bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal behavior and non-isothermal decomposition reaction kinetics of catalyzed hniw-cmdb propellant
Authors: Xu S Y , Zhao F Q , Yao E G , Jiang H Y , Yi J H , Li M , Pei Q , Hao H X
Published: July 2020

The thermal behavior under pressure of 0.1, 4, and 7 MPa and non-isothermal decomposition reaction kinetics under pressure of 4 and 7 MPa of the composite modified double base propellant containing hexanitrohexaazaisowurtzitane (HNIW-CMDB propellant) was investigated by differential scanning calorimetry (DSC). The results showed that there are two exothermic peaks on DSC curve under 0.1 MPa. The exothermic peak temperature decreases with surroundings pressure increasing. There is only one exothermic peak on every high pressure DSC curve. The exothermic peak temperature under every pressure increases with heating rate increasing. The exothermic decomposition kinetic parameters of the propellant changed while the reaction mechanism function didn’t change when catalyzer was added into propellant or testing surroundings changed. The kinetic equation of exothermic decomposition reaction mechanism under 4 MPa and 7 MPa are Avrami-Erofeev (n=2/3).
Design and performance of NiCr-based micro-heater with lower excitation energy
Authors: Liu W , Su Q , Xue Y , Xie R Zh , Ren X M , Liu L
Published: July 2020

Low energy and miniaturization are two main development directions for the MEMS (Micro-Electro-Mechanical System)-based initiator. The MEMS-based initiators or called fire components were fabricated by the way of that the secondary explosive charges were coated or synthetized with in-situ method onto the NiCr-based micro-heater surface. The firing voltage experiments of the fire component under capacity loading were performed. The fire voltages of the fire components with rectangle micro-heater increase linearly with the increasing of micro-heater’s width, and decrease with the increasing of micro-heater’s thickness. The fire voltages of the fire components with Pyrex7740 substrate cut down to 50%, compared to the fire component with silicon substrate. The fire component with lower explosive density contributes to reduce the fire voltage. The micro-heater with parallel connection structure or called parallel micro-heaters cannot have lower fire voltage than the single micro-heater, but have more reliability to initiate the secondary explosive.
Assessment of second-order Møller-Plesset perturbation theory for isomerization and dissociation energies of nitramide
Authors: Yu T , Liu Y Zh , Lai W P , Ma Y D , Ge Zh X
Published: July 2020

Based on the optimized molecular geometries at the B3LYP/cc-pVDZ level, the electronic and nuclear repulsion energies of nitramide (NH2NO2), O-nitrosohydroxylamine (NH2ONO), 1-hydroxydiazene 1-oxide (NH=N(O)OH), the transition state between NH2NO2 and NH2ONO, the transition state between NH2NO2 and NH=N(O)OH, NH2 radical, NO2 radical, H2O, N2O, H2, N2, O2, H, N and O were calculated by various second-order Møller–Plesset perturbation theory (MP2) methods. The domain based local pair natural orbital (DLPNO), explicitly correlated F12, density fitting (RI), spin-component scaled (SCS) and orbital optimized (OO) calculations were employed in MP2 calculations. The isomerization and dissociation energies of NH2NO2 were estimated by CCSD(T)-F12-RI as benchmark method. The testing results indicate that the deviations can be reduced by SCS method efficiently.
Quasi-static mechanical behaviors of different inert particle reinforced Al/PTFE reactive composites
Authors: Yuan Ying , Liu Zhenyang , Geng Baoqun , Wang Haifu
Published: July 2020

In this paper, the quasi-static mechanical behaviors of particle reinforced aluminum/polytetrafluoroethylene (Al/PTFE) reactive composites are studied. The mechanical behaviors of composites with the volume fraction of 30% W, WC, SiC and SiO2 respectively are compared by the quasi-static compression test, and the failure mechanism is analyzed. Test results show that SiC/SiO2 particle reinforced composites show better toughness, while W/WC particle reinforced composites show more brittleness. The failure mechanism analysis indicates that the failure of particle reinforced composites is mainly caused by matrix fracture and particle spalling from the matrix.
Study of the uniformity of mixing components of energy-saturated heterogeneous composite material
Authors: Kryvanos AK , Ilyushchanka APh , Piatsiushyk YY
Published: July 2020

The features of mixing the components of an energy-saturated heterogeneous composite material (EHCM) were considered. The conditions for the uniform distribution of the components of the solid phase over the entire volume of the composite material were estimated and the possibility of obtaining their most dense packing was analyzed. Appropriate proportions of the particle sizes of the fine and coarse fractions of the components of the solid phase were determined, as well as their proportion. The amount of liquid phase necessary to wet the surface of the particles of the solid phase, as well as to fill the voids between them, is determined. According to the results of the calculations, the criteria were chosen for evaluating the quality of mixing EHCM components.

