bluuebunny/crossref_metadata_2025 huggingface dataset:
A parameter-adaptive variational mode decomposition approach based on weighted fuzzy-distribution entropy for noise source separation
Authors: Zhou Qidi , Zhang Junhong , Zhou Tianyi , Qiu Yongbo , Jia Hongjie , Lin Jiewei
Published: July 2020

Due to limitations in the generalisation ability of currently proposed improved variational mode decomposition (VMD) methods, it is hard to precisely and efficiently discern signal characteristics from different power systems. Meanwhile, it is difficult to separate non-order noise sources in current studies. To address this issue, a novel scheme is proposed based on parameter-adaptive VMD and partial coherence analysis (PCA) for separating noise sources. In this approach, weighted fuzzy-distribution entropy (FuzzDistEn) is constructed to optimise the VMD to adaptively obtain the optimal parameters, considering the complexity of the signal system, and the mutual information between the decomposition components and the original signal. To verify the effectiveness and superiority of the proposed method, the paper respectively compares the decomposition results of the simulated signal using different objective functions, and shows that the weighted FuzzDistEn has a better decomposition effect. For the other issue, PCA is adapted to estimate the coherence between component vibration and radiated noise. In a case study, the parameter-adaptive VMD-PCA approach is implemented in a diesel engine noise identification field based on bench experiments. The results show that the proposed method can successfully separate five surface radiated noise sources. The research offers a new perspective on feature extraction problems.
Understanding the effect of rolling friction in the inclined track
experiment
Authors: Maslova K , de Jesus V L B , Sasaki D G G
Published: July 2020

In general, undergraduate experimental physics laboratories do not usually have
experiments designed to address rolling friction and to measure the value of the
rolling friction coefficient. This work explores an experiment, which has the
potential to arouse students’ curiosity about rolling friction by
addressing a counterintuitive aspect of the behavior of a sphere that rolls up,
stops and then rolls down on an inclined track. In fact, due to the difference
in the net static friction in the upward and downward movements caused by the
rolling friction term, the sphere’s acceleration when rolling upward is
higher than when rolling downward. This difference, which had been predicted
theoretically, was easily demonstrated graphically by video analysis, using both
rubber and mouse balls. For two steel balls, this difference was more subtle,
but it was still possible to detect it numerically. The experimental setup
employed typical laboratory equipment and the free video analysis software
Tracker to collect position and velocity data. The rolling
friction coefficient was calculated with good precision by means of an angular
coefficient of a fitted first-degree function involving appropriate
variables.
Wigner function and photon number distribution of a superradiant state in semiconductor heterostructures
Authors: Vasil’ev Peter P , Penty Richard V
Published: July 2020

Advanced quantum technologies require sources of non-Gaussian and non-classical light. For the understanding of properties of quantum light it is necessary to reconstruct its quantum state. Here, we use time-domain optical homodyne tomography for the quantum state recognition and reconstruction of the femtosecond optical field from a nonequilibrium superradiant coherent electron–hole state formed in a semiconductor GaAs/AlGaAs heterostructure. We observe severe deviations from the Poissonian statistics of the photons associated with the coherent state when the transformation from lasing to superradiance occurs. The estimated Mandel parameter Q of the superradiant states is in the range of 1.08–1.89. The reconstructed Wigner functions show large areas of negative values, a characteristic sign of non-classicality, demonstrating the quantum nature of the generated superradiant emission. The photon number distribution and Wigner function of the superradiant state are very similar to those of the displaced Fock state.
Microfluidic inertial switch with delay response characteristics
Authors: Nie Weirong , Liu Guowei , Zhang Runduo
Published: July 2020

This paper proposes an innovation microfluidic inertial switch structure with precise time delay response characteristic, which can be used in the fuze safety and arming system. The switch works on the principle of fluidic inertial force and capillary valve, which makes it sensitive to the unidirection acceleration load and has the ability to recognize the acceleration amplitude. The microfluidic inertial switch has a structure of a J-shaped reservoir, capillary valves, a serpentine delay microchannel and a U-shaped latching microchannel. The acceleration threshold is analyzed theoretically considering the surface tension coefficient of the gas-liquid interface. The delay response time of the switch is studied by finite element simulation based on the Gambit 2.4 and Fluent 6.3 software. The prototype is fabricated by wet etching technology and magnetron sputtering metal technology. Many tests have been done to verify the functions of the switch. The experimental results are matched well to the results of calculation and simulation. When the capillary valve throat widths are 80μm, 120μm, 160μm, the thresholds of the switch are 75.1g, 46.6g, 36.5g. When the switch is loaded with a 75g acceleration load, the delay response is 146.7ms. Finite element simulation and experimental results show that the switch can effectively identify the acceleration threshold, and can achieve a precise delay response under a certain load.
Study on precise detecting and controlling technology of lag angle based on image processing
Authors: Zhan K , Shan L , Xu L , Dong X , Bo G
Published: July 2020

