Table of Content

31 October 2019, Volume 40 Issue 10

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Contents

2019, 40(10):  0. 

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Paper

Geometry Design and Contact Force Analysis of C-shaped Monolithic Armature

FAN Wei， SU Zizhou， FAN Tianfeng, ZHANG Tao， ZHANG Honghai， LIU Yong

2019, 40(10):  1969-1976.  doi:10.3969/j.issn.1000-1093.2019.10.001

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The proper electrical contact performance in the initial section of rail is the necessary condition to ensure the normal firing of railgun. In order to enhance the electrical contact performance, an optimal design of C-shaped monolithic armature structure is proposed from two aspects of contact surface and contact pressure. The influence of contact surface on the electromagnetic characteristics of armature is analyzed to obtain the current density and electromagnetic force curves by using high frequency eddy current simulation method. The optimum size and position of contact surface are obtained through comparison and analysis. In order to avoid the contact failure during initial motion, the traditional contact pressure design method (“1 g/1 A”) was modified and optimized to form a transient application method of “1 g/1 A”. The proposed method can be used to simulate the transient characteristics of contact pressure effectively. The proposed method is applied to calculate the contact forces on the different contact surfaces during the initial stage of launching. The calculated results show that the contact force curves of armature and rail are all above the equivalent“1 g/1 A” force curve, which proves that the method can ensure a proper contact between armature and rail. The armature designed by using the transient application method of “1 g/1 A” was tested under the optimal contact surface, in which the better electrical contact in the initial section of rail was achived. Key

Fractional Maxwell Model of Start-up Flow for a Viscoelastic Elastomer Shock Absorber

WANG Zhiqian, MAO Baoquan, FENG Shuai, YANG Yuying, ZHU Rui

2019, 40(10):  1977-1986.  doi:10.3969/j.issn.1000-1093.2019.10.002

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The viscoelastic elastomer has a strong viscoelasticity when it flows inside a shock absorber. The start-up flow models for simulating and studying a viscoelastic elastomer in the orifice and gap of shock absorber have been rarely reported. A fractional Maxwell model with quasi-property is proposed to study the start-up flow of viscoelastic elastomer shock absorber. The start-up flows in the orifice and gap of shock absorber are simplified by unidirectional accelerated flows in a pipe and between two parallel plates of which one is accelerating and the other is at rest. The fractional Maxwell model is developed using finite difference method with real-world initial and boundary conditions. The eproposed model was proved by test. The numerical and test results indicate that the fluid simulated by the fractional Maxwell model had good viscoelasticity, and its stress increase linearly; the curvatures of flow velocity distribution curve of Maxwell model decrease with the increase in the model parameters α, β and ζ; the shape of start-up flow of viscoelastic elastomer in the orifice captured by the test system evolves from a flat shape to a parabolic shape, of which the variation trend is the same as with the result simulated by the fractional Maxwell model; and the simulated maximum fluid level and maximum curvature distance of the fractional Maxwell model are in good agreement with the test results. The maximum errors are 4.79% and 4.67%, respectively. The results show that the proposed fractional Maxwell model can be used to simulate the start-up flow characteristics of viscoelastic elastomer in the orifice or gap of a shock absorber. Key

Analysis of Dynamic Stability of Fixed Canard Dual-spin Projectile

MA Guoliang, CAI Hongming, CHANG Sijiang

2019, 40(10):  1987-1994.  doi:10.3969/j.issn.1000-1093.2019.10.003

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Dynamic stability of a fixed canard dual-spin projectile under the condition of arbitrary time-varying roll angle input is investigated. Force equations and moment equations are presented in body fixed plane frame for fixed canard dual-spin projectile, and a state space model for angular motion is established. Dynamic stability is addressed by using Lyapunov method. The dynamic stability of projectile can be determined by solving a Riccati-type linear matrix inequality. The stability factor equation is derived by using complex square root calculation method, and the H_∞ norm of absolute stability is defined based on the bounded real lemma. Absolute stability criteria for fixed canard dual-spin projectile is proposed，including stability factor constraint and H_∞ norm constraint of absolute stability, and the correctness of stability criteria is validated by using exterior ballistic simulation results. Key

Investigation into the Penetrating Mechanism of Rifle Bullet against the Gelatin Target with Soft/hard Composite Armor

