Table of Content

24 August 2018, Volume 39 Issue 8

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Contents

2018, 39(8):  0. 

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Paper

Research on the Application of Shaped Charge Metal Jet in Antenna

PAN Xu-chao， SUN Meng-xiao， HE Yong， SHEN Jie， CHEN Hong， ZHANG Jiang-nan

2018, 39(8):  1457-1465.  doi:10.3969/j.issn.1000-1093.2018.08.001

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Transient miniaturized antenna is a hot topic in antenna technology research. For the application of shaped metal jets in miniaturized antennas, a research method combining theoretical analysis and numerical simulation is used. 50 mm conical shaped charge is taken as research object, a dipole antenna formed by a shaped metal jet antenna is theoretically analyzed, and the applicability of the shaped metal jet antenna to the charge structure and explosive material is numerically studied using finite element software LS-DYNA. The results show that the metal jet antenna formed by shaped charge meets the characteristics of transient miniaturization and has the length, continuity and good interface matching with the wavelength. The shaped metal jet needs to have a certain length and body when it is used as an electromagnetic pulse radiating antenna, larger gain can be obtained with a transition between the jet diameter and the slug diameter and the small change in the slug. The input impedance is minimized when the metal jet is not fully formed. The metal jet formed by the small cone angle cover better meets the antenna requirements. When the thickness of liner is 2.1-2.3 mm, the length of the formed metal jet antenna is the largest, and there exists an extreme value of radiation frequency. The forming velocity of jet antenna due to B-explosive charge exploding is greater than that of the JH-2 and TNT, and the B-explosive charge explodes to produce a metal jet with the best fracture time, the largest slug radius is moderate, and the longest antenna length is available at the time of fracture. When used as an antenna, the radiated frequency range is the largest and is more suitable for use as a shaped metal jet antenna. Key

Research on Fatigue Damage of Transmission Shaft in the Process of Main Clutch Engagement During Starting of a LightTracked Vehicle

ZHAO Zi-ye， LIU Hai-ou， CHEN Hui-yan， XU Yi

2018, 39(8):  1466-1472.  doi:10.3969/j.issn.1000-1093.2018.08.002

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This paper tries to figure out the fatigue damage of transmission shaft of transmission system caused by the engagement of main clutch under typical operating conditions, and then analyze the main factors causing the fatigue damage of transmission system. A dynamic model of vehicle starting is built to obtain the relationship between the vehicle transmission system load and the engagement displacement value of main clutch. A testing platform of tracked vehicle is built to get the test data of transmission system under typical operating conditions. The dynamic tests of stepper engagement of main clutch are designed to collect the torque data transmitted by the transmission system in the process of main clutch engagement. Finally, the rain-flow counting method and rain-flow filtering method are used to process the original data, and then the linear fatigue cumulative damage theory is used to calculate the fatigue damage of transmission shaft in transmission system to determine the engaging state of main clutch when the maximum fatigue damage is caused to the transmission system. The results show that the displacement point at which the axial moving speed of the driven plate changes the most is the danger point when the maximum fatigue damage is caused to the transmission shaft, which is accounted for 73.86% of the total damage, and the damage degree is 2.87 times of the main clutch fully synchronized state. Key

Heat Balance Experiment of Polyether Oxygenated Fuel for Diesel Engine in Plateau Environment

WANG Xu-dong， XIONG Chun-hua， LU Chang-bo， AN Gao-jun， WANG Feng

2018, 39(8):  1473-1478.  doi:10.3969/j.issn.1000-1093.2018.08.003

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A type of military vehicle diesel engine is taken as the research object for heat balance experiment in a simulated environment of an elevation of 4 500 m. The heat distributions of the diesel engines fueled with automobile diesel fuel and oligomeric polyoxymethylene dimethyl ether oxygenated fuel under the same power condition are compared and analyzed. Results show that the ignition delay period is shorten, the pressure rising rate is decreased, the heat losses in coolant and exhaust are decreased, and the heat efficiency is improved when the diesel engine is fueled with the oxygenated fuel in the simulated plateau environment. The oxygenated fuel could alleviate the engine burning delay and thermal load aggravation in plateau environment effectively. These results suggest that the oligomeric polyoxymethylene dimethyl ether is a suitable fuel for diesel in plateau environment. Key

