Table of Content

30 September 2015, Volume 36 Issue 9

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Paper

In-cylinder Tumble Organization and Utilization of an Opposed-piston Two-stroke Gasoline Engine

MA Fu-kang, ZHAO Chang-lu, ZHAO Zhen-feng, WANG Hao

2015, 36(9):  1601-1609.  doi:10.3969/j.issn.1000-1093.2015.09.001

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The processes of intake, mixture formation and combustion of opposed-piston two-stroke (OP2S) gasoline direct injection engine are simulated by AVL-Fire code. The effects of three scavenging system configurations, viz., flat piston-uniform scavenging chamber, flat piston-non-uniform scavenging chamber and pit piston non-uniform scavenging chamber, on the in-cylinder fluid flow and scavenging process are comparatively analyzed. Test verification is also carried out. The effects of flat piston- non-uniform scavenging chamber and pit piston-non-uniform scavenging chamber on the mixture formation and combustion process are comparatively analyzed. Results show that the uniform scavenging chamber can organize swirl and increase scavenging efficiency, and the non-uniform scavenging chamber can organize tumble and increase turbulent kinetic energy. Pit top surface of piston with non-uniform scavenging chamber is favorable to organize tumble and maintain the in-cylinder turbulence intensity. It helps to form the combustible mixture around spark plug at ignition. Compared with flat piston- non-uniform scavenging chamber, the turbulent kinetic energy of pit piston-non-uniform scavenging chamber is increased by 150 percent and its fuel evaporation is increased by 10 percent at ignition, which is favorable to form more uniform mixture and accelerate combustion process.

Thermal Analysis of Tank Armor Based on Lumped Parameter Method

HU Jin-suo, ZHOU Guo-yin, WANG Pu-kai, WU Hang, CHEN Qing-chang， CHU Qing-guo

2015, 36(9):  1610-1614.  doi:10.3969/j.issn.1000-1093.2015.09.002

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In order to master the thermal characters of tank armor, the tank armor is divided into many units based on lumped parameter method. Thermal balance equations are established and the thermal networks of the armor are constructed. Then a computing method of thermal balance is also determined. The temperature of a certain type of tank armor is computed in design, the high temperature areas with distinct thermal features are reached, and influence reason is analyzed. The temperature of a certain type of tank armor is measured through experiments, and then it is compared with computing temperature. The maximum deviation between them is 6.92%, which proves that the model is reasonable.

Friction Torque Characteristics of Thrust Ball Bearings

DENG Si-er，JIA Yong-chuan

2015, 36(9):  1615-1623.  doi:10.3969/j.issn.1000-1093.2015.09.003

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The dynamic analysis model and the mathematical model of the friction torque of thrust ball bearings are obtained based on the dynamic theory of rolling bearing. The effects of the structural parameters and operating conditions on the frictional torque of thrust ball bearings are analyzed and verified. The results show that the friction torque caused by spin-sliding is approximately 70% of the total friction torque of the thrust ball bearings. From the perspective of the design of the thrust ball bearings, the friction torque can be reduced by increasing the number of balls and the cage pocket clearance appropriately on the premise that the stability of the cage can be ensured. However, the priority should be given to the number of balls, which has more obvious effect on the friction torque and minimal influence on the bearing structure. With the increase in groove curvature radius coefficient of shaft (house) washer, the bearing friction torque decreases in exponential form. The groove curvature radius coefficient of shaft (house) washer has a little effect on the friction torque when its value is over 0.56. In consideration of the bearing carrying capacity, the groove curvature raidus coefficient of shaft (house) washer is better between 0.56 and 0.58. From the perspective of the use of the thrust ball bearings, the capsized moment, impact load and rotation speed have great effect on friction torque, but the influence of the impact load on it is the worst.