The calculation results are compared with observed data obtained experimentally. An appropriate technique was developed to evaluate experimental samples. The results of comparing the calculated and experimental data make it possible to build the correlation dependences of the technological characteristics of the mixing of EHCM components.
Thermodynamics and performance of Al/CuO nanothermites with different storage time
Authors: Wang Ch A , Xu J B , Shen Y , Wang Y T , Yang T L , Zhang Z H , Li F W , Shen R Q , Ye Y H
Published: July 2020

The storage stability of energetic materials is important for their application. In our previous work, Al/CuO nanothermites was applied to a MEMS-based solid propellant micro thruster (SPM) array because of its short ignition delay and high reaction rate.

In the current work, the storage stability of Al/CuO nanothermites, which were prepared by electrospray method and stored with different storage time, was systematically researched. The activation energy of Al/CuO nanothermites were measured by DSC. The ignition temperature and the curve pressure history of Al/CuO nanothermites were measured using T-jump and constant-volume pressurization tests, respectively. Further, the nanothermites were characterized by XRD, XPS, SEM and TEM.

The results show that the morphology and mixture uniformity of the nanothermites after a long-time storage did not change significantly. The slow decomposition of NC and the thickening of oxide layer of Al NPs existed in the storage of Al/CuO nanothermites, analysed by XPS. The activation energy (Ea
) of Al/CuO nanothermites after storage for different time was determined using the method of Kissinger, as shown in Figure 1. Ea
was decreased from 272.8 kJ/mol to 154 kJ/mol after storage for 13 months. When stored for 0, 7 and 13 months, the peak pressures of Al/CuO nanothermites were 685.8 kPa, 626.3 kPa and 625.5 kPa, respectively. In addition to the ignition temperature, it was 775 °C, 739 °C and 754 °C, respectively. This result indicated that the ignition and combustion properties of Al/CuO nanothermites are obviously reduced when stored for a long time, at room temperature.

The full version of this extended abstract will appear in Defence Technology in 2020.
The Influence of Energy Content and Its Expenditure on the Impact Sensitivity of High-Nitrogen Energetic Materials
Authors: Zeman Svatopluk
Published: July 2020

Based on the analysis of a large amount of experimental data, Licht has stated [1] that a high level of performance is usually accompanied by an enhanced sensitivity and that insensitive explosives do not exhibit top performance. This statement might be taken as a rule [1,2,3]. Nevertheless, there are some exceptions to it [2,3] (the opposite run of the corresponding relationship), mainly in pure, technically attractive nitramines [3] and in some highly thermostable polynitroarenes [4]. Only recently, the energy gain from the explosion of energetic materials (i.e. the heat of explosion) in that type of studies has been replaced by their energy content, i.e. by their enthalpy of formation, ΔHform
[5]. So far, we have dealt with compounds with nitro groups in the molecule. However, the research in the last two decades has focused on energetic materials, mainly with a high nitrogen content, which is bound in their molecules mostly in another form than the nitro groups.
Equivalent design of stiffened panel bvased on load characteristics
Authors: Li J C , Huang F L , Lu Y G , Yu C X , Chen H
Published: July 2020

In order to use a cheaper and homogeneous steel plate to replace the real stiffened panel in warhead tests, we numerically simulated and analyzed the deformation and failure characteristics of the stiffened panel as well as the force characteristics of the projectile in the warhead-target interaction. Based on the energy equivalence method, we first used the acceleration curve of the warhead in actual target penetration process as the reference for equivalent design and replaced it using a three-layered homogeneous steel plate. To visually assess their equivalence, we introduced Pearson correlation coefficient in statistical analysis to reflect their correlation. The results showed that the equivalent design method based on load characteristics make both consistent not only in the kinetic energy loss but also in the warhead’s target-piercing acceleration process, thus realizing the equivalence from process to final state.
Effect of inner liner material on penetration behavior of reactive material double-layered liner shaped charge
Authors: Guo H G , He S , Ma H B , Sun T , Zheng Y F
Published: July 2020

To improve the insufficient penetration depth of the traditional single reactive liner shaped charge, the penetration enhancement behaviors of a reactive material double-layered liner (RM-DLL) shaped charge are investigated. This RM-DLL consists of an inner liner with metal materials and an outer liner with (polytetrafluoroethylene) PTFE/Al reactive materials. Based on the platform of AUTODYN-2D code, the influence of inner liner material on the jet formation of RM-DLL shaped charge and its penetration performance of multi-layered space plates were conducted. The numerical results indicated that, during the jet formation stage, the inner metal liner mainly formed a high-velocity precursor jet and the outer reactive liner became a major part of the slug. With increasing the material density of inner liner, the jet tip velocity and tip diamater decreased, and the effective mass of precursor jet also dropped off. For a given penetration time, with the increase in the material density of inner liner, the penetration capability of the RM-DLL shaped charge increased, whereas the mass of reactive materials entering the penetrated steel target decreased significantly. This RM-DLL shaped charge, incorporating the penetration capability of a precursor metal jet and the deflagration effects of the follow-thru reactive materials, will produce extremely damage to the desired target, typically such as the armored fighting vehicles.
Study on the influencing factors of underwater unexploded ordnance destruction based on shaped charged jet
Authors: Wu J Y , Zhong M Sh , Liu Y , Xie X B , Ji Ch
Published: July 2020