A precise method of detecting and controlling of lag angle during the optical fiber winding procedure is described in this paper. The system is composed of three modules, image collection, image processing and PC controller. Images of lag angle are collected by an industrial high-speed camera. Binary treatment on lag angle images of the motive optical fiber is done by global threshold method. Image identification of lag angle of the motive optical fiber is realized by Hough transform, thus the digital values of lag angel are obtained. PC outputs controlled variables to modify the winding motion based on detecting results so as to limit the lag angel in a precise range. The research result indicates that application of image collection and identification technology to optical fiber winding can avoid winding flaw effectively such as gap and lamination thus to improve the quality and efficiency of optical fiber winding.
Critical deflagration criterion of PTFE/Al/W reactive materials
Authors: Zheng Yuanfeng , Ma Hongbing , Guo Huanguo , Su Chenghai
Published: July 2020

The unique reaction regime of reactive materials includes processes of impact-induced fracture, pre-ignition, post-perforation dispersion, local initiation, and deflagration. The complex interaction between reactive materials and target leads to difficulty in describing critical deflagration criterion of reactive materials. As such, a fundamental projectile/target interaction condition for the complete deflagration of reactive material fragment is derived based on the 1-dimensional shock wave relationships. The critical deflagration pressure Pc of reactive materials is fitted based on the energy release experiments of reactive material fragments. The results show the importance and necessity of the fracture behavior to the deflagration, and the deflagration behavior depends on impact velocity, geometry of reactive material fragment, target material and thickness, et al. As for the deflagration of fractured reactive materials behind the target, the critical deflagration size for reactive material debris is obtained based on the Grady energy model.
The research on transparent armor material technology
Authors: Zhang C , Cao J W , Guo J B , Liu F F , Wang C , Hasi G W , Guo Z Z
Published: July 2020

Transparent armor is a kind of protective material integrating of structure and function, which has high transparency and high physical-chemical properties. It is widely used in ground vehicles, air platforms, personnel protective masks and other equipments. As a kind of highly strategic protective material, the new transparent armor with light weight, high transparency and high protection factor has a broad application prospect. The paper focuses on the research progress of new transparent armor materials at home and abroad, compares the current situation, analyzes the difference and puts forward some insights.
Study on preparation and properties of aramid/stainless steel fiber blended electromagnetic shielding fabric
Authors: Wu Yilin , Li Yonggui , Ma Wenxiao
Published: July 2020

In order to develop electromagnetic shielding (EMS) fabric with high-performance, aramid / stainless steel fiber blended yarns were used to achieve it, and its electromagnetic shielding effectiveness (EMSE), flame retardancy and tensile properties were tested. The effects of fabric structure, fabric thickness, and fabric overlap angle on fabric properties were studied. The results showed that the plain weave fabric has the best EMSE among three kinds of fabrics with plain, twill and satin weaves. The EMSE of the satin weave is the worst. When the fabric thickness increased, the EMSE enhanced. The EMSE at the fabric overlap angle of 45° is the highest when the overlap angle is changed from 0° to 90°.
Analysis of architecture framework and intelligent development of air-to-ground precision strike system
Authors: Ma X D , Tian Zh F , He X L , Wang X G , Zhao H Y , Li J H
Published: July 2020

By the analytical method of system engineering, the air-to-ground precise strike system is set up. Using DoDAF (Department of Defense Architectural Framework, DoDAF), the concept of air-to-ground precision strike is built. The organization is definite and the capability requirement is analyzed. On the basis, the intelligent applications of command and control system, aircraft platform and guided munition are summarized. At last, some suggestion is put forward for the intelligent development of air-to-ground precision strike system.
Experimental study on initial ballistic characteristics of cased telescoped ammunition
Authors: Cao Y J , Yue W L , Li X S , Li Z F , Li J
Published: July 2020

There is a loading process after the projectile of the cased telescoped ammunition (CTA) fired in the chamber, which has important influence on the stability of interior ballistics, the firing accuracy and the gun barrel life. In order to study the characteristics of velocity and attitude in the initial motion of the projectile of the CTA, a special projectile for the initial ballistic test was designed, and an initial ballistic test system based on the high-speed camera was built. The loading process after firing was observed and the loading velocity was measured. The results show that the loading speed of the projectile is about 30m/s. The initial ballistic parameters of the projectile can be studied quantitatively and the motion attitude of the projectile can be examined qualitatively by using the initial ballistic test system based on the high-speed photography.
An active disturbances rejection controller based on fuzzy compensator
Authors: Ling Cai , Ying Zhang
Published: July 2020

