Table of Content

30 December 2017, Volume 38 Issue 12

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Contents

2017, 38(12):  0. 

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Paper

Power Flow Control Strategy of Hybrid Power System of Electric Drive Armored Vehicle

LIAO Zi-li, XIANG Yu, LIU Chun-guang, LI Jia-qi

2017, 38(12):  2289-2300.  doi:10.3969/j.issn.1000-1093.2017.12.001

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A multi-algorithm-based power flow control strategy is established for a kind of power source of series hybrid drive system, in which the disparate control objectives are realized by using different algorithms. The wavelet transform is used to separate the high and low frequency components of the load demand power. The frequency values are distributed to the super capacitor and the power sources with low output cutoff frequency to realize the matching of load frequency characteristic and power source output characteristic. The fuzzy controller is used to realize the optimal control of battery state of charge. A secondary allocation strategy is designed to control optimally the instantaneous efficiency of system when the low frequency component of optimal load demand power is allocated between battery and engine-generator set. The simulation analysis and vehicle test results show that the proposed power flow control algorithm can be used for the multiobjective optimization control of multi-power source system, and it is suitable for power flow control of armored vehicle hybrid power system.Key

Steering Control Driver Model of Skid Steering Vehicle Based on Gaussian Mixture Model-Hidden Markov Model

WANG Bo-yang， GONG Jian-wei， GAO Tian-yun， CHEN Hui-yan， XI Jun-qiang

2017, 38(12):  2301-2308.  doi:10.3969/j.issn.1000-1093.2017.12.002

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In order to solve the unmanned lateral control problem of the skid-steering vehicle based on clutch and brake steering structure, the GMM-HMM model is used to predict the steering mode. The skilled driver's steering operation data acquired from the numerous filed tests is applied to establish the model. The observation states of the HMM model are made up of the velocity and the heading deviation based on the GMM model. The hidden states of the HMM model are made up of the cluster labels of the steering stick position including both of the left and the right sides. The driver-vehicle interaction model of the skid-steering vehicle based on clutch and brake steering structure is established from data training. The driving skills and the vehicle dynamics are described in the statistics way. The model is applied to estimate the steering mode, and the results have proved that the steering mode can be estimated properly based on the driving skills. Key

Analysis about Motion of Centripetal Tracked Omnidirectional Mobile Platforms

ZHANG Yu-nan， YANG Huai-bin， HUANG Tao， ZHANG Shu-yang， FANG Yuan

2017, 38(12):  2309-2320.  doi:10.3969/j.issn.1000-1093.2017.12.003

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For the deficiencies of current wheeled omnidirectional platform in loading capability and vibration, centripetal tracked omnidirectional mobile platforms are designed based on the structure of omnidirectional mobile track, and their motion characteristics are analyzed. The layout forms of three-and four-track omnidirectional platforms are presented, and the kinematics and dynamics models are established. Anisotropies of omnidirectional platforms are analyzed to achieve the distribution rules of maximum speed and maximum acceleration, and determine the most suitable offset angles of α≥π3 rad and α≥π4 rad. Selecting same roller offset angle to compare the motion characteristics of mobile platforms, the four-track platform has greater improvements than the three-track platform in speed and acceleration, but the three-track platform has better motion balance. The advantages and disadvantages of two platforms in volume, weight, control and other aspects are compared. The virtual prototypes of two platforms are developed using ADAMS, and three kinds of typical motions are simulated: longitudinal motion, lateral motion, central steering motion. The motion characteristics of the platforms are verified. The simulated results show that the centripetal platforms have omnidirectional mobile ability. Key

Research on the Natural Frequencies of a Large-caliber Howitzer Barrel Based on Radial Point Interpolation Method