HAN Ruiguo, JIN Yongxi, LU Haitao, WANG Shu, WANG Jianzhong

2019, 40(10):  1995-2004.  doi:10.3969/j.issn.1000-1093.2019.10.004

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In order to investigate the penetrating mechanism of a rifle bullet against the gelatin target with soft/hard composite armor in detail, a numerical model is established by using finite element analysis software ANSYS/LS-DYNA. The blunt impact phenomena during penetrating process and the transient response of gelatin and simulated using the proposed model, and are validated by experiment. The investigation results show that the kinetic energy of rifle bullet is mostly dissipated during the process of penetrating a ceramic plate. The temporary cavity in the gelatin presents in the basic form of ellipsoid, and the maximum depth and expansion velocity of cavity are 25.6 mm and 35.7 m/s, respectively. The pressure wave propagates in gelatin in the form of spherical wave with the largest peak pressure at the impact location, and the pressure amplitude decreases with the increase in travelling distance. The velocity of rifle bullet decreases firstly while the absolute value of acceleration increases, and then they both gradually attenuate to 0. The failure of ceramic plate is mainly caused by the interaction of the compressive and tensile stresses. The numerical results are coincided with the experimental results. Key

Analysis about the Dynamic Stability of Flexible Spinning Vehicle under Thrust and Drag Load

PAN Chenglong, RONG Jili, XU Tianfu, XIANG Dalin

2019, 40(10):  2005-2013.  doi:10.3969/j.issn.1000-1093.2019.10.005

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The dynamics stability under thrust and drag load is researched for dynamics stability of a flexible spinning vehicle. Spinning vehicle is simplified as a non-uniform free-free Timoshenko beam model considering gyroscopic effect. The transverse vibration equation of spinning vehicle in the transient coordinate system is derived using rotor dynamics theory and finite element method. Dynamic stability and transverse vibration response effect of flexible spinning vehicle in the mean axis system and the transient coordinate system are analyzed from spinning speed, thrust and drag. Results show that the drag can be used to improve the stability of spinning vehicle, and the spinning speed has no effect on the instability region in the transient coordinate system; in the mean axis system, the drag leads to the reduction in the stability of vehicle and the decrease in critical thrust and critical speed, and the spinning speed can result in the increase in instability region and make the static instability become the dynamic instability. The moment of inertia and shear effect reduce the system stability. The shear effect has a greater influence especially on the second-order frequency compared with the moment of inertia of transient coordinate system.Key

Analysis of Kinetic Energy of Behind-armor Debris Generated during the Normal Penetration of EFP into Armor Steel

XING Boyang, HOU Yunhui, LI Taihua, ZHANG Dongjiang, LIU Rongzhong, GUO Rui

2019, 40(10):  2014-2021.  doi:10.3969/j.issn.1000-1093.2019.10.006

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The normal penetration of explosively formed penetrator (EFP) into armor steel is test and simulated to obtain the origin and axial position of behind-armor debris (BAD) with bigger kinetic energy. The axial distribution of velocity and mass of BAD generated during the normal penetration of EFP into armor steel under the conditions of different thicknesses of target (30-70 mm) and different impact velocities of EFP (1 650-1 860 m/s) were analyzed by the simulation method. The results indicate that the velocities of BAD from target and EFP increase approximately linearly with its axial position, the slope of envelope line is also constant when the target thickness or impact velocity of EFP is constant, and the intercept of envelope lines is affected weakly by debris origin (generated by target or EFP); the heavy (>10 g) BADs from target are in the middle of BAD cloud or close to target, and the heavy (>10 g) BADs from EFP are far from target; and the BADs with bigger kinetic energy are generated by EFP and far from target. Key

Simulation Analysis of Distribution of Fragments of Hypervelocity 93W Projectile Impacting on a Steel Plate Target