Modeling and Control of Pointing-stabilizing-tracking System for Marching Guns

LI Wei， JIANG Jun-feng， REN Hai-bo， ZHANG Guang-hui

2018, 39(8):  1479-1490.  doi:10.3969/j.issn.1000-1093.2018.08.004

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A stabilizing and tracking control strategy of using a strapdown inertial navigation system(SINS) to measure the pointing direction and angular rate of gun barrel is proposed to enable the mar-ching guns to track targets and stabilize at a large fire angle, in which the stabilizing and tracking control are accomplished in the geodetic coordinate system. The conventional three-loop control is applied and improved, and the reference and feedback values of position loop and velocity stabilization loop are given in the geodetic coordinate system. As the position feedback, the azimuth and pitch angular rates of SINS are resolved based on the geodetic coordinate system. The measured values of gyros in SINS mounted on the gun are transformed to the azimuth and pitch angular rates in the geodetic coordinate system, and re multiplied by the drive ratios of drive mechanisms as the feedback of velocity stabilization loop. A dynamic coupling model of gun, turret and carrier is established using Lagrange equation in consideration that the rotary center of turret and carrier is misaligned, and the carrier moves in six degrees of freedom. The simulation validation of the proposed control scheme is conducted based on SINS measurement model, two-motor drive model and control model of motor servo system. The result shows that the two-channel independent control, the high-accurate stabilizing control of pointing direction of gun at a large fire angle, the high tracking performance in a certain range of firing angle, and the isolation of wider frequency band disturbance from carrier can be realized. Key

Design and Trial-manufacture of a Coaxial Pulsed Power Cable

LI Zhen-xiao， JIN Yong， YANG Dong， WAN Gang， LI Bao-ming

2018, 39(8):  1491-1498.  doi:10.3969/j.issn.1000-1093.2018.08.005

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According to the research requirement of engineering in an electrothermal-chemical gun, a pulsed power cable was designed and developed, which is suitable for coaxial breech transmission system. The index parameters of pulsed power cable are analyzed and determined based on the pulse current and internal overvoltage data obtained from launch tests and the experience of common commercial high power cables. The structure design of pulsed power cable is carried out. Compared with common commercial high power cable, the shielding enhancement and semi-conductive layers are added in pulsed power cable. The strengthening shielding layer is used to improve the mechanical strength, which can restrain the strong electrodynamic force produced by the core dislocation of outer conductor, thus preventing the deformation and burst of cable, and improving the electromagnetic shielding effect. The semi-conductive layer is used to eliminate the air gap and balance the electric field. The electromagnetic field and thermal analyses of pulsed power cables are carried out by using simulation software, which assists in aided design of electrical strength, mechanical strength and temperature rise characteristics. In view of the breaking and tearing of the inner core end of pulse power cable in other systems, a steel core was designed to improve the tensile strength of inner conductor. Withstand voltage test and pulse discharge test show that the performance of pulsed power cable meets the requirements of the development. It is not damaged under the action of 25 kV/5 min voltage, and is not deformed under the action of pulse current with amplitude of 203 kA and half peak time greater than 2 ms. Key

Research on the Volume and Line Fractal Dimensions of Fragments from the Explosion of Warhead Shell

YANG Yun-chuan, ZHU Jian-jun, ZHENG Yu, LI Wen-bin, WANG Xiao-ming, QIAO Xiang-xin， LI Rui

2018, 39(8):  1499-1506.  doi:10.3969/j.issn.1000-1093.2018.08.006

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The fragment characteristics and inherent features of metal shells under instantaneous explosion loading are presented. An experiment is designed to measure the fragmentation of a steel cylinder shell filled with high explosives. The expressions for the volume and line fractal dimensions of the fragments are obtained by using fractal mathematical models. The volume fractal dimension D₃, which is used to describe the mass or size distribution of the fragments, and the line fractal dimension D₁, which is used to describe the projected contour of fragments, are measured by using a MATLAB mathematical model. The results reveal that the characteristic mass distribution and morphology of the fragments are statistically self-similar and can be characterized by the fractal dimension. The line fractal dimension D₁ is 1.298 7, the volume fractal dimension D₃ is 2.385 9, and the resulting volume and line fractal dimensions meet the relationship D₃+2D₁=5. Key

Experimental Research and Numerical Simulation of Coupling Combustion of Pulsed Jet and AP/HTPB Propellant

