Table of Content

30 May 2018, Volume 39 Issue 5

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Contents

2018, 39(5):  0. 

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Paper

Research on Joint Estimation and Detection of Submarine Target in Airborne Magnetic Anomaly Detection

ZHOU Jia-xin， CHEN Jian-yong， SHAN Zhi-chao， CHEN Chang-kang

2018, 39(5):  833-840.  doi:10.3969/j.issn.1000-1093.2018.05.001

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To solve the problem that underwater submarine target signals are corrupted by the strong magnetic background noise and interrupter in the aeromagnetic anomaly detection, a joint estimation detection method is proposed. A signal model of target measured by optical pump magnetometer is established for submarine target based on magnetic dipole. The target signal model is determined by 7 unknown parameters: position vector x，y，z, magnetic moment vector M_x,M_y,M_z, and course angle θ. According to the observation sample, the unknown parameters are searched by genetic algorithm and the prior information of submarine target, and the fitness function is constructed by Fréchet distance. Then the test statistic of mean correlation is proposed based on the target estimated signal, and the correlation detector using target estimated signal is designed. The performance analysis using measurement data shows that the detector is still with good detection performance in the low signal-to-noise ratio condition. Compared with the traditional detection based on decomposition of orthonormal basis and the aeromagnetic anomaly detection for moving target, the performance of the joint estimator and detector using target estimated signal is better, and it can improve the signal-to-noise ratio and reduce the false alarm probability. Key

Analysis of Headspace in Locking Mechanism with Locking Lug Shifting in Considering Part Deformation

LUO Shao-min, XU Cheng

2018, 39(5):  841-850.  doi:10.3969/j.issn.1000-1093.2018.05.002

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Headspace is a typical assembly requirement in automatic weapon assembly, which directly affects the performance and safety of automatic weapon. To research the headspace under actual working condition, a calculation method of part deformation based on finite element analysis is put forward, and an analysis model of assembly tolerance considering deformation is established. For the assembly accuracy of machine gun with locking lug shifting, an analysis model for locking mechanism is established, the assembly precision change of headspace in considering deformation caused by temperature is analyzed, and the influence of temperature on headspace is studied. The influence of deformation on headspace in counter-recoil and the influence of part deformation during the launching process are investigated. The results show that the distribution center of headspace is obviously offset, and the distribution range contracts with the increase in temperature after considering the deformation induced by temperature. The headspace is decreased by 0.015 mm in considering deformation at barrel chamber temperature of 300~600 ℃. Considering the deformation caused by the impact in counter-recoil, the headspace is increased by 0.02 mm. Elastic deformation of parts is 0.14 mm during the launch process. The transverse fracture of cartridge case will not happen when headspace is between 0.38~0.47 mm, but, will occur when headspace is 0.47~0.48 mm. Key

Effect of Magnetic Field Direction on the Flow and Heat Transfer Characteristics of High Temperature Conductive Gas in Cylinder Structure

LI Cheng， MAO Bao-quan， BAI Xiang-hua， LI Xiao-gang

2018, 39(5):  851-858.  doi:10.3969/j.issn.1000-1093.2018.05.003

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The propellant gas is ionized to form thermal plasma at high temperature, which has good conductivity. For the problem of thermal ablation of weapon barrel by high temperature propellant gas, a method to reduce the surface temperature of barrel bore by using magnetron plasma is presented. A turbulent dissipation model of high temperature conductive gas in cylinder structure is constructed by using the magnetic fluid description method. The influences of different magnetic field directions on the viscosity effect of conductive gas and the wall temperature of cavity are studied. The effect of coaxial magnetic field on the heat transfer characteristics of conductive gas is tested by infrared thermal imaging technology. The results show that magnetic field which is perpendicular to the direction of flow can effectively reduce the turbulent kinetic energy and turbulent viscosity of conductive gas and weaken its heat transfer capability, the flow distribution has the anisotropy characteristics, and the turbulent kinetic energy and turbulent viscosity along the magnetic field direction are lower than those in the direction perpendicular to the magne-tic field. The coaxial magnetic field can limit the radial diffusion of charged particles and reduce the heat transfer of conductive gas to the wall of cylinder, thereby reducing the wall temperature. Key

Numerical Simulation and Analysis of Bore Premature of Armor Piercer Caused by Foreign Matter Obstruction