MA Kun, LI Mingrui, CHEN Chunlin, FENG Na, ZHAO Nan, KE Ming, ZHOU Gang

2019, 40(10):  2022-2031.  doi:10.3969/j.issn.1000-1093.2019.10.007

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In order to study the distribution of fragments of hypervelocity 93W projectile impacting on a steel plate target, the AUTODYN software is used to do the smoothed particle hydrodynamics simulation, and the GRAY solid-liquid phase equation of state is added as a user subroutine in the software. The hypervelocity impact process under the conditions of different impact velocities and body diameters was simulated, and the simulated results were verified by the experimental results. The distribution characteristics of mass, quantity, momentum, temperature and other parameters of the fragments were obtained based on the breadth-first search algorithm for fragments recognition. The study results show that the quantity and quality of fragments are mainly concentrated at the front part of fragment group, are less at its middle part, and are increased at its tail part. The big mass fragments are mainly concentrated at the front and tail parts of fragment group, and their lateral velocities are low. The front part of the fragment group has higher quality, and higher axial and lateral momenta, which represents the damage power of fragment group. High temperature fragments mainly distribute in the middle to front part of the fragments group, and there are many low temperature fragments at the front and tail part of the fragment group. The resultant velocity of high temperature fragments is above the medium velocity of all fragments, and the fragments with high resultant velocity are distributed in all temperature sections. A fragment group with more fragments and higher total mass can be produced by increasing the diameter of projectile than increasing the impact velocity. The change of diameter of projectile or impact velocity has a more significant effect on the front part of fragment group, so the damage power of fragment group can be effectively improved. Key

Research on Dynamic Properties of Aluminum Foam Sandwich Structure Impacted by Projectiles with Different Shapes

GUO Yazhou, LIU Xiaochuan, HE Siyuan, WANG Jizhen, YANG Hai

2019, 40(10):  2032-2041.  doi:10.3969/j.issn.1000-1093.2019.10.008

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The experiments of impacting the aluminum foam sandwich panels by spherical, pointed and flat nose projectiles launched from gas gun were carried to study the dynamic properties of aluminum foam sandwich structure. Based on LS-DYNA software, the impacts of different projectiles on aluminum foam sandwich panels are simulated, and the influences of different projectile shapes and speed on the energy absorption characteristics of sandwich panels are analyzed. The experimental results are well in agreement withe the simulated results. The results show that the deformation mode of pointed projectile is basically the same as that of spherical projectile, the flat nose projectile damages the sandwich panels more seriously during penetrating, the front and rear panels exhibit a tear failure mode, and the compacted aluminum foam is bonded to the rear panel after penetration. The head of pointed projectile is sharp, the contact area between the warhead and the target is small, and the penetration force is large. The contact area between the warhead of flat noise projectile and the target is large, and the penetration force is small, but the target damage area is large and the impact is more effective. The impact effect of spherical projectile is between those of pointed and flat nose projectiles: the improvement in the thicknesses and material properties of front and sandwich panels can better improve the penetration resistance of aluminum foam sandwich panel at low impact speed; the proportion of energy absorption of rear panel increases gradually, the improvement in the thickness and material properties of rear panel can improve the penetration resistance of sandwich panel at high impact speed. Key

Calibration of Seeker Angle-measuring Error with Block Three-order Polynomial

YUAN Dongming， DING Yalin, ZHANG Jian

2019, 40(10):  2042-2049.  doi:10.3969/j.issn.1000-1093.2019.10.009

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An angle-measuring error calibration method based on block three-order polynomial is proposed to reduce or eliminate the effects of machining error, assembly and adjustment error, sensor error on the angle-measuring accuracy of a laser seeker. With the consideration on the characteristics of each systematic error and the impact of random error during the experiment on calibration, the mapping relations between the pitch and yaw angles of the detector output and the real pitch and yaw angles of pointing vector are established through the block three-order polynomial for the calibration of angle-measuring error. The research results show that the calibrated means of yaw and pitch angle errors are decreased from 0.136 0° and 0.336 4° to 0.004 7° and 0.001 5°, respectively, and the standard deviations of yaw angle error and pitch angles are reduced from 0.382 0° and 0.375 2° to 0.026 9° and 0.022 7°, respectively. The proposed calibration algorithm has high accuracy and fine consistency in the field of view of seeker, and is easy to be used. A complicated mathematic model needs not to be established for parameter recognition when the proposed calibration method is used. Moreover, the method can be used for the error calibration of similar systems. Key

Effect of Friction on Electric Linear Load Simulator and Research on Friction Suppression