In order to study the influence of the stand-off distance and the waterproofness on the penetration effect of liner shaped charge (LSC) jet to destroy underwater unexploded ordnance, the LS-DYNA finite element program was applied to simulate the process of the metal jet formation and penetration into steel plate under different stand-off distances and waterproof condition. On the basis, the model experiment was carried out. And combing the experimental and numerical result, it can be found that, if no waterproof measures is adopted the metal jet will directly get contact with the water, the unexploded ordnance will not be successfully destructed, moreover, with the increase of the stand-off distance, the shaped charge jet works more ineffectively.
Bandgap calculation of shock-resistant metamaterials and evaluation of shockwave resistance
Authors: Li X R , Wang Zh G , Wang G H , Ma Y W
Published: July 2020

Theoretical bandgap calculation and numerical simulations were carried out in order to evaluate the shockwave resistance of the structures made of metamaterials, specifically in real applications. Assuming that the microstructures of the shockwave-resistant metamaterials are the same as that of the phononic crystals, a bandgap calculation model was constructed based on the wave function and the Bloch theory. Besides, the bandgap calculations of certain specific structures were carried out. Using the Abaqus dynamic simulation analysis software, the shockwave resistance of specific metamaterial structures and ordinary steel plates were compared and analyzed in terms of their response to stress and displacement. Consequently, the shockwave resistance and the results of bandgap calculations of the metamaterials were verified. The results showed that the bandgap model, constructed for the metamaterials, is highly accurate and the metamaterials with the structures of photonic crystal were found to be more resistant to shockwave. This investigation can provide a theoretical reference for future structural designs of shockwave-resistant metamaterials.
Research on the damage effect of semi-armor-piercing warhead on combined cabins of warships
Authors: Miao R , Wang W L , Du M H
Published: July 2020

Explosion test of 30kg Semi-armor-piercing warhead in the combined cabin of warship is completed. In the test, Upper and lower cabins are completely disintegrated. Cabins are broken in the weld zone. Maximum overpressure of lower cabin is 6.5 MPa and that of upper cabin is 0.6 MPa. By using numerical simulation method, influence of missile hole position and explosive charge velocity on damage effect is analyzed. Results show that difference of hole position will affect superposition of detonation products in cabin, thus changing position where the first structural fracture occurs in the cabin, leading to difference of damage. Increasing velocity of charge will make damage of positive direction bulkhead more serious, but damage degree of negative direction will be reduced. When velocity of charge exceeds 2 Ma, detonation products will not be able to affect cabin in negative direction of velocity.
Theoretical and Numerical Simulation of Small High-speed Projectiles Penetrating Brick Masonry
Authors: Li Z Q , Chen A J , Gong C A , Wang S , Yan W M , Wang C Z
Published: July 2020

The process of small high-speed projectiles penetrating brick masonry was studied. The cavity expansion theory used in the study of small high-speed projectile penetration was programmed and the penetration process was calculated. At the same time, LS-DYNA was used to simulate the mechanical process of small high-speed projectiles as they penetrate brick masonry. The results show that the numerical simulation results are more consistent with the theoretical calculation results; the numerical simulation of the finite boundary of the brick masonry and the mortar layer will cause some errors, making the brick masonry less resistant to small high-speed projectiles; When the masonry is compressible, the brickwork has less resistance to small high-speed projectiles; the larger the CRH value describing the geometry of the small high-speed projectile head, the maximum penetration depth and remaining of the small high-speed projectile The speed is greater.
The characteristics of fragments from embedded warhead
Authors: Gao Y G , Yan X M , Zhang B , Wu S Y , Xiao X , Feng Sh Sh
Published: July 2020

The Embedded warhead is a kind of warhead which is embedded into the target plate by its own kinetic energy and uses its effective fragments and whole or residual projectile to interdict the target. The fragments generated by the embedded warhead embedded in the target plate will impact the target plate and ricochet, which makes the dispersion of the fragments significantly different from that of warhead which is detonated in the air. However, there are no relevant researches which have been published. Therefore, in this paper, the dispersion of fragment from embedded warhead was investigated based on the experiment results, and the embedded warhead was detonated at center of the tail end. According to the experiment results, the fragments ricocheted from the target plate because the incident angle was too large. According to the statistics of fragments on the distribution plate, the average direction Angle of fragments went up (about 6°) due to part of fragments ricocheting from the target plate, which increased the damage effect of embedded warhead. The blocking diameter was 25m for human being. This study can provide a reference for the optimal design of embedded warhead.
Study on the influence of rigid wall surface on the bubble characteristics of underwater explosion
Authors: Meng L , Huang R Y , Qin J , Wang J X , Liu L T
Published: July 2020