Terminal Target Contour Reconstruction Algorithm Based on RF Imaging for GIF

WANG Xuan, DENG Jia-hao, LI Hui, LU Man-jun

2015, 36(9):  1624-1631.  doi:10.3969/j.issn.1000-1093.2015.09.004

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The real-time accurate target recognition and localization are the key factors to implement the guidance integrated fuzing (GIF) technique and enhance the performance of terminal guidance and the accuracy of burst control. A real-time and accurate terminal target contour reconstruction algorithm for RF imaging GIF technique is proposed based on the principle of RF imaging and the target properties. The gray values with target information are extracted by gray mapping transform, thus decreasing the data quantity and the power-law transformation for image enhancement. Based on threshold segmentation and corner detection, the statistical methods are utilized to filter the background noise and suppress the target boundary interference. The target contour reconstruction is achieved by the convex hull technique, which is the optimal convex coveringa target area. Both the simulation and theoretical analysis results show that the time complexity of the proposed algorithm is lower, thus it can be used to achieved the real-time and accurate terminal target recognition and localization for RF imaging GIF.

Research on Influence of Selected Factors on Fuel Surface Regression Rate of PMMA in Solid Fuel Ramjet

CHEN Xiong， ZHU Guo-qiang， ZHENG Jian

2015, 36(9):  1632-1639.  doi:10.3969/j.issn.1000-1093.2015.09.005

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Numerical simulation and direct connected test methods are used to study the influences of selected factors on the fuel surface regression rate of polymethylmethacrylate (PMMA) in a solid fuel ramjet. The influences of air mass flux and fuel internal diameter on the solid fuel average regression rate and local regression rate are studied. The results show that the temperature, heat flux and local regression rate of the solid fuel surface firstly increase and then decrease gradually along the axial direction, and reach the maximum values at the reattachment point in the end of the recirculation zone. The local regression rate of the fuel surface increases with the inner radius of fuel, but decreases with the mass flux of the air. The average regression rate of the fuel shows an increasing power function relation with air mass flux and a decreasing power function relation with fuel internal diameter. The numerical simulation results are coincident with the experimental results, and are slightly larger than experimental results. The maximum error is less than 10%.

Numerical Simulation of Cook-off Characteristic of Solid Rocket Motor in Different Flame Environments

YANG Hou-wen, YU Yong-gang, YE Rui

2015, 36(9):  1640-1646.  doi:10.3969/j.issn.1000-1093.2015.09.006

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In order to study the thermal safety problems of solid rocket motor in unexpected flame environment, a two-dimensional model for cook-off of a small solid rocket motor is established, in which the composite solid propellant AP/HTPB is taken as a loading object. The cook-off characteristics of the solid rocket motor are calculated in 800 K, 1 000 K and 1 200 K flame environments, respectively. The results show that the initial ignition position of AP/HTPB is occurred in an annular region on the outer wall of propellant close to the nozzle. With the improvement of the flame temperature, the ignition delay period is shortened quickly, and the ignition temperature is gradually increased. Heat insulating effect of the insulating layer increases as the flame temperature increases. The initial slow decomposition temperature of AP component in the composite solid propellant increases with the increase in flame temperature.

Converting and Evaluation Method for Submarine-launched Interior Ballistic Functional

HU Song-wei

2015, 36(9):  1647-1653.  doi:10.3969/j.issn.1000-1093.2015.09.007

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Converting and evaluation methods for submarine-launched interior ballistic functional test are summarized: according non-design condition and small trial sample status. A method is put forward to convert the functional parameter of submarine-launched interior ballistic by developing a simulation software and estimating the environmental factor among normal samples with Monte-Carlo way. Evaluation method of interior ballistic functional parameter is also set up. Based on this method, the exact main environmental factors are defined by choosing multiple regression way, which can be used to comprehensively analyze the influence factors of functional parameter , and to improve the estimation precision of normal environmental factors. The composition of simulation and estimation software system and the design method of simulation experiment are described in detail. The simulated and estimated results of condition factor among normal samples are given by taking the environmental factor of velocity for example.

