Table of Content

29 May 2015, Volume 36 Issue 5

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Paper

Study of Launch Control for Heavy-duty Off-road Vehicles Based on Clutch Engaging Speed

MIAO Cheng-sheng, LIU Hai-ou, ZHAO Yi-nong, YUE Fu-ying, CHEN Hui-yan

2015, 36(5):  769-776.  doi:10.3969/j.issn.1000-1093.2015.05.001

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According to dynamic modelling and evaluation indicator of launch process,a dry clutch subsection control strategy based on the clutch engaging speed is proposed by selecting the appropriate control parameters, such as rotate speed and displacement, etc. A subsection control model is established and the thresholds of control parameters are obtained from test database. The vehicle launch test under this control strategy is carried out in flat road conditions, and the control performance is evaluated using the indicators of the equivalent longitudinal jerk, start time and slipping rotation numbers.The results show that the control strategy based on the clutch engaging speed can meet the requirements of smoothness and fast starting, which lays a good foundation for the subsequent research on optimization control adapting to all conditions.

Experimental Study of Influence of Outlet Pressure on Discharge Characteristics of Diesel Injector

QIU Tao， FENG Xiang， LEI Yan， DAI He-fei， XU Hui， ZHANG Chuan-xia

2015, 36(5):  777-780.  doi:10.3969/j.issn.1000-1093.2015.05.002

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The high-speed flow of fuel in the injector of the high pressure fuel system for the diesel engine is easy to induce the cavitation in nozzles, which affects the injection characteristics. A set of test rigs is built to adjust the different outlet pressures for the study of the influence of outlet pressure on the discharge characteristics of injector. The injection characteristics of a high-pressure common-rail under different injection and outlet pressures are measured to investigate the influence of outlet pressure on fuel delivery rate. The test results show that the outlet pressure has little influence on the fuel delivery rate at the constant injection pressure; but as the flow chokes due to cavitation, the discharge coefficient increases with the increase in the outlet pressure.

Application of Adaptive Fuzzy Wavelet Neural Network in AC Servo Control System

HOU Run-min， LIU Rong-zhong， GAO Qiang， WANG Li， DENG Tong-bin

2015, 36(5):  781-788.  doi:10.3969/j.issn.1000-1093.2015.05.003

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A novel indirect stable adaptive fuzzy wavelet neural（FWNN）controller is proposed to control the nonlinearity, wide variation in loads, time-variation and uncertain disturbance of the high power AC servo system in a certain weapon. In the proposed approach, the self-recurrent wavelet neural network (SRWNN) is employed to construct an adaptive self-recurrent consequent part for each fuzzy rule of Takagi-Sugeno-Kang (TSK) fuzzy model. A back-propagation (BP) algorithm offers the real-time gradient information to the adaptive FWNN controller with the aid of an adaptive SRWNN identifier, which overcomes the effects of parameter variations，load disturbances and other uncertainties effectively. It has a good dynamic performance. The stability of the closed loop system is guaranteed by using the Lyapunov method. The simulation result and the prototype test prove that the proposed method is effective and suitable.

Structural Dynamics Optimization of Gun Based on Neural Networks and Genetic Algorithms

LIANG Chuan-jian, YANG Guo-lai, WANG Xiao-feng

2015, 36(5):  789-794.  doi:10.3969/j.issn.1000-1093.2015.05.004

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In order to study the optimization of muzzle disturbance, a new method of gun structural dynamics optimization based on nonlinear finite element method, experimental design, neural networks and genetic algorithms is proposed. A dynamic model of a large caliber gun is established based on the nonlinear finite element method, and the structural dynamics analysis of the gun is made based on experimental design. With experimental data as training samples, a back-propagation (BP) neural network is established to simulate the nonlinear mapping between the structural parameters and muzzle disturbance index based on Bayesian regularization algorithm. The optimal objective function of muzzle disturbance is constructed, the genetic algorithms is applied to solve the objective function, and the optimal design for structural parameters of the gun is realized. The results show that nonlinear relationship between the structural parameters and muzzle disturbance index established by the method is proved to be highly reliable, and the method is accurate and feasible to optimize the muzzle disturbance.

