查看更多>>摘要：Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol％)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded together into 3-layer laminated plates using hot isostatic pressing(HIP).The laminates were ballistically tested and demonstrated superior performance.The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates.The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces be-tween different adjacent layers in the laminate.Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP,which provides an unprecedented increase in the hardness of the layered com-posites.It is argued that the combination of the used two technologies,BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.
Mohammad Hossein KeshavarzSedigheh Heydari BaniReza BakhtiariSeyyed Hesamodin Hosseini...
15-22页
查看更多>>摘要：Nitrogen-rich heterocyclic energetic compounds(NRHECs)and their salts have witnessed widespread synthesis in recent years.The substantial energy-density content within these compounds can lead to potentially dangerous explosive reactions when subjected to external stimuli such as electrical discharge.Therefore,developing a reliable model for predicting their electrostatic discharge sensitivity(ESD)becomes imperative.This study proposes a novel and straightforward model based on the presence of specific groups(-NH2 or-NH-,-N=N+-O-and-NNO2,-ONO2 or-NO2)under certain conditions to assess the ESD of NRHECs and their salts,employing interpretable structural parameters.Utilizing a comprehensive dataset comprising 54 ESD measurements of NRHECs and their salts,divided into 49/5 training/test sets,the model achieves promising results.The Root Mean Square Error(RMSE),Mean Absolute Error(MAE),and Maximum Error for the training set are reported as 0.16 J,0.12 J,and 0.5 J,respectively.Notably,the ratios RMSE(training)/RMSE(test),MAE(training)/MAE(test),and Max Error(training)/Max Error(test)are all greater than 1.0,indicating the robust predictive capabilities of the model.The presented model demonstrates its efficacy in providing a reliable assessment of ESD for the targeted NRHECs and their salts,without the need for intricate computer codes or expert involvement.
查看更多>>摘要：Shaped charge liner(SCL)has been extensively applied in oil recovery and defense industries.Achieving superior penetration capability through optimizing SCL structures presents a substantial challenge due to intricate rate-dependent processes involving detonation-driven liner collapse,high-speed jet stretching,and penetration.This study introduces an innovative optimization strategy for SCL structures that em-ploys jet penetration efficiency as the primary objective function.The strategy combines experimentally validated finite element method with machine learning(FEM-ML).We propose a novel jet penetration efficiency index derived from enhanced cutoff velocity and shape characteristics of the jet via machine learning.This index effectively evaluates the jet penetration performance.Furthermore,a multi-model fusion based on a machine learning optimization method,called XGBOOST-MFO,is put forward to optimize SCL structure over a large input space.The strategy's feasibility is demonstrated through the optimization of copper SCL implemented via the FEM-ML strategy.Finally,this strategy is extended to optimize the structure of the recently emerging CrMnFeCoNi high-entropy alloy conical liners and hemispherical copper liners.Therefore,the strategy can provide helpful guidance for the engineering design of SCL.
查看更多>>摘要：High purity and ultrafine DAAF(u-DAAF)is an emerging insensitive charge in initiators.Although there are many ways to obtain u-DAAF,developing a preparation method with stable operation,accurate control,good quality consistency,equipment miniaturization,and minimum manpower is an inevitable requirement to adapt to the current social technology development trend.Here reported is the micro-fluidic preparation of u-DAAF with tunable particle size by a passive swirling microreactor.Under the guidance of recrystallization growth kinetics and mixing behavior of fluids in the swirling microreactor,the key parameters(liquid flow rate,explosive concentration and crystallization temperature)were screened and optimized through screening experiments.Under the condition that no surfactant is added and only experimental parameters are controlled,the particle size of recrystallized DAAF can be adjusted from 98 nm to 785 nm,and the corresponding specific surface area is 8.45 m2·g-1 to 1.33 m2·g-1.In addition,the preparation method has good batch stability,high yield(90.8％-92.6％)and high purity(99.0％-99.4％),indicating a high practical application potential.Electric explosion derived flyer initiation tests demonstrate that the u-DAAF shows an initiation sensitivity much lower than that of the raw DAAF,and comparable to that of the refined DAAF by conventional spraying crystallization method.This study provides an efficient method to fabricate u-DAAF with narrow particle size distribution and high reproducibility as well as a theoretical reference for fabrication of other ultrafine explosives.