PAN Weidong, FAN Yuanxun, LEI Jianjie, CAO Dawei, LU Pengcheng, XU Zhiwei

2019, 40(10):  2050-2059.  doi:10.3969/j.issn.1000-1093.2019.10.010

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In order to suppress the effect of friction on electric linear load simulator (ELLS), the simulation analysis and experimental methods are used to analyze the effect of friction on ELLS, the genetic algorithm is used to identify the friction model in ELLS, and the relationship between friction and velocity is obtained. A hybrid control method of friction feedforward and variable gain PID is proposed, the friction feedforward compensation is used to eliminate the effect of friction, and the variable gain PID is used to further suppress the phase lag of ELLS at low velocity. Comparative simulation and experiment were made. The simulated analysis and the experimental results show that, compared with traditional PID control, the loading wave distortion of ELLS using the friction feedforward and variable gain PID is suppressed, and the loading error and phase lag are significantly reduced. The proposed control method can better suppress the effect of friction on ELLS and improve the loading accuracy. Key

Distributed Guidance Law for Multi-UAV Cooperative Tracking

FENG Yunduo， WU Yanxuan, CAO Haozhe

2019, 40(10):  2060-2069.  doi:10.3969/j.issn.1000-1093.2019.10.011

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The multi-unmanned aerial vehicles (UAVs) cooperative tracking can not only get the information of targets in various directions, but also respond to the interference of obstacles and reduce the probability of losing the targets. A distributed guidance law is presented for multi-UAV cooperative tracking that relies only on information of target and neighboring UAVs. The distributed guidance law is used to avoid the dependence of UAV formation on the leaders in traditional leader-follower method and improve the robustness of formation. A distributed cooperative guidance law of multi-UAVs based on relative distance and bearing angle was designed for stationary targets, and the stability of the cooperative guidance law was proved. The guidance law is used for tracking the targets with constant and variable speeds. The hardware-in-the-loop simulation of multi-UAVs tracking the targets was made by using the X-Plane software, MATLAB/Simulink software and flight controller (hardware). The simulated results show the effectiveness of proposed guidance law.Key

Research on Evaluation Method for Testability Index and Modeling of Missile System Based on GSPN

ZHAI Yuyao, SHI Xianjun, L Jiapeng

2019, 40(10):  2070-2079.  doi:10.3969/j.issn.1000-1093.2019.10.012

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A modeling method based on generalized stochastic petri net (GSPN) is proposed for the determination of missile testability indexes. Based on the GSPN model of three-dimensional structure of missile system, the planar GSPN model of each subsystem is taken as the research object, and the fault detection and maintenance process of missile system are analyzed. The missile system failure mode is classified according to the national military standard. The reachable marking graph based on GSPN model is isomorphic to the embedded Markov chain, the real state set and the disappeared state set are used to characterize the change of the library, and the isomorphic method is used to solve the testability indicators. Taking a certain missile subsystem as an example, the testability indicators were evaluated, and 92% of fault detection rate and 90% of isolation rate were obtained. The effectiveness of the proposed modeling method and corresponding algorithms are verified by using the testability indicators. Key

The Application of Fixed-interface Level Set Method in the Calculation of Detonation Wavefront Propagation

ZHANG Li， WU Kaiteng

2019, 40(10):  2080-2087.  doi:10.3969/j.issn.1000-1093.2019.10.013

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A fixed-interface Level Set method is proposed for the deviation of interface position caused by reinitialization. The basic idea of the fixed-interface Level Set method is to construct a condition that keeps the interface immobile in the process of reinitializing the two adjacent iterations, thus deducing the calculation formula for the smooth parameters. The proposed method is used to correct the fixed smooth parameters to the changed smooth parameters. The numerically simulated results show that, compared with the traditional Level Set method, the fixed-interface Level Set method can fix the interface position well in the process of reinitialization, and the mass conservation is improved. The fixed-interface Level Set method effectively avoides the deviation of detonation wavefront caused by error accumulation. It is suitable for solving the propagation problem of detonation wavefront. Key