ZHANG Hong-jun， QIAN Lin-fang， CHEN Guang-song， XU Bin

2017, 38(12):  2321-2327.  doi:10.3969/j.issn.1000-1093.2017.12.004

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Considering the influence of muzzle brake and breech ring, an elastic dynamics equation of the barrel is established. Combining the advantages of the finite element method and the meshless method, an element supported domain radial point interpolation method is proposed based on the radial basis point interpolation method, in which the element supported domain is treated as the interpolation domain of the integration point to establish the discrete elastic dynamics equation. The natural frequencies of barrel are estimated by solving the dynamic equation. Finally, the effectiveness of the proposed method is demonstrated by numerical examples and experiments, and the results show that the proposed method can provide more accurate results with the same element number，which can coincide with the experimental results. Key

Analyses of Parameter Sensitivity for Position and Attitude of Projectile at Muzzle

LUO Zhong-feng， GUAN Xiao-rong， XU Ya-dong， XU Cheng

2017, 38(12):  2328-2336.  doi:10.3969/j.issn.1000-1093.2017.12.005

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The influences of cannon structure parameters on position and attitude of projectile at muzzle are reasonably assessed to improve firing accuracy. To solve the problem above, an interaction model of projectile and cannon was established firstly, which describes the position and attitude of projectile at muzzle with the input variables of 6-degrees-of-freedom rigid body trajectory equations. An approach of dynamic sensitivity analyses is presented, which is based on the theory of absolute correlation degree. The proposed approach is primarily used to compute the degrees of closeness among actual sequences of system performance indexes and their target sequences in different given conditions. Then on the basis of calculated results, statistical analyses are conducted, which shows the influences of controlled variables on system performance indexes in the given ranges and their optimum ranges. The dynamic sensitivity analysis of position and attitude of projectiles at muzzle is conducted with the help of the above model and the suggested approach on account of barrel and projectile's parameters. The proposed approach and relevant results were proved to be reasonable and feasible by comparisons. Key

Design and Development of Integrated Software for Design and Analysis of Rotary Locking Mechanism of Firearms

WEI Zhi-fang, LIU Wei, LAN Xuan, WANG Zhi-wei

2017, 38(12):  2337-2347.  doi:10.3969/j.issn.1000-1093.2017.12.006

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In order to improve the design quality and efficiency of rotary locking mechanism of firearms, the design and analysis integration idea is taken into the design process, and an integrated design and analysis software is researched and developed for the rotary locking mechanism. In consideration of the design characteristics of locking mechanism, the software should include the basic modules of structural parameter design, parametric modeling of parts, automatic assembly and interference analysis, mechanism motion analysis, structural strength analysis and data management. The overall framework of software based on UG software integration calculation programs and function module is put forward. Key technologies, such as software integration framework design and development, UG/OPEN API function call, UG/MOTION/ADVANCED SIMULATION module application and secondary development, data management and transfer, are worked out. According to Visual Studio 2010 programming tools and secondary development of UG, the integrated design and analysis software for rotary locking mechanism is developed. The feasibility and practicability of the software are verified by concrete examples. The results show that the software can make the design, parametric modeling, simulation analysis of rotary locking mechanism easy to complete in the UG unified environment, and shorten the time of data exchange between design and analysis. Key

Breakdown and Protection of Semiconductor Device in a Sequentially Fired Pulse Forming Network

LI Zhen-chao， JIN Chao-liang， DAI Ling， CHEN Chong， JU Lan， LIN Fu-chang

2017, 38(12):  2348-2353.  doi:10.3969/j.issn.1000-1093.2017.12.007

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In military applications, pulse forming network (PFN) needs to generate a flat-top current waveform by sequentially firing pulse forming units (PFUs)for the uniform acceleration of armature. However, when PFN works under this condition, a fly-wheel diode in PFN withstands a high reverse recovery voltage which may cause the failure of the fly-wheel diode. An approach in which the damage of semiconductor device can be eliminated by preventing from the reverse voltage is proposed through the theoretical analysis of reverse recovery process of diode. The mathematical expression of the proposed approach is derived from the equations of PFN circuit. This expression is used to calculate the parameters of a 600 kJ pulse power supply (PPS) constituted of 8 individual 75 kJ PFN modules. The PPS successfully generates an approximate flat-top current waveform without device damage. The test results show that the reverse recovery voltage can be eliminated by selecting proper circuit parameter. Key