WANG Yun-ze, WANG Shu-shan, WEI Ping-liang, SHU Bin, LIANG Zhen-gang

2018, 39(5):  859-866.  doi:10.3969/j.issn.1000-1093.2018.05.004

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The dynamic responses of projectile and barrel under the foreign matter obstruction are numerically simulated based on the background of the premature of a certain armor piercer. The mechanism of bore premature is discussed, and the basis and reference are given for fault analysis and zeroing. Two typical forms of foreign matter obstruction are presented: the foreign matter obstruction leads to a sudden decline of projectile velocity or bayonet chamber; and the projectile directly impacts the foreign matter in chamber at high velocity. AUTODYN software is used for numerical calculation of different conditions, the dynamic characteristics of gas flow field, the deformation and rupture shapes of barrel, and the dynamic response of structure and the deformation and rupture of projectile during the high velocity impact are obtained. The results show that the abrupt obstruction and the rapid decrease of velocity in the chamber result in forming the shock wave and local high pressure in the bottom gas. The presence of local high pressure zone can lead to bore premature. The simulated results are consistent with the actual fault condition.The fault repetition test is carried out. Key

Research on Numerical Simulation of Submunition Dispenser with Gas Generant and Airbag

WANG Qi， JIANG Jian-wei， WANG Shu-you

2018, 39(5):  867-874.  doi:10.3969/j.issn.1000-1093.2018.05.005

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For the numerical simulation of submunition dispenser with gas generant and airbag, a model of airbag dispersing is built by using software LS-DYNA and solid-liquid coupling ALE algorithm, in which the mass flow rate of gas is considered as the input parameter of numerical simulation. On the basis of interior ballistic theory and closed bomb vessel experiment, the nominal combustion rate equation of gas generant and the mass flow rate equation are presented. The typical structure of submunition dispenser fileed with different amount of gas generant is simulated to obtain the velocity of submunition dispensed from airbag and the change of overload peak with the amount of gas generant. The simulated results are in agreement with the test results. The results show that the proposed method could be used to predict the velocity and acceleration of submunitions in practical tests. Key

Forced Conical Motion Stability Conditions for Pneumatic Eccentric Projectile under the Action of Nonlinear Moment

SHU Jing-rong， LI Hong-xing， LI Hong-ling

2018, 39(5):  875-882.  doi:10.3969/j.issn.1000-1093.2018.05.006

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An angle of attack equation of pneumatic eccentric projectile under the action of cubic nonlinear static moment and quadratic nonlinear equatorial damping moment is established for the structure design and aerodynamic design of pneumatic asymmetric projectiles, such as non-parachute terminal sensitive projectile, and the approximate analytical solution of the equation and linear variational equation are solved by using average method. On this basis, the asymptotic stability conditions of forced conical motion for pneumatic eccentric projectile is obtained according to Hurwitz criterion, and the physical meaning of the conditions is analyzed. The numerical calculation example is used to verify the conditions. Result shows that the projectile under the action of cubic nonlinear static moment and quadratic nonlinear equatorial damping moment can achieve steady forced conical motion at fixed angle of attack when spin velocity and pneumatic eccentric angle satisfy certain constraint conditions. Key

Investigation on the Damage Mechanism of Blunt Projectile against Thin Plate

XU Wei, HOU Hai-liang, ZHU Xi, CHEN Chang-hai, LI Mao

2018, 39(5):  883-892.  doi:10.3969/j.issn.1000-1093.2018.05.007

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The ballistic tests were carried out to explore the failure modes of target impacted by the blunt projectile. The deformation of of projectiles and the damage modes of targets at different initial velocities were analyzed. The interaction between projectile and target is simulated using ANSYS/LS-DYNA for analyses of penetration mechanism. The fitting curve of final target deformation in the dishing area was acquired according to the test results. The plastic deformation energies of projectile and target are analyzed, and a simplified analytical model for residual velocity is proposed based on principle of conservation of energy. It is shown that mushrooming deformation is observed in the projectile. The target material fails due to sheering and stretching, and accordingly the failure modes of targets are global dishing deformation with local sheering and tensile failures. The residual velocity drawn from the formula proposed in this paper is in good agreement with the test data, which testifies the applicability of the proposed model. Key

Non-ordinary State-based Peridynamic Simulation of Damage and Failure Process of Polymer Bonded Explosives