Digital servo system has a wide application in military equipment. Position controller is one of the important parts in a servo system. Therefore control performance affect system’s capacity directly. The paper introduces an Active Disturbances Rejection Controller (ADRC) based on fuzzy compensator, which uses the fuzzy and active disturbances rejection control technique. Using Tracking Differentiator (TD) to track command signal and feedback signal, transferring them to smooth signal and separating the differentiator signal from them, which are used to build the element of front feed and error control. Fuzzy control technique is used to compensate Extended State Observer (ESO), which decreases variations range of control object. Then increase the estimate precision of extended state observer. An active disturbances rejection controller with perfect control quality is applied in a digital alternating servo system position controller. The results of measurements taken from a laboratory are shown that the proposed controller has an excellent follow precision, good instant response and high output quality. The proposed method solves several difficult problems of servo system position control, such as input signal smoothing, motional disturbance, and hard matching among parameters due to strict requirements on system precision, stability and quick response in position control.
Investigation on large responses of the streamwise velocity with the effect of spanwise Lorentz force
Authors: Zhang Cheng-Long , Jiang Dai-Wen , Zhang Hui
Published: July 2020

The flow of a weakly conductive fluid (i.e. seawater) can be controlled by Lorentz forces generated by the suitably chosen magnetic and electric fields, which has significant effects for applications in the drag reduction and oscillatory suppression. However, the control efficiency is very low due to the application of large amplitude for Lorentz force. Therefore, the large response, induced by a small Lorentz force, is the key to enhance the flow control efficiency. In this paper, the amplification mechanism of the velocity response with the effect of Lorentz force in weakly conductive fluids is investigated, where the Lorentz force is applied on the lower wall in the channel. The analytic solutions of the velocity responses in linear stage are derived with linear stability theory, when the amplitude of Lorentz force is far less than 1. From the discussions of the analytic solutions, the mechanism is revealed on large responses which is induced by the small Lorentz force in the flow field. The results show that the flow along the spanwise direction is induced by Lorentz force, which leads to the momentum exchange of fluids in the wall-normal direction. Therefore, the large responses of velocity are generated due to the high-speed fluids transferring to the wall. Moreover, the responses depend on the parameters of Lorentz force, i.e. wave number Kz
, effective penetration Δ, including proportional to amplitude A and square of Reynolds number Re2. With the increase of Kz
, the response decreases monotonously. However, with the increase of Δ, the response increases first (Δ<0.4), reaches the maximum at Δ=0.4, and then decreases (Δ>0.4). Finally, the maximum response is obtained and the corresponding amplification is 480, when the two parameters are optimized, i.e. Kz=2, Δ=0.4.
The differentiated generations of air bomb base on landmark technology
Authors: Hu L F , Guo J M , Wang X G , Ma X D , Fhe X , Li J H
Published: July 2020

The development of air bomb was closed to 100 years from World War I. In this study, the typical technologies applied in air bomb were analyzed, and the characteristics of air bomb using various technologies were summarized. The differentiated generations based on landmark technology were developed to describe air bomb, and the various types of air bomb were illustrated on corresponding.
Correlation filter for object tracking with temporal-spatial constraint
Authors: Wei Junxu , Yang Lifeng , Pu Tian , Li Jian , Peng Zhenming
Published: July 2020

In this work, inspired by the Passive-Aggressive learning (PA), we proposed a Temporal-Spatial Constraint Correlation Filter (TSCF) model to simultaneously constrain the spatial mask and the update direction of the filter. Firstly, the spatial regular term ensures that the background redundancy information does not interfere with the filter update during the tracking process. Secondly, the temporal regular term ensures that the spatial mask and the filter do not change dramatically. Thirdly, our proposed TSCF model can be effectively solved based on the alternate direction method of multiplier (ADMM), where each sub-problem has a closed solution. Finally, our experiments on the OTB100 benchmark shows that our tracker has efficient performance compare with many advanced algorithms, which get an AUC score of 0.599 and an accuracy of 0.794.
The influence of energy content and its expenditure on the impact sensitivity of high-nitrogen energetic materials
Authors: Zeman S.
Published: July 2020

On 17 high-nitrogen energetic materials (including six azido-derivatives), the paper demonstrates the relations between their impact sensitivities (Edr
) on the one hand and the volume heats (ρQmax
) or a representative of detonation pressure (ρD2
) of their explosion or their enthalpies of formation (ΔHform
) on the other. The semi-logarithmic subrelations between the Edr
and ρQmax
values are limited by the mechanism of primary fission. While the mentioned relations between Edr
and ρQmax
values for azido derivatives predominantly show the expected course, in the case of the remaining high-nitrogen EMs, the opposite is the case, i.e. an increase in ρQmax
values corresponds to a decrease in impact sensitivity. The same is valid for ρD2
values as an independent variable. Taking the energy content of the studied EM molecules, represented by ΔHform
values, instead of the heat of explosion, yields unambiguous semilogarithmic relations, according to which the growth of the ΔHform
values increases impact sensitivity. The results obtained indicate that it is necessary to distinguish between the influences of the performance and the energetic content of high-nitrogen energetic materials on their initiation reactivity.
A Novel Method for Oblate Spherical Powder with Adjustable Combustion Property
Authors: Gu H , Ding Y J , Xiao Zh L , Ying S J , Wu W L
Published: July 2020