Design and Experiment of Compact Explosively Driven Ferromagnetic Generator

LIU Peng, ZHANG He, MA Shao-jie, SHI Yun-lei

2017, 38(12):  2354-2362.  doi:10.3969/j.issn.1000-1093.2017.12.008

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A compact explosively driven ferromagnetic generator for explosive magnetic flux compression generators was developed. Its working principle and process are analyzed by establishing a magnetoelectric transformation model. The static magnetic field of open magnet in the electrical source is analytically calculated and numerically simulated. The calculation method of magnetic flux of magnet section is presented, and a design method of pulse source is provided. The pulse sources of different magnet materials and detonation method are test. The results show that the N35 explosively driven ferromagnetic electrical source (double-ended detonation) outputs 1 100 A pulse current at 1.2 μH inductive load; higher output current and energy parameters in the load could be obtained by using high-performance magnet material; the energy conversion efficiencies of single-ended detonation and double-ended detonation are η_t≮14.6% and η_t≮24.4%, respectively; the explosively driven ferromagnetic generator is only suitable for driving a lower impedance load, and the indirect feed mode is more reasonable when it is used for HMFCG' initial energy source.Key

Numerical Investigation on the Effect of Rotating Band on Aerodynamic Characteristics of High-speed Spinning Projectile

MENG Peng， CHEN Hong-bin， QIAN Lin-fang， LI Ren-feng， LE Gui-gao

2017, 38(12):  2363-2372.  doi:10.3969/j.issn.1000-1093.2017.12.009

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To investigate the effect of rotating band on the aerodynamic characteristics of high-speed spinning projectile, the second-order Roe-type upwind scheme and SST k-ω turbulence model are used to solve the three-dimensional Navier-Stokes equations. Moving boundary caused by the spinning of projectile is processed using sliding mesh method. The aerodynamic characteristics of 155 mm spinning projectile without rotating band are calculated, and the numerical results are in good agreement with the wind tunnel test data presented in Ref.［6］. The flow fields over high-speed spinning projectiles with and without rotating band are simualted under the conditions of different Mach numbers and angles of attack. By analyzing the differences of flow-field structures and aerodynamic characteristics, the conclusions are drawn as follows: the pressure distributions of two projectile models in front of rotating band are basically identical, but the rotating band structure increases the aerodynamic resistance area of the projectile, thus leading to the increase in resistance coefficient, and there is a great difference between the pressure distributions of the two spinning projectiles in the rear of the rotating band. This proves that the impact of the rotating band structure on the aerodynamic characteristics of spinning projectile cannot be neglected. Key

Numerical Simulation on the Characteristics of Muzzle Flow Field of Embedded Aircraft Gun

GUO Ze-qing, QIAO Hai-tao, JIANG Xiao-hai

2017, 38(12):  2373-2378.  doi:10.3969/j.issn.1000-1093.2017.12.010

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In order to study the influence of flight velocity on the muzzle flow field characteristics of embedded gun, the field development processes in four different conditions are numerically simulated based on the Navier-Stokes equations and the k-ε turbulence model. The basic characteristics of the muzzle flow field under static condition and supersonic flight condition are compared, and the changes of blast intensity are analyzed. The result shows that the muzzle flow field structure of embedded aircraft gun during the supersonic flight includes propellant gas shock wave, separation shock wave, slip surface and so on; the magnitude of separation shock wave at a certain flight velocity is positively correlated with the Mach number; and the peak overpressure of blast changes with the Mach number. Key

Research on Dynamic Fracture Behavior of Polymer Bonded Explosive Simulant Based on Cohesive Crack Model