In order to investigate the influence of rigid wall surface on the bubble characteristics of underwater explosion, the underwater explosion experiment under the boundary conditions of free surface and rigid wall surface was carried out on 2.5g cylindrical charge TNT in a 2×2×2m tank. The time history curves of shock wave and bubble pulsation were obtained by underwater pressure sensor, and the bubble pulsation process was observed by high-speed photography. The experimental results show that compared with the free surface underwater explosion, the shock wave peak pressure and the bubble pulse peak pressure in rigid wall surface underwater explosion are increased, and a large cavitation area appeared at the junction of rigid wall and water surface. After the bubbles contacted the rigid wall surface, the bubble morphology changed significantly, the first bubble pulsation period and the maximum radius of bubble expansion became larger. After the first bubble pulsation, the bubble partially collapsed and split into two parts, bubbles continued to pulsate in the direction of the rigid wall and the bottom of the water. Finally, combined with the experimental data of rigid wall surface at different explosion depths, the relationship between the first bubble pulsation period, the maximum bubble expansion radius and the explosion depth of 2.5gTNT under rigid wall conditions is given.
Study on fuze-guidance integration technology for improving air target striking capability of fortification storming/heat missiles
Authors: Zhao J M , Hu G H , Li X G , He J , Chen Y , Chen S Ch
Published: July 2020

In order to realize air-ground integration strike capability of the fortification storming/HEAT missiles, with the study background of addition of a laser proximity fuze to the missile, this paper proposes a fuze-guidance integration design method based on combination of image guidance and laser proximity fuze detection. By utilizing the missile-target encounter images, the gimbal angle of the seeker, the velocity and attitude of the missile, as well as the bearing and distance of the target detected by the laser proximity fuze, our design method establishes the space geometric equations of the relative motion of the missile and target, and of the equivalent conical plane of the dispersion center of the warhead fragments in the coordinate system of the missile body. Meanwhile, by solving the equations, a fully formulaic optimal time delay model of fuze-warhead matching is obtained, and the optimal detonation time of the warhead is given. The results show that this integration design method can effectively improve the damage effect of the missile on the helicopter target under complex encountering conditions, and realize the integrated air-to-ground strike capability of the fortification storming/HEAT missile.
Experimental study on knocking combustion in compressionignition engines under high-altitude conditions
Authors: Li H Y , Zhang X Q , Qiang Y P , Zhu W Q , Li Y Z , Li Y F
Published: July 2020

Diesel engine combustion becomes very rough or even detonation under high altitude conditions, which is harmful to components durability. In this study, combustion characteristics were experimentally investigated on a V6 heavy-duty diesel engine using by a plateau simulation test bench to simulate altitude conditions of 1000 m, 3000 m and 4500 m. Results show that extremely high peak pressure rise rates of above 50bar/°CA exist at low speeds under the altitude of 4500 m. This indicates that not only does knocking combustion exist in spark-ignition (SI) engines, but also can be found in compression-ignition (CI) engines. Knock intensity (KI) is calculated by the pressure oscillation with high-pass filtering (HPF). Approach of cycle to cycle variation was adopted to study combustion characteristics on the comparisons of knock and non-knock states. Also, the correlation between KI and peak pressure rise rate was revealed through the linear regression method.
Dynamic fracture of the AISI 1045 steel cylinders under internal blast loading
Authors: Ma Y , He Y , Wang CT , He Y , Guo Z P , Hu X B
Published: July 2020

Dynamic fracture failure of the AISI 1045 steel cylinders with variable depth grooves under internal blast loading was investigated. Lateral and longitudinal grooves were curved on the wall of steel cylinders along with radial direction. All grooves have a V-shape with 20° angle. After blast, the morphology of fragments recovered by multi-layer wooden plank showed relative consistency. Microstructure in cross and longitudinal section of the fragments was examined by scanning electron microscope (SEM). The microstructure observation suggested that there were some undeveloped shear bands and the dynamic fracture modes were similar in the all tests but the different fracture mode in two directions. Relevant numerical simulation by LS-DYNA were carried out to analyze the expanding and fracture process of cylinders under internal blast loading. Numerical results have acceptable agreement with experiment results. The mass loss rate of shell after explosion is negatively correlated with the depth of grooves.
Structure of copper shaped charge liner evolution law based on die forging process
Authors: Zhang M Y , Gao P , Yan Z F , Tian T , Cai W Z , Jia X B
Published: July 2020

Numerous studies have addressed the effect of grain size of materials on the overall penetrating performance of warheads. However, the use of the forging process to illustrate the grain heat-treatment refining technology has not been reported. In this experiment, the grain size of copper was observed and evaluated during the main processes of preparing copper shaped charge liners using the die forging process. Through this study, the evolution law for the structure of copper shaped charge liners was examined. In the as-cast condition, the grains of the copper ingots were mostly evenly distributed large flaky equiaxed crystal. Pre-forging and die forging make the grains appear more like strips. After the recrystallization heat treatment, the grain size of the copper shaped charge liner was refined and more uniform. Using these results, this study presents an evolution curve for copper shaped charge liners prepared using the forging process. The results can be used as a technical reference to solve the problem of grain size deviation in the production process of copper shaped charge liners.
Analysis characteristics and causes of adiabatic shear bands produced during the artillery barrel explosion
Authors: Zhang Zh W , Wang F , Liu S F , Li Zh J , Sun Y D , Zhang Y
Published: July 2020