Preparation of Nano-sized Copper Chromite via a Mechanical Grinding Method and Its Effect on Thermal Decomposition ofAmmonium Perchlorate

HAO Ga-zi, LIU Jie, XIAO Lei, GAO Han, JIANG Wei, LI Feng-sheng,

2015, 36(9):  1654-1659.  doi:10.3969/j.issn.1000-1093.2015.09.008

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Nano-sized CuCr₂O₄ (copper chromite) with a particle size of 60 nm is prepared in large-scale via a HLG-5 type nanometer grinder. The microstructure and morphology of sample are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalytic effects of industrial CuCr₂O₄, nano-CuCr₂O₄ prepared by coprecipitation method and nano-CuCr₂O₄ prepared by mechanical grinding method on thermal decomposition of ammonium perchlorate (AP) are investigated by a differential scanning calorimeter (DSC). The results show that nano-CuCr₂O₄ prepared by mechanical grinding method has the best catalytic effect on AP as compared to the former two, improving the reaction rate constant and decreasing the high temperature decomposition activation energy. Nano-CuCr₂O₄ prepared by mechanical grinding method is promising as a high-performing combustion catalyst in AP-based composite propellants.

Combustion Performance of a Traveling Charge

LIANG Tai-xin， LYU Bing-feng， MA Zhong-liang， XIAO Zhong-liang

2015, 36(9):  1660-1664.  doi:10.3969/j.issn.1000-1093.2015.09.009

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In order to solve the problems of the ignition delay control and the energy release stability of traveling charge, a new traveling charge scheme is presented. The validity of time delay unit, stability of energy release and burning rate of traveling charge are studied by the closed bomb and 30 mm gun test. The results show that the ignition delay time of traveling charge can be controlled by the time delay unit based on its high density. There is an appropriate thickness of time delay unit, which can obtain an optimum effect of traveling charge, when the main charge remains constant. The experimental results are basically stable, which preliminarily verified the structural reliability of traveling charge, basic stable combustion performance and favorable energy release rule. The traveling charge has higher burning rate and gas release rate. When the content of porous propellant 125 charge is 95%, the maximum burning rate of traveling charge is 46 times as fast as 6/7 propellant, and the maximum dynamic vivacity reaches 7.4 MPa^-1 · s^-1. The burning rate and gas release rate of traveling charge can be adjusted by changing the content of porous propellant 125 charge.

The Experimental Study of Transient Droplets Particle Size and Concentrationin Confined Spaces

WANG Yue， BAI Chun-hua， LI Bin， LIU Xue-ling

2015, 36(9):  1665-1670.  doi:10.3969/j.issn.1000-1093.2015.09.010

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In order to study the influence of droplets particle size and concentration on the explosion parameters of the gas-liquid two-phase mist, the total light scattering detection system is established based on confined space. The water is used as the liquid medium in this experiment. The Sauter mean diameter D₃₂, droplets particle size distribution and concentration are measured in the 20 L vessel. Two sets D₃₂ (31.24 μm, 46.09 μm), droplets particle size distribution and various concentration of water/air mixtures are obtained through various mixture ration tests of pneumatic pressure and liquid dose. The results indicate that there is a linear relationship between the spray dose concentration and actual measuring concentration in the two sets of D₃₂. Furthermore, the D₃₂ of the flammable liquid in the turbulent air under the same condition is concluded by the fragment theory, and a new experimental method is proposed for the explosion parameters of the gas-liquid two-phase fuel/air mixtures.

Experimental Research on Velocity Field of Impinging Atomization of Gel Gasoline

YANG Jian-lu, WENG Chun-sheng, BAI Qiao-dong, HU Hong-bo

2015, 36(9):  1671-1679.  doi:10.3969/j.issn.1000-1093.2015.09.011

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Gel gasoline samples of QNJ-4 and QNJ-5 are prepared to investigate the influence of the factors, such as gel content, impinging angle and injection pressure, on velocity field of impingement atomization. The apparent viscosity of gel gasoline is researched by rotational rheometer with cone-and-plate configuration, and the power-low model is used to fit the apparent-viscosity to shear-rate curves of QNJ-4 and QNJ-5. The velocity field of impinging atomization with impinging angles of 60°, 75°, 90°, 105°and 120° and injection pressures of 0.50 MPa, 0.75 MPa, 1.00 MPa and 1.25 MPa is researched by the particle image velocity (PIV) system. The results indicate that the consistency index k increases with the increase in gel content maintaining while the flow index n decreases at the same time. The velocity of drops, which is produced by impinging atomization of gel gasoline, is decreased with the increase in gel content. The drop velocity on the axis of atomization area becomes smaller and smaller from impinging point to downstream, and there is the same fluctuation of the speed which is induced by the circular instable waves generating from the impact point. The core speed of gel gasoline drops is decreased with the increase in impinging angle and the reduce in injection pressure.