CUI Yun-xiao, CHEN Peng-wan, GUO Bao-qiao, David A. Cendón, ZHOU Zhong-bin

2017, 38(12):  2379-2385.  doi:10.3969/j.issn.1000-1093.2017.12.011

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The dynamic tensile fracture behavior of polymer bonded explosive simulant was investigated. The experimental test was performed on notched semi-circular bending (NSCB) samples of the material by using the split Hopkinson pressure bar(SHPB) apparatus. With the aide of a high-speed camera, the dynamic displacement and strain field during the dynamic fracture process were obtained by the digital image correlation (DIC) technique. Based on cohesive crack model (CCM), the numerical simulation of the same conditions was performed. Compared with the results obtained by simulation and experiment, the good agreement was found for the time history of tensile stress and the displacement and strain fields during dynamic fracture. The behavior of crack propagation of PBX during NSCB test was analyzed by the CCM. Furthermore, the width of crack in NSCB sample is about 15% smaller than the experimental results. Key

Modeling and Simulation of Rigid-flexible Coupling Dynamics of Vehicular Cold Launch System

YAN Pan-yun， LIANG Guo-zhu， LYU Yong-zhi， QI Zhi-hui， LIU Hu

2017, 38(12):  2386-2394.  doi:10.3969/j.issn.1000-1093.2017.12.012

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In order to analyze the influences of long span flexible chassis and lifting auxiliary bracket on the dynamic response of vehicular cold launch system and meet the requirements of fast and accurate simulation, the Cartesian coordinate method is used to describe the motion of the body to fit the characteristics of complex constraints, and then the floating coordinate system method is used to describe the deformation of the flexible body, and the degree of freedom of system is reduced by modal synthesis method. The Hertz contact model is proposed to reproduce the release process of the missile weight. A rapid simulation model of rigid-flexible coupling dynamics of vehicle cold launch system is established. The simulation model is verified by the experimental results based on the launch simulation test system and the simulated results based on a real vehicular cold launch system, and then the rigid-flexible coupling dynamic response analysis is made for the vehicular cold launch system. The results show that the proposed simulation model is able to quickly and effectively analyze the dynamic responses of the launching process of vehicular cold launch systems and meet the requirements of the engineering design, and the flexible chassis model is more reasonable than the rigid chassis model. Furthermore, the singular point of phase portrait of the canister mouth's x-coordinate is a stable focus during the launch process, thus indicating that the vehicular cold launch system can be restored to a stable equilibrium state. Key

Research on Dynamic Response of Rock under Blast Loading and Active Confining Pressure

HE Cheng-long, YANG Jun

2017, 38(12):  2395-2405.  doi:10.3969/j.issn.1000-1093.2017.12.013

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An experimental equipment including active confining pressure part and cylindrical charge part is set up for studing the fracturing process of deep rock under impact loading. The dynamic test technique, High-speed (HS) photography and digital image correlation (DIC) method are used to obtain the strain field and surface crack propagation of rock under static and dynamic loads.The breaking process of rock with different confining pressures is simulated based on Johnson-Holmquist (J-H) constitutive model. The results show that the circumference pre-stress field is produced by initial confining pressure, and decreases the circumference tensile failure from explosive loading. The number and size of radial cracks and the broken radius are significantly reduceed with the increase in confining pressure. With the increase in distance from borehole, the strength of explosion shock wave reduces and the confining pressure prevents cracks from propagating. The elastic mechanics and cylindrical elastic wave theory are used to study the propagation of stress wave, and find the pre-compression stress from initial confining pressure to reduce the tensile failure in circumferential direction after blast loading, which is the same as the experimental result. The numerically simulated results show that Mises stress increases and circumference tensile damage reduces with the increase in confining pressure, and the radius of broken zone and the crack shape are well agreed with experimental results. Key

Cooperative Spectrum Sensing Algorithm against Spectrum Sensing Data Falsification Based on Dempster-Shafer Evidence Theory