LI Pan, HAO Zhi-ming, LIU Yong-ping, ZHEN Wen-qiang

2018, 39(5):  893-900.  doi:10.3969/j.issn.1000-1093.2018.05.008

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The dynamic relaxation method for obtaining the steady-state solutions of equilibrium equations in non-ordinary state-based peridynamic theory is studied. The hourglass force is incorporated to suppress the zero-energy modes. In the foundation of considering the influence of damage on force state, an influence function damage defining method is proposed, in which the effects of damage on approximate deformation gradient and shape tensor are calculated. Therefore, the problem of stress release in damaged region is overcome. The non-ordinary state-based peridynamic theory is applied to the simulation of damage and failure behaviors of polymer bonded explosives in Brazilian disc experiment. It shows that the simulated results of the modified method are in better accordance with the experimental results.Key

Design of Decoupling Controller for Spinning Fin Stabilized Projectile Based on Off-line Predictive Control

CHEN Wei, SUN Chuan-jie, LI Yong-ze, BAI Yun-shan

2018, 39(5):  901-909.  doi:10.3969/j.issn.1000-1093.2018.05.009

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In order to achieve the stable flight, a decoupling controller is necessary for a spinning fin stabilized projectile with low spin rate in flight with considering aerodynamic cross-linking, inertial cross-linking and control cross-linking. Since the model predictive control method has the advantages of good decoupling ability and less demand on modeling accuracy, but has the large on-line computing burden, thus an off-line model predictive control method with command filter is proposed. The off-line solved control parameter matrix and the on-line look-up table are used to reduce the on-line computing burden to meet the real-time control requirements. The state of command filter and the integral of tracking error are added into the prediction model to make full use of the dynamic characteristics so that the control parameter matrix can cope with the change of command signal. The effectiveness of the proposed algorithm is verified by the attitude control simulation. The designed controller can ensure the stability tracking of the flight command.Key

Missile Formation Guidance Algorithm Independent of Data Communication

HUANG Wei, XU Jian-cheng, WU Hua-xing, LI Jun-bing

2018, 39(5):  910-918.  doi:10.3969/j.issn.1000-1093.2018.05.010

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To solve the control problem of missile formation without support of weapon data-link, a new guidance algorithm for systems grouped by the leader-follower structure based on multi-agent consensus theory is proposed, which only requires the motion parameters, such as relative distance and relative speed among missiles, which can be measured by the followers’ active radar seeker. The proposed algorithm needs no data communication among missiles and absolute positions of formation members, but can make all members approach to ideal positions and consistent velocity simultaneously. Algebraic graph theory is employed to prove the asymptotic stability of closed loop control system, and a model of required force for missile formation control is built based on coordinate conversion and missile motion equation. Simulated results are used to verify the validity of the proposed algorithm and its application prospect for general design of missile formation system. Key

Radar and Infrared Compound Guidance Method for Air-to-ground Missile Attacking Ground Group Target

LI Bo， HAN Yue， DING Xiang， LI Xi-tong

2018, 39(5):  919-926.  doi:10.3969/j.issn.1000-1093.2018.05.011

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In a single radar guidance mode, air-to-ground missiles often fail to attack the ground targets since the radar seeker can't lock onto a target in the terminal guidance phase. To solve this problem, a radar/infrared compound guidance antenna radar seeker model and a six radiometer infrared seeker model are established, and a radar/infrared compound guidance scheme is designed, including radar guidance, radar/infrared compound guidance and infrared guidance. The attack effects in single radar guidance mode and composite guidance mode are analyzed by comparing the seeker angle error, missile overload and miss distance parameters. It is found that, under the condition of a large number of targets, the missile in compound guidance mode is more stable in overload and has higher hit accuracy compared with the single radar guided mode.Key

Experimental Investigation on Mitigating Effect of Water Mist on the Explosive Shock Wave inside Cabin

CHEN Peng-yu, HOU Hai-liang, LIU Gui-bing, ZHU Xi, ZHANG Guo-dong

2018, 39(5):  927-933.  doi:10.3969/j.issn.1000-1093.2018.05.012

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In order to analyze the mitigating effect of water mist on the explosive shock wave inside a cabin, a series of TNT explosion experiments in the center of a cabin were carried out, from which the wall pressure and quasi-static pressure inside the cabin in different cases with and without water mist were measured. Results show that water mist truly has an evident effect on attenuating the overpressure peak of blast wave and the quasi-static pressure. In the experiment of 27.5g TNT exploding in cabin, the attenuation rate of initial shock wave overpressure is 26.47%, the attenuation rate of secondary reflected wave pressure is is about 27.27%, and the attenuation rate of quasi-static pressure is about 31.82%. For the same water mist density, the mitigating effect of water mist on the blast wave decreases with the increase in TNT charge. Key

