Table of Content

23 July 2014, Volume 35 Issue 7

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Paper

Simulation Study into Effect of Intake Air Oxygen Concentration on Combustion Process in Diesel Engine

MA Xiao-kang, ZHANG Fu-jun, HAN Kai, ZHANG Zhen-yu

2014, 35(7):  945-952.  doi:10.3969/j.issn.1000-1093.2014.07.001

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In order to investigate the effect of intake air oxygen concentration on the combustion process in diesel engine, computation fluid dynamics (CFD) software FIRE is used to simulate the combustion process in terms of the ratio of oxygen and nitrogen in intake air. The results show that intake air oxygen concentration affects the quality of fuel-air mixture. With the decrease in intake air oxygen concentration, the rich fuel-air mixture increases, which leads to a decrease in heat release rate in the stage of diffusion combustion. The decrease in intake air oxygen concentration reduces the in-cylinder peak pressure and combustion temperature, and the quality of combustion becomes worse. The oxygen-enriched combustion leads to a remarkable increase in NOx emission and a decrease in soot emission; with a decrease in intake air oxygen concentration at part load, both NOx and soot emissions decrease.

Technical Research on the design of Variable Cross-section Rod Warhead

NING Hui-jun, WANG Hao, RUAN Wen-jun, JIANG Kun

2014, 35(7):  953-959.  doi:10.3969/j.issn.1000-1093.2014.07.002

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The major technique of improving the damage effect of kinetic energy (KE) rod warheads is to improve the impact velocity and control the flight attitude of rod. A new concept of KE rod warhead named variable cross-section rod warhead is proposed, and the basic theory of variable cross-section rod warhead design is described. The driving process of rods deployed by detonation of the explosive is numerically simulated by ANSYS/LS-DYNA. And the deployed velocity and the change rule of flight attitude are obtained from the numerical simulation results. Considering the influence of the aerodynamics on flight attitude of variable cross-section rod after detonation, the aeroelastic deformation of deformed variable cross-section rod is simulated by CFD/CSM .The numerical simulation results indicate that the aeroelastic deformation of variable cross-section rod is so small that it has little influence on its flight attitude. Based on the theoretical research, a static rod deployment test was performed, and the test results reached the expected effect. The research results show that the variable cross-section rod warhead design is reasonable. Moreover, the results also provide the reliable theoretical basis for engineering design.

Optimization of Ultra-wideband Radio Antenna

SHEN Lei， HUANG Zhong-hua

2014, 35(7):  960-964.  doi:10.3969/j.issn.1000-1093.2014.07.003

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A new ultra-wideband radio antenna is designed for the match of ultra-wideband fuze transmitter with antenna bandwidth and power. The feeding point and opening angle of triangular symmetrical dipole antenna are optimized by CST. The results show that the best feeding point of the ultra triangular symmetrical dipole antenna is at the top, and the best opening angle is 60°. The time domain analysis is more suitable for the simulation and optimization of radio antenna by analyzing the voltage standing wave ratio (VSWR), antenna bandwidth, antenna gain and radiation signal amplitude of ultra-wideband radio antenna.

Projectile Impact-point Prediction Method Based on Radial Basis Function Neural Network and Unscented Kalman Filter

ZHAO Han-dong, LI Zhi-peng

2014, 35(7):  965-971.  doi:10.3969/j.issn.1000-1093.2014.07.004

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A new prediction method based on radial basis function (RBF) neural network and an unscented Kalman filter technology is proposed for the precise and quick prediction of impact-point without exact flight data. Firstly, RBF neural network approximated external ballistics equation is used to predict the projectile impact-point, and the improved quantum-behaved particle swarm optimization algorithm is used to optimize the training method. On this basis, the tentative prediction data is processed with unscented Kalman filter. At last, the prediction simulation is carried out. The results show that a high prediction precision can be reached under the condition of input data with noise. The method proposed in this paper is efficient and available for impact-point prediction.