MIAO Cheng-lin, LI Tong, LYU Jun， LI Hao

2017, 38(12):  2406-2413.  doi:10.3969/j.issn.1000-1093.2017.12.014

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The malicious users forge and get command of the secondary users, which causes the spectrum sensing data falsification (SSDF) to decrease the performance of existing cooperative spectrum sensing algorithm. A cooperative spectrum sensing algorithm against SSDF is proposed. The SSDF attack is divided into Class Ⅰ and Ⅱ. User weight and decision threshold are set to distinguish the malicious users of Class Ⅰ and Ⅱ malicious users, and trusted secondary users by using Dempster-Shafer (D-S) evidence theory. Only trusted spectrum detection data can be used in information fusion to judge the spectrum usage and improve the detection performance. Theoretical analysis and simulated results show that the proposed algorithm can effectively confront SSDF attack interference, and its judgment performance is superior to that of existing D-S evidence fusion spectrum sensing algorithm. Key

Study of the Coupling Efficiency of Spatial Light into Single-mode Multi-core Fiber

FAN Xue-bing, WANG Chao, TONG Shou-feng, NAN Hang, GUAN Shu, HAO Shi-cong, JIANG Hui-lin

2017, 38(12):  2414-2422.  doi:10.3969/j.issn.1000-1093.2017.12.015

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In space laser communication, the coupling efficiency of spatial light into single-mode fiber is a key parameter of studying the performance of the system receiver. In order to reduce the difficulty of spatial light coupling into single-mode fiber, a single-mode multi-core fiber is used to receive signal light, a coupling efficiency model is established by taking seven-core fiber for example, and the effect of numerical aperture on the coupling efficiency of seven-core fibers with different fiber core arrangements is analyzed. The coupling efficiency of seven-core fiber increases first and then decreases with the increase in numerical aperture; the coupling efficiency of fiber which fiber cores are arranged in regular hexagon is higher than that which fiber cores are arranged in line. The coupling efficiencies in the presence of tilt, defocus and random angular jitter are studied. In the presence of lateral offset, the coupling efficiency of seven-core fiber has a periodic change. When the lateral offsets are 10 μm, 15 μm and 17 μm, the coupling efficiencies of seven-core fiber are about 14.4%, 39.6% and 36.9% higher than those of single-core fiber with the same core area, respectively. When the axial offset is 0.1 mm, the coupling efficiency of seven-core fiber is about 12.9% higher than that of single-core fiber with the same core area. When the standard deviation of random jitter amplitude is 6μm, the coupling efficiency of seven-core fiber is about 7% higher than that of single-core fiber with the same core area. Accordingly, the multi-core fiber inhibits tilt, defocus and random angular jitter. Key

Electronic Subdivision Reading Method of Zero Measuring Instrument and Its Implementation

LIANG Xu, WANG Jin-song, ZHOU Xu-yang

2017, 38(12):  2423-2428.  doi:10.3969/j.issn.1000-1093.2017.12.016

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An electronic subdivision reading method is proposed to improve the resolution and accuracy of zero testing instrument for day and night sights of small arms. The alignment readings are compensated by simulating an infinity target with the built-in flat glass collimator and adjusting the two pieces of flat glasses which are in horizontal and pitch dimensions, respectively, to offset the infinity target image. Two high-resolution angular displacement sensors are used to measure the deflection angles of the flat glasses in two dimensions, the measured angle values are digitally processed by using the microcontroller and displayed on an organic light-emitting diode (OLED) display, and the image on OLED is coupled to the collimated light path through a coupling prism. A theoretical model of measurement is established, and the measured results are calibrated using high precision photoelectric theodolite. The result shows that the resolution of the method is up to 0.001 mil and the error is less than 0.03 mil. Compared with the traditional mechanical subdivision reading method, the resolution and measuring accuracy of the proposed method are improved significantly. Key

Research on the Dynamic Linearity Calibration Method of High-g Accelerometers

YUAN Kang-bo, GUO Wei-guo

2017, 38(12):  2429-2437.  doi:10.3969/j.issn.1000-1093.2017.12.017

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The key problems in the dynamic linearity calibration of high-g accelerometers using Hopkinson bar system are studied. A single gun barrel system is proposed to achieve the synchronous impacts of two projectiles in the dynamic linearity calibration of accelerometers, in which the two projectiles are fastened by small-sized screws near their rear ends. The influences of geometry and material of projectile, impact velocity and pulse shaper on the excitation signals are investigated by using numerical method. It is found that that the amplitude of excitation pulse could be changed by adjusting the relative area of two projectiles and impact velocity. A certain frequency bandwidth could be achieved by using the projectile made from proper material. The single-barrel system is employed to calibrate the dynamic linearity of 988-1198 accelerometers, which proves the practicability of the proposed calibration system. Key