Landing Footprint Computation Based on Particle Swarm Optimization

ZHAO Jiang，ZHOU Rui

2015, 36(9):  1680-1687.  doi:10.3969/j.issn.1000-1093.2015.09.012

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To enforce the flexibility of the landing footprint computation, a hybrid optimization method based on the constrained particle swarm optimization (PSO) and bank angle reversal logic is proposed for the lifting hypersonic reentry vehicles. The parameterized bank angle profile is developed in order to reduce the searching space of the unknown variables. An improved PSO algorithmis used to optimize the reentry gliding trajectory satisfying both the path and the terminal constraints. The set of bank angle commands is obtained by imposing the forward and backward bank angle reversal logics, which can fast generate the approximate landing footprint for hypersonic reentry vehicles. Based on the high-lifting common aerial vehicle (CAV-H) model, a numerical simulation is performed. The results show that the hybrid optimization method is simple in design and independent of the initial estimation of the unknown parameters. The results also demonstrate the feasibility of the proposed algorithm for rapid generation of the landing footprint.

Hybrid Theoretical Variance Analysis for Random Error Properties of Optic Gyroscope

TANG Xia-qing, CHENG Xu-wei, GAO Jun-qiang

2015, 36(9):  1688-1695.  doi:10.3969/j.issn.1000-1093.2015.09.013

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For the sake of testing and analyzing the random error properties and identifying the noise amplitude of optic gyroscope more effectively, a new hybrid theoretical variance(TheoH) strategy is proposed to analyze the gyroscope output, which is integrated with the Allan variance and theoretical variance #1 with auto-bias removal. The problems of that the averaging time calculated with Allan variance is half of total data length and the confidence decreases at long-term averaging time are perfectly solved. A new method for analyzing the random error properties of optic gyroscope is proposed. The proposed method is compared with the Allan and theoretical variance#1, and the noise types and noise levels of white noises and real gyroscope output are identified. The experimental results show that the TheoH can improve the confidence efficiently and has higher evaluation precision than the conventional Allan method in long-term τ-values.

Experimental and Numerical Study of Dynamic Behavior of Bubble around Vertical Boundary under Hypobaric Condition

CUI Jie， ZHOU Sai-bei， WANG Yi， HE Bao

2015, 36(9):  1696-1703.  doi:10.3969/j.issn.1000-1093.2015.09.014

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In order to research the interaction between near-field bubble and nearby boundaries, a multi-function experimental apparatus operating under reduced air pressure is designed. A three-dimensional numerical model is established based on the potential flow theory. By comparison of experimental and simulated results, the numerical model is found to have good accuracy in simulating the bubble oscillation in the first period. Besides, the motion of bubble near a vertical wall after the first period is studied experimentally. The toroidal motion of the bubble after being penetrated by the jet is studied under different buoyancy effects; the variation of the jet angle with the standoff distance is shown. The work provides reference for relevant numerical and experimental studies in structural damage induced by bubbles.

Gammatone Subband Denoising and HHT-based Feature Extraction for Underwater Targets

WANG Shu-guang, ZENG Xiang-yang, WANG Zheng, WANG Qiang

2015, 36(9):  1704-1709.  doi:10.3969/j.issn.1000-1093.2015.09.015

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Underwater target recognition, as a key technique, places a great role in underwater acoustic detection. The inevitable noises decrease the performance of the system in the complex underwater acoustic environments. An underwater target recognition algorithm which includes Gammatone filter bank, wavelet threshold denoising and Hilbert-Huang transform (HHT) is proposed based on auditory perception mechanism. Gammatone filter bank is used for the simulation of auditory perception, and the wavelet threshold denoising is applied to enhance the noise robustness of the system. Hilbert-Huang transform is employed as the time frequency analysis tool and used for feature extraction. At last, the efficiency of the proposed algorithm is testified by using the measured underwater target data in the recognition experiment. The results show that the proposed method has a robust performance and good accuracy under the condition of low SNR.