Numerical Simulation of Dispersal Process of Solid-liquid Mixed Fuel

CHEN Jia-chen， ZHANG Qi， MA Qiu-ju， HUANG Ying， LIU Xue-ling， SHEN Shi-lei， LI Dong

2014, 35(7):  972-976.  doi:10.3969/j.issn.1000-1093.2014.07.005

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The solid-liquid mixed fuel explodes to form a fuel air cloud. The detonation strength depends largely on the air cloud state. The cloud distribution is the base of the design of cloud detonation devices. The dispersal process of solid-liquid mixed fuel is investigated by numerical simulation, and a numerical simulation method of solid-liquid mixed fuel is explored. The diffusion process of fuel dispersal in space and time are obtained. The radial dispersal velocity, cloud range and turbulent diffusion process in simulation agree well with the experimental results. The results show that the numerical model established in this study can simulate the dispersal process of the solid-liquid mixed fuel, which opens a new way of research for the optimal design of FAE devices.

Research on Near-infrared Online Monitoring for Blend Uniformity of Modified Double-base Absorbent Powders

ZOU Quan， DENG Guo-dong， GUO Xiao-de, JIANG Wei, LI Feng-sheng

2014, 35(7):  977-981.  doi:10.3969/j.issn.1000-1093.2014.07.006

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The conventional way takes a long time to determine the uniformity of absorbent powders in blend procedure, which is an obstacle to automation and continuation of production process of solid propellant. Near-infrared (NIR) analysis is proposed to solve that problem. A micro NIR spectrometer is used to collect the spectra of absorbent powders that are stirred continually, and the moving block of standard deviation (MBSD) algorithm is utilized to quantitatively analyze the difference between spectra of absorbent powders. The uniformity and endpoint are presented from the standard deviation-time curve. In addition, the accuracy of NIR analysis on the collected samples is confirmed through high performance liquid chromatography (HPLC). The results show that NIR analysis is efficient, eco-friendly and safe. It is feasible to apply NIR analysis to monitor the blend uniformity of modified double-base absorbent powders online and determinate the endpoint of blend process in real-time.

Consensus Analysis of Multi-missile Decentralized Cooperative Guidance Time with Time-delays and Topologies Uncertainty

WANG Qing, HOU De-long, LI Jun, DONG Chao-yang

2014, 35(7):  982-989.  doi:10.3969/j.issn.1000-1093.2014.07.007

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The multi-missile cooperative salvo attack problem with communication time-delay and topological structure uncertainty in fixed topology and dynamic switching topology is studied. Based on graph theory, the asymptotic consensus problem of multi-missile cooperative guidance time is converted to the asymptotic stability problem of different system. Then the asymptotic stability problem of different system with network transmission delay and topological structure uncertainty is analyzed based on Lyapunov function method. The method can get the condition of time-delays which satisfy the asymptotic consensus. This method is expanded to the situation of network transmission time-delay and topological structure uncertainty under switching topology for the analysis of guidance time consensus. The simulation results are coincident with the theoretical consensus analysis.

Investigation of Fracture Mechanism and Fracture Energy of HTPB Propellant/liner Interface Debonding

ZHOU Qing-chun， JU Yu-tao， WEI Zhen， ZHOU Chang-sheng

2014, 35(7):  990-995.  doi:10.3969/j.issn.1000-1093.2014.07.008

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Debonding along the propellant/liner interface is one of the major forms in which rocket motor structural integrity can fail. The double cantilever sandwich beam experiments are performed to investigate the mode-I fracture of HTPB propellant/ linear interface. These experiments show that a craze damaged zone which is consisted of voids and fibers exists in the crack tip.The crack initiation and extension are essentially to be local crazing initiation, thickening and micro-fiber fracture.The failure mechanism of the interfacial debond is the growth and coalescence of near-tip voids, while the typical fracture mode of the interface includes the cohesive failure within the adhesive, interfacial failure and mixed failure. The shape of the damaged zone ahead of the crack tip is found to be related to the constraints imposed by the adjacent components when the crack propagates stably. The concept of the effective crack length could be used to eliminate the effects of the plastic deformation and blunting ahead of the crack tip on the fracture energy.