Structural Durability Optimization Design Method Based on Improved Cuckoo Search Algorithm

LIU Qin, SUN Zhi-li, LIU Ying, GUO Zhi-ming, CHEN Yan

2017, 38(12):  2438-2446.  doi:10.3969/j.issn.1000-1093.2017.12.018

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A structural durability optimization design method is studied by combining durability analysis with the cuckoo search algorithm. The durability optimization models with reliable life as object or constraint are developed. In order to solve the strong non-linear function and multi-extreme value problem for complex structural durability, an improved cuckoo search algorithm for structural durability optimization is proposed by introducing a new type of swarm intelligence algorithm. The convergence and efficiency of the cuckoo search algorithm are improved in terms of migration strategy, convergence criterion, and constraint handling. A steady improved cuckoo search algorithm for durability based optimization is proposed by using the probability optimization strategy that is to solve the reliable-life object by double-loop performance measure approach and process the reliable-life constraint by single-loop performance measure approach. The proposed algorithm can be used for global optimization. The proposed method is demonstrated with a gear box for light-weight vehicle. The results validate the effectiveness of the proposed method, and the weight of gear box can be lightened while meeting the durability constraint. Key

Demand Forecasting of Equipment and Materials by Weibull Distribution Based on Bayesian Estimation and Monte Carlo Simulation

WU Long-tao, WANG Tie-ning, YANG Fan

2017, 38(12):  2447-2454.  doi:10.3969/j.issn.1000-1093.2017.12.019

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The demand of new equipment and materials cannot be mastered well because of less historical demand data and undefined demand. To address this problem, a demand forecasting method based on Weibull distribution is proposed for equipment and materials in the case of small failure samples. The parameters of equipment and material life distribution are estimated by Bayes estimation and MCMC simulation for K-S goodness-of-fit test, including scale and shape parameters. A Monte Carlo simulation-based forecasting method for the annual demand of equipment and materials is presented, in which repairing maintenance, preventive maintenance and service time of equipment and materials are considered. The analysis of examples shows that the life distribution model derived from Bayes estimation has higher degree of fitting in the case of few samples, and the Monte Carlo simulation-based forecasting method is simple and effective. Key

Analysis and Experimental Verification of Dynamic Shear Test for Hat-shaped Specimen

ZHOU Gang-yi， DONG Xin-long， FU Ying-qian

2017, 38(12):  2455-2462.  doi:10.3969/j.issn.1000-1093.2017.12.020

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The stress states of shear zone for hat-shaped specimens loaded by split Hopkinson pressure bars are studied by theoretical analysis and numerical simulation. The shear test for the closed flat hat-shaped specimens of TA2 titanium is carry out, and the shear strain is measured directly by the two-dimensional digital image correlation (DIC-2D) method. The results show that it can be used as state of pure shear only if the Lode parameters μ_σ meet the condition of -0.46<μ_σ< 0.46 and the experimental data processing error is less than 3.4%. The dynamic constitutive curves obtained by shear testing are in agreement with the curves of cylindrical compression. The shear testing stress-strain curve softens once adiabatic shear bands (ASBs) form in the hat-shaped specimens, and the stress-strain curve reflects the initiation and evolution processes of ASBs. Key

Anti-impact Analysis of Sacrificial Claddings of Cellular Material with Temperature Gradient

