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Shock-induced chemical reaction characteristics of PTFE-Al-Bi_(2.O_(3)reactive materials

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Defence technology（防务技术） 2024年第6期36卷 1-12页

作者： Chunlan Jiang Rong Hu Jingbo Zhang Zaicheng Wang Liang Mao State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China

A ternary system of PTFE/Al/Bi_(2.O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive *** effects of Bi_(2.O_(3)in the PTFE/Al/Bi_(2.O_(3)on both mechanical properties and the energy release were investigated through various tests such as thermogravimetry-differential scanning calorimetry,adiabatic oxygen bomb test and split Hopkinson pressure bar *** microstructure observed through scanning electron microscope and Xray diffraction results are used to analyze the ignition and reaction mechanism of PTFE/Al/Bi_(2.O_(3).The results indicate that the PTFE/Al/Bi_(2.O_(3)are capable of triggering the exothermic reaction of molten PTFE/Bi_(2.O_(3)and Al/Bi_(2.O_(3)over the PTFE/Al reactive materials,thereby promoting *** excessive aluminum in the ternary system is beneficial for increasing energy *** ignition of shock-induced chemical reactions in PTFE/Al/Bi_(2.O_(3)is closely related to the material *** dominant mechanism for hot-spot generation under Split Hopkinson Pressure Bar test is the frictional temperature rise at the microcrack after failure.

关键词： PTFE/Al/Bi_(2.O_(3) Shock-induced chemical reaction Energy release

Enhanced structural damage behavior of liquid-filled tank by reactive material projectile impact

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Defence technology（防务技术） 2024年第1期31卷 211-229页

作者： Jianwen Xie Yuanfeng Zheng Zhenyang Liu Chengzhe Liu Aoxin Liu Pengwan Chen Haifu Wang State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China

A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks,and the corresponding hydrodynamic ram(HRAM) was studied in ***/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering *** projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 12.0 m/*** corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system,and further compared to those of steel and aluminum *** different from the conical cavity formed by the inert metal projectile,the cavity formed by the RMP appeared as an ellipsoid with a conical *** RMPs were demonstrated to enhance the radial growth velocity of cavity,the global HRAM pressure amplitude and the front panel damage,indicating the enhanced HRAM and structural damage ***,combining the impact-induced fragmentation and deflagration characteristics,the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was *** mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse ***,the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and *** was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior.

关键词： Reactive material projectile Hydrodynamic ram Enhanced structural damage Liquid-filled tank Impact

Ballistic performance of additive manufacturing 316l stainless steel projectiles based on topology optimization method

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Defence technology（防务技术） 2024年第5期35卷 1-17页

作者： Hao Xue Tao Wang Xinyu Cui Yifan Wang Guangyan Huang State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China

Material and structure made by additive manufacturing(AM)have received much attention lately due to their flexibility and ability to customize complex *** study first implements multiple objective topology optimization simulations based on a projectile perforation model,and a new topologic projectile is *** two types of 316L stainless steel projectiles(the solid and the topology)are printed in a selective laser melt(SLM)machine to evaluate the penetration performance of the projectiles by the ballistic *** experiment results show that the dimensionless specific kinetic energy value of topologic projectiles is higher than that of solid projectiles,indicating the better penetration ability of the topologic ***,microscopic studies(scanning electron microscope and X-ray micro-CT)are performed on the remaining projectiles to investigate the failure mechanism of the internal structure of the topologic *** explicit dynamics simulation was also performed,and the failure locations of the residual topologic projectiles were in good agreement with the experimental results,which can better guide the design of new projectiles combining AM and topology optimization in the future.

关键词： Additive manufacturing Topology optimization Ballistic performance Projectile design

Assessing the energy release characteristics during the middle detonation reaction stage of aluminized explosives

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Defence technology（防务技术） 2024年第3期33卷 270-277页

作者： Kun Yang Lang Chen Danyang Liu Bin Zhang Jianying Lu Junying Wu State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China

Afterburning behind the detonation front of an aluminized explosive releases energy on the millisecond timescale,which prolong the release of detonation energy and the energy release at different stages also shows significant ***,at present,there are few effective methods for evaluating the energy release characteristics of the middle reaction stage of such explosives,which can have a duration of tens to hundreds of *** present work demonstrates an approach to assessing the midstage of an aluminized explosive detonation based on a water push test employing a high degree of *** this method,the explosive is contained in a steel cylinder having one end closed that is installed at the bottom of a transparent water *** detonation,the gaseous products expand in one direction while forcing water ahead of *** resulting underwater shock wave and the interface between the gas phase products and the water are tracked using an ultra-high-speed framing and streak *** shock wave velocity in water and the expansion work performed by the gaseous detonation products were calculated to assess the energy release characteristics of aluminized explosives such as CL-2. and RDX in the middle stage of the detonation *** the middle stage of the detonation process of these aluminized explosives,the aluminum reaction reduced the attenuation of shock waves and increased the work performed by gas phase products.A higher aluminum content increased the energy output while the presence of oxidants slowed the energy release *** work demonstrates an effective means of evaluating the performance of aluminized explosives.