The Influences of Thermophysical Properties of Enclosure on the System Energy Consumption and the Object Thermal ControlEffects under Periodic Environmental Conditions

YE Hong, ZHANG Hai-tao

2015, 36(9):  1710-1721.  doi:10.3969/j.issn.1000-1093.2015.09.016

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The influences of thermophysical properties of an enclosure on the energy consumption of an active ventilated thermal control system and the thermal control effects, such as time stability and space uniformity of the object surface temperature, under periodic environmental conditions are investigated. The effects of the thermal conductivity and volumetric heat capacity of enclosure on the average power consumption of system and the thermal control effects of object are studied based on a simplified model under the actual weather conditions. It is discovered that the influence of the volumetric heat capacity depends on the value of the thermal conductivity, the inlet air temperature as well as the average temperature of ambient air. When the average ambient air temperature is higher or lower than the inlet air temperature, the thermal conductivity becomes a dominant factor. However, when the average ambient air temperature is close to that of the inlet air, the volumetric heat capacity has little effect on the average power consumption and the thermal control effects if the thermal conductivity is less than 0.1 W/(m·K); if the thermal conductivity is higher than 0.1 W/(m·K), the increase in the volumetric heat capacity could not only reduce the average power consumption but also enhance the time stability and the space uniformity of the object surface temperature as well.

Study of Digital Infrared False-color Imaging Technology

WU Jian-ye， ZHANG Shuan-qin， YIN De-fei

2015, 36(9):  1722-1726.  doi:10.3969/j.issn.1000-1093.2015.09.017

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The infrared false-color imaging detection technology has been paid attention to. With the development of the remote sensing technology in recent years, the infrared false-color imaging detection has widely been used in the detection of vegetation, ground resources and aquatic pollution. And with the development of digital technology, the traditional photographic film would phase out. The false color film has stopped production in our country. A solution of using digital camera and near-infrared filter to achieve infrared false-color imaging is proposed by analyzing the principle of infrared false-color imaging by traditional false color film, and the algorithm is verified by experiment.

Modeling and Prediction of Cutting Forces in End Milling of Curved Surfaces

LUO Zhi-wen, ZHAO Wen-xiang, JIAO Li, WANG Xi-bin, TAN Fang-hao, LIU Zhi-bing, LIANG Zhi-qiang

2015, 36(9):  1727-1735.  doi:10.3969/j.issn.1000-1093.2015.09.018

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A novel mechanistic cutting force model is presented for end milling of curved surfaces, including the effect of instantaneous feed direction. In machining of curved geometries where the curvature varies continuously along tool path, the cutting parameters, such as feed per tooth, entry/exit angle, and instantaneous undeformed chip thickness, vary along tool path. The cutting process of curved surface is discretized into a series of steady-state cutting processes at intervals of feed per tooth, and a vector model for these parameters of each segmented cutting process is presented. The Fourier series expansion is used for deriving the cutting force model. Combined with the milling force coefficients fitted by a series of slot milling tests, the predicted cutting forces in machining PCrNi3MoVA workpiece with circular and Bezier curve geometries are achieved, respectively. The prediction accuracy of the model is validated experimentally and the predicted and measured results correspond well with each other.

Abrasive-assisted Copper Electroforming Process with Offset Anode in Sulfate Bath

REN Jian-hua, ZHU Zeng-wei, SHEN Chun-jian, TANG Xiao-cong, ZHU Di

2015, 36(9):  1736-1742.  doi:10.3969/j.issn.1000-1093.2015.09.019

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Based on the theory of two-step reduction of cupric ions in copper electrodeposition, a novel abrasive method is proposed for the abrasive-assisted copper electroforming process to make mechanical friction in sulfate solution bath. A cathode mandrel is employed to revolve in horizontal type, and the cathode basket is filled with moderate non-conductive free beads. Additionally, an offset anode is just fitted on the upper side corresponding to the area without free beads. During the electrodepositing process, for the lower electric field intensity with nonconductive free beads shielding the lower semicircle surface of the mandrel evenly, the copper ions deposit firstly on the cathode area facing the anode, and then the nonconductive and the hard beads are forced to continuously and slightly polish the coverage area on cathode surface. Consequently, the abrasive-assisted electrodeposition process is improved and the quality of the electroformed layer is improved，refraining from the burrs. The result shows that the copper ions are electrodeposited firstly by the theory of two-step reduction of cupric ions with offset anodes, and then the deposits are polished in the copper electrodeposition process. Moreover，a smooth-surfaced electroformed copper layer prepared in an abrasive-assisted way at low speed is achieved from sulfate acid bath without additives, which microstructure had been effectively modified. The grains are also refined at the same time. The microhardness of the electroformed layer is up to 139 HV, and the tensile strength is about 333 MPa at a revolving speed of 5 r/min. When insoluble anode is employed, the mechanical property of the coating is improved significantly. Eventually, a copper electroformed layer with tensile strength of 460 MPa is produced.