查看更多>>摘要：This paper investigates the attitude tracking control problem for the cruise mode of a dual-system convertible unmanned aerial vehicle(UAV)in the presence of parameter uncertainties,unmodeled un-certainties and wind disturbances.First,a fixed-time disturbance observer(FXDO)based on the bi-limit homogeneity theory is designed to estimate the lumped disturbance of the convertible UAV model.Then,a fixed-time integral sliding mode control(FXISMC)is combined with the FXDO to achieve strong robustness and chattering reduction.Bi-limit homogeneity theory and Lyapunov theory are applied to provide detailed proof of the fixed-time stability.Finally,numerical simulation experimental results verify the robustness of the proposed algorithm to model parameter uncertainties and wind distur-bances.In addition,the proposed algorithm is deployed in a open-source UAV autopilot and its effec-tiveness is further demonstrated by hardware-in-the-loop experimental results.
查看更多>>摘要：The launch dynamics theory for multibody systems emerges as an innovative and efficacious approach for the study of launch dynamics,capable of addressing the challenges of complex modeling,diminished computational efficiency,and imprecise analyses of system dynamic responses found in the dynamics research of intricate multi-rigid-flexible body systems,such as self-propelled artillery.This advancement aims to enhance the firing accuracy and launch safety of self-propelled artillery.Recognizing the shortfall of overlooking the band engraving process in existing theories,this study introduces a novel coupling calculation methodology for the launch dynamics of a self-propelled artillery multibody system.This method leverages the ABAQUS subroutine interface VUAMP to compute the dynamic response of the projectile and barrel during the launch process of large-caliber self-propelled artillery.Additionally,it examines the changes in projectile resistance and band deformation in relation to projectile motion throughout the band engraving process.Comparative analysis of the computational outcomes with experimental data evidences that the proposed method offers a more precise depiction of the launch process of self-propelled artillery,thereby enhancing the accuracy of launch dynamics calculations for self-propelled artillery.
Norliza IsmailWan Yusmawati Wan YusoffNor Azlian Abdul ManafAzuraida Amat...
86-102页
查看更多>>摘要：In the realm of military and defence applications,exposure to radiation significantly challenges the performance and reliability of solder alloys and joints in electronic systems.This comprehensive review examines radiation-induced effects on solder alloys and solder joints in terms of microstructure and mechanical properties.In this paper,we evaluate the existing literature,including experimental studies and fundamental theory,to provide a comprehensive overview of the behavior of solder materials under radiation.A review of the literature highlights key mechanisms that contribute to radiation-induced changes in the microstructure,such as the formation of intermetallic compounds,grain growth,micro-voids and micro-cracks.Radiation is explored as a factor influencing solder alloy hardness,strength,fatigue and ductility.Moreover,the review addresses the challenges and limitations inherent in studying the effects of radiation on solder materials and offers recommendations for future research.It is crucial to understand radiation-induced effects on solder performance to design robust and radiation-resistant electronic systems.A review of radiation effects on solder materials and their applications in electronics serves as a valuable resource for researchers,engineers,and practitioners in that field.