Effect of Laser Quenching on Tensile Properties and Fracture Analysis of 40CrNiMo High Strength Steel

KONG De-jun, ZHANG Lei, FU Gui-zhong

2014, 35(7):  996-1002.  doi:10.3969/j.issn.1000-1093.2014.07.009

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The surface of 40CrNiMo high strength steel is treated with CO₂ laser, the effect of laser quenching on tensile property of the sample is investigated through the tensile comparative test, and the fracture morphologies of 40CrNiMo before and after surface laser quenching are analyzed by scanning electron microscope and energy dispersive spectrometer, respectively. The results show that the yield strength, tensile strength and elongation of 40CrNiMo steel after laser quenching are increased by 25.3%, 24.4% and 7.1%, respectively, while the section shrinkage is decreased by 7.6%. 40CrNiMo steel has obvious yield stage after laser quenching, showing a continuous yield feature. Compared with the primitive sample, the yield strength and tensile strength of 40CrNiMo steel after laser quenching increase, but there are no obvious improvements in the tensile failure mode and the delamination, and the quasi cleavage morphology and low porosity appear at the fracture near the surface of the sample after laser quenching.

Dynamic Modeling and Control of Space Manipulator with Flexible Joints and Links

YANG Yong-tai, RONG Ji-li, LI Jian, LIU Bin, HU Cheng-wei

2014, 35(7):  1003-1008.  doi:10.3969/j.issn.1000-1093.2014.07.010

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Only joint flexibility or link flexibility is considered in the dynamic modeling of the space manipulator by most researchers, and the assumed mode method, only suitable for small deformation, is usually utilized to describe the flexible deformation of link. Both nature coordinate formulation (NCF) to model the flexible joint and absolute nodal coordinate formulation (ANCF) to model the flexible link are used to obtain the dynamic equations of the space manipulator, which include both joint flexibility and link flexibility and are able to precisely describe both small and large deformations. The joint trajectory is developed by quintic polynomial function, and then the actuator torque is obtained by the inverse dynamics as feedforward. PID control scheme is used as feedback input. The two-link flexible manipulator is used to evaluate this method. Results show that the proposed control scheme is effective in both the tracking of joint trajectory and suppressing of vibration.

Study of Shock-induced Polycrystalline Iron Phase Transition with DEM

LIU Chao, SHI Yi-na, QIN Cheng-sen, LIANG Xian-hong

2014, 35(7):  1009-1015.  doi:10.3969/j.issn.1000-1093.2014.07.011

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Numerical simulations on α-iron and polycrystalline iron are conducted using discrete element method (DEM) combined with undiffused two-phase transition model, thermodynamic consistent free energy function, and phase transition kinetics of relaxation equation. The phase boundary and Hugoniot relation are obtained through numerical simulation. The simulation result of polycrystalline iron shows that the shock-front irregularities rise when the propagation distance of shock wave increases; and the shock-front is more irregular in the coarse grain model than in the fine grain model; the phase transitions in the polycrystalline are heterogeneous, and the transitions are observed first along grain boundaries. The curve of local average pressure and transformed mass fraction is obtained.

Experimental and Numerical Study of Adiabatic Shear Failure of TA2 Titanium Alloy under Dynamic Compression

DONG Xin-long， FU Ying-qian

2014, 35(7):  1016-1020.  doi:10.3969/j.issn.1000-1093.2014.07.012

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Adiabatic shear is known to be a precursor to the failure of metals processed at high strain rate. The present study focuses on the adiabatic shear failure characteristic of TA2 titanium alloy under dynamic compression. The dynamic stress-strain behavior is tested by split Hopkinson pressure bar (SHPB), and adiabatic shear bands (ASBs) are investigated by means of optical microscopy. The metallographic analysis reveals that the ASBs pattern in specimen is symmetrical bi-conical. Furthermore, a comprehensive finite element analysis of shear localization of the deformed cylindrical specimens is carried out. The numerical simulations are in agreement with the experimental results, and the frictional force between the specimen and the Hopkinson bars significantly affects the evolution of shear localization.

Dynamic Modeling and Simulation of UAV Ground Maneuvers

GUAN Yong-liang, HOU Yu-xiu, JIA Hong-guang, LIU Bo, MA Wu-yuan

2014, 35(7):  1021-1026.  doi:10.3969/j.issn.1000-1093.2014.07.013

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A dynamic model of tricycle-undercarriage-UAV ground maneuvers is established using elastic tire theory. With full consideration of loads applied to UAV, the model can describe the process of the UAV ground maneuvers exactly. The simulation is based on a series of parameters of a real UAV. The constraints are put forward by analyzing some data from simulation, which affect the ground maneuvers of UAV. At last, the available range of UAV ground maneuvers is given.