LI Zhi-bin， LU Fang-yun

2017, 38(12):  2463-2471.  doi:10.3969/j.issn.1000-1093.2017.12.021

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Considering the applications of cellular materials as the sacrificial claddings in protecting the major structure from impact/blast load, a design method of cellular foam claddings with temperature gradient under high initial velocity impacts is presented. An one-dimensional model for the compaction of cellular foam claddings with temperature gradient is developed for the striker-rod impact scenario based on the rigid-perfectly plastic-locking (R-P-P-L) model. The predictions of the proposed model are compared to FE simulations by using the realistic R-PLH material model based on the actual experimentally derived stress-strain curves. The predictions of the dependence of critical length, critical impact velocity and impact force of the cellular foam rod with temperature gradient on the temperature distribution and the relation between critical impact velocity of an aluminum foam rod with a given length and the temperature contrast at its two ends are compared well with the numerical simulations results. Key

Investigation on Mesoscale Failure Mechanism of Alumina under Shock Compression

FENG Xiao-wei, LI Jun-cheng, CHANG Jing-zhen, WANG Hong-bo, HU Wen-jun

2017, 38(12):  2472-2479.  doi:10.3969/j.issn.1000-1093.2017.12.022

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With the aid of the VISAR, the velocity histories of rear free surface of the alumina with different thicknesses under plate impact loading were recorded. The failure wave trajectory was obtained from the recompression signals observed in the temporal curves of rear free surface velocity of samples. The results indicate that the generation and propagation mechanisms of failure wave are closely related to the mesoscale failure properties of alumina. The mesostructure properties of tested alumina were studied according to the SEM of alumina samples. Based on these properties, a mesoscopic model of alumina, including alumina grain phase and glassy phase, is established. Further, mesoscale simulations were presented to analyze the mesoscale failure properties of alumina. And the generation and propagation mechanisms of failure waves in shocked alumina were researched at the mesoscale. The results show that the nucleation and growth of rapid in-situ grain boundary microcracks under impact loading give rise to the failure wave phenomenon, and the failure wave propagation may be governed by diffusion processes. Key

Research on Combustion Process of Small Air-cooled Diesel Engine Based on Emission Characteristics

LIU Sheng-ji， ZHAO Yu-chao， LIU Rong-li, WANG Jian， SUN Yong-fu

2017, 38(12):  2480-2487.  doi:10.3969/j.issn.1000-1093.2017.12.023

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Higher CO and HC emissions of small air-cooled diesel engine are due to the compact structure and high cooling intensity at small and medium loads. To explore the generation mechanisms of CO and HC, and meet China Ⅲ emission standard of non-road diesel engines, the emission characteristics of pollutants under different compression ratios and exhaust gas recirculation test conditions are studied for an 186F air-cooled diesel engine. The results show that the change in the specific emission of NO_x is less than 4%, but the changes in the specific emissions of CO and HC are 41.1% and 53.9%, respectively, at two different compression ratios, which are 19.5% and 22.5%, respectively, without EGR. Through the analysis of indicator diagrams, it is concluded that the production of CO and HC is mainly related to the compression temperature during ignition delay. CO and HC emissions can be efficiently decreased when the temperature at the end of compression reaches to 860 K under 10% load. The emission values can be lower than the emission limits of CHINA Ⅲ emission standard based on the different technical schemes and the optimization of combustion process. Key

Bonding Defect Detection Method of Aeronautical Insulating Compsites Based on Coplanar Capacitance Imaging Reconstruction

YANG Li-jun, TIAN Hong-gang, AN Li-ming, WEN Yin-tang, LUO Xiao-yuan

2017, 38(12):  2488-2496.  doi:10.3969/j.issn.1000-1093.2017.12.024

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Coplanar capacitance imaging is a detection technique based on the sensitive field mechanism, which can display 2D or 3D medium distribution images in real time. In order to achieve the visual detection of adhesive deffects in aeronautical insulating composites, a imaging algorithm based on Kalman filter is proposesd based on the analysis of of uniplanar capacitance imaging model and image reconstruction principle, and the optimal estimate is achieved by adjusting the degree of dependence on the estimated and measured capacitance values continuously. The validity and feasibility of the proposed algorithm are verified through experiment. Compared with traditional imaging algorithm, the proposed image reconstruction algorithm greatly improves the image reconstruction precision of adhesive defect. Key