Research on Intelligent Precision Grinding Method and Control Model of Annular Inner and Outer sphere

HU De-jin

2015, 36(9):  1743-1749.  doi:10.3969/j.issn.1000-1093.2015.09.020

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The intelligent precision grinding method of the annular inner and outer spheres is proposed. Its principle is that the spherical center is located on the origin of the coordinate system, and the sphere rotates around y axis. In grinding process, the swing angle of grinding wheel spindle is controlled so that the center line of spindle and the normal of spherical bus grinding point always remain coincident. The size of sphere is detected in real time, the loss of the grinding wheel is automatically compensated, and the whole grinding process is automatically finished. The prototype is developed using the proposed method. The research results show that the proposed method can effectively realize intelligent precision grinding of the annular inner and outer sphere with simple control model.

Study of the Dynamic Behaviors of Ti-5553 Alloy Based on Taylor Bar Impacting Test

DU Wen-wen，WANG Lin，ZHAO Deng-hui，ZHI Mao-sheng，XU Xin

2015, 36(9):  1750-1756.  doi:10.3969/j.issn.1000-1093.2015.09.021

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The dynamic behaviors of Ti-5553 alloy under high strain rate are investigated by Taylor bar impact test and numerical simulation. Ti-5553 alloy achieves equal-axis microstructure and duplex microstructure with different mechanical properties after it is processed through two kinds of heat treatment processes. By means of numerical simulation with ANSYS/LS-DYNA software， the influences of yield stress σ_s and failure strain ε_f on the processing parameters and impact results，such as kinematic energy，velocity and acceleration， are studied on the base of Taylor bar impact tests. The yield stress is set to 1 170 ~1 400 MPa and the failure strain is set to 0.1~0.8. The experimental and numerical simulation results demonstrate that the value of yield stress has little influence on kinetic energy，velocity and acceleration during the Taylor impacting test. The higher the yield stress is，the lower the final strain of projectile is. The changing rates of energy，velocity and acceleration improve slightly. For Ti-5553 alloy with the equal-axis microstructure， the changing rates of energy，velocity and acceleration increase with strain rate for ε_f<0.7，and the projectile has no spring back. For ε_f ≥0.7，the curves of processing parameters coincide with each other and the projectiles spring back. When failure strains are defined as 0.75 and 0.35 for the equal-axis and duplex microstructure alloys, respectively，the numerical simulation results are in good accordance with the actual Taylor experimental results.

The Method of Gear Residual Stress Measurement Based on Ultrasonic Technology

PAN Qin-xue， LIU Shuai， XIAO Ding-guo， JIN Xin

2015, 36(9):  1757-1765.  doi:10.3969/j.issn.1000-1093.2015.09.022

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Gear has been widely used in each field, such as equipment manufacturing, due to its important role in mechanical transmission. With the development of defense industry, the higher performance requirements of gears, such as fatigue life, transmission efficiency and reliability, are raised. Gear always fails in its service life. The fatigue pitting and fatigue crack are two main fatigue failure modes of gear. The two fatigue failure modes seriously influence the transmission performance and reliability. The residual stress is one of the main factors of fatigue failure. The traditional methods are difficult to measure the residual stress accurately and fast due to the complex shape of gear and the limited space. A new method is proposed to measure the gear residual stress by using L_CR. Propagation laws of critically refracted longitudinal wave on the tooth surface and near the tooth root are studied, and a special transducer and an automatic detection device for measuring the residual stress are designed. The experimental results indicate that the residual stress of gear can be measured accurately and fast with L_CR.