An Investigation on Mitigation Effect of Water Surrounding an Explosive on Reflected Overpressure of Shock Wave

XU Hai-bin, ZHANG De-zhi, QIN Xue-jun, LIU Jun-ling, SHI Guo-kai, LIU Wen-xiang

2014, 35(7):  1027-1031.  doi:10.3969/j.issn.1000-1093.2014.07.014

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The mitigation effect of water on blast shock is investigated. The explosion is tested in a confined space without and with water in order to estimate the influences of the parameters, such as water-to-explosive weight ratio and scaled distance, on the reflected overpressure of shock wave. The results indicate that the reflected overpressure of explosion immersed in water firstly increases and then decreases with the increase in scaled distance compared with that without water. It is found that the reflected overpressure significantly increases with the increase in the water-to-explosive weight ratio when the scaled distance is not larger than 0.255 m/kg¹³. Typically, the overpressure increases eight-fold when the ratio is 6. The overpressure can be decreased by 60% by using water when the scaled distance is 1.21 m/kg¹³.

Research on Improved Divided Difference Particle Filter under Non-stationary Non-Gaussian Noise Background

WANG Hong-jian，XU Jin-long，LI Juan，ZHANG Ai-hua

2014, 35(7):  1032-1039.  doi:10.3969/j.issn.1000-1093.2014.07.015

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An improved divided difference particle filter (IDDPF) is proposed to improve the low accuracy of state estimation and divergent tend problem which may be caused by divided difference particle filter (DDPF) in the condition of the non-stationary non-Gaussian measurement noise (NSNGN). The IDDPF algorithm adopts Gaussian mixture density function to approximately estimate the measurement noise, instead of the Gaussian density function usually adopted in DDPF. The noise parameters are estimated by maximizing the log likelihood function of the measurement noise model. The model is then used to calculate the particle weight, which avoids the particle degeneracy problem. The IDDPF algorithm is tested by establishing bearing-only tracking of underwater target under the glint measurement noise background. The results of 50 Monte-Carlo simulation experiments show that the IDDPF algorithm has the advantages of fast tracking response, high estimated precision and robustness, etc. under NSNGN background.

Research on Hydrodynamic Characteristics of Conical Cavitator

LI Fu-yuan， ZHANG Yu-wen， DANG Jian-jun， TENG Peng-hua

2014, 35(7):  1040-1044.  doi:10.3969/j.issn.1000-1093.2014.07.016

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In order to explore the hydrodynamic characteristics of conical cavitator, the experimental study of conical cavitators with different cone angles in water tunnel is conducted to obtain their hydrodynamic parameters. The influence of cone angle on hydrodynamic characteristics is analyzed. The hydrodynamic characteristics of conical cavitator with flat head and the drags under different flat head areas are also studied. The results show that the cone angle has effect on drag and lift coefficients; the position derivatives of lift coefficient are distinct at different cone angles; and the drag coefficient dose not change obviously. The cavitator can be approximated as a full conical cavitator when the flat head area is small. The experimental results provide a reference for practical use of conical cavitator and analysis of control characteristics of supercavity vehicle.

Estimation of Underwater Target Motion Parameters Based on Homomorphic Filtering

WANG Yan， ZOU Nan， FU Jin， LIANG Guo-long

2014, 35(7):  1045-1051.  doi:10.3969/j.issn.1000-1093.2014.07.017

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The eanalysis of target motion in near field is difficult when the space of measurement platform is limited. A novel underwater target motion analysis (TMA) method is proposed based on the multipath structure of the ray acoustics in shallow water, A three-dimensional multipath time delay model of target in uniform speed rectilinear movement is established. The nonlinear function expression of time delay between direct sound and surface reflected sound is derived by taking the movement parameter as a variable. Based on the characteristics of typical underwater acoustic channel, the expression of channel in cepstrum domain is achieved. Then the time delay between direct sound and surface reflected sound is estimated by the homomorphic filtering technique with the ability of deconvolution.The optimal solution of the nonlinear equation is solved by combining with Levenberg-Marquardt method. The quadratic approximation correction method is proposed to decrease the influence of actual hydrological condition on parameter estimation. The simulation results show that the proposed method is practicable, and the estimation precision meets the demand of practical application.