YE Zhen-wei， YU Yong-gang

2018, 39(8):  1507-1514.  doi:10.3969/j.issn.1000-1093.2018.08.007

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An AP/HTPB two-dimensional sandwich combustion model is established to study the oscillating combustion process of AP/HTPB under the action of pulsed jet. A two-step total package reaction is used for the gas phase zone. The effect of pulsed jet is simulated by user defined functions (UDF). In the coupling combustion experiment of AP/HTPB and igniter, the numerical simulation is carried out at the pulse frequency of 125-500 Hz, and the peak value of heat flux is 1.9-3.9 MW/m². The results show that the gas-phase thermal feedback is weak relative to the pulsed jet in the initial stage of oscillating combustion. X component (NH₄ClO₄) is periodically changed because of the leading effect of pulsed jet. After the gas phase temperature rises, the gas phase thermal feedback is stronger than the effect of pulsed jet, the outflow effect is lost, and the AP/HTPB combustion is stabilized. The increase in heat flux density of ignition jet significantly inhibits the oscillating combustion of AP/HTPB, and the increase in ignition jet frequency has weaker inhibitory effect on AP/HTPB oscillating combustion.Key

Optimal Trajectory Correction in Midcourse Guidance Phase Considering the Zeroing Effort Interception

ZHOU Jin， LEI Hu-min

2018, 39(8):  1515-1525.  doi:10.3969/j.issn.1000-1093.2018.08.008

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An optimal midcourse trajectory correction algorithm considering the zeroing effort interception is designed for the defensive combat in near space. The zeroing effort interception condition is derived by analyzing the relative motion of interceptor and target in the terminal guidance phase, which is uniquely determined by the velocity ratio of target and interceptor and the respective angles among their velocity vectors and the line-of-sight. In terms of the cases where the nominal trajectory fails to satisfy the zeroing effort condition due to the updated target information, a scheme of optimal trajectory correction in the midcourse guidance phase is proposed to modify the interceptor states to re-satisfy the zeroing effort interception condition at the handover moment in the midcourse and terminal guidance phases. The compensation commands of control are derived by further differentiating the first order optimal conditions and transversality conditions that are satisfied by the nominal trajectory. The deviations of interceptor initial states and terminal constraints are considered in the resolving of compensation commands. The simulated results testify the effectiveness and the superiority of the proposed method.Key

Infrared Dim Small Target Detection Based on Multi-scale Local Contrast and Multi-scale Gradient Coherence

LIU De-peng， LI Zheng-zhou， ZENG Jing-jie， XIONG Wei-qi， QI Bo

2018, 39(8):  1526-1535.  doi:10.3969/j.issn.1000-1093.2018.08.009

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A novel algorithm based on multi-scale local contrast method and multi-scale gradient coherence method is proposed for the high false alarm of infrared dim small target caused by complex background and heavy clutter. The multi-scale local contrast method is used to enhance the infrared dim small target in infrared image, and the multi-scale gradient coherence method is used to avoid the false alarms caused by complex background and heavy clutter. The proposed algorithm is compared with max-mean, max-median, top-hat, IPI and MGDWIE algorithms in terms of signal-to-noise ratio（SNR）gain, mean absolute value of residual background, detectivity and false alarm rate. The proposed algorithm achieves higher SNR gain, lower mean absolute value of residual background, higher detectivity and lower false alarm rate compared to the baseline algorithms. The experimental results show that the proposed algorithm can effectively reduce the false alarm rate under the disturbance of complex background and heavy clutter.Key

Analysis of Astern Moving Performance of Bionic Water-surface Vector Propeller

ZHANG Zhong-zhi, LYU Jian-gang, SONG Bin, LIU Jin-hua, ZHU Wen-jie

2018, 39(8):  1536-1547.  doi:10.3969/j.issn.1000-1093.2018.08.010

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For the complex astern moving structure of amphibious platform and its performance study, a new mode of astern moving is presented based on the water-surface bionic vector propeller, and a new amphibious platform is designed. The straight astern moving of 0.7 m/s and the astern steering of small-radius of about 0.75 m are realized by rotating the propeller reversely. A fluid dynamics model of propeller is set up to analyze the influences of height, spoke length, rotational velocity and blade angle on three-dimensional output performance of astern moving with periodic output. So the study of the flow due to rotating of flat plates is further enriched. And the calculation model is validated by using the open water test system of vector propeller. The results show that the turning moment decreases with the increase in height of propeller axle; the down push force and drag force are linear with the spoke length, and the turning moment is quadratic functions to spoke length; and three-dimensional driving outputs increase with the increase in rotational velocity of propeller. Key