Application of MPI-based ISAT Accelerated Algorithm in Gaseous Detonation Numerical Simulation

WU Jin-tao, DONG Gang, LI Bao-ming

2018, 39(5):  934-944.  doi:10.3969/j.issn.1000-1093.2018.05.013

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In the numerical simulation of gaseous detonation process with the detailed chemical reaction mechanism, the computation of chemical source term takes a large amount of CPU times due to the stiffness and nonlinearity of the term. To improve the computational efficiency without the loss of the computational accuracy for chemistry computation, two algorithms of in situ adaptive tabulation (ISAT) based on multi-threaded parallel integration (MPI) are proposed to replace the original direct integration (DI) method, and then applied in the computation of two-dimensional gaseous detonation process for H₂/O₂ medium with detailed chemical mechanism. In the parallel algorithms, two types of tabulation, namely the local tabulation for each processor and the global tabulation for all processors, are proposed, and the effect of the tabulation mode on the computational efficiency is investigated. Further, the influences of error criterions and numerical schemes on the computational efficiency of the algorithms are also examined. The results show that both the proposed algorithms can provide satisfactory computational accuracy compared with the results of DI, and the computational efficiency of the local tabulation for each processor with the chemical speedup ratio of 2.17~2.43 is higher than that of the global tabulation for all processors. The proposed parallel accelerated algorithms can not only accurately describe the propagation process of two-dimensional gaseous detonation wave, but also improve the parallel computational efficiency of of chemically reactive flows.Key

Research on Congestion Control Algorithm of Satellite Network Based on Forword Direction Delay

GUAN Shi-jie， JIANG Yue-qiu， GUAN Qi-xue， GUO Qin-chao

2018, 39(5):  945-951.  doi:10.3969/j.issn.1000-1093.2018.05.014

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In satellite networks featuring asymmetric bandwidth, the bandwidth of reverse (earth-to-satellite) links is narrow, and congestion is more likely to occur in these links. Congestion occurring in a reverse link is alleviated by decreasing the send window at the sending end, during which, however, the throughput of forward (satellite-to-earth ) links in the network is also lowered. Vegas_FD, a TCP Vegas forward congestion control algorithm based on forward direction delay, is proposed so as to tackle the foregoing problems. The proposed algorithm judges whether a communication link is congested or not by measuring the forward direction delay time of data packets, and adopts different control strategies as per different congestion types of the communication link, so as to ensure that the congestion control algorithm could keep a high throughput when the reverse link is congested. With these functions, the algorithm is adapted to the asymmetry of the satellite network’s bandwidth. The simulated results based on Opnet software show that Vegas_FD algorithm is used to improve remarkably the throughput in satellite networks compared to Vegas and Westwood algorithms. Key

Design and Performance Test of a Novel Piezo-scanning Stage

WANG Geng， WANG Shuai-qi

2018, 39(5):  952-960.  doi:10.3969/j.issn.1000-1093.2018.05.015

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A compact piezo-scanning stage based on a novel compound flexible hinge is designed. A kind of flexible drive hinge with two-stage magnification is proposed for piezo-scanning stage. The motion range of its deflection angle is calculated by analytical calculation and finite element analysis, respectively. The structure and working principle of piezo-scanning stage is presented. The deflection angle range and resonant frequency of the stage prototype are tested. A series of experiments for open loop and closed loop controls are conducted to validate the performance of the stage after its deflection angle is calibrated. Experimental results show that the angle resolution of the stage is 1.5 μrad; better positioning performance can be achieved because the steady-state peak-to-valley error is 4.2 μrad within ±3 μrad of the final steady state value when a staircase step signal is positioned by closed loop control; better control effect of deflection angle can be obtained by closed loop control compared with open loop control in quasi-static operation mode, because the closed-loop positioning error is 1.9% with a significant decline while the open loop error is 25.0% of the whole range when 1 Hz triangle wave is tracked. Key

Research on the Initial Flow Field Characteristics of Underwater Supersonic Gas Jets