Research on Accuracy of Localization Algorithm for T²-R Multistatic Sonar

XU Jing-feng， SHU Xiang-lan， HAN Shu-ping, MA Xin

2014, 35(7):  1052-1059.  doi:10.3969/j.issn.1000-1093.2014.07.018

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A geometrical model for geometrical localization of T²-R multistatic sonar is established. A multistatic time-bearing-localization (MTBL) algorithm is proposed, and the error of geometrical dilution is presented. The effects of baseline length, sonar deployment and measurement error on the localization accuracy of algorithm are studied through numerical simulation, and other indispensable influencing factors are qualitatively analyzed. The simulation results show that the localization accuracy in most regions is improved with the increase in length of baseline. For the given deployment mode, the localization accuracy is sensitive to the time measurement error, but the bearing measurement error has a limited impact on the performance of the algorithm. The proper deployment of sound sources can enhance the mean localization accuracy. The study provides a well theoretical evidence for underwater localization of T²-R multistatic sonar.

Research on Lateral Vibration and Vibration-induced Electromagnetic Noise of Underwater Electric Field Antenna

ZHU Si-hua，ZHU Xue-shan，LIN Hong-wen，HU Hao

2014, 35(7):  1060-1064.  doi:10.3969/j.issn.1000-1093.2014.07.019

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Lateral vibration is the dominating vibration source caused by seawater ripples for the underwater electric field antenna, and the lateral vibration-induced electromagnetic(EM) noise is dominant in EM noises for long wave communication，which has a significant influence on the receiving depth and quality of long wave communication. The lateral vibration model of towed antenna is established, and the response of lateral stochastic vibration is educed. The generating mechanism and characteristic of lateral vibration-induced EM noise are analyzed．Furthermore，the simulation and analytic results of EM noise are given．All the results indicate that the calculation of vibration-induced EM noise under the assumption of Bernoulli beam and the excitation of stochastic fluctuating stresses is feasible and exact, and the antenna configuration is optimized and the vibration-induced EM noise is decreased based on the results of lateral vibration-induced EM noise.

Influences of Sound Absorbing Materials on Acoustic Characteristics of Underwater Platform

LIANG Guo-long， PANG Fu-bin， ZHANG Guang-pu

2014, 35(7):  1065-1071.  doi:10.3969/j.issn.1000-1093.2014.07.020

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In order to decrease the reflection coefficient of underwater platform and promote its stealth performance, a method of covering a sound absorbing material on the platform is proposed. The transfer matrix method is used to calculate the reflection and transmission coefficients of composite structure in underwater platform in the case of oblique incidence of sound waves. The influences of the arranging sequence and parameters of sound absorbing materials on the acoustic characteristics of underwater platform are analyzed. The results show that the reflection coefficient of platform without sound absorbing material is close to 1 ; the constant reflection coefficient curve of the platform with sound absorbing material is a hyperbolic curve as the functions of incident angle and frequency, and its reflection coefficient obviously descreases at high frequency. This shows the frequency selectivity in the absorbing performance of platform, and the absorption wave band of platform transfers to lower frequencies by increasing the thickness of sound absorbing material. When the loss coefficient of material raises, the reflection coefficient of platform goes down. The experimental results coincides well with the theoretically calculated results.

Explosion Breakup Debris Distribution of Simulated Satellite

YU Qing-bo, XU Feng-yue, WANG Qin-zhi, JIN Xue-ke, WANG Hai-fu

2014, 35(7):  1072-1076.  doi:10.3969/j.issn.1000-1093.2014.07.021

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The explosion breakup debris distribution of the cylindrically simulated satellite with thin-walled aluminum alloy is researched by the sandpit retrievable experiment and theoretical analysis. The experimental results show that the explosion breakup behavior of simulated satellite is significantly influenced by the wall thickness and the residual propellant mass. The amount of explosion breakup debris increases with the decrease in wall thickness and the increase in residual propellant mass. Moreover, the explosion breakup debris mass shows a wide range from less than 0.2 g particles to more than 100 g irregular debris. By incorporating the experimental results into the covered explosive explosion breakup model and simulated satellite low intensity explosion breakup model, respectively, both the amount and mass distribution models of simulated satellite explosion breakup debris are presented, contributing to the assessment of satellite breakup debris distribution characteristics in accident.