Equivalent Static Load Dynamic Coefficient for Blast Load

GENG Shaobo, GE Peijie, LI Hong, XU Peng

2019, 40(10):  2088-2095.  doi:10.3969/j.issn.1000-1093.2019.10.014

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Elastic and elastic-plastic equivalent single-degree-of-freedom (SDOF) differential equations are established for blast load. The relation of load equivalent duration and load real duration can be reached using the same values of overpressure peak and positive overpressure impulse. The displacement solutions are solved for linear and exponential attenuation blast loads. Elastic-plastic process is divided into later and earlier entering elastic-plastic stages for entering plastic time. The function expressions of ductility ratio and dynamical coefficient are deduced for linear and exponential attenuation blast loads with elastic-plastic stages. Three dynamical coefficients for linear and exponential attenuation blast loads with shape adjustment parameters a of 1.27,1.44 and 1.61 were calculated according to a of exponential attenuation blast load and current anti-blast design specifications. The results show that the linear exponential blast load model adopted by anti-blast design code is more suitable for structure design with ductility ratio β＜3.0. The exponential attenuation blast load model can be used for structure design with ductility ratio β≤5.0, especially β≥3.0. Key

Consistency Algorithm for Resource Management of Shipborne Phased Array Radar Network

YANG Shanchao， TIAN Kangsheng， WU Changfei

2019, 40(10):  2096-2104.  doi:10.3969/j.issn.1000-1093.2019.10.015

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In the distributed resource management of shipborne phased array radar network, the inconsistent problem of resource management schemes is due to the estimated deviation of node states and the noise disturbance during information transmission between nodes. A consistency management algorithm for resource which is suitable for different topologies is proposed to solve the problem above. The topology of radar network is represented by using the graph theory, and the requirement analysis of consistency resource management is conducted for shipborne phased array radar network. A local optimization model for resource management is constructed from two aspects: radar load balancing and minimum resource consumption. A local resource management scheme of each radar is generated through this model. The consistency algorithm is used to obtain a global consistency resource management scheme through the information transmission between radar nodes of network. Simulated results show that the proposed algorithm is effective, and it can be applicated to conduct resource management for radar networks regardless of the topology and information transmission noise.Key

Site Selection and Coverage Optimization of Ground-to-air Ultra-short Wave Data Link

LIU Hongbo, MENG Jin, LIU Qintao, MA Junkai

2019, 40(10):  2105-2110.  doi:10.3969/j.issn.1000-1093.2019.10.016

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For the selection of data link site, a mathematical modeling is carried out by using raster analysis method, and the data link site selection optimization is transformed into 0-1 integer programming problem. Based on the maximum coverage area model and the maximum coverage value model, the procedure for solving the coverage area by radio spectrum planning and management software is presented, and the calculation cases of selecting 4 sites in the existing 5 sites are designed. On the basis of the user-defined coverage area, allowableable station establishing area, type ofestablished station, type of receiving station, and the number of established stations, a coverage scheme is determined, the parameters, such as site layout conditions, coverage conditions and evaluation conditions, are set, and the cost evaluation analysis and the coverage optimization are made. The fast optimization technology combining electronic map and coverage model is used to improve the computing efficiency of site selection process. The research method is suitable for the construction demonstration, and operation and maintenance management of data link site.Key

The Influence of Wetted Area of Vehicle on the Wake Structure of Cavity

WANG Wei, WANG Cong, LI Conghui, SONG Wuchao

2019, 40(10):  2111-2118.  doi:10.3969/j.issn.1000-1093.2019.10.017

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In order to study the influence of wetted area of vehicle on the wake structure of ventilated supercavity, the CFD method was used to simulate the unsteady variations of the wetted area and the vorticity in the wake of a supercavitating vehicle in the process of changing the angle of attack. The transformation mechanisms of different flow structures in the wake of a cavity are revealed by analyzing the changes of pressure and vorticity in the wake flow field. The results show that, under the low Froude number, a high pressure zone exists above and below a twin-vortex tube at the tail of cavity. Due to the influence of environmental pressure difference, the pressure below the tube is higher than that above it. The flow direction between the two vortices is upward to form a pair of twin vortices rolled up in the center. With the increase in the angle of attack of vehicle, the wetted area causes the cavity to form the wake structure of three-vortex tube. The pressure in the high pressure area below the vortex tube is lower than that above it, and the flow direction between the two vortices below the cavity is downward to form a pair of twin vortices rolled down in the center. During the transition from the twin-vortex tube to the three-vortex tube, the pressures and velocities of the upper and lower parts of cavity wake change alternately, thus forming the wake structure of four-vortex tube. Key

A Cooperative Localization Method for AUVs Based on RBF Neural Network-assisted CKF