ZHANG Chun， YU Wei， WANG Bao-shou

2018, 39(5):  961-968.  doi:10.3969/j.issn.1000-1093.2018.05.016

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To investigate the complex multiphase flow of supersonic gas jets in still water, an underwater ignition experiment of solid rocket motor is conducted in the pressure tank, and the numerically simulated results of gas-water coupling for the same case are obtained by using Reynolds-averaged Navier-Stokes(RANS) method and volume of fluid(VOF) model. The results show that, after underwater gas jets achieve supersonic flow, the gas bubble appears to be cap-like due to the jet impact effect. Then the gas bubble gradually evolves into an ellipsoid-shaped gasbag with average axial expansion velocity of about 40 m/s. The flow structures inside the gas bubble are very complex, where two shear vortex rings and repeated shock cells exist. The interaction between the boundaries of gas jet and gas bubble may induce the instability of gas jet in the subsequent evolution stage. It is also demonstrated that there exists a part of high pressure in the flow field, and the pressure peaks gradually match with the environmental pressure in the oscillation process. The pressure of opening nozzle closure and the area of nozzle outlet are the two important factors that affects thrust peak value.Key

A Detection Method for Ship Wake Based on Polarization Characteristic

TIAN Jing, BAI Guang-fu, JIANG Yang

2018, 39(5):  969-975.  doi:10.3969/j.issn.1000-1093.2018.05.017

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The polarization characteristics of laser after scattering from bubbles and seawater are theoretically analyzed, and the geometric model of ship wake and the distribution law of bubbles are studied. A laser detection method for ship wake based on polarization characteristic is proposed. The allo-informations of bubbles and ship wake are analyzed, and the feasibility experiment of the proposed detection method is conducted. Experimental results show that the polarization detection device can effectively detect the scattered echo signals from the ship wake region and non-wake region through the proposed detection method. When the laser passes through the different-scale and density bubble regions, the detectors receive the different echo signals. This shows that the proposed detection method can be used for identifying the allo-information of ship wake.Key

Experimental Research on Anti-penetration Performance of Stacked Structure of Ceramic/Kevlar Composite Laminates

HU Nian-ming, CHEN Chang-hai, ZHU Xi, HOU Hai-liang

2018, 39(5):  976-982.  doi:10.3969/j.issn.1000-1093.2018.05.018

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The influence of ceramic panel on anti-penetration performance of Kevlar composite laminates during the penetration of high-speed projectile into Kevlar composite laminates is studied. The anti-penetration performances of 8 mm Kevlar composite laminates, 16 mm Kevlar composite laminates, 3 mm SiC ceramic + 8 mm Kevlar composite laminates, and 3 mm Al₂O₃ ceramic + 8 mm Kevlar composite laminates under high-speed penetration with 13.5 g FSP are experimentally investigated. The Deformation modes of projectile and Kevlar laminates with and without ceramic plate and the average absorbed energy per unit area density are analyzed. The results show that the projectile occurs large deformation and is accompanied by a quality abrasion when penetrating the target with front ceramic plate. The front ceramic plate reduces the shear damage degree of Kevlar laminates, and increases the tensile deformation and inter-layer delamination. Compared with pure Kevlar composite laminates, the front ceramic structure has a stronger anti-penetration ability at higher projectile speed. Key

Research on Dynamic Response and Electrical Output Characteristics of PZT-5H Piezoelectric Ceramics under Strong Shock

TANG En-ling, LI Yue, WANG Rui-zhi, HAN Ya-fei, WANG Li, XIANG Sheng-hai, LI Zhen-bo, GAO Guo-wen, LIN Xiao-chu, LIU Mei, XU Ying-liang