Fault Diagnosis for Automata Based on Local Wave Noise Reduction and Bispectral Analysis

PAN Hong-xia, LAN Hai-long, REN Hai-feng

2014, 35(7):  1077-1082.  doi:10.3969/j.issn.1000-1093.2014.07.022

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Feature extraction is a key of mechanical fault diagnosis, which directly affects the accuracy of fault diagnosis and the reliability of early prediction. The vibration signal components of automata surface are complex, including rich information on the motion states of components and parts, and a lot of noise components. Interference information should be effectively removed in order to make a correct assessment and analysis of the signal. The vibration signal of automata surface has obvious short impact characteristics, and is a typical non-Gaussian, nonlinear signal. Bispectral analysis has certain advantages especially in dealing with non-Gaussian signal and identifying nonlinear system failures. Automata vibration signal is noise-reduced and analyzed by the local wave theory and the Bispectral analysis.

The Fault Diagnosis of Electromagnetic Valves Based on Driving Current Detection

LIU Zhi-hao, GAO Qin-he, NIU Hai-long, GUAN Wen-liang, LI Jing-yue

2014, 35(7):  1083-1090.  doi:10.3969/j.issn.1000-1093.2014.07.023

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The fault diagnosis of electromagnetic valves based on driving end current detection is proposed. The current characteristics of the faulted electromagnetic valves and the failure signal are analyzed. The four conditions of the valve are detected, including normal state, spring break state, spool seizure and un-resetting state. Variation trend is the character signal on terms of the direct-current characteristic. For the trait of the current signal, the wavelet packet decomposition is used to distill the corresponding frequent band energy as feature vector. The feature database is combined with the each frequent band energy which is produced after reconfiguration. The feedforward-back propagation network is used to identify the fault type of the electromagnetic valves. The result shows that the diagnosis method of energy-fault can distinguish the different conditions of the electromagnetic valves，and the feedforward-back propagation network after training can identify the 3 fault conditions. The method is an effective assistant method for the maintenance of the electromagnetic valves，which can be widely used for the fault diagnosis of other electromagnetic valves.

Research on Process Parameters of Toroidal Cutter in High-speed Milling of Die Steel S50C

WANG Yi-qiang， YAN Guo-chen， YUAN Xiu-hua， GU Yan， YANG Lin-lin

2014, 35(7):  1091-1096.  doi:10.3969/j.issn.1000-1093.2014.07.024

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In order to explore the effect of process parameters on surface roughness in high-speed milling, the multifactorial orthogonal experiments of die steel S50C are conducted, and the surface roughness is measured under different parameters such as spindle speed, feed rate, axial depth, radial width and pose angle. The artificial neural network and genetic algorithm are used to establish a prediction model of surface roughness and an optimization model of process parameters. In addition, the validity of two models is verified. Results show that the approach may be used for the prediction of surface roughness and optimization of the process parameters before machining. Moreover, this research also provides a valid means to study the process parameters of other materials.

Three-dimensional Reconstruction of Temperature for Asymmetric Plasma Arc

SUN Jing, ZHENG Qing-yu, XU Wen-ji, HUANG Shuai, LIU Xin

2014, 35(7):  1097-1102.  doi:10.3969/j.issn.1000-1093.2014.07.025

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Plasma processing technology has been concerned in the forming and preparation of various difficult machining materials. The temperature of plasma arc is the decisive factor of influencing processing quality. The most existing studies on temperature characteristic were completed under the assumptions of arc radial symmetry. In order to solve this problem, a three-dimensional temperature reconstruction method for asymmetric plasma arc based on gray value is presented. A three-dimensional model of asymmetric plasma arc appearance which has correlation with temperature field is established based on gray value. A blackbody furnace is used to calibrate the formula of colorimetric temperature measurement. The correspondence between gray value and temperature in the image of plasma arc is obtained by colorimetric temperature measurement. Finally, the temperature value is introduced into the appearance model to accomplish the three-dimensional reconstruction for the temperature field of asymmetric plasma arc. The results show that the method can descride the temperature distribution of the plasma arc and achieve the non-contact measurement of temperature field of asymmetric plasma arc.