In order to obtain the oblate spherical power with adjustable combustion property, a novel method was put forward combining the microporous technology and the polymer deterring technology. In this work, the oblate spherical power was foamed with the cell structure by supercritical carbon dioxide (SC-CO2), and then poly(neopentanediol adipate) (NA) was employed as the deterrent to modify the energy releasing rates in the surface. The combustion property of oblate spherical power under different processing conditions was investigated by the closed bomb tests. The results indicated that the microporous oblate spherical powder displayed the desired progressive combustion, and the combustion property of microporous oblate spherical powder could be adjusted by controlling the desorption time, foaming temperature, NA content, desensitization time and desensitization temperature. The spherical powder with skin-core structure foamed by SC-CO2 and deterred by NA provides a novel and promising method to realize the progressive combustion performance without dibutyl phthalate (DBP).
Research of environmental factors on SCB electrode plug corrosion
Authors: Li F , Zhang R , Fu D X , Du Zh H , Ma H L
Published: July 2020

The accelerated life test of SCB electrode plugs under different environmental stresses is designed and the test results are analyzed. The results show that single temperature stress will not cause corrosion of SCB electrode plug. Temperature and humidity stress will cause slow corrosion of SCB electrode plug. If chloride ion is introduced in the environment where temperature and humidity exist, it will lead to rapid corrosion of SCB electrode plug. At the same time, the relationship between the resistance and the corrosion degree of the SCB electrode plug bridge area and solder joint shows that the deeper the corrosion degree of the bridge area and the solder joint, the larger the resistance value of the SCB electrode plug.
Numerical simulation and experimental study on slow cook-off response characteristics of composite B
Authors: Deng H , Shen F , Liang Zh F , Wang H
Published: July 2020

The response characteristics of compose B explosives (Shellless and shelled) under slow heating strips were numerically simulated using a zero-order reaction kinetics model. And the slow cook-off experiment was carried out on shell explosives and shellless explosives respectively. Comparing the experimental results with the calculated results, the key parameters such as melting process, temperature field evolution, ignition time, ignition temperature and ignition area of the slow cook-off test of the cast-casting charge were obtained. The results show that when the casting explosive is heated slowly, it is a heat conduction process before melting, the internal temperature gradient is large, the temperature of the liquid explosive tends to be uniform after melting, and the upper layer temperature is slightly higher than the lower layer temperature; When the temperature rises to a certain value, the explosive decomposes to generate a large amount of gas, and can be discharged from the pressure relief hole of the casing; Eventually, a high temperature region is formed in the middle of the top layer of the liquid explosive, and the ignition reacts violently.
Influence of afterburning suppression on the combustion of solid propellants: Recent progress and outlook
Authors: Li H J , Yi J H , Qin Zh , Sun Zh H , Xu Y , Wang Ch J , Zhao F Q
Published: July 2020

The exhaust gas, CO and H2, occupy about a half amount of combustion products, and they make the oxidative reaction with oxygen in the ambient air entraining into the plume during the combustion of solid propellants, producing shock wave, visible flash and increased infrared radiation. In order to inhibit the afterburning plume of solid rocket motors, one of the best ways is to utilize potassium salts as suppression in the propellant formulation. This review discussed and summarized the influence of a great number of potassium salts including inorganic (K2SO4, KHCO3, KCl, KNO3, KBF4, and K3Co(NO2)6 etc.) and organic (K2C2O4, Potassium biphthalate, KD, energetic K(NNMPA) and ADNPK) compounds on the decomposition kinetics, flame structures and temperature, burning rate, combustion wave structures, quenched surface of solid propellants, especially the plateau burning effect. The equipment of plume tests involves in the pressure differential scanning calorimetry, infrared (IR) radiation signature, afterburning flame length and nitrogen-filled pressure-regulating burner etc. The mechanism by which chemical inhibition occurs when certain powders are added to fuel-air flames was shown and discussed. Moreover, the exhaust properties and electron density of solid propellants were modeled and calculated. Finally, future research trends are suggested from different perspectives involving the KOH testing inside the solid rocket motors, plume signature testing and novel insoluble K compounds.
Combustion Study of Power Cartridge in Closed and Semi-Closed Vessel for Water Disruptor Application
Authors: Parate B A , Dixit V K , Chandel Sunil , Shekhar Himanshu
Published: July 2020

The present study deals with combustion study for comparison of power cartridge in closed (CV) and semi-closed vessel (SCV) for water disruptor application using statistical methods. The cartridges are fired in the test vessels such as CV and SCV. CV is perfectly leak proof from all sides. SCV is provided with vent 5 mm diameter keeping the same volume as that of CV. To evaluate the comparative internal ballistic performances, the firings of cartridges are carried out in CV and SCV. The gas pressure generated by the power cartridges are measured using the pressure transducer fitted over the body. It is vital task to understand the effect of vent on maximum pressure inside a test vessel. The motivation behind this experiment is to assess the maximum pressure developed and respective time inside SCV to simulate the motion of projectile to some extent through barrel. The internal ballistic parameters are evaluated in CV and SCV. The percentage drop in pressure and time are calculated. From this study, it is inferred that pressure drop in SCV is 16 percentage to that of CV. Further, an experiment revealed that pressure drop in CV is 1.2 times of SCV.
Safety design and numerical simulation of twin screw extruder for energetic materials
Authors: Ji Dandan , Xiao Yong , Huang Qiuan , Shi Huifang
Published: July 2020