查看更多>>摘要：Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This study is based on developing a safer laser driven flyer plate prototype comprised of a laser initiator and a flyer plate subsystem that can be used with secondary explosives.System parameters were optimized to initiate the shock-to-detonation transition(SDT)of a secondary explosive based on the impact created by the flyer plate on the explosive surface.Rupture of the flyer was investigated at the mechanically weakened region located on the interface of these subsystems,where the product gases from the deflagration of the explosive provide the required energy.A bilayer energetic material was used,where the first layer consisted of a pyrotechnic component,zirconium potassium perchlorate(ZPP),for sustaining the ignition by the laser beam and the second layer consisted of an insensitive explosive,cyclotetramethylene-tetranitramine(HMX),for deflagration.A plexiglass interface was used to enfold the energetic material.The focal length of the laser beam from the diode was optimized to provide a ho-mogeneous beam profile with maximum power at the surface of the ZPP.Closed bomb experiments were conducted in an internal volume of 10 cm3 for evaluation of performance.Dependency of the laser driven flyer plate system output on confinement,explosive density,and laser beam power were analyzed.Measurements using a high-speed camera resulted in a flyer velocity of 670±20 m/s that renders the prototype suitable as a laser detonator in applications,where controlled employment of explosives is critical.
查看更多>>摘要：Flame temperature and spectral emissivity were the important parameters characterizing the sufficient degree of fuel combustion and the particle radiative characteristics in the Rocket Based Combined Cycle(RBCC)combustor.To investigate the combustion characteristics of the complex supersonic flame in the RBCC combustor,a new radiation thermometry combined with Levenberg-Marquardt(LM)algorithm and the least squares method was proposed to measure the temperature,emissivity and spectral radi-ative properties based on the flame emission spectrum.In-situ measurements of the flame temperature,emissivity and spectral radiative properties were carried out in the RBCC direct-connected test bench with laser-induced plasma combustion enhancement(LIPCE)and without LIPCE.The flame average temperatures at fuel global equivalence ratio(α)of 1.0b and 0.6 with LIPCE were 4.51％and 2.08％higher than those without LIPCE.The flame combustion oscillation of kerosene tended to be stable in the recirculation zone of cavity with the thermal and chemical effects of laser induced plasma.The differ-ences of flame temperature at α=1.0b and 0.6 were 503 K and 523 K with LIPCE,which were 20.07％and 42.64％lower than those without LIPCE.The flame emissivity with methane assisted ignition was 80.46％lower than that without methane assisted ignition,due to the carbon-hydrogen ratio of kerosene was higher than that of methane.The spectral emissivities at 600 nm with LIPCE were 1.25％,22.2％,and 4.22％lower than those without LIPCE at α=1.0a(with methane assisted ignition),1.0b(without methane assisted ignition)and 0.6.The effect of concentration in the emissivity was removed by normalization to analyze the flame radiative properties in the RBCC combustor chamber.The maximum differences of flame normalized emissivity were 50.91％without LIPCE and 27.53％with LIPCE.The flame radiative properties were stabilized under the thermal and chemical effects of laser induced plasma at a=0.6.
查看更多>>摘要：The interfacial interaction between HMX molecules and coating materials is the key to the safety per-formance of explosives and has received extensive attention.However,screening suitable coating agents to enhance the interfacial effect to obtain high-energy and low-sensitivity explosives has long been a major challenge.In this work,HMX-PEI/rGO/g-C3N4(HPrGC)composites were innovatively prepared by a multi-level coating strategy of two-dimensional graphite rGO and g-C3N4.The g-C3N4 used for desen-sitization has a rich π-conjugated system and shows outstanding ability in reducing friction sensitivity.The hierarchical structure of HPrGC formed by electrostatic self-assembly and π-π stacking can effec-tively dissipate energy accumulation under heat and mechanical stimulation through structural evolu-tion,thus exhibiting a prominent synergistic desensitization effect on HMX.The results show that rGO/g-C3N4 coating has no effect on the crystal structure and chemical structure of HMX.More importantly,the perfect combination of g-C3N4 and rGO endows HPrGC with enhanced thermal stability and ideal me-chanical sensitivity(IS:21 J,FS:216 N).Obviously,the new fabrication of HPrGC enriches the variety of desensitizer materials and helps to deepen the understanding of the interaction between explosives and coatings.
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