Residual Life Analysis of Repairable Systems Based on Universal Generating Function Approach

ZHOU Jin-yu, XIE Li-yang, HAN Wen-qin, ZHU Fu-xian

2014, 35(7):  1103-1109.  doi:10.3969/j.issn.1000-1093.2014.07.026

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The residual life of systems is an important analysis index for multi-lifecycle-based design, manufacture and service of mechanical and electrical equipment. Based on the renewal process theory, a practical method for residual life probability analysis of components and the whole system in a finite time interval is put forward by means of the universal generating function (UGF). For systems undergoing stationary stochastic load process with global uncertainty, the conditional life UGFs of components are constructed according to failure data under all constant-amplitude stress levels, and the corresponding conditional residual life UGFs of the whole system can be figured out by using self-defined composition operators of UGFs. Statistical average of UGFs is employed to obtain the residual life distribution of the repairable system. When the composition operators are executed, the computational costs can be reduced by a big margin by means of collecting like terms. The new model is suitable for random variables with arbitrary distributions and embodies the failure dependence attributed to the uncertainty of equivalent stress amplitude of each component.

Research Notes

Track Tension and Its Influencing Factors

HUANG Xue-tao, GU Liang, LYU Wei-wei， YANG Cong-bin, GAO Xiao-dong, ZHU Xing-gao

2014, 35(7):  1110-1118.  doi:10.3969/j.issn.1000-1093.2014.07.027

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The distribution of track tension on track link is studied for the complex track tension problem, and the theoretical estimation formula of track tension is established. The theoretical estimation and dynamic simulation of track tension in static balance and uniform speed conditions are conducted by using the multi-body dynamic model of tracked vehicle, and the rationality of theoretical estimation formula is verified. The influencing factors of track tension are also analyzed, and the influence of each factor on track tension is discussed using the method of combining theory calculation and dynamic simulation. The results provide a theoretical basis for the design of tracked vehicles.

Lethality of Forward Enhanced Lethal HE Projectile Against Personnel Targets

LI Chao， LI Xiang-dong， CHEN Zhi-bin， LI Qiang

2014, 35(7):  1119-1123.  doi:10.3969/j.issn.1000-1093.2014.07.028

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In order to analyze the lethality of a forward enhanced lethal HE (high explosive) projectile against personnel targets, the static explosion experiments are made on the forward enhanced lethal HE projectile and the conventional HE projectile, which have same structural characteristic parameters. A calculating model of the lethality against personnel targets is established. The lethal powers of two kinds of projectile against personnel targets in same terminal conditions are comparatively calculated. The result shows that the forward enhanced lethal HE projectile can produce a fragment damage area compared with the conventional HE projectile so that it makes the killing area for personnel targets being increased by 147.3%. Its lethality against personnel targets is enhanced effectively.

Optimal Design of Synchronous Multi-frequency/multi-beam Jamming Based on Second-order Cone Programming

LEI Lei, ZHOU Qing-song, ZHANG Jian-yun, HUANG Zhong-rui

2014, 35(7):  1124-1130.  doi:10.3969/j.issn.1000-1093.2014.07.029

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The present multi-frequency/ multiple beamforming methods for radar jamming have the disadvantages of low efficiency and difficulty to form synchronous multi-frequency/multi-beam jamming. A new beamforming method based on second-order cone programming (SOCP) is proposed for the synchronous multi-frequency/multi-beam radar jamming. The optimal design problems can be formulated into the mathematical description in the case of different norm criteria. And then the mathematical description is translated into a SOCP one by taking L₂ norm criteria for example. Moreover, this SOCP problem can be solved effectively via CVX or SeDuMi. The simulation results show that the approach can solve the optimal design problem efficiently.

Research on Reliability Model Considering Maintenance

ZHANG Zhi-hua, LI Da-wei, ZHONG Qiang-hui, LIANG Sheng-jie

2014, 35(7):  1131-1136.  doi:10.3969/j.issn.1000-1093.2014.07.030

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Maintenance is a good means to retain or recover the product state. In order to understand the reliability law of products under the condition of periodic maintenance, a performance deterioration rule model is established based on the composite Poisson process. In the model, the failure mechanism and the product deterioration character are fully considered in the case of periodic maintenance. The model can be used to determine the reliability and failure rate. An analytical expression, which can specify the maintenance effect, is presented by analyzing the change law of failure rate. The model can exactly describe the reliability law of product by taking the pump rotor for example. It also can portray the maintenance effect more objectively and intuitively.