XU Bo, LI Shengxin, JIN Kunming, WANG Lianzhao

2019, 40(10):  2119-2128.  doi:10.3969/j.issn.1000-1093.2019.10.018

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For cooperative localization of autonomous underwater vehicles (AUVs), a multi-AUV cooperative localization method based on radial basis function (RBF) neural network-assisted cubature Kalman filter (CKF) is proposed to solve the problem that the cooperative localization performance is restricted by various factors, such as internal and external factors of cooperative localization system. When a basic reference position is available, the filtering innovation, prediction error and filtering gain, which are extracted from the nonlinear filtering CKF, are used as the inputs of the input layer of RBF neural network, and the filtering error value is used as an output to train the RBF neural network. When the reference signal is interrupted, the trained RBF neural network is used to compensate the estimated value of CKF filter state, and then a new estimated state is obtained. The cooperative localization experiment with the input error of multi-AUV cooperative localization system was simulated based on the lake area test data. The experimental results show that the average positioning error of the proposed method is reduced by 70% compared to average positioning error of RBF without CKF. Key

Acoustic Scattering Characteristics of Underwater Air-filled Cavity Corner Reflector

LUO Yi， CHEN Xin

2019, 40(10):  2129-2135.  doi:10.3969/j.issn.1000-1093.2019.10.019

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In accordance with the weakness of low target strength and obvious frequency characteristics of underwater elastic metal plate corner reflectors, a new air-filled cavity elastic corner reflector is designed. The scattering acoustic fields of underwater air-filled cavity corner reflector and single layer metal sheet corner reflector are simulated and compared by using the structural finite element coupled fluid boundary element method (IBEM). The influences of thickness and incident angle on the target strengths and scattering mechanisms of different corner reflectors within 5-15 kHz frequency of incident wave are analyzed and verified through experiment. The research results show that the air-filled cavity corner reflector has great scattering intensity and no obvious frequency characteristics, and the decoupling effect is obvious. The simulated results are in basic agreement with the experimental results. Compared with the cumbersome single layer metal corner reflector with weak reflection intensity, the air-filled cavity corner reflector has better acoustic reflection performance and lighter weight, and is an ideal underwater acoustic reflection device. Key

Research on Preparation and Performance of Green Camouflage Aqueous Foam

WANG Xiang, YUAN Jian, JIANG Xiaojun, LU Yanli, MU Jingyang

2019, 40(10):  2136-2141.  doi:10.3969/j.issn.1000-1093.2019.10.020

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For the incompatibility between foaming power and stability，and poor optical camouflage performance of aqueous foam, a new camouflage material is studied. A green camouflage aqueous foam with high stability was made by mixing anionic surfactant sodium dodecyl sulfate and cationic surfactant octadecyl trimethyl ammonium chloride, and using the color matching technology of green camouflage colorant. The stability and optical camouflage performance of aqueous foam were analyzed. The results show that the structure of aqueous foam is closed-pore alveolate, the shape is irregular, and the size is uneven. The average size of aqueous foam is 0.9-2.5 mm. When the ambient temperature is -2-30 ℃ in climate simulation experiment, the foaming ratio of aqueous foam is 21-32, and the duration is 73-185 h, which show that the foaming power is compatible with the foam stability. The field experimental shows that the duration of aqueous foam meets the temporary camouflage requirement. The green camouflage aqueous foam has the same colour and spectral reflection characteristics as the green plants in the range of 380-1 100 nm, which shows that the material has visible-near infrared camouflage properties. Thus the degree of aqueous foam application in military camouflage is improved. Key

Failure Characteristics of High-lock Bolts for Composite Structures under Dynamic Combined Loading

XI Xulong, LIU Xiaochuan, BAI Chunyu, ZHANG Yu, SHU Wan, GE Yujing

2019, 40(10):  2142-2150.  doi:10.3969/j.issn.1000-1093.2019.10.021

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In order to study the failure characteristics of high-lock bolts used in composite structures under dynamic combined loading, a special experimental support device is designed based on the high velocity hydraulic servo-testing machine, and a loading method of collision type is proposed. Failure tests of CFBL1001-6-6/ CFNT1003CY6 high-lock bolts were conducted under the conditions of 0.01 m/s, 0.10 m/s and 1.00 m/s loading speeds, and pure tensile, 30° tensile-shear coupling, 45° tensile-shear coupling, 60° tensile-shear coupling and pure shear state, and the parameters of failure equation were obtained by fitting the experimental results. The experimental results show that the failure parameters of high-lock bolts under dynamic combined loading can be effectively obtained by using the proposed experimental method, and the failure mode and failure load of high-lock bolts are affected greatly by the loading mode and less at the loading speed.The experimental results are good agreement with the predicted results of failure equation, which indicates that the failure characteristics of high-lock bolts can be well represented by the failure equation. Key