To improve the safety performance of twin screw extruder for energetic materials, the finite element method is used to simulate the explosive moment of energetic materials in the twin screw barrels with different pressure venting structures. The explosive pressure distribution rule and the deformation of barrels are compared. The results show that the maximum pressure and maximum shear rate which can lead to explosion both appear on the top of screw flight and in the intermeshing region. When the explosion occurs in the horizontal split barrel, the second explosive pressure peak is significantly reduced and the deformation of the barrel is much smaller. In the twin screw barrel with the pressure releasing holes, two explosive pressure peaks are both high and the fixed part of barrel has large deformation. Therefore, using the clamshell type barrel can reduce the damage of equipment and improve the safety of twin screw extruder for energetic materials.
Research on high efficiency muzzle brake technology of small caliber automatic gun
Authors: Liu J B , Huang H Sh , Zhu W F , Liu Y , Zhang L
Published: July 2020

Muzzle brake provides a recoil force by controlling the powder gas flow distribution and velocity to reduce the recoil energy, so the study on the muzzle brake efficiency in reducing the recoil energy plays a great role. A new muzzle brake is developed, and the muzzle flow field is simulated and analyzed by Fluent. According to the simulation results, the muzzle brake structure is optimized. Precision casting technology was used to solve the manufacturing problem of complex special-shaped holes. The prototype was processed and verified by experiments. The experimental results show that the braking efficiency of the new muzzle brake is nearly twice that of the traditional structure, and the recoil force of the automatic gun can be reduced by more than 40%.
The dynamic response of cylindrical shell and square plate with pre-formed holes under blast loading
Authors: Li W , Qian L X , Feng G P , Li H M
Published: July 2020

The dynamic response of cylindrical shells and square plate with pre-formed holes under blast loading was studied by numerical simulation. The numerical model was calibrated by the experimental data of square plates with pre-formed holes. The dynamic responses and deformation of cylindrical shells with pre-formed holes subjected to blast loading was investigated by the same numerical model. The structure response process has been divided into four specific stages which has been discussed systematically. According to the comparison of structure response process, stress concentration between these two structures under blast loading, it is concluded that the square plates have a better performance than that of cylindrical shell with or without pre-formed holes and the influence of pre-formed holes on blast-resisting of square plate is bigger than that of cylindrical shell. In addition, the global and local deformation characteristics are mainly result from the space configuration and pre-formed holes, respectively.
Selection and analysis of material models in copper jet penetration into water
Authors: Li G , Chen X W
Published: July 2020

A reliable choose of material models is quite important to correctly conduct the numerical simulation of copper jet into water. In the present paper, we compared three copper models, i.e., Steinberg Guinan, Piecewise JC and Zerilli Armstrong models and two water EOS of Mie-Grüneisen and Polynomial. With referencing the experimental results, the numerical simulations of copper jet into water were carried out and analysed by employing different material models in Euler algorithm of AUTODYN. It concluded that Zerilli Armstrong model was suitable for copper and Shock EOS was suitable for water.
Experimental investigation on the velocity of the secondary fragments of reinforced concrete slabs under intensive dynamic load
Authors: Yang J Ch , Wang X , Gao W L , Sun G J
Published: July 2020

The initial velocity of the secondary fragments of reinforced concrete slabs under blast loading is the basic data for the analysis of damage effect and it can also serve as important basis for the damage evaluation. In this study, three different types of reinforced concrete target slabs with different thicknesses were designed and prepared. These target slabs were investigated by local damage effect tests, the flying processes of the produced secondary fragments were recorded, and the velocities of the secondary fragments corresponding to different collapse coefficients were calculated by fragment back tracking. The results demonstrate that the initial velocity of the fragments was lower at a larger collapse coefficient. Based on the dimensional analysis results, the empirical formula of the initial velocity of the secondary fragments was derived. The errors between the calculated values according to the empirical formula and the experimental data were compared and found to be within 16% at a collapse coefficient in the range1.20–3.20m/kg1/3. Thus, the derived empirical formula can be used for predicting the initial velocity of the secondary fragments produced during the collapse of reinforced concrete slabs and also providing insightful reference for analyzing the damage power of the produced secondary fragments.
Research on the equivalent relationship of torpedo penetrated by underwater supercavitation projectile based on energy consumption model
Authors: Zhao Y L , Yan P , Li X , Tan B , Wei P
Published: July 2020