Modeling and Simulation of Echo Signal of Ultra-wideband Radio Fuze

SHEN Lei， HUANG Zhong-hua

2015, 36(5):  795-800.  doi:10.3969/j.issn.1000-1093.2015.05.005

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The target signal of ultra-wideband radio fuze is always submerged in the noise due to the signal radiation of ultra-wideband, surface scattering and target signal frequency of ultra-wideband radio fuze. In order to get the echo signal of ultra-wideband radio fuze, the target signal mathematical expressions of ultra-wideband radio fuze are derived by starting from the diffuse reflection characteristics and multipath effects of ultra-wideband signal. The target signal of ultra-wideband radio fuze is simulated with the help of time domain analysis and Matlab. The simulation results show that the time for scattered signal returning to the antenna is different because of the distance from fuze antenna to the antenna beam is different, resulting in broadening effect. The broadening effect is more obvious with the increase in height；the amplitude of ultra-wideband radio fuze echo signal decreases with the increase in height. The correctness of the model is verified by comparing with the measured waveform.

Research on Ranging Method for Linear Frequency Modulation Radio Fuze Based on Fractional Fourier Transform

YUE Kai， HAO Xin-hong， LI Ping， TAO Yan， LI Yong-liang

2015, 36(5):  801-808.  doi:10.3969/j.issn.1000-1093.2015.05.006

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To improve the ranging accuracy of the frequency modulation（FM）radio fuze under the limit of the little frequency deviation, two ranging methods, i.e. instantaneous initial frequency estimation method and fractional correlation method, for linear FM radio fuze based on fractional Fourier transform (FRFT) are proposed. The ranging principles of the two methods are described, their range resolutions and anti-noise performances are analyzed, and the simulations are carried out to validate these methods. The simulation results demonstrate that the ranging resolutions of the two methods which are affected by the modulation bandwidth rarely are much better than that of the ranging method based on the harmonic wave method. For the known frequency modulation rate, the complexity of the methods is reduced and acceptable for engineering realization. The fractional correlation method is better than the instantaneous initial frequency estimation method in anti-noise performance and can be used in the low signal-to-noise ratio circumstance.

Research on Solubility of Gun Propellant Combustion Residue Via Microscopy Method

ZHANG Kai-shuan， WU Bin， YU Xu-hua， ZOU Zhi-qiang

2015, 36(5):  809-812.  doi:10.3969/j.issn.1000-1093.2015.05.007

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To solve the cleaning problem of gun propellant combustion residue in gun barrel, the dissolution process of residue is studied via microscopy method, the dissolution ratios of residue in different solvents are analyzed. The formulation of solvent is optimized by orthogonal test, which can remove more than 99% of the residue. The experimental results show that the microscopy method can be used to observe the dissolution process in real-time, which can be used as an effective solubility testing method.

Modeling of Celestial Positioning Error and Analysis of Error Characteristics Based on Distribution of Guide Stars

ZHAO Hui, XIONG Zhi, WANG Li-na, PAN Jia-liang, YU Feng, DAI Yi-jie

2015, 36(5):  813-822.  doi:10.3969/j.issn.1000-1093.2015.05.008

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Guide stars are the basis of celestial positioning. The performance of celestial positioning is not only determined by the accuracy of astronomical sensors, but also affected by the distribution of guide stars. To analyze the impact of star distribution on celestial positioning, an error model of celestial positioning is established based on the basic principle of celestial positioning. The error characteristics under the different distributions of stars are researched. In addition, the error weight k used for determining the performance of celestial positioning is presented, and the optimum star geometries are given with certain measuring accuracy. Simulation results show that the proposed error model of celestial positioning can be used to analyze the performance of celestial positioning effectively.