It was studied that the characteristics and causes of adiabatic shear bands produced during the artillery barrel explosion when launching medium caliber projectiles. It shows that at the breech position, the strain required for the adiabatic shear band can be achieved, resulting in the adiabatic shear band, which is in a state of discontinuity and has an angle of about 20∼45 degrees with the barrel. After the appearance of adiabatic shear band, the strain rate is very high, and high heat is produced locally due to large plastic distortion, which can not be output, resulting in the intensification of deformation and the bursting of barrel. And the same time, the critical shear strain and temperature of the adiabatic shear band are calculated under this condition.
Study on mechanical properties and fragmentation under detonation loading of different types of tungsten alloys
Authors: Tang J J , Liang Zh F , Qu K P
Published: July 2020

In practical engineering, the fragments of warhead may be deformed and broken due to strong extrusion, material softening and other factors, which seriously affects the damage strength of warhead. In this paper, 93W-Ni-Fe, which is commonly used as fragment material, was selected as the research object. The static and dynamic properties of 93W fragments obtained by two different heat treatment processes were tested, and the crushing property and dynamic stress-strain curve were obtained. The static explosion test was also carried out. After the fragments were recovered, it was found that 1# fragment can basically ensure the integrity, 2# fragment had more fragmentations. The study showed that the fragmentation of tungsten alloy fragments was closely related to its structural characteristics and dynamic properties. The low stress and large deformation characteristics of 2# fragile specimen may be related to the distribution of the bonding phase.
Simulation and experimental study on the shock response of vehicle add-on modules subjected to blast loading
Authors: Wang J , Jiao L J , Li J S , Li N , Tao Z G , Song C M
Published: July 2020

Explosion of landmines is recognized as one of the vital threat to armoured vehicles. The detonation of mines may also threaten the survivability of the occupants inside the vehicle by the high intensive blast waves transmitting from vehicle structures. Bottom add-on modules can be very useful to vehicle in blast protecting. The dynamic response of three different add-on structures under bottom explosion was analysed by simulations and experiments. The optimal structure was obtained by computational results and experimental results, and the protection mechanism was summarized based on the research.
Shock wave compressibility of composite materials based on aramid fibers
Authors: Mochalova V M , Utkin A V
Published: July 2020

Using a VISAR laser interferometer, the experiments on investigation of the shock wave structure, spall strength and determination of Hugoniot parameters were performed for two composite materials based on the aramid fibers. Textolite and Kevlar were made using the same epoxy resin and aramid fibers, but had a different structure - unidirectional fibers and plies of woven fibers, respectively. The density of these materials is approximately 1.27 g/cm3. To study the shock wave compressibility of composite materials under high pressure, the explosive propellant charges were used to provide a flat throw of aluminum flyer plates with velocities from 0.7 to 5.05 km/s. As a result of experiments, particle velocity profiles on the composite/water boundary were obtained. On the velocity profiles for kevlar and textolite with transverse orientation of the fibers, after the initial shock jump, oscillations are observed due to the heterogeneous structure of the investigated materials. Unlike the composite materials with transverse orientation of the fibers, in the case when a shock wave propagates along the fibers, a two-wave configuration is recorded, which is due to the anisotropic structure of material. It was found that Hugoniots of composites with perpendicular orientation of the fibers are parallel to each other and differ only in the first coefficient determined by the sound speed of the material. Also a study of spall strength of textolite and Kevlar was performed. It was found for both materials that the value of spall strength along the fibers is higher than that for the transverse direction.
Fabrication and dynamic compressive response of reaction sintering H-BN ceramic
Authors: Gao X J , Sun M Y , Huang W P , Zhang M Y , Wu Y Ch , Zhang W , Wang Ch
Published: July 2020

Hexagonal boron nitride ceramic (h-BN) based on the nitridation of B powders was obtained by reaction sintering method. The dynamic compressive response was investigated using a Split Hopkinson pressure bar tester at high strain rates in a range of 0.8×103−1.6×103s−1. By increasing the strain rate, the dynamic strength and the failure strain increased continuously. The compressive stress–strain curves exhibited universal three deformation regions, including inelastic deformation region, rapid loading region and failure region. The failure mode of the h-BN ceramic depended upon the strain rate.
Experimental and numerical investigations of interface properties of Ti6Al4V/CP-Ti/Copper composite plate prepared by explosive welding
Authors: Mahmood Yasir , Chen Pengwan , Zhou Qiang , Bhatti Ashfaq Ahmad
Published: July 2020