Supercavitation projectile is one of the research hotspots of underwater defence technology. The cost of underwater damage test is such high that equivalent test on land is often considered as a possible alternative. In this paper, the equivalent relationship between torpedo and related materials penetrated by underwater supercavitation projectile is studied. Firstly, a typical torpedo structure model consisting of the torpedo shell and 14 key components is constructed; Secondly, the process of underwater supercavitation projectile penetrating torpedo is divided into two stages, that is, the underwater motion of projectile before penetration and the projectile penetrating torpedo. And the energy consumption models of projectile penetrating water medium and the energy consumption models of projectile penetrating torpedo are established respectively, considering the influence of water medium on torpedo. Because the equivalent targets obtained by the vertical impact of the projectile are different at different positions of the torpedo, two typical penetration directions and typical cabin sections of the control section of the torpedo are considered in this paper. Finaly, combined with the water medium model and torpedo structure model, and based on the principle of equivalent ultimate penetration velocity and equal minimum penetration energy consumption, the full torpedo equivalent simulation model of transverse penetration and longitudinal penetration torpedo control section under underwater penetration condition considering the influence of water medium is established.
An investigation into the ballistic response of stitched plain weaves
Authors: Li H , Zhou Y
Published: July 2020

It has been widely accepted that yarn pull-out and windowing plays a vital role in absorbing impact energy in a protective fabric system. Stitching within the fabric has been devised to constrain the transverse and lateral displacement of the primary yarns, using conventional cotton sewing threads. This paper reports the experimental and numerical methods and results of an investigation on the mechanisms that enable higher impact energy absorption of woven fabrics with designed yarn stitching. Penetration tests were performed over a range of impact velocities from the ballistic limit up to 180 m/s. The experimental results showed that the energy absorption of the stitched fabric sample is over four times higher than that of unstitched one. For mass-normalized metrics, stitching the fabric on every other yarn yields a 146% improvement in energy absorption capacity when compared to unstitched samples. The numerical predictions suggested that yarn pull-out could be delayed or even eliminated on stitched samples, enabling the fabric to absorb more strain and kinetic energy.
Influence of pre-ignition quasi-isotropic turbulence on burning velocity of diethyl ether/air mixtures
Authors: Liu X L , Wang Y , Zhang Qi
Published: July 2020

This paper presents a detailed investigation on turbulent burning velocity of diethyl ether (DEE)/air mixtures under different pre-ignition quasi-isotropic turbulence. The concentration of DEE/air mixtures is the equivalence ratio ø= 1.1. The experimental result of the laminar burning velocity (uL)is 0.55 m/s, and the largest data of turbulent burning velocity (u
t) are 1.8 m/s at pre-ignition quasi-isotropic turbulence velocity at 6.2 m/s. In this work the model gives the expression on the laminar burning velocity (UL
)and turbulent burning velocity (ut
)versus the pre-ignition turbulence velocity Urms
in accordance with Williams’s theoretical model.
Numerical simulation and experimental research on EFP penetrating the ceramic composite armored target
Authors: Bai L H , Miao Ch , Wu H L , Zhong T , Lu R J , Zhong Ch F , Guo Y Y
Published: July 2020

To research the protective performance of the newly designed ceramic composite armored target against 50mmRHA EFP, this paper used AUTODYN numerical simulation software to simulate the process of EFP penetration into the ceramic composite armored target, and verified the simulation results through the target test. The results showed the mass of EFP has a great impact on its penetration capability; the designed ceramic composite armored target with 274kg/m2 areal density could effectively prevent the penetration of 50mmRHA EFP; the vertical penetration depth was about 30 mm; and the back plate had a slight back convex phenomenon. The research results can provide reference for the protective structure design of light tanks and armored vehicles.
Experimental research on thermal ignition of typical shell aluminized mixed explosive under fast thermal action
Authors: Zhao S W , Zhou G , Wang C L
Published: July 2020

In order to obtain the thermal ignition characteristics of the typical aluminized mixed explosive with shell under fast thermal action, this research takes the casting TNT RDX Al (THL) explosive and casting PBXN-109 explosive as the research target, and establishes the thermal ignition experiment platform for fast heating shell explosives and thermal ignition model of explosive with shell, and carries out the thermal ignition experiment of two explosives under different sizes. It uses the fast heating device to generate fast thermal action, and heat the explosives in steel restraints, which uses the thermocouple to tests the temperature history to obtain the explosion temperature and delay time of the explosive thermal ignition. The results show that: ①The explosion temperature and delay time of the two kinds of explosives increase with the ratio of heating range to explosive size decrease, and both of them are larger than the 5s brustpoint. ②In a certain error range, the model calculation values and experimental results are basically consistent, which can be used for semi quantitative predicting explosion temperature and delay time. ③THL explosive is casting type with high density and high hardness, which damaged greatly after thermal ignition. PBXN-109 explosive is a casting plastic bonded explosive with low density and soft quality, and its damage is not so serious as the THL explosive after thermal ignition.
Analysis on the two-dimensional effect of long-rod penetration
Authors: Jiao W J , Chen X W , Li J C
Published: July 2020