Cavity and Hydrodynamic Characteristics of Sphere Entering into Water during Film Boiling

LI Jia-chuan, WEI Ying-jie, WANG Cong, DU Yan-feng

2018, 39(8):  1548-1555.  doi:10.3969/j.issn.1000-1093.2018.08.011

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The cavitation evolutions in water entry processes of sphere during film boiling and the hydrophilic and superhydrophobic room temperature spheres were recorded using a high-speed video camera. The curve of water entry depth is obtained by image processing. Based on computational fluid dynamics method, the volume of fluid (VOF) multiphase flow model and evaporation-condensation model are used to simulate the water entry process of sphere. The numerical results are in good agreement with the experimental results. The results show that the film boiling sphere can produce the same smooth cavitation as the superhydrophobic sphere does. The line of contact between the superhydrophobic sphere surface and the cavity wall is slightly above the center of the sphere. A vapor layer exists between the bottom of film boiling sphere and the water, the cavity wall does not contact with the surface of sphere, and the cavity diameter near the sphere is relatively large. When the water is shallow, the drag coefficient of hydrophilic sphere is relatively large; and when the water is deep, the drag coefficients of superhydrophobic and film boiling spheres are relatively large. Key

Hydrodynamic Properties and Motion Analysis of Hybrid-driven Underwater Glider with Flying Wings

WANG Jin-qiang， WANG Cong， WEI Ying-jie， ZHANG Cheng-ju

2018, 39(8):  1556-1564.  doi:10.3969/j.issn.1000-1093.2018.08.012

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A new hybrid-driven underwater glider with flying wings is designed to improve the comprehensive properties of underwater glider. The shear stress transmission （SST） turbulence model based on Openfoam software is used to investigate the hydrodynamic characteristics of underwater glider at the velocities ranging from 0.5 m/s to 3.0 m/s, and the angle of attack or drift angle ranging from 0° to 21°. And the numerical results are validated by comparing with the experimental data. In addition, the dyna-mics and kinematics models based on the multi-body dynamics are presented to simulate the motion characteristics, with considering the various velocities of moving sliders and the pump system quality. The numerical results are validated by comparing with the experimental data. The results indicate that the numerical results are in well agreement with the experimental data, which verifies the accuracy of the proposed numerical method. Compared with the traditional hybrid-driven underwater glider, the hybrid-driven underwater glider with flying wings has more excellent hydrodynamic performance and gliding economy, its drag coefficient increases faster with the increase in angle of attack, and increases slower with the increase in drift angle. Key

Research on Macroscopic and Microscopic Mechanisms of Deformation of Armor Steel in Multilayer Heterogeneous CompositeTarget Subjected to Projectile

GAO Hua， XIONG Chao， YIN Jun-hui

2018, 39(8):  1565-1575.  doi:10.3969/j.issn.1000-1093.2018.08.013

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The anti-penetration experiments of composite targets with different structures were carried out to study the influence of the arrangement of armored steel in multi-layer heterogeneous composite target on the microscopic mechanism and force state of plastic deformation. The microscopic mechanism of plastic deformation of bullet holes in armor steel is studied based on the theory of metal materials science. The surface hardness distribution and microstructure evolution of armored steel craters are analyzed. The internal relation between the mechanical behavior and deformation mechanism of projectile penetrating into the armored steel is studied through numerical simulation. The results show that the wave impedance matching is from high to low, the stress wave generated by projectile impact is reflected from the interface between the layers, resulting in the formation of a tensile wave and the crack propagation to reduce the projectile penetration resistance; the internal structure of adiabatic shear zone is affected by temperature and extrusion load, producing high-hardness martensite grains and hindering continued plastic deformation; and the higher the strength and stiffness of armored steel backplanes are, the more is the dislocation movement caused by plastic deformation of armor steel hindered, which is conducive to improve the penetration resistance of target plate. Key