Explosive welding is widely used in many industries. Explosive welding is a joining technique of the same or different kinds of metal alloys that cannot easily be welded by any other welding methods. Interlayer plays an important role to improve the welding quality and decrease the brittle intermetallics. The interlayer is added in between two parallel plates (flyer and base). Since it is a try layered combination, in which flyer is getting accelerated through explosive, and first strikes with interlayer, and then composite plate (flyer + interlayer) collides with base plate. Therefore two types of interfaces are formed (a) flyer-interlayer (b) Interlayer-base. Similarly, the energy dissipation, impact pressure and plastic strain during impact are divided into two interfaces. Explosive welding is short interval process, and it isn’t easy to measure these parameters by experiment. However, these parameters can be predicted by using numerical simulation.
Simulation study on the influence of liquid level on anti-jet penetration ability of single-cell composite structure
Authors: Cai Y E , Huang Z X , Shen X J , Zu X D , Jia X , Ji Q
Published: July 2020

The liquid composite armour produces transverse interference to the sharped charge jet through the backflow of liquid in the inner cavity, which affects the subsequent penetration ability of the jet. Within this article, a single-cell structure filled with water is take as the research target. Through numerical simulation, the process of shaped charge jet penetrating the single-cell structure at different liquid level is reproducing, and the parameters of the remaining jet after penetration, the interference of jet, and the deformation and energy absorption of shell are obtained. The results showed that the liquid level of liquid-filled single-cell structure has a significant influence on the anti-jet penetration ability of the single cell structure. When the liquid level was 60mm to 65mm, the water-filled single-cell structure has the best interference effect on the incoming shaped charge jet.
Performance test and application of the large diameter multi-point ring initiator for a shaped charge
Authors: Yu Rui , Wang Ping , Zhang Xin Ming
Published: July 2020

A series of experiments were conducted to investigate the synchronicity of the large diameter multi-point ring initiator applied to a shape charge(SC). With the multi-point ring initiator applied to SC, the penetration capability of the SC to penetrate in the reinforced concrete targets were studied. The output Synchronicity of all points of the multi-point ring initiator with diameter of 366mm was measured by the DL-32.II time interval tester. It shows that the output synchronicity of all points is good and the maximum time difference is less than 105ns. The SCs with two different initiation diameters were initiated to penetrate into the reinforced concrete targets. Experimental results show that the dimension of crater and inlet increase with initiation diameter of SCs.
Optimization design for countersink depth error prediction and compensation of CFRP/Al stacks
Authors: Zhang Yuxi , Wu Dan
Published: July 2020

The countersink depth accuracy is one of the most important quality indexes of the rivet holes in modern aerospace industry, especially in the drilling of thin-walled carbon fiber reinforced plastic (CFRP) and aluminum (Al) stack. However, the carbon fiber of CFRP is a kind of typical difficult-to-machine material, which results in the terrible wear of the cutting tool, and then the continuously increase of thrust force in the practical machining process, leading to the significant stack deformation and making it difficult to achieve the required countersink depth tolerance. Focusing on the countersink depth control in the drilling of the thin-walled CFRP/Al stack, this paper attempts to optimize the integrated methodology [10] in order to predict and compensate for the stack deformations more accurately. In this paper, an analytical flexible countersinking thrust force model that considers both tool wear and stack deformation is first developed with detailed theoretical analysis. Then a finite element model is established to identify the key features of the stack deformation in the countersinking process. An optimized iterative algorithm, which consists of three nested iterative loops, is designed to calculate the feasible stack deformation and make decision for the error compensation. Finally the optimized methodology are verified by groups of cutting experiments, and the results have shown that the methodology could effectively guarantee the countersink depth accuracy. The work in this paper enables us to understand the generating mechanisms of the countersink depth error in the drilling of the thin-walled CFRP/Al stack, and provides a novel approach to improve the countersink depth accuracy.
Study on reaction productions and morphology of Al-Ti-C-SiC master alloy in self-propagating high temperature synthesis
Authors: Zhang Guowei , Niu Jingwei , Xu Hong
Published: July 2020

Al-Ti-C-SiC master alloys were prepared by self-propagating high-temperature synthesis method with the aluminum powder, titanium powder, graphite powder and nano-SiC powder. The reaction productions and morphology of Al-Ti-C-SiC master alloy were systematically investigated. The results show that with the addition of SiC nano-particles, the reaction sequence of self-propagation synthesis of Al-Ti-C alloy was changed. During the reaction, the SiC nano-particles reacts with the titanium powder, which leads to an increase amounts of the TiC particles, In the self-propagation products of Al-Ti-C-SiC system, the size of TiC particles decreases first and then increases with the increase of SiC nano-particles mass fraction. When the mass fraction of SiC nano-particles is 10%, the size of TiC particles becomes nanometre, which size reach 100nm-200nm. When the mass fraction of SiC nano-particles is more than 10%, SiC nano-particles can be found in the master alloy product.
Stiffness-similar models for wind tunnel tests based on 3D printing
Authors: Zhu W , Zuo Z , Li D , Tian X , Luo M , Shang J , Li D , Ding X , Sun Y , Zhang Z , Zhang B , Zhang Z
Published: July 2020