A Method to Eliminate the Influence of Material Properties on Pulsed Eddy Current Defect Profile Reconstruction

ZHU Hong-yun, WANG Chang-long, WANG Jian-bin, JIANG Tao

2015, 36(9):  1766-1771.  doi:10.3969/j.issn.1000-1093.2015.09.023

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When pulsed eddy current testing signal is used to reconstruct defect profile, the signal features of the same defect for different materials are different, and the reconstruction accuracy of defect profile is influenced by the material properties. In order to eliminate the influence of material properties on defect profile reconstruction, a defect profile reconstruction method based on invariance function is proposed. The two features that can characterize the same defect are utilized to construct the invariance function which can eliminate the influence of material properties. A nonlinear mapping model from testing signal to defect profile is established, and the defect profiles of different materials are reconstructed. The approach is utilized to reconstruct the defect profiles of different materials. The results indicate that the proposed approach can eliminate the influence of material properties effectively and reconstruct the defect accurately, and the performance of noise interference suppression of the method is high. It is an effective and feasible approach for defect reconstruction.

Research on Variation Law of Fatigue Crack-tip Displacement and Strain Fields Based on High-speed Digital Image CorrelationMethod

GAO Hong-li， LIU Huan， QI Zi-cheng, LIU Hui， ZHENG Huan-bin

2015, 36(9):  1772-1781.  doi:10.3969/j.issn.1000-1093.2015.09.024

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In order to research the variation laws of displacement and strain fields on the fatigue crack tip area of the compact tension（CT）specimen in the stage of steady crack propagation under high frequency sinusoidal alternating load, a method based on the digital image correlation (DIC) and digital high-speed photography technology is proposed. A series of digital speckle images of CT specimen under sinusoidal alternating load are collected by digital high-speed photographic equipment, and the displacement and strain fields on the crack tip in each image are calculated by DIC. The sinusoidal changing strain curve of the feature point on the fatigue crack tip area is obtained by the least square sine wave fitting method, and the characteristic parameters of sinusoidal strain, such as amplitude, frequency, phase and mean load, are calculated. The images of characteristic position in a stress cycle are obtained by comparing the fitted sine curve of strain with the corresponding speckle images. Then the strain values at the tip of CT specimen during one stress cycle are measured by dynamic strain gauge. The results show that the maximum measurement error of strain by DIC method is 4.12% . On this basis, the resonant fatigue crack propagation test is carried out based on the high-speed photography and digital image correlation method, the relationship between strain amplitude values at crack tip and fatigue cycle number before the fatigue crack extension, and the variation laws of displacement and strain fields on crack tip area with the different lengths of fatigue crack are studied.

Stress Analysis of Single-strand Wire Rope Based on Elastic-plastic Constitutive Model

REN Zhi-qian, YU Zong-yue, CHEN Xun, WANG Yan-lei

2015, 36(9):  1782-1789.  doi:10.3969/j.issn.1000-1093.2015.09.025

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In order to reveal the failure of single-strand wire rope under impact load, the structural elastic-plastic attributes are analyzed by using the dimensional finite element model (FDM). According to the experiment data and wire structure, the parameters of the elastic-plastic model are determined, and a 3D FEM is established. Von Mises stress and plastic strain of the internal wire are deduced by calculating the static loading and impact loading. The results show that the Von Mises stress and plastic strain of the contact area are bigger than those of other areas, which is the main reason for the rope break.

Nonlinear Dynamic Characteristics of Cracked Rotor System Based on Fractional Order Calculus

LI Zhi-nong, WANG Hai-feng, XIAO Yao-xian

2015, 36(9):  1790-1798.  doi:10.3969/j.issn.1000-1093.2015.09.026

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Nonlinear dynamics model of cracked rotor system with fractional order damping under the condition of nonlinear eddy is investigated and simulated by the Runge Kutta method and continued fractional expansion Euler method. The effects of derivative order, rotating speed ratio and crack depth on the nonlinear dynamic characteristics of cracker rotor system with fractional damping are discussed. The simulation results show that the model of cracked rotor system established with fractional order can reveal the nonlinear dynamics characteristics of a rotor system with fractional characteristics. In the same crack depth and fractional order, the rotor system gets chaotic, period-doubling and periodic motions as the factional order increases. In the same rotating speed ratio and fractional order, when the crack depth is small, the rotor system doesn’t appear complex bifurcation and chaos phenomena. With the increase in crack depth, the stiffness of rotor system reduces and the rotor system presents the complex vibration characteristics. The crack fault feature becomes more obvious. The rotor system gets from periodic motion to period-doubling motion. The double frequency component is dominant, and simultaneously other frequency multiplication component also appears. These valuable conclusions provide the important reference for the fault diagnosis of cracked rotor.