Experimental Research on the Influence of ERA on Penetration Efficiency of EFP

NIE Yuan, JIANG Jian-wei, WANG Shu-you, LIU Han

2018, 39(8):  1576-1581.  doi:10.3969/j.issn.1000-1093.2018.08.014

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The experiment of stretched rod copper explosion formed projectile (EFP) formed by the shaped charge penetrating into main target add-on typical explosive reactive armor（ERA）with different oblique angle were conducted to reveal the effect of sandwich ERA on penetration efficiency of EFP. The pulsed X-ray photographs of the interaction between ERA and EFP were obtained by flash X-ray experiment, together with residual depth of penetration (RDOP) of residual EFP. The results show that RDOP has a nonlinear decreasing tendency as oblique angle raises. The drop of penetration depth of EFP passing through ERA exponentially increases with ERA oblique angle. When the oblique angles of ERA are 0° and 30°, RDOP and drop of penetration depth keep stabile. But when it grows from 30° to 60°, RDOP declines from 0.50 D to 0.19 D, and the drop of penetration depth grows rapidly from 41% to 77%. On the other hand, the increment of layer thickness results in a heavier reduction in RDOP and the increase in the drop of penetration depth. ERA with 0.027 D layer thickness makes the drop of penetration depth higher 8% on average than it with 0.018 D. The reason for RDOP reduction is analyzed for researching the mechanism of action of EFP and ERA. Key

On the Deformation of Thin Plates Subjected to Confined Blast Loading

ZHENG Cheng， KONG Xiang-shao， ZHOU Hu， XU Wei-zheng， WU Wei-guo

2018, 39(8):  1582-1589.  doi:10.3969/j.issn.1000-1093.2018.08.015

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In confined explosion, the quasi-static pressure in the enclosed space exists for a long time, and has an important effect on the ultimate deformation of structures so that the dynamic response of structures under confined blast loading is quite different from that under free air blast loading. The dynamic response of square plates under confined blast loading is analyzed. Based on the deformation regularity of thin plates under impact load, a new dimensionless damage number with clear physical meaning is proposed for the deformation prediction of structures under confined blast loading. The influences of the volume of enclosed space, explosive energy, structural dimensions,and strength of material on the deformation response of structure are considered for the dimensionless damage number. The analysis result shows that there is a clear linear relation between the mid-point deflection-thickness ratio and the new dimensionless damage number. An empirical expression with good correlation is presented for deformation prediction of structures under confined blast loading. The influences of membrane force and plate thickness on the structural response are considered in the new dimensionless damage number, which makes it have a wider application with regard to deformation prediction of plates subjected to confined blast loading, especially when the plate experiences large deflection.Key

An Improved Discrete Krill Herd Algorithm for Complex Product Assembly Scheduling Problem

ZHUANG Cun-bo， XIONG Hui， LIU Jian-hua， TANG Cheng-tong

2018, 39(8):  1590-1600.  doi:10.3969/j.issn.1000-1093.2018.08.016

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An improved discrete krill herd (IDKH) algorithm is proposed for the complex product assembly scheduling problem. The objective is to minimize the makespan. An assembly scheduling model is established by analyzing the characteristics of a complex product process flow. The transformation between scheduling solution and population individual is realized by using permutation-based coding and heuristic-based decoding methods. A local search and a restart operation procedure are presented to improve the exploitation and global exploration ability of basic krill herd (KH). The parameters of the proposed IDKH are calibrated by using a design of experimental approach. And a comparative evaluation is conducted with the well-known algorithms. The results show that the proposed IDKH has advantage over genetic algorithm, estimation of distribution algorithm, gravitational search algorithm, and basic KH in terms of quality and stability. Key

Simulation Experiment of Centrifugal Casting Based on 1∶80 Scale Reduction Experimental Machine

XU Xin-li， ZHANG Xin-ming， CAI Peng， YU Yang， ZHAO Li-xin

2018, 39(8):  1601-1606.  doi:10.3969/j.issn.1000-1093.2018.08.017

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The centrifugal casting technology of large aperture aspherical mirror is studied for the centrifugal casting experiment of aspherical mirror in the laboratory environment, and the feasibility of the method is verified. A 1∶80 scale experimental machine was designed by studying the similarity criterion of temperature field and the matching method of scaled model parameters in the centrifugal casting process of large aperture aspherical mirror, and the physical simulation experiment was carried out. The temperature field, stress field and final surface shape deviation of mirror were measured. The experimental results are compared with the simulated results. The relative error between the measured and simulated temperatures of temperature field is between 1.0% and 1.4%. The maximum compressive stress is reduced to 0.98 MPa when the aspherical mirror is properly insulated near t_g. The measured surface shape deviation of aspherical mirror is -83.823 3 μm, which is consistent with the simulated result. The non-observable parts in the process of centrifugal casting can be studied through simulation and experiment. Key