The two-dimensional (2D) effect is observed in experiments and simulations of long-rod penetration. Different nose shapes may occur in the penetration of long rods made by different materials, which will have an effect on the penetration performances. Base on the 2D model established in authors’ previous work, combining with the experimental and simulation results, the 2D effect of long-rod penetration is analyzed in present paper. According to the analysis, the basic assumption of the 2D model, the nose shape of long rods keeps invariant during the primary phase, is verified. In addition, the 2D model can briefly reflect the 2D effect shown in experiments and simulations.
Microstructure and mechanical properties of Mg-Mn alloys by friction stir welding
Authors: Luan Z J , Li M , Sun J B
Published: July 2020

Mg-Mn alloy is welded by friction stir welding technology to manufacture liquid-cooled components in radar equipment. The effect of welding processes on microstructure and mechanical properties of Mg-Mn alloy was analyzed. The results show that the rotation speed has little effect on the microstructure structure when it is above 1200 rpm. The strength is increased by the increase of rotation speed from 900 rpm to 1500 rpm. The highest ultimate tensile strength is about 175 MPa. Most of the welding joints show brittle fracture during tensile test.
Spatial 4U quadrilateral rolling mechanism
Authors: Wang Z Q , Liu Ch , Liu X J
Published: July 2020

A novel of rolling mechanism constructed by four U joints is proposed. The shape of the mechanism is quadrilateral, which consists of four U joints and four links. The straight and turning rolling can be achieved by two actuators. The DOF (degree of freedom) of the mechanism is computed by using screw theory. The rolling motion analysis and the trajectory analysis are carried out. In addition, a prototype is manufactured and a series of experiments are performed to verify the rolling capability of the mechanism.
One-legged hop of compliance control based on minimum-jerk
Authors: Zhao J X , Yao Q Ch , Xing B Y , Xu P , Liang Zh G , Jiang Ch X , Su B
Published: July 2020

Aiming at the trajectory planning and compliance of the one-legged hop of a quadruped robot, a method for designing the optimal trajectory of the bouncing by minimizing the jerk index is proposed, and active compliance control is used to reduce the impact of the end of the foot and improve the compliance of the one-legged. First, design a one-legged bounce strategy. The bounce is divided into three phases: take-off phase, vacant phase, and buffer phase, and trajectory optimization is performed for each phase. Secondly, a compliance control method is designed. During the bouncing process, the impact of the foot end is large, which will affect the stability of the robot and even destroy the mechanical structure of the leg. The joint level adopts force-position mixed control, and the one-legged level adopts impedance control to eliminate the impact of ground impact on one-legged. Finally, a one-legged model of a quadruped robot was established in the Vortex multi-body dynamics system. Simulation experiments have proved the feasibility of trajectory optimization and compliance control.
Foot terrain impact modeling and motion performance research of hexapod robot based on passive elastic leg
Authors: Liu Y F , Su B , Zhou L , Gao H B , Ding L , Jiang L , Zou F Q , Ma C Y
Published: July 2020

In order to improve the performance of the multi-legged robot, the impact of foot-terrain is an important target to measure the performance of the robot. In order to ensure the compliance contact of foot-terrain for the legged robot, it is essential to add passive spring between the calf and foot. The mechanical structure makes the leg of hexapod robot retractable passive elastic structure. For multi-legged robots with passive elastic legs, the foot-terrain impact model is presented to measure the dynamic performance and provide theoretical support for the low impact force motion planning. The traditional planning method will cause additional impact for the switching case between the swing and stance phase. This paper presents a motion planning method that considers the deformable leg structure and impact performance. The experiments have been carried out, and the results have demonstrated the effectiveness of the foot terrain impact model and motion planning method in comparison with a conventional method.
Metallic reactive materials application in fragmentation warhead
Authors: Chen J , Chen Y J , Li X , Liang Zh F , Zhou T , Xiao Ch
Published: July 2020

The composition, structure, manufacturing process and properties of Metallic reactive materials are introduced. The typical ternary mixture of Ni-Al-W have high density of 7.37g/cm3 and static tensile strength of 228MPa, which make the reactive fragments gain high penetration capability to perforate the target&s skin and can survive under explosive. The Ni-Al-W fragments undergo intermetallic reaction and oxidation reaction upon impacting. The energy release characteristics of Ni-Al-W reactive material were analysed. The chemical energy and pressure generated by reaction of the reactive material have a linear relationship with the impact velocity. A warhead prototype of Ni-Al-W fragment warhead was designed and the warhead explosion testing was carried out. The results show that the Ni-Al-W fragments are capable of withstanding to explosive loading with acquiring initial velocity of 2256m/s. The Ni-Al-W fragments also have advantage of perforation in area against the bi-layered space plates. The metallic reactive fragment warhead can increase the lethality of fragmentation warheads against aircrafts and phased array antenna, which increasingly get mature and have a wide application prospect.
Research on energy-absorption and failure of carbon fiber reinforced epoxy resins double cone structure
Authors: Zhao Ch F , Zhou Zh T , Ren J , Xing Ch L , Zhong J L , Zhang K B , He B
Published: July 2020

