking performance in free space and constrained space. The realtime expectation force adjustment satisfies the diversity of grasping target, and the adaptive adjustment of the desired position realizes the tracking of the desired force. References | Related Articles | Metrics

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Analysis on Hybrid Automata Model of Three-Phase Grid Inverter LI Donghui,ZHENG Hongyu,YAO Lele 2019, 53 (3):  348-354.  doi: 10.16183/j.cnki.jsjtu.2019.03.013 Abstract ( 927 )   PDF (858KB) ( 270 )   Save A new controller design method based on hybrid automaton model is proposed to solve the problem that grid current harmonics is large and the dynamic response time is long after the disturbance happens in the three-phase inverter, and a stability analysis method based on finite time stability is proposed on this basis. First of all, for a certain three-phase inverter, the state equations based on switching function are established. Then, on the basis of the working mode of the three-phase inverter, the hybrid automaton model is established from the angle of changing the switching range of the power frequency cycle and reducing the current harmonics. And the bus voltage is divided into 12 intervals to get the corresponding control rules. Finally, the stability analysis of the improved controller based on the hybrid automaton model is carried out according to the finite time stabilization method. The simulation results verify that the proposed automaton model and its controller can effectively reduce the harmonic distortion rate of the grid current to less than 0.56%. Furthermore, dynamic regulation time can be reduced when disturbance occurs. References | Related Articles | Metrics

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Key Technology Study of Power Supply for Multi-Transient Electromagnetic Method Transmitter WANG Xuhong,ZHANG Yiming,LIU Wei 2019, 53 (3):  355-365.  doi: 10.16183/j.cnki.jsjtu.2019.03.014 Abstract ( 817 )   PDF (1587KB) ( 175 )   Save A novel active soft-switching converter is presented for an multi-transient electromagnetic method (MTEM) transmitter. The topology and operation principle of the MTEM transmitter are introduced in detail. Compared with the conventional converter, the proposed converter can operate in passive, single active and dual active soft-switching modes to achieve zero voltage switch over the entire load range, and the output power is greatly expanded. MTEM transmitter has the characteristics of large output-power, high-efficiency and strong-stability. The research has provided a solution for the development of other transmitters. At present, a 50kW prototype has been completed and achieves 1000V/50A output in the field. References | Related Articles | Metrics

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Positioning Correction Algorithm for Long Baseline System with Uncertain Sound Speed HUANG Jian,YAN Shenggang 2019, 53 (3):  366-372.  doi: 10.16183/j.cnki.jsjtu.2019.03.015 Abstract ( 1012 )   PDF (850KB) ( 179 )   Save In long baseline positioning system, the error induced by uncertain sound speed is the most damaging factor affecting the positioning accuracy. A long baseline system positioning correction algorithm with uncertain sound speed is proposed by setting the acoustic signal to propagate between the target and different hydrophones at different sound speed. First, a multi-parameter optimization function is built to estimate the effective sound speed using the redundant information in the long baseline system. Then the particle swarm optimization algorithm is utilized to solve the optimization function, and the effective sound speeds between the target and each hydrophones are obtained. Finally, the target is positioned by the resulting effective sound speed. The simulation results show that the proposed algorithm can effectively improve the positioning accuracy of long baseline positioning system compared with the existing algorithms. References | Related Articles | Metrics

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ffect of Inorganic Nanoparticles on the Thermal and Mechanical Properties of Wood Fiber/HDPE Composites QI Ruige,HE Chunxia,FU Jingjing,ZHAO Limei,JIANG Caiyun 2019, 53 (3):  373-379.  doi: 10.16183/j.cnki.jsjtu.2019.03.016 Abstract ( 1036 )   PDF (895KB) ( 217 )   Save In order to investigate the thermal and mechanical properties of the wood powder/high-density polyethylene (HDPE) composites that filled with different kinds of inorganic nanoparticles (calcium carbonate NPCC, montmorillonite NMMT and alumina NAL), the thermal properties of the composites were analyzed by simultaneous thermal analyzer and expansion coefficient meter, the mechanical properties of the composites were also tested and analyzed. The results showed that all the three kinds of inorganic nanoparticles had a significant effect on the performance of wood flour/HDPE composites. Among them, NPCC could greatly lower the linear thermal expansion coefficient of wood-plastic materials by 38.95%. The composite material also has better thermal stability that the initial pyrolysis temperature increased by 2.8℃ during the heating process，and the carbon residue rate increased by 39.1% at 600℃.The tensile strength, flexural strength and impact toughness of NPCC modified wood fiber/HDPE composites also had great improvement (the increases were 32.86%, 11.05%, 35.30%, respectively). References | Related Articles | Metrics

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Rheological Properties of Magnetorheological Grease Under Shear Mode WANG Huixing,ZHANG Guang,OUYANG Qing,WANG Jiong 2019, 53 (3):  380-386.  doi: 10.16183/j.cnki.jsjtu.2019.03.017 Abstract ( 1088 )   PDF (955KB) ( 206 )   Save Magnetorheological grease (MRG) has wide application prospect in the field of engineering due to the distinguished advantages such as, no settlement, simple sealing and simple preparation. The rheological properties of MRG are the basis for the design of magnetorheological absorber. In this study, lubricating grease based MRG with 30%, 50% and 70% weight fraction of carbonyl iron (CI) were prepared. Rheological properties including shear viscosity and shear stress of MRG with different CI weight fraction were examined from steady shear with and without magnetic fields applied. It is found that the constitutive relation of MRG can be described by Bingham model, and the higher the weight fraction of CI particles is, the wider adjustable range of shear viscosity and shear stress of MRG can reach. The critical strain between linear viscoelastic range and nonlinear viscoelastic range of MRG with 70% CI weight fraction obtained by using the large amplitude oscillatory shear method is 0.02%. In addition, the yield stress is 24.7kPa under the magnetic field of 0.96T; the maximum magneto-induced storage modulus is 1.17MPa; the relative magnetorheological effect reaches as high as 3814%. References | Related Articles | Metrics