A Perturbation-theory-based Analytical Method for the Dual-mode Dielectric Resonator Measuring the Dielectric Properties

YUAN Cheng-wei， CHEN Ming， LUO Wei-feng， ZHANG Qiang

2018, 39(8):  1607-1611.  doi:10.3969/j.issn.1000-1093.2018.08.018

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A simple analysis method based on cavity perturbations theory is proposed to reduce the data processing complexity of using the dual-mode dielectric resonator to measure the dielectric properties of medium. The positioning steps in the resonator are considered as a perturbation structure. The cavity structure perturbation theory and material perturbation theory are used to obtain an approximate calculation method. Dielectric constants and loss tangents of several samples are analyzed and compared with the results obtained by mode matching method. The maximum relative deviations of calculated dielectric constants and loss tangents obtained by the two methods are less than 0.5% and about 5%, respectively. Key

Research on On-machine Measurement Method for Outer Diameter of Spinned Ultra-thin-walled Rotational Parts

WEN Xue， TAN Jian-ping， LIU Su-qi， LI Xin-he

2018, 39(8):  1612-1621.  doi:10.3969/j.issn.1000-1093.2018.08.019

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For more precise measurement of outer diameter of spun ultra-thin-walled rotational parts, the on-machine measurement of the equivalent outer diameter based on the reconstructed cross section contour curve is proposed. In this method, three sets of line laser displacement sensors are distributed uniformly along the circumferential direction， and the outer contour data of the cross section of rotational part at any axial position is obtained by using the three sets of line laser displacement sensors and the axial movement module of the spinning roller frame. The complete cross section outer contour data is spliced by the coordinate transformation and matching of the cross section data obtained by the three sensors, the contour curve is reconstructed by the shape preserving curve reconstruction method of discrete data points, and the equivalent outer diameter of the cross section is calculated according to length invariance of the same closed curve. Finally, the outer diameters of the mandrel and the thin-walled rotational parts are mea-sured. The experimental results show that the proposed method can be used to precisely measure the outer diameters of ultra-thin-walled rotational parts with measuring accuracy of 0.019 mm. Key

Research on a New Reliability Assessment Method for Zero-failure Data

LI Hai-yang, XIE Li-yang, LI Ming, LI Qiang, ZHONG Hai

2018, 39(8):  1622-1631.  doi:10.3969/j.issn.1000-1093.2018.08.020

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In order to analyze the reliability of the high reliability electronic and electromechanical products, a modified unilateral confidence limit analysis method under the condition of zero-failure data is proposed, which introduces the failure information into the confidence limit analysis. The failure rate of the product is estimated by Bayes parameter, and the data of the product with different truncation times are obtained. The time coefficients are equivalently replaced according to the proposed method, and then the reliability of product and the mean time between failures can be known. Based on the zero-failure data of a robot stepping motor, the calculated results of the proposed method is compared with those of the other unilateral confidence limit methods. The results show that, under the confidence level of 0.99, the mean time between failures of the product is 37 080 h, which is less than the calculated result of other confidence limit methods. The reliability of the product is estimated to be 0.973 by using the proposed new method when the mission time reaches 1 000 h. The example analysis proves the effectiveness of the new method in the reliability evaluation of zero-failure data products, and can prevent the product reliability and the mean time between failures estimation from occurrence.Key

Modeling of Inventory Allocation of Equipment Repairable Spare Parts in Two-echelon System Based on (TS) Inventory Policy

WU Long-tao， WANG Tie-ning， KE Rong-bo， CAO Yu

2018, 39(8):  1632-1638.  doi:10.3969/j.issn.1000-1093.2018.08.021

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The dominant multi-echelon inventory models for repairable spare parts are based on (S-1, S) inventory policy, which means that the failed item is sent back to a depot immediately and a spare part application is issued to the depot at the same time once an item fails at a base. The army has a lot of items to manage, however, frequent application and transportation will bring considerable fare and work-load. In order to address this problem, a two-echelon inventory allocation model is established based on (T, S) inventory policy. The support process of repairable spare parts based on (T, S) inventory policy is illustrated, in which both the returning of failed items and the application of spare parts are completed in a period instead of immediate. The evaluation indexes of spares support effectiveness are presented with the consideration of obsolescence rate and application delay, aiming to minimize the support expense while satisfying the equipment availability constraint. An adapted marginal analysis is then proposed to find the best answer of the model. Finally, an example is shown to prove the effectiveness of the proposed model, and (T, S) and (S-1, S) are compared. The result shows that, compared to (S-1, S), (T, S) is more suitable for spare parts with relative high failure-rate and low price.Key