关键词： Aluminized explosive Non-ideal detonation Water push test Energy release

Reactive molecular dynamics insight into the thermal decomposition mechanism of 2.6-Bis(picrylamino)-3,5-dinitropyridine

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Defence technology（防务技术） 2024年第3期33卷 134-146页

作者： Jianbo Fu Hui Ren Xinzhou Wu Yongjin Chen Mi Zhang Yazhi Cheng State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China

2.6-bis(picrylamino)-3,5-dinitropyridine(PYX)has excellent thermostability,which makes its thermal decomposition mechanism receive much *** this paper,the mechanism of PYX thermal decomposition was investigated thoroughly by the ReaxFF-lg force field combined with DFT-B3LYP(6-311++G)*** detailed decomposition mechanism,small-molecule product evolution,and cluster evolution of PYX were mainly *** the initial stage of decomposition,the intramolecular hydrogen transfer reaction and the formation of dimerized clusters are earlier than the denitration *** the progress of the reaction,one side of the bitter amino group is removed from the pyridine ring,and then the pyridine ring is *** final products produced in the thermal decomposition process are CO_(2.,H_(2.O,N_(2.,and H_(2..Among them,H_(2.O has the earliest generation time,and the reaction rate constant(k_(3))is the *** clusters are formed during the decomposition of PYX,and the formation,aggregation,and decomposition of these clusters are strongly affected by *** low temperatures(2.00 K-2.50 K),many clusters are *** high temperatures(2.50 K-32.0 K),the clusters aggregate to form larger *** 3500 K,the large clusters decompose and become *** the late stage of the reaction,H and N in the clusters escaped almost entirely,but more O was trapped in the clusters,which affected the auto-oxidation process of ***'s initial decomposition activation energy(E_(a))was calculated to be 12..58 kJ/*** work contributes to a theoretical understanding of PYX's entire thermal decomposition process.

关键词： PYX Thermal decomposition ReaxFF-lg MD simulations Excellent thermostable explosives

Influence of ambient temperature on the CO_(2.emitted of light-duty vehicle

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Journal of Environmental Sciences 2024年第6期140卷 59-68页

作者： Dan Tan Yachao Wang Jianwei Tan Jiachen Li Changyu Wang Yunshan Ge School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

Because of global warming,people have paid more attention to greenhouse gas emitted by *** quantify the impact of temperature on vehicle CO_(2.emissions,this study was conducted using the world light vehicle test cycle on two light-duty E10 gasoline vehicles a ambient temperatures of-10,0,2.,and 40℃,and found that CO_(2.emission factors of Vehicle1 in the low-speed phase were 2..07%and 2..2.%higher than those of Vehicle 2.at cold star and hot start under-10℃.The reason was vehicle 1 had a larger displacement and more friction pairs than vehicle *** was the highest CO_(2.emission at the low-speed phase due to low average speed,frequent acceleration,and *** CO_(2.temperature factor and the ambient temperature had a strong linear correlation(R2.0.99).According to CO_(2.temperature factors and their relationships,CO_(2.emission factors of other ambien temperatures could be calculated when the CO_(2.emission factor of 2.℃was obtained,and the method also could be used to obtain the CO_(2.temperature factors of different *** separate the effect of load setting and temperature variation on CO_(2.emission quantitatively a method was *** results showed that the load setting was dominant for the CO_(2.emission *** with 2.℃,the CO_(2.emission for vehicle 1 caused by load setting variation were 62.83 and 47.42.g/km,respectively at-10 and 0℃,while those fo vehicle 2.were 45.01 and 35.63 g/km,respectively.