Predictor-corrector Reentry Guidance Based on Feedback Bank Angle Control

ZHAO Jiang， ZHOU Rui

2015, 36(5):  823-830.  doi:10.3969/j.issn.1000-1093.2015.05.009

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To eliminate the phugoid trajectory oscillation and enforce the thermal protection, a predictor-corrector guidance method based on the feedback bank angle control is proposed for the lifting hypersonic vehicles. The design of the guidance method is independent of the traditional quasi equilibrium glide condition (QEGC) that might be out of work in some specific cases. The longitudinal guidance is first developed by predicting the longitudinal range error and correcting the magnitude of the guidance command. The altitude rate is modified in real time by using the feedback bank angle law. The reversal logic of bank angle is designed for the lateral guidance based on the crossrange error and the heading angle error. The numerical simulations show that the phugoid trajectory oscillations of the hypersonic vehicle can be eliminated without QEGC. The Monte Carlo results of the reentry guidance with random initial dispersion also demonstrate the robustness of the proposed algorithm.

Research on Three-loop Autopilot for Rolling Missile Based on Linear Quadratic Optimal Control Theory

FAN Shi-peng， LIN De-fu， YAO Huai-jin, LU Yu-long， QI Zai-kang

2015, 36(5):  831-838.  doi:10.3969/j.issn.1000-1093.2015.05.010

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A dynamical model including cross-coupling effects of rolling missile is built. The couplings among the channels are regarded as external interference. The linear quadratic（LQR）optimal control theory is used to propose a design method of three-loop autopilot and analyze its general features. The research on the relationship between the weight coefficient matrix and the autopilot performance could assist a designer in choosing the weight coefficient matrix. The dynamical model is perceived as multiple-input multiple-output（MIMO）system, and the corresponding control system of rolling missile is designed. The results show that the three-loop autopilot using single-channel design do well in restraining the influence of couplings in rolling missile with state couplings, which has little difference from the control law derived by MIMO design. The simulation validates the correctness of the above conclusion.

Relationship between Integral Time and Two-point Non-uniform Correction for HDR Imaging of Cooled Focal Plane Array

DUN Xiong， FAN Yong-jie， JIN Wei-qi， WANG Xia

2015, 36(5):  839-845.  doi:10.3969/j.issn.1000-1093.2015.05.011

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Variable integral time is an effective means to realize the high dynamic range (HDR) of infrared system. Unfortunately，it would lead to serious residual non-uniformity. The relationship between the correction parameters (gain and offset) of two-point non-uniform correction（NUC）and integral time is derived based on the infrared system response model. The result shows that the gain parameters are independent of integral time, and only the bias parameters change with integral time. The correctness of the above conclusions is confirmed by testing it against standard two-point NUC method. The result can provide a reasonable evidence for NUC of infrared system with variable integral time, which only updates the offset parameters but maintain same gain parameters.

Under-dense Meteor Trail Interference Suppression Algorithm for Over-the-horizon Radar

BO Chao， GU Hong， SU Wei-min， CHEN Jin-li

2015, 36(5):  846-853.  doi:10.3969/j.issn.1000-1093.2015.05.012

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An under-dense meteor trail interference suppression algorithm is proposed to solve the problem of that under-dense meteor trail interference severely affects the target detection performance of over-the-horizon radar (OTHR).The dyadic wavelet transform (DWT) algorithm is utilized to calculate the position of meteor trail interference, and Hankel tensor of three orders is constructed by the data of meteor trail interference. Then the noise component of tensor is refrained and the parameter of meteor trail interference is resolved by higher order orthogonal iteration（HOOI）algorithm and total least squares (TLS) algorithm, thus attaining the echo data of meteor trail interference in time domain. The meteor trail interference is subtracted from echo data to obtain the echo data after the meteor trail interference is refrained. Compared with existing meteor trail interference suppression methods, the proposed method could improve signal-to-clutter and noise ratio (SCNR) of target.