Research Notes

Study of Control Strategy for Power Train Based on ISG Hybrid System

XIAO Lei, HAN Xue-feng, CHEN Rui, XING Jie, HUANG Guan-fu

2015, 36(9):  1799-1804.  doi:10.3969/j.issn.1000-1093.2015.09.027

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A high density power-train system based on ISG motor is designed for the future military hybrid vehicles, and the structure of the system is designed. The line-based control strategy of the power-train system is established，and also the control objectives and working mode are divided. A backward-simulation model of ISG hybrid system based on ADVISOR is established. The performance of ISG hybrid system based on the parameters of a subsection ISG motor and diesel engine is simulated. The result shows that the power-train system can improve the torque characteristic greatly, and enhance the torque ratio-t ranges. The power-train system can also optimize the working points of engine to reduce the average fuel consumption rate of diesel engine.

Research on Evaluation Method of Armored Vehicle Crew's Mental Workload Based on Task-network Model

LIU Wei-ping， NIE Jun-feng， JIN Yi， BAI Ya-juan

2015, 36(9):  1805-1810.  doi:10.3969/j.issn.1000-1093.2015.09.028

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A method of evaluating the mental workload of armored vehicle crew based on task-network model is proposed based on multiple resource theory (MRT), and a crew's task-network model based on information executive channel is built in terms of information processing method under consideration of armored vehicle crew's operation characteristics. An example of target discovering and firing task of an armored vehicle gunner is analyzed and evaluated. The results indicate that the proposed method could describe the change of crew's mental workload during the whole task. The time nodes and reasons of abnormal mental workload could be found out effectively using the proposed method and the mental workload of crew could be quantitatively evaluated.

Research on Gun Pointing Control of a Full Closed-loop Aiming System

LI Wei, YANG Gang, CHEN Teng-fei, HAN Chong-wei

2015, 36(9):  1811-1818.  doi:10.3969/j.issn.1000-1093.2015.09.029

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A strapdown inertial navigation system (SINS) is used to measure the pointing of gun barrel for aiming for a tracked self-propelled gun. However, it causes the control coupling of pitching servo and azimuth servo, and the aiming accuracy can be easily affected by vehicle posture. According to the full closed-loop aiming system model under vehicle coordinates, the servo control model under quasi geodetic coordinates including the disturbance of mismatched uncertainty is obtained. Active disturbance rejection controllers (ADRCs) are designed for each axial servo system, considering the coupling and modeling errors to be external disturbance. ADRC can observe the external disturbance and compensate the nonlinear state error feedback controller to eliminate the overshoot caused by it. Thef servo aiming system is simulated under the conditions of initial attitude of vehicle level and inclination of 6 degree. The results show that, compared with the adaptive sliding mode variable structure control, the servo system using ADRC strategy obtains more steady and more accurate targeting results, and gets smoother controller output, meanwhile suppresses the unmatched uncertain interface effectively.

The Influence of Dynamically Changing Firing Zone on Weapon-target Assignment under Ship Swaying

YU Xu-tong, WU Ling, LU Fa-xing

2015, 36(9):  1819-1824.  doi:10.3969/j.issn.1000-1093.2015.09.030

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The dynamic change of firing zone under ship swaying and its effect on the weapon-target assignment (WTA) are studied. A target moving model in the deck reference system is built, and a ship swaying error angle (SSEA) model is proposed, which can illustrate the relationship between the target position and the firing zone under swaying. The rules of WTA under swaying are drawn with the SSEA as an evaluation index. The maximum SSEAs in four sway modes are computed via simulations. The results show that the maximum SSEA can be used as a valid basis for WTA under the ship swaying and provides a reference for designing the firing overlap zone.