关键词： CO_(2.emission Ambient temperature E10 gasoline Light-duty vehicle WLTC

Effect of the vortical structures on the hydrodynamic performance of a pitching hydrofoil

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Journal of Hydrodynamics 2024年第2期36卷 406-420页

作者： Rui Yuan Hui-yun Hao Qin Wu Yun-qing Liu Biao Huang School of Mechanical Engineering Beijing Institute of TechnologyBeijing100081China

The objective is to study the vortical structural behaviors of a transient pitching hydrofoil and their effects on the hydrodynamic performance. The pitching motion of the hydrofoil is set to pitch up with an almost constant rate from 5° to 15° and then back to 5°, with the Reynolds number 4.4×10^(5) and the frequency 2.Hz. The results show that the main coherent structures around the pitching hydrofoil include small-scale laminar separation bubble (LSB), large-scale second vortex (SV) and trailing edge vortex (TEV) which are all vortical. The relationship between the vortical structure and the lift is investigated with the finite-domain impulse theory. It indicates that the major part of the lift is contributed by the LSB, whereas the shedding and the formation of the SV and TEV cause the fluctuation of the lift. The proper orthogonal decomposition (POD) method is applied to capture the most energetic modes, revealing that the LSB mode occupies a large amount of energy in the flow field. The dynamic mode decomposition (DMD) method accurately extracts the dominant frequency and modal characteristics, with the first mode corresponding to the mean flow, the second mode corresponding to the LSB structure and the third and fourth modes corresponding to the vortex shedding.

关键词： Hydrodynamics vortical structures finite-domain impulse theory proper orthogonal decomposition(POD) dynamic mode decomposition(DMD) Pitching hydrofoil

Full lifetime demonstration of a Micro-Cathode-Arc thruster evolution characteristics

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Chinese Journal of Aeronautics 2024年第6期37卷 38-49页

作者： Zhe ZHANG Zijing ZHAO Xiangyang LIU Ningfei WANG School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

Ground lifetime test is the most crucial experiment to assess the performance,*** flight qualification of electric propulsion,and it can bring new insights for understanding the operation *** work demonstrates a full lifetime test of 140000 cycles on a Micro-Cathode-Arc Thruster(μCAT)with 160μs charging time and 86 mJ charging energy.A four-probe resistivity measurement method is utilized to investigate variations in the conductive film thickness and resistivity throughout the thruster *** film parameters show that the lifetime of theμCAT can be divided into three *** the initial stage,the film thickness decreases by 1.2.m and the resistivity increases significantly due to the high discharge intensity and intense film ablation;In the steady stage,the change of the film thickness is within 5%,and the resistivity of the film increases slowly from 0.050Ω·mm to 0.2.3Ω·*** the end stage,the resistivity exponentially increases from 0.2.3Ω·mm to 1.176Ω·mm,with the increase accounting for 81%,ultimately resulting in the failure of the thruster open ***,the evolution of discharge parameters,and the variation of plume parameters are measured throughout the *** discharge characteristics also show significant differences in the duration of voltage and current in these three *** results of plume shape and plasma parameters are also well con-sistent with the discharge parameters and film *** results suggest that,for evaluating the steady stage lifetime of thrusters,the film thickness is the best indicator compared to the variations in resistivity and voltage-current *** the end stage,the plasma plume *** duration,and plume parameters can conveniently and clearly characterize the thruster failures and irregularity.

关键词： Electric propulsion Lifetime test Micro-Cathode-Arc Thruster(uCAT) Conductive film Discharge characteristics Plasma parameters

A novel predictive braking energy recovery strategy for electric vehicles considering motor thermal protection

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Science China(Technological Sciences) 2024年第4期67卷 1253-1269页

作者： YANG Chao SUN TongLin YANG LiuQuan ZHANG YuHang WANG WeiDa School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100084China

Braking energy recovery(BER)aims to recover the vehicle's kinetic energy by coordinating the motor and mechanical braking torque to extend the driving range of the electric vehicle(EV).To achieve this goal,the motor/generator mode requires frequent switching and prolonged operation during *** this case,the motor temperature will unavoidably rise,potentially triggering motor thermal protection(MTP).Activating MTP increases the risk of motor component failure,and the EV typically disables the BER ***,maximizing BER while reducing the risk of motor overheating is a challenging *** address this issue,this article proposes a predictive BER strategy with MTP using the non-smooth Pontryagin Minimum Principle(NSPMP)for ***,a Markov long short-term memory(MLSTM)model is designed to obtain future velocity ***,the BER problem with MTP in the studied EV is embedded in a model predictive control(MPC)***,under the MPC framework,the NSPMP strategy is proposed to resolve the problem of ***,the performance of the proposed strategy is verified through simulation and a hardware-in-loop *** results show that in two real-world driving cycles,compared to the rule-based strategy,the proposed strategy reduced power consumption by 1.2.%and0.96%,respectively,and effectively limited motor ***,under global cycle conditions,this strategy demonstrated better MTP control performance compared to other benchmark strategies.

关键词： electric vehicle braking energy recovery strategy motor thermal protection non-smooth PMP