Infrared Target Recognition Algorithm Based on Contour Fragment Matching and Graph Searching

SU Juan, YANG Luo, ZHANG Yang-yang

2015, 36(5):  854-860.  doi:10.3969/j.issn.1000-1093.2015.05.013

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A target recognition method based on contour fragment matching and graph searching is proposed for complicated background interference and contour fragment missing in forward looking infrared (FLIR) target recognition. The contour features are extracted from the reference image and the real-time image, and decomposed into the fragments，and the orientation information of each fragment are utilized to realize the fragment matching and construct the matching graph. Under the constraint of the spatial relationship between the reference contour fragments, the graph searching strategy is used to traverse the matching graph to obtain candidate target contour fragment combinations. Finally, the global similarity measure is used to obtain the final recognition. Experimental results show that the proposed method has good adaptability and robustness to complicated background interference and contour fragment missing.

Calibrator Automatic Calibration System for Headlamp Tester of Motor Vehicle Based on Image Processing

PAN Yue， XU Xi-ping， ZHANG Fan， JIANG Zhao-guo， QIAO Yang， LI Yan-di

2015, 36(5):  861-868.  doi:10.3969/j.issn.1000-1093.2015.05.014

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In order to make sure the measurement accuracy of calibrator for the headlamp tester, the optic axial angle and the light intensity of the calibrator should be detected periodically. In consideration that the degree of automation in the traditional testing scheme is insufficient and the repeatability of test is difficult to guarantee, a testing method is proposed. This method is based on the combination of image processing and the high-precision electric turntable. The automatic detection of calibrator with a high precision is realized by using the equal ratio relationship between practical displacement and pixel displacement, as well as the linear relationship between image plane’s illuminance and object plane’s illuminance. The experimental data obtained under different illuminances is fitted by the use of least squares. And the regression linear equation can be got, and the equiluminous curve of vertified calibrator is drawn. The experimental analysis shows that the measurement accuracy of optic angle can reach 40″ and the relative measurement uncertainty of illuminance is less than 1% at the distance of 10 m.

A Vehicle Detection Method with Envelop Delay-and-sum Based on Linear Sensor Array

TAO Liang-xiao， JIN Ping， WANG Tong-dong， ZHU Wei

2015, 36(5):  869-873.  doi:10.3969/j.issn.1000-1093.2015.05.015

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Detecting the vehicles via acoustic and vibration signals has been widely used in battlefield surveillance, security, and anti-terrorism. A new method based on the features and similarity of signal envelops is proposed and applied in vehicle detection. The envelop delay-and-sum is used not only to improve the detection efficiency of moving vehicle, but also provides the direction and speed of its movement. The analysis of experimental data shows that all vehicles could be detected except for several vehicles passing through at the same time. Compared with the detected results from a single sensor in signal-noise-ratio and signal duration, the false alarm rate is decreased from 61% to 0%，while the missed detection rate is increased from 7.8% to 12.5%.

Research on Optimization Algorithm Design of 3D Intelligent Network Based on Ad Hoc Wireless Sensor Networks

JIN Xin， LOU Wen-zhong， WANG Fu-fu

2015, 36(5):  874-878.  doi:10.3969/j.issn.1000-1093.2015.05.016

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Ad Hoc wireless sensor network (WSN) is a kind of acentric and self-organizing wireless network. In order to improve the stability of dynamic network，the topological structure needs to be generated by proper networking algorithm. In the multi-frequency classified ad hoc network structure，a cluster head is responsible for the communication among cluster members as well as the communication between cluster heads. Therefore, how to choose the most rational node to be the cluster head becomes the key point. Based on existing researches on networking algorithm，a new clustering networking algorithm based on 3D prediction model is proposed，and a 3D networking topological structure is established based on the Matlab software. A hierarchical network is generated by clustering algorithm，and the numbers of cluster heads that generate a network and the degree of clustering balance are analyzed. The simulation results show that the proposed clustering networking algorithm is feasible and the clustering structure is stable.

Research on the Sonobuoy System and Algorithm for Rapid Inversion of Sound Speed Profile

ZHANG Wei

2015, 36(5):  879-884.  doi:10.3969/j.issn.1000-1093.2015.05.017

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A sonobuoy system with the functions of difference global positioning system (DGPS) and short-wave communication is presented to acquire the sound speed profile (SSP) in a large area of sea as quickly as possible. The conventional SSP inversion algorithms based on sound transmission time have to trace eigen ray for every SSP, influencing the inversion speed. A perturbation method is proposed to calculate the sound transmission time quickly, and the time is used as cost function to invert SSP in some area of South China Sea. Results indicate that the sonobuoy is stable and reliable under four level sea state. Although the root mean square (RMS) error is doubled in comparison with that by conventional algorithms, the calculating time can be reduced from 10 hours to 3 seconds by perturbation method. Therefore the sonobuoy system and inversion algorithm introduced in this paper can satisfy the demand of real-time SSP monitoring.