2018, 39(5):  983-990.  doi:10.3969/j.issn.1000-1093.2018.05.019

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The test systems for impact pressure of polyvinylidene fluoride (PVDF) and electrical output characteristics of piezoelectric ceramics were built to study the influence of impact pressure on the electrical output characteristics of PZT-5H piezoelectric ceramics. The one-stage light gas gun is used as a loading means, and the experiments of which the cylindrical aluminum alloy projectiles vertically impact an composite target plate (steel sheet-piezoelectric ceramic-plexiglass) at the speeds of 195 m/s, 487 m/s, 532 m/s and 613 m/s are conducted. The projectile impact on target is analyzed by using ANSYS/LS-DYNA. The time histories of shock pressure of PZT-5H at the different speeds are analyzed. A simplified model of stress wave propagation is established based on the experimental system, and the pressure peak of PZT-5H in the composite structure is calculated by the proposed model. The change rules of PZT-5H piezoelectric ceramics under different peak pressure are analyzed from the time histories of shock pressure, output voltage of piezoelectric ceramics, and charging voltage of energy-storing capacitance. The research results show that the calculated impact pressure peaks are consistent with the simulated and experimental results; the output voltage peak of PZT-5H piezoelectric ceramics rises with the increase in impact pressure peak in the range of pressure peak of 200-700 MPa; the conversion efficiencies of kinetic and electric energies are low when PZT-5H piezoelectric ceramics is impacted by high-speed projectile. As the ratio of energy storage capacity to piezoelectric ceramic capacitance is 5.9∶1, the energy conversion rate of piezoelectric ceramics is 1.1% compared to the primary kinetic energy of projectile.Key

Research on Remaining Useful Life Predictive Model of Machine Parts Based on SVM and Kalman Filter

YU Zhen-liang, SUN Zhi-li, CAO Ru-nan, WANG Peng

2018, 39(5):  991-997.  doi:10.3969/j.issn.1000-1093.2018.05.020

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A new remaining useful life (RUL) predictive model for machine parts is proposed, which combines support vector machine (SVM) and non-linear Kalman filter. The proposed model is expected to fix the awkward situation in that the degradation data from both database and the predicted part cannot be used at the same time by most of the exiting RUL models. The SVM regression model trained by data from full-life tests is treated as the status update equation of non-linear Kalman filter. The time update equation is constructed according to the degradation characteristics of machine parts. RUL estimations and corresponding confidence intervals of point-in-time are computed iteratively after setting the initial RUL value and its variance. The proposed model makes the best use of data from both full-life tests of the same or similar parts and current part during its degradation. The accuracy of RUL estimation, the stability and practical values of the proposed model are illustrated by analyzing a certain type of antifriction bearings. Key

Research on Equivalent Effects of Dilution Ratio and Temperature on Premixed Combustion of Natural Gas

HAN Zhi-qiang， QIAN Yun-shou， TIAN Wei， XIA Qi

2018, 39(5):  998-1005.  doi:10.3969/j.issn.1000-1093.2018.05.021

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The equivalent effects of initial temperature and dilution ratio on premixed combustion of natural gas in the constant volume combustion bomb are studied. The initial pressure p_u and equivalence ratio  are set to be 0.3 MPa and 1.0 in experiment, respectively, and the ball type flame extension method by high speed schlieren photography is used in the experiment. Stretched flame propagation velocity S_n, unstretched flame propagation velocity S_L, Markstein length L_b, laminar combustion velocity u_L and NO_x emission are analyzed in detail. The results show that S_L, flame development duration and combustion duration are nearly identical, but the laminar burning velocity u_L has a big difference at the operating points that have similar S_n value. The influence of dilution ratio on S_L and u_L is greater than that of initial temperature when the dilution ratio is small. Further research finds that the temperature difference ΔT_u= 50 K has equivalent effect on combustion process compared with dilution ratio ΔDR=2%. Under the boundary conditions of the similar S_n, the NO_x emission is lower under the conditions of higher initial temperature and dilution ratio compared with the smaller initial temperature and dilution ratio. Key

Research on Virtual Reality Registration Method for Optical See-through HUD System

AN Zhe, XU Xi-ping， YANG Jin-hua, QIAO Yang, LYU Yao-wen, LIU Yang

2018, 39(5):  1006-1011.  doi:10.3969/j.issn.1000-1093.2018.05.022

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A method for registrating the virtual reality without identification is presented for virtual reality registration of optical see-through automotive head-up display (HUD) in augmented reality system. The composition of HUD system is introduced, the coordinates of each part of the system are defined, and the transformation relations of each coordinate system are established. The initial registration matrix is obtained. Then the image pairs are got to extract the features of image, and the relationship between the images is established by using the method of gray measuring error. Finally, the virtual reality registration matrix of HUD system is obtained by synthesizing the initial matrix and the current matrix. The experimental results show that the correlation distance between the registered value and the real value of the system is 0.088 9, which meets the requirement of registration accuracy. Compared to other methods, the algorithm speed has been improved.Key