Research Notes

Experimental Investigation into the Damage Effect of Methane Explosion Shock Wave on Animals in Enclosed Pipeline

WANG Hai-bin, ZHAO Ying-hu, GAO Li, TAN Ying-xin, WANG Lin-bian, YANG Liu

2018, 39(8):  1639-1647.  doi:10.3969/j.issn.1000-1093.2018.08.022

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The pathological features and specific causes of lung, liver and spleen injury of rats induced by methane explosion in a pipeline are analyzed to provide evidences for the clinical treatment of injury caused by gas explosion. The damage effects of shock wave on the rats in different positions in the pipeline are observed by using the model of methane-air premixed gas explosion shock wave impacting on rats. The damage effect of shock wave on lung，liver and spleen and its mechanism are studied from the histopathology. The results show that the severity of injury of rat in the front end of pipeline is more serious than that in the rear end after the explosion of methane. However, the injury of its lung tissue at the rear end of pipeline is damaged by shock wave more significantly than that of rats in the front end. The alveolar collapse is obvious, and the connection between type Ⅰ lung cells and type Ⅱ lung cells is broken and disappeared. One of 5 rats died at the front end of pipeline, and 5 rats all died in the rear end of pipeline. The damage of liver tissue is mainly vacuolar degeneration of liver cells, blood sinus congestion, and significant hemorrhage. Some varying degrees of congestion, bleeding, inflammatory cell infiltration, and necrosis and abscission of bile duct epithelial cells appear in portal area. It is found that the neutrophils of survival animals were infiltrated. The injuries of lung, liver and spleen can be observed in methane explosion model. The lung injury is obvious and fatal. Microstructure and ultra-structure of lung indicate that lung is the most sensitive organ, which is the primary target organ impacted by shock wave. Key

Modeling and Simulation of Micro-cutting Mechanism of Single Crystal SiC by Molecular Dynamics

WANG Chao， LI Shu-juan， CHAI Peng， YAN Jun-chao， LI Yan

2018, 39(8):  1648-1654.  doi:10.3969/j.issn.1000-1093.2018.08.023

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Single crystal SiC has high hardness and brittleness, resulting in its processing difficulties. The surface quality and processing precision of single crystal SiC can be significantly improved only when it is processed in the nano-scale plastic range. At the nanoscale, however, the change of material at femtosecond/picosecond cannot be obtained using finite element and experimental methods. The molecular dynamics（MD） is used to model the cutting process of single crystal 3C-SiC. The cutting force is changed at different cutting speeds and depths. The results show that the average tangential cutting forces are 737.34 nN, 635.29 nN and 587.09 nN at the cutting speeds of 50 m/s, 100 m/s and 200 m/s, respectively, and an appropriate cutting speed is helpful to reduce the cutting force for the single crystal SiC. Key

Research on Round-based Modeling Method for Firepower Distribution Optimization Problem

XUE Hui， LIU Tie-lin， QIAO Zhi-jun， YANG Zhao-kun

2018, 39(8):  1655-1664.  doi:10.3969/j.issn.1000-1093.2018.08.024

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For the difficulty in the quantitative evaluation of target threat, and the great difference in the damage effects of different weapons with different ammunition against different targets, an firepower distribution optimization model is established, in which the maximum combat effectiveness index is taken as the objective function, and an weapon-ammunition-target assignment method is proposed based on weapon-target assignment. In the proposed model, the combat effectiveness index of weapon is taken as a basis of firepower distribution, which can effectively determine the threat degrees of different targets. The model is used to determine the equipment combat effectiveness, ammunition consumption and equipment utilization scheme during rounds, and also effectively solve the wasting of fire resources caused by dynamic change of target and the difficulty of calculation caused by the real-time dynamic assignment. The genetic algorithm is applied to solve the proposed model. The calculated results show that the proposed model is feasible and effective. Key