Application of Cyclic Postfix in the Time Reversed-OFDM-based Underwater Communication

WANG Chi, YIN Jing-wei, DU Peng-yu, CHEN Yang

2015, 36(5):  885-890.  doi:10.3969/j.issn.1000-1093.2015.05.018

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A signal with the strongest energy may arrive at the receiver later than other signals do in the underwater acoustic channel on account of the sound velocity gradient distribution and the relative location between the receiving and sending nodes, etc. If the time-tracking is inexact, using a cyclic prefix only as guard interval may make the data of the current orthogonal frequency division multiplexing (OFDM) symbol for fast Fourier transform (FFT) be polluted by the data from the next symbol, thus destroying the orthogonality between subcarriers. The cyclic postfix is used in the OFDM underwater acoustic communication system to solve the above problems. Meanwhile, the cyclic postfix combines with the time reversal mirror technology for application in the OFDM underwater acoustic communication system to suppress the impact of sidelobe before the main peak of the time reversal channel and improve the channel equalization and the system performance. Theoretical analysis and simulation results show that the use of cyclic postfix in the OFDM underwater acoustic communication system is feasible and effective.

Information Coupling Degree-based Fission Control Algorithm for Autonomous Underwater Vehicles withoutVelocity Measurements

YANG PAN-pan， LIU Ming-yong， LEI Xiao-kang， WU Xiao-jin

2015, 36(5):  891-897.  doi:10.3969/j.issn.1000-1093.2015.05.019

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The fission control of autonomous underwater vehicles（AUV）presents a behavior of that a cohesive AUV swarm is split into multiple sub-swarms under external stimulus. An information coupling degree-based fission control algorithm is proposed for the fission control of swarm AUVs（SAUVs）without velocity measurements. Information coupling degree is utilized to denote the interaction intensity between AUVs, which realizes the behavior divergence of AUVs by adjusting their motion states. For the absence of velocity measurements, a distributed velocity observer is designed to estimate the velocities of AUVs in real time. By integrating the position information of the most correlated neighbor into the fission control law, the spontaneous fission behavior of AUVs can be achieved without velocity measurements. Both theoretical analysis and experimental simulation demonstrate the feasibility and effectiveness of the proposed fission control algorithm.

The Preparation and Characterization of Self-assembly Magnetocapsules

ZHANG Shao-shuai， ZHANG Chi-jun, YAN Jing-hui, YAO Shuang, KANG Zhen-hui

2015, 36(5):  898-903.  doi:10.3969/j.issn.1000-1093.2015.05.020

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Superparamagnetic Fe₃O₄ nanoparticles, using polyacrylamide as surfactant, are synthesized by one-step hydrothermal method. And then the sacciform magnetic material is obtained by changing the dosage of surfactant. The structure, morphology and magnetism property of the samples are characterized via X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer. The results show that the outside diameter of the magnetocapsules is about 200 nm. The size of Fe₃O₄ nanoparticles, composing the magnetocapsules, is about 30 nm. The magnetocapsules manifests a superparamagnetism, and the saturation magnetization intensity of the magnetocapsules is 62.5 emu/g.