Wind tunnel testing is a reliable means for R&D aerial vehicles of aerospace, e.g. aircraft, missiles, rockets etc. The wind tunnel models are the objects used in the tests, and stiffness-similar models are important for the structural and aerodynamic design of aerospace vehicles. The accuracy and economy of the model design and fabrication have a significant impact on the quality and cycle of vehicle R&D. The review will first give an overview introduction of the wind tunnel models with stiffness-similarity, and then detail design procedure and fabrication processing, which are developed by the author’s group based on 3D printing. The review can provide new methods to design and fabricate stiffness-similar models for wind tunnel tests for designers and researchers concerning the structural and aerodynamic studies in the aerospace industry.
An initiator integrated the AI/MoO3 multilayer nanothermite and bridge-wire electrode plug
Authors: Ni D B , Dang P Y , Yu G Q , Chu E Y
Published: July 2020

Lead styphnate is a primary explosive with low brisance, and is extensively applied into civil and military devices. Whereas the electrostatic sensitivity of LTNR is extremely high, it is disadvantageous for the safety of ignition system. In this paper, a novel initiator was integrated with Al/MoO3 multilayer film and bridge wire by magnetron sputtering. The thickness of Al/MoO3 multilayer was 3um with period of 20nm/30nm. The heat release of Al/MoO3 multilayer film was and 1164J/g, which was characterized by differential scanning calorimetry (DSC). And the combustion speed of film was about 5.3 m/s, it was characterized by high speed cameral and laser ignition system. The firing sensitivities was measured by Langly method, the 50% and 99.9% firing-current sensitivity of initiator was 0.08A and 0.11A, respectively, and the 50% and 99.9% firing-voltage sensitivity of initiator was 2.30V and 2.56V, respectively. The firing sensitivities of Al/MoO3 multilayer film was almost equal to the LTNR. The insensitive ignition composition of B-KNO3 tablet was easily fired with in the gap of 2.12 mm. And the initiator can easily fire the lead azide in detonator. All of these, it is suggested that Al/MoO3 multilayer film will expect to be a substitute for LTNR and improve the ignition ability and safety of ignition system and has a significant influence on the design of explosive devices.
Real-time localization, mapping and navigation for quadruped robots
Authors: Pan Y Y , Ding X Q , Yang T , Wang Y , Xiong R , Jiang L
Published: July 2020

Autonomous quadruped robots require localization and mapping for navigation. Different from mobile robots, quadruped robots need local dense maps with more detailed information for motion planning. A key challenge, limited by the capacity of computers on robots, the perception systems have to balance the properties of the speed and accuracy to ensure that robots reach their destinations quickly and safely. In this paper, we propose a complete solution for the autonomous movement of quadruped robots. Localization is achieved by the Extended Kalman Filter which is updated by the results from laser based the ICP algorithm. Dense maps are created by raw ranger sensor data and accumulated base on accurate localization results. And then, dense maps are transformed to the occupancy grid maps which contain free and occupied space information for planning. For implementations, we demonstrate the effectiveness of our approach in a complex outdoor environment.
Full attitude tracking control of a tiltrotor UAV on SO(3)
Authors: Dong Shimeng , Zhang Tao
Published: July 2020

This paper presents novel results for the attitude tracking control of a tiltrotor unmanned aerial vehicle (UAV). This kind of UAV has two tiltable rotors while both thrust force and thrust direction can be controlled, and thus has four input degrees of freedom. A nonlinear dynamic model defined on SO(3) is proposed and analysed. An attitude tracking controller is developed using Lie Group and Lie Algebra theory, achieving smooth attitude tracking and avoiding the singularity problem of Euler Angles. Numerical simulation shows the controller has desirable closed loop performance and global asymptotic stability.
Bionic design and anti-slip characteristics study of quadruped robot foot
Authors: Tian W J , Xu Y J , Xu W , Xu P , Zhang Q , Cong Q
Published: July 2020

Quadruped robot has been widely used in the field of national defense because of its high adaptability. The stability and balance capacity is the important performances needed during the quadruped robot moving under uneven terrains, and the slip resistance of the foot affects the balance performance of robot. As the goat hoof with irregular surface morphology adapts to rugged terrain, its plantar geometric shape was reconstructed using reverse engineering technology based on the point clouds which were obtained by using a 3D hand laser scanner. The bionic foot was designed based on goat hoof plantar surface, and the anti-slip characteristics were analyzed by finite element method, and then compared with the spherical foot and cylindrical foot. The frictions between these feet and soils or rocks at different pressures were investigated, and the result shows that the maximum static frictions between bionic and soil and rock are greater than that of the two others, which means bionic foot has better anti-slip performance.
Slam algorithm for aruco landmark array based on synchronization optimization
Authors: Xing B Y , Dang R N , Xu P , Jiang C X , Jiang L
Published: July 2020