One of the research hotspot in strategic missile is to develop a multifunctional and lightweight composite launcher, which has a certain bearing capacity and anti-fragment penetration capability. On this basis, this paper designs the launcher’s wall by using carbon fiber reinforced epoxy resin composite double cone structure (CFREPDCS) as sandwich core layer. Due to obtain the high-speed impact energy-absorption and failure characteristic of the CFREPDCS, the quasi-static collapse experiment and the LS-DYNA finite element simulation were used. The experimental results and the scanning electron microscope show that the failure mode of the carbon fiber reinforced epoxy resin composite (CFREP) circular tube is progressive failure, which includes matrix fragmentation and fiber fracture. The CFREP circular tube with larger wall thickness has higher specific energy-absorption (SEA), approximately 58.6 J/g. The coupled relationship between SEA and mid-diameter height shows that the maximum SEA occurs while mid-diameter height reaches 8 mm. On the other hand, the change of the mid-diameter height also reflects the influence of loading direction on SEA. This study provides the significant guide to design and manufacture of sandwich carbon fiber composite launcher.
Research progress in advanced polymer matrix composites for armor protection systems
Authors: Xu J L , Chen Y W , Wang R H , Li F Q , Liu A Y , Wei H Z , Wang D Y , Li S H
Published: July 2020

With the changes of modern warfare modes and the development of missiles and weapons, the battlefield survivability of military vehicles is facing severe challenges. Vehicles must have high protection performance and better mobility. However, both of them are contradictory each other. The advanced resin-based composites has excellent mechanical properties and strong designability, and is one of the main technical means to solve the above problems, but it also encounters a bottleneck. In view of these situations, this paper summarizes the development of advanced composites in recent years, and discusses in detail the protection mechanism of advanced composite materials, material selection and manufacturing processes, and the latest developments and future application trends of advanced composite materials for armor protection systems.
Dynamic response analysis of discrete supported electromagnetic railgun
Authors: Wu J G , Lin Q H , Li B M , Wen Sh B , Chen D
Published: July 2020

In order to analyze the dynamic deformation of rails subjected to transverse moving magnetic pressure, a 3D simulation model consisting of the launcher and integrated launch package was constructed and solved with dynamic finite element method. Critical velocity effects of rail dynamics were obviously observed in the simulation results. The effects not only enlarge the rail deflections but also affect the contact status between the armature and rails. To mitigate this problem, discrete supports with different stiffness were applied in the simulation. By locally enhancing the stiffness of support, especially for the part of rails where the critical velocity happens, the dynamic responses can be effectively controlled.
The summary of missile electromagnetic catapult technology
Authors: Su Zizhou , Zhang Tao , Zhang Bo , Fan Wei , Luo Shuai
Published: July 2020

Missile electromagnetic catapult technology is the important application of electromagnetic launch technology in the field of missile and a great breakthrough compared with tradition catapult technology. Inducing main components and technological advantages of missile electromagnetic catapult system. Sketching technical characteristics of three missile electromagnetic launcher including coil launch, DC motor and rail launch. Introducing current development situation of missile electromagnetic catapult technology in home and abroad. Carding key technologies which restrict practicability of missile electromagnetic catapult technology. Expecting prospects for development of missile electromagnetic catapult technology.
Simulation analysis of thermal management of inductor applied to pfn under continuous discharge condition
Authors: Ma Fuqiang , Liu Xiangrong , Hao Shuangpeng , Li Zhenxiao , Li Baoming
Published: July 2020

The pulse forming network (PFN) is an important component of the electromagnetic launch system, and its continuous discharge performance at same frequency is of great significance for the development of electromagnetic launch system. Pulse inductor is one of the key components of PFN, which has a decisive influence on the amplitude, pulse width and wave front time of discharge current. In order to study the thermal management scheme that could meet the temperature control requirements of pulse inductors under continuous discharge condition, an electromagnetic-thermal-fluid coupling model is established, and the temperature change of pulse inductor under the condition of liquid cooling and natural cooling is analyzed. It is concluded that the natural cooling scheme cannot meet the temperature control requirements, while the liquid cooling scheme can meet it. But the disadvantage of the liquid cooling scheme is that the maximum temperature difference inside the inductor will be increased.
Research on application of bus-bar in electromagnetic launching weapon system
Authors: Ren R , Ye W , Dong Z , Liu J , Huang K , Zhang Y
Published: July 2020

At present, the electromagnetic launching weapon system is steadily turning to its engineering applications. Among them, the bus-bar, as a necessary link of the pulse power supply to transmit energy to the electromagnetic launcher, has high engineering requirements on its high power, miniaturization and lightweight. This paper analyzes and studies the high power, miniaturization, lightweight and other aspects of the bus-bar, puts forward a disk bus-bar, and compares it with other bus-bar, finally determines that the bus bar has the advantage of high power and miniaturization, and realizes the vehicle-mounted application.