The Effect of Pulsed Magnetic Field on Friction and Wear Properties of High Speed Steel Tool Materials

LIANG Zhi-qiang， MA Li-ping， WANG Xi-bin， XIE Li-jing， ZHAO Wen-xiang， YAO Hong-min

2015, 36(5):  904-910.  doi:10.3969/j.issn.1000-1093.2015.05.021

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The effect of pulsed magnetic field on the friction and wear mechanisms of high speed steel （HSS） cutting tool material W9Mo3Cr4V is investigated. The wear rate, friction coefficient and surface morphology of HSS material are detected under the different conditions of magnetic field strength, frequency and magnetization time in the pulse magnetization friction experiments. The experimental results show that the pulse magnetization treatment results in the improved wear resistance of HSS, the reduced friction coefficient, and the flat friction surface topography. Especially in certain parameters of pulsed magnetic field, the effect of HSS magnetization treatment is better with a lower coefficient of friction and better wear resistance. The comparative analysis of microstructures before and after magnetization treatment shows that a large number of dispersed carbides in the material are separated out after magnetization treatment. Dispersion strengthening is the main mechanism of pulsed magnetization treatment to enhance the wear resistance of the material.

Chip Formation Mechanisms and the Process Model during Ultra-precision Turning of SiC_p/Al Composite

GE Ying-fei， XU Jiu-hua, YANG Hui

2015, 36(5):  911-920.  doi:10.3969/j.issn.1000-1093.2015.05.022

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Single crystal diamond and polycrystalline diamond tools are selected for ultra-precision turning of SiC particulate reinforced aluminum matrix composites (SiC_p/2024Al and SiC_p/ZL101A). The appearance and the metallurgical microstructure of chip are observed in order to investigate the formation mechanisms of chip using micromechanics and metal cutting theory analytical methods. The chip formation process models are also established. The results show that a saw-toothed chip with semi-periodic thickness is formed. It is pointed that the dynamic behavior of microcracks and the periodic variation of shear angle are the two main mechanisms for this type of chip. A great number of microcracks and microvoids are produced on this kind of material during machining due to the inherent defects and, non-uniformity of the materials and the presence of the reinforcement particles. The periodic variation of shear angle is determined by the workpiece microstructure and the mechanical properties and the periodic slip-stick phenomenon. Volume fraction of reinforcement, cutting speed, feed rate and tool edge radius are the main factors that affect the chip formation.

Research on Classification Discriminating Method of Copper Matrix Composites

MA Run-bo， DU Jian-hua， XU Shi-meng

2015, 36(5):  921-927.  doi:10.3969/j.issn.1000-1093.2015.05.023

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Surface microtopography of copper matrix composite is partitioned by orthogonal method, and the subgraphs are selected as training set at random. The characteristics of graphite particles are extracted by selecting and designing a basic element model, and the statistical inference of distribution law is made. It is known that the diameter center, slope, fractal dimension and density of graphite particles obey normal distribution, and its long axis and minor axis submit to logarithmic normal distribution. The distribution law of graphite particles can be inferred to be consistent by the way of significance test. The factor analysis method is used to determine the primary indices which characterize the complex surface microtopography of copper matrix composites, and the support vector machine principle is used to classify and discriminate the copper matrix composites with different graphite contents. The results show that, through the analysis of surface morphology, the classification accuracy of copper matrix composites, of which and mass fraction of graphite is 16%, reaches 83.333%, the classification accuracy of the two kinds of copper matrix composites, of which the mass fractions of graphite are 10% and 20%, between them reaches 100%.

Calculation Model of Ball Spinning Force of Thin-walled Tubes

ZHAO Chun-jiang， WANG Chen， GENG Ming-chao

2015, 36(5):  928-932.  doi:10.3969/j.issn.1000-1093.2015.05.024

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An analytical model is presented to calculate the 3D ball spinning force. The spatial relation expression of the ball and workpiece is simplified through the rotation of spatial coordinates according to the track of the ball. The contact boundary equations of the ball and the workpiece are obtained based on the theory of space analytic geometry and the assumption that the spinning workpiece is a semi-infinite body，and the 2D curves are obtained by projecting on the coordinate planes. The projection of spatial contact area on each coordinate plane is calculated. The unit pressure in the deformation zone is given based on the assumption that the average pressure is approximately equal to that while a rigid ball is pressed into the space of semi-infinite body，and then the total spinning force and its components could be calculated. The comparison between theoretical results and experimental data shows that the proposed model is accurate.