High precision mapping algorithm is the core of two-dimensional(2D) landmark array(the ArUco landmark is used in this paper) localization application. In most of the existing mapping algorithms, the accumulated errors of online methods can not be eliminated, meanwhile, the manual calibration and off-line methods are inefficient and time-consuming. In order to overcome those shortcomings, a real-time simultaneous localization and mapping(SLAM) algorithm for landmark array based on synchronized optimization is proposed in this paper. The proposed algorithm updates and corrects the global map online, and the accumulated errors is optimized based on minimizing the re-projection error of the landmarks ’ vertexes. In order to verify the proposed algorithm, several contrast experiments with other mapping systems are presented. The experimental results show that the proposed algorithm has the advantages of high map precision and small accumulative error.
Research on multi-address autonomous access technology of uav cluster data link based on priority statistics
Authors: ZHang J L , Wa F , Hao Q
Published: July 2020

As a uav cluster that can change the future combat situation, its data link has the requirements of high speed, low delay, dynamic networking and large network capacity. In this paper, a priority statistics based multi-address autonomous access technology for uav cluster data link is studied. Firstly, the channel load is detected and predicted by time-frequency analysis for different priority services. Then, multi-node information fusion is adopted for multi-address decision-making. Finally, the designed technology is simulated by Qualnet software. The simulation results show that the proposed multi-address autonomous access technology based on priority statistics can effectively reduce in-network channel collisions and realize low-delay transmission of high-priority services.
Prediction of creep performance during long-term storage of composite directors based on nonlinear viscoelasticity
Authors: Sun T S , Yu C G , Wang Q , Yang W C , Zhong J L
Published: July 2020

In order to investigate the long-term storage creep performance of composite directors for multiple launch rocket systems, E-glass fiber reinforced epoxy matrix composite laminates were prepared and the 60/60-minute creep/creep-recovery tests were carried out at different stress levels. The master curves of long-term creep compliance were obtained by shifting the short-term creep compliance based on the superposition principle, and then the parameters of linear-transient creep compliance model were obtained by a curve fitting procedure. The functional relation between the Schapery’s nonlinear parameters and the average matrix octahedral shear stress was developed by an analytical procedure. Finite element method and the user-defined material subroutine (UMAT) are used to establish the long-term storage numerical analysis model of composite directors, and the creep deformation after 15-years stacking storage was predicted.
Prediction of three-dimensional elastic behavior of filament-wound composites based on the bridging model
Authors: Yin D M , Li B M , Ch Xiao H
Published: July 2020

With the high specific stiffness, specific strength and designable ability, filament-wound composites have been widely applied in many industries, such as aerospace, energy and transportation, and they are also the one of more ideal choices for the lightweight structural design of weapon system. However, their complex structures, which including the cross-overs, undulations, and overlaps between different winding passages of the fiber bundles, make it difficult to obtain their macro mechanical properties. And this work will provide a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle. The representative volume element (RVE) in the meso-scale is defined on the basis of the filament winding pattern, which characterizes all the micro-architecture details of the filament wound composites, such as fiber undulation, winding angle and lamination arrangement. Referring to the principle of volume average in the analysis method of braided composites, a theoretical prediction model for the three-dimensional equivalent elastic constants of the filament wound composites is established by adopting the bridging model. Through this method, the results obtained for the previous experimental model are in good agreement with the experimental ones, which verifies the reliability of this model. In addition, the effects of some winding parameters, such as winding angle, on the equivalent elastic behavior of the filament-wound composites are analyzed. And the rules gained can provide a theoretical reference for the optimum design of filament-wound composites.

The full version of this extended abstract will appear in Defence Technology in 2020.
Study on single-lap joints tensile properties under fire and thermal conductivity of Z-pin reinforced thermal protection composites
Authors: Li L S , Li Y , Huan D J
Published: July 2020

Quartz fiber reinforced phenolic (QFRP) resin composites were often used in thermal protection structures such as the engines and tip of missiles or rockets, but its anti-erosion performance needs to be further optimized. Z-pin technology can improve the anti-erosion performance because Z-pin effectively improved the inter-laminar shear strength of composite materials. However, it will increase the through-thickness thermal conductivity (TC), resulting in a decrease of its thermal protection performance. This paper successfully established the equation about through-thickness TC of Z-pin reinforced composites based on theoretical analysis and experimental results and tested the single-lap joints tensile strength of the samples compared with the blank and Z-pin samples under fire which characterized the interlayer performance of Z-pin reinforced thermal protection composites at high temperatures. Research showed that the through-thickness TC of the composite increases regularly with the TC and content of Z-pin, and this is because the pins act as a thermally conductive pathway. The TC increases by 13.19%, 12.34% and 12.13% when the Z-pin implantation volume fraction is 2.18%, 0.785% and 0.401%, respectively. Z-pin samples have an increase in shear strength of 63.85%, 78.97% and 88.31% compared with blank samples when the ablation time is 20s, 40s and 60s, respectively, indicating that Z-pin technology effectively could reduce the shear strength of single-lap joint with the increase of ablation time. These results prove the controllability of the through-thickness TC enhancement and effectiveness of interlayer strength by Z-pin, and guide the structural design of Z-pin reinforced thermal protection composites.