Research on Flow Field in Pre-stage of Jet Deflector Servo Valve

LI Jing， YAN Hao， REN Yu-kai， XU Ling-ling， DONG Li-jing

2018, 39(5):  1012-1021.  doi:10.3969/j.issn.1000-1093.2018.05.023

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A precise and complete mathematical model for the flow field in the pre-stage of jet deflector servo valve is established for the design and research of pilot-stage servo valve. The jet process is divided into four stages: initial jet, deflector pressure recovery, secondary jet, and pressure recovery at receiver opening. In the process of two jets in the pre-stage, the different theoretical models are adopted to build the complete mathematical model of flow field in the pre-stage, and the evolution of jet pattern is described in detail. It is found through analysis that the oil enters the flow field in pre-stage and impacts on the side wall of deflector, and then the flow pattern changes, one part of oil flows out of the deflector along its side wall, the flow velocity of the other part of oil decreases, and a high pressure zone is formed downstream. The oil is affected by the flow divider when it flows out of the deflector, and flows into different channels. The flow and pressure characteristic equations are used to derive the pressure gain, and a mathematic relation between load pressure and deflector offset is established. In the process of numerical simulation, the different turbulence models are adopted to analyze the pressure distribution of flow field in the pre-stage. The effectiveness and rationality of the proposed model describing the jet characteristics is verified by comparing and analyzing the numerically simulated results, the external characteristic experimental results and the calculated results of jet model.Key

Research Notes

Research on Distribution Law of Residual Stress in Surface Layer of Cold Roll-beating Spline

CUI Feng-kui , SU Yong-xiang , XIE Ke-ge, DING Ze-han, LI Yu-xi, LI Yan, LI Chun-mei

2018, 39(5):  1022-1032.  doi:10.3969/j.issn.1000-1093.2018.05.024

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The involute spline is studied to improve the surface quality of a spline. The contour method is used to determine the spatial distribution of residual stress during cold roll-beating, and the experimental results are analyzed. The effects of cold roll-beating forming parameters on the distribution of residual stresses and the depth distribution of residual compressive stress at the dedendum, the reference circle and the addendum of spline tooth profile formed by cold roll-beating are studied. The result shows that the surface layer of tooth profile during cold roll-beating has residual compressive stress on it, which is the highest when the depth of spline tooth profile at reference circle reaches at 0.35-0.45 mm. The residual compressive stress at the dedendum is higher than those at reference circle and addendum, and the residual compressive stress at the addendum is the smallest. The increase in the rotational speed can lead to the increase in the peak value of residual compressive stress and the reduction in the depth of residual compressive stress layer of tooth profile of cold roll-beating spline shaft. The increase in the feed rate can lead to the increase in the peak value of residual compressive stress and the layer depth of a tooth profile of cold roll-beating spline. At reference circle the layer depth of residual compressive stress is 0.68~0.98 mm, and the stress peak value is 67.4~80.8 MPa. Key

Descrete Approach to Integrated Design of Clamping Force and Clamping Point Based on Iterative Analysis of Fixturing Performance

WANG Hua-min, QIN Guo-hua, LIN Feng, ZUO Dun-wen, TANG Jia-hui

2018, 39(5):  1033-1040.  doi:10.3969/j.issn.1000-1093.2018.05.025

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In order to guarantee the successful machining of a workpiece, a multiple fixturing is usually used to assure proper clamping forces. A fixturing model and its analysis method of existence of solutions are formulized to judge the fixturing performance of multiple fixturing layout. A clamping surface is meshed as candidate clamping points, and then two adjacent clamping forces are selected with a given step from the beginning of the first candidate clamping point with force-closure. The decreasing coefficient of the current step can be determined according to the the similarities and differences of selected clamping forces. The clamping force at current clamping point can be obtained until the current step is less than the threshold. The planning of “1-clamping force” is completed after the last clamping point with force-closure is found. Each polar angle can be discretized into minimum angles by describing n-clamping forces as a function of one polar radius and n-1 polar angles. “1-clamping force” planning algorithm is called to calculate the magnitudes and placements of “n-clamping forces” at each minimum angle with force-closure. Finally, “n-clamping forces” planning algorithm and analytical method are used to calculate the clamping forces for typical double fixturing layout. Results show that the maximum relative errors of “n-clamping forces” planning algorithm is only 0.979%. The proposed method can be used to transform the continuous design issue of multiple clamping forces into the discrete analysis issue of fixturing performance. Therefore, it can not only apply to the complex workpiece, but also benefit the implementation of automated fixture design. Key