Durability-based Design Optimization of Torsion Shaft under Random Loading

LIU Qin， QIAN Yun-peng， JI Guang-zhen, SUN Zhi-li

2015, 36(5):  933-937.  doi:10.3969/j.issn.1000-1093.2015.05.025

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The eight-level spectrum of torque is established by using the stochastic loading history of torsion shaft of military vehicles on various types of standard road surface. In consideration of the randomness of factors such as material performance, and fatigue influence coefficient, etc., the durability model is built by applying fatigue reliability theories. An optimization model, which takes the maximum durability of torsion shaft as the objective function when a vehicle travels for 6 000 km, is built based on the constraints such as rigidity reliability, structure dimension and so on. The approach that introduces the double-loop strategy for durability object conversion and the single-loop strategy for reliability bounds conversion is presented for this optimization model. The high computing accuracy of object value and the high efficiency of optimal computation are obtained. The results show that the durability of torsion shaft is improved obviously.

Numerical Simulation on Porous Rotary Active Magnetic Regenerator in Room Temperature

HOU Pu-xiu, LIU Chao-peng, WU Jiang-hong

2015, 36(5):  938-945.  doi:10.3969/j.issn.1000-1093.2015.05.026

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A novel two-dimensional porous model of active magnetic regenerator (AMR) is established in consideration of the different grain sizes and random distribution of magneto-caloric materials (MCMs) in the cross-section of AMR lattice. The active magnetic regenerator is numerically simulated. The simulated results are compared with the experimental results. The calculated temperature curve is similar to the experimental temperature curve. In some region, a calculation error exists , which is in a acceptable range. The effects of mass flow rate of heat transfer fluid (HTF), AMR's rotary speed and magnetic field intensity on cooling capacity are investigated. The simulation results show that the increase in the HTF's mass flow rate is helpful to neutralize the unfavorable influence of the residual HTF. With the increase in rotary speed, the heat transfer time between HTF and the MCM shortens, which is harmful to the refrigerator performance. However, this harmful influence can be weaken when the mass flow rate increases. The higher intensity of magnetic field is also useful to reduce the effect of the residual HTF on the cooling capacity.

Research on Mechanical Properties of the Contact Surfaces in Bolt Joints

ZHANG Yi-hua， LIN Dan-yi， YANG Guo-yu

2015, 36(5):  946-952.  doi:10.3969/j.issn.1000-1093.2015.05.027

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The continuous smooth derivable principle of micro-convex asperity contact surface within the elastic, elastic-plastic and plastic contact deformations is applied to demonstrate the contact strength and the continuity and regional disparity of the practical contact surfaces under loading. A bolt structure model is established using the mixed-element method, and the practical contact area and the contact stress distribution are solved. The predicted results from finite element analysis（FEA）are highly correlated with the ones obtained from ultrasonic physical tests. The correctness and validity of the model are verified. The transmission effect of stress along the bolt joint direction is investigated through series of models, the continuity of the contact stress of the bolt joint in the annular region is further proved, and the effect laws of changing the pretightening force and structure geometric parameters on the bolt joint contact strength and the range of contact stress are discussed.

Optimality Analysis of Index Policy for Offense-defense Shooting Process

LI Long-yue， LIU Fu-xian， ZHAO Lin-feng， WANG Dong-xu

2015, 36(5):  953-960.  doi:10.3969/j.issn.1000-1093.2015.05.028

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The index policy for offense-defense shooting process, namely, how a single red shoots at a collection of blue targets to maximize the return obtained from killed blue targets, is discussed. In consideration of the limitations of previous research and the balance of the red’s excepted return and survival probability, Gittins index is introduced and expanded to solve the shooting problems. The optimality of index shooting policy is discussed. Theorem 1 and 2 are extended, and Lemma 1 is presented. Three different shooting policies, such as myopic policy, exhaustive policy and round-robin policy, are introduced for comparison, and the optimality theorem 3 of myopic policy is proposed. 2 shooting scenes are set in numerical study. The red’s mean return, mean numbers of killed blue targets and red’s death rate are calculated for 4 policies. Simulation study outcome verified the optimality of index policy.