Numerical Calculation and Performance Study of Aerostatic Bearing with Multi-hole Integrated Restrictor

LU Zhiwei， ZHANG Jun'an， LIU Bo

2019, 40(10):  2151-2160.  doi:10.3969/j.issn.1000-1093.2019.10.022

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An aerostatic bearing with multi-hole integrated restrictor is designed to reveal the changing law of load-bearing performance of aerostatic bearing with concentrated throttle orifices, and the load-bearing capacity and stiffness of the bearing are studied. The governing equations in polar coordinates are established based on the physical model of aerostatic bearing with multi-hole integrated restrictor. The governing equations were deduced by discrete difference method and solved numerically by finite difference method and flow balance principle, and the pressure distribution of the gas film flow field was obtained. The bearing capacity, stiffness and other performance parameters of aerostatic bearing were analyzed and verified by experiments. The results show that the film pressure of aerostatic bearing increases gradually with the decrease in air clearance. In the case of the same air clearance, the bearing capacity of bearings increases gradually as the number of throttle orifices increases and the orifice diameter increases. In the case of a certain air clearance, the bearing has the optimum stiffness. The bearing stiffness increases first and then decreases gradually with the increase in the number of throttle orifices. As the bearing supply pressure increases, the bearing capacity and optimum stiffness of aerostatic bearing increase significantly. The experimental results are in good agreement with the numerical results, which has verified the feasibility and correctness of numerical calculation and numerical method. Key

The Design of Large-scale Full Solar Spectrum Irradiation System for Solar Simulator

LIU Jianhe, BAI Hailong, ZHAO Yudan

2019, 40(10):  2161-2169.  doi:10.3969/j.issn.1000-1093.2019.10.023

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Large-scale full solar spectrum irradiation system is an important part of the solar simulator. Irradiation non-uniformity is one of the key technical indexes for the large-scale solar simulator. Some technical problems about difficultly meeting the national standard and the poor optical spectra matching property of light sources exist in traditional solar simulators. Regarding the present issues of the large-scale solar simulators, a full-spectrum irradiation system was designed, and the irradiation uniformity of the system was simulated by using the software Zemax. An innovative concept, irradiance decay pattern, is put forward, and the irradiation uniformity is optimized in this way. A plasma light source produced by So-laronix, Switzerland is used, and the spectrum of full-spectrum solar irradiation system can reach Level A of IEC standard. The irradiance of the proposed system was tested by using a spectral radiometer in the full-spectrum scope. The test results show, when the irradiance is 280 W/m², the irradiance nonuniformity is 5.7% if the irradiance decay pattern is switched on, or 8.4% if the pattern is off. Referring to the national standard GB/T12637—90 General specification for solar simulator, in the effective radiation area of 2 400 mm×6 000 mm, the irradiance uniformity is better than Level C, and almost reaches Level B. Key

Research Notes

Influence of Ultrasonic Elliptical Vibration Cutting Trajectory Change on Surface Morphology

JIANG Yu'an, PI Jun, YANG Guang, JIANG Tao, SHEN Zhihuang

2019, 40(10):  2170-2176.  doi:10.3969/j.issn.1000-1093.2019.10.024

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The motion characteristics of tool tip trajectory in ultrasonic elliptical vibration cutting are studied by changing the tool nose's amplitude and phase difference. The influences of elliptical vibration cutting trajectory shape and trajectory deviation on the machined surface morphology are analyzed, and a residual height model formed by the change in elliptical vibration cutting trajectory in cutting direction is established. A self-developed ultrasonic elliptical vibration cutting device is used to accurately control the change of elliptical vibration cutting trajectory achieved by changing the phase difference, and the influence of cutting trajectory change on the machined surface quality is analyzed. The experimental results show that the residual height in cutting direction and the change of tool dynamic angle caused by the cutting trajectory change are the important factors affecting the machined surface quality. A phase difference in ultrasonic elliptical vibration cutting is beneficial to restrain the burr and edge collapse and improve the surface quality. Key