Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used.Three types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and tested.The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over time.Moreover,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact.From simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy cluster.The unique formation structure determines the damage modes of the aluminum plate and the steel plate.Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content.With increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration.However,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.

Study on jet formation behavior and optimization of trunconical hypercumulation shaped charge structure

Combining the methods of theoretical,numerical and experimental,this research focuses on the jet formation behavior and optimization of trunconical hypercumulation shaped charge structure.With the three-stage division,formation theory of trunconical hypercumulation shaped charge jet is established based on micro element method.By dimensional analysis,main control parameters are identified and their effect on jet formation are analyzed.Through numerical modelling and orthogonal optimization method,influence of the factors and their levels over the indicators of jet tip velocity and jet length as well as order of the significance of each factor and level are obtained.Penetration experiments of trunconical hypercumulation shaped charge based on the orthogonal optimization reveals its advantage over traditional conical shaped charge structure,and finally determines the optimal influence factor level combination.The research and results would provide useful guide for the design and application of trunconical hypercumulation shaped charge structure.

Experimental investigation on enhanced damage to fuel tanks by reactive projectiles impact

Enhanced damage to the full-filled fuel tank,impacted by the cold pressed and sintered PTFE/Al/W reactive material projectile(RMP)with a density of 7.8 g/cm3,is investigated experimentally and theoretically.The fuel tank is a rectangular structure,welded by six pieces of 2024 aluminum plate with a thickness of 6 mm,and filled with RP-3 aviation kerosene.Experimental results show that the kerosene is ignited by the RMP impact at a velocity above 1062 m/s,and a novel interior ignition phenomenon which is closely related to the rupture effect of the fuel tank is observed.However,the traditional steel projectile with the same mass and dimension requires a velocity up to 1649 m/s to ignite the kerosene.Based on the experimental results,the radial pressure field is considered to be the main reason for the shear failure of weld.For mechanism considerations,the chemical energy released by the RMP enhances the hydrodynamic ram(HRAM)effect and provides additional ignition sources inside the fuel tank,thereby enhancing both rupture and ignition effects.Moreover,to further understand the enhanced ignition effect of RMP,the reactive debris temperature inside the kerosene is analyzed theoretically.The initiated reactive debris with high temperature provides effective interior ignition sources to ignite the kerosene,resulting in the enhanced ignition of the kerosene.

The effect of sintering and cooling process on geometry distortion and mechanical properties transition of PTFE/Al reactive materials

In this research,the effect of the sintering and cooling process on geometry distortion and mechanical properties of PTFE/Al reactive material is investigated.Six particularly selected sintering temperatures,three different cooling modes(annealing cooling,normalizing cooling and rapid cooling),three different initial cooling temperature s,as well as six different final cooling temperatures were designed to compare the effects of sintering temperature,cooling rate,initial cooling temperature and final cooling temperature on the properties of reactive materials.Geometry distortion was quantitatively analyzed by a statistic on the dimensional changes of the specimens and microscopic morphology.A mechanical response properties transition from brittle to ductile was found and analyzed.By combining the thermodynamic properties of PTFE and unsteady heat conduction theory,mechanisms of cooling induced morphology change,temperature induced distortion and strength decrease were obtained.The results showed that the cooling rate has the most significant effect on the morphology transformation,while initial cooling temperature has more significant effect on the dimensional distortion than final cooling temperature.As to the mechanical properties transition from brittle to plastic,a more prominent effect of initial cooling temperature than cooling rate and final temperature was revealed.

Penetration and internal blast behavior of reactive liner enhanced shaped charge against concrete space

Penetration and internal blast behavior of reactive liner enhanced shaped charge against concrete space were investigated through experiments and simulations.The volume of the enclosed concrete space is about 15 m^(3).The reactive liner enhanced shaped charge utilizes reactive copper double-layered liner,which is composed of an inner copper liner and an outer reactive liner,while the reactive material liner is fabricated by PTFE/Al(Polytetrafluoroethylene/Aluminum)powders through cold-pressing and sintering.Static explosion experiments show that,compared with the shaped charge which utilizes copper liner,the penetration cavity diameter and spalling area of concrete by the novel shaped charge were enlarged to 2 times and 4 times,respectively.Meanwhile,the following reactive material had blast effect and produced significant overpressure inside the concrete closed space.Theoretical analysis indicates concrete strength and detonation pressure of reactive material both affect the penetration cavity diameter.To the blast behavior of reactive material inside the concrete space,developing TNT equivalence model and simulated on AUTODYN-3 D for analysis.Simulation results reproduced propagation process of the shock wave in concrete space,and revealed multi-peaks phenomenon of overpressure-time curves.Furthermore,the empirical relationship between the peak overpressure and relative distance for the shock wave of reactive material was proposed.

Reaction characteristic of PTFE/Al/Cu/Pb composites and application in shaped charge liner

In this paper, the reaction characteristic and its application in shaped charge warhead of a novel reactive material, which introduced copper(Cu) and plumbum(Pb) into traditional polytetrafluoroethylene/aluminum(PTFE/Al), are studied. The thermal analysis and chemical reaction behavior of the PTFE/Al/Cu/Pb mixture are investigated by Differential Scanning Calorimetry(DSC),Thermo-gravimetry(TG), and Xray Diffraction(XRD) techniques. Then, the shaped charge liners with PTFE/Al/Cu/Pb reactive materials are fabricated, and the X-ray experiments show that they could form reactive jets with excellent performance under the detonation effects of the shaped charge. Based on that, the penetration experiments of shaped charge with PTFE/Al/Cu/Pb reactive liner against steel plates are carried out, and the results demonstrate that the PTFE/Al/Cu/Pb reactive jets could produce a deeper penetration depth compared to the traditional PTFE/Al reactive jets. Meanwhile, the PTFE/Al/Cu/Pb reactive jets also show significant inner-blast effects, leading to dramatically cracking or fragmentation behavior of the penetrated steel plates. This new PTFE/Al/Cu/Pb reactive liner shaped charge presents enhanced penetration behavior for steel targets that incorporates the penetration capability of a high-density and ductility jet, and the chemical energy release of PTFE-matrix reactive materials.

Trans-scale study on the thermal response and initiation of ternary fluoropolymer-matrix reactive materials under shock loading

To investigate the thermal response and initiation behavior of ternary fluoropolymer-matrix PTFE/Al/W reactive materials,a research combining shock loading tests and trans-scale modelling is conducted.On the basis of a good agreement of the numerically simulated and tested shock wave propagation,the significant impact of component ratios and particle sizes on the evolution of mesoscopic temperature,hot-spots and initiation is well characterized and analyzed.Results demonstrate that as the content of W increases,the range of mesoscopic high-temperature area increases and tends to distribute more uniform,while material with smaller W particles causes more intense particle deformation and larger temperature rise.The time to reach the critical temperature shows positive correlation to the content of W,while the critical temperature of hot-spots shows negative correlation to the particle size of W.For PTFE/Al/W of high density,with the increase of W particle size,the reaction rate decrease,however the time to reach the peak reaction rate shortens.

IDCGAN及其在滚动轴承故障诊断中的应用

目前以人工神经网络为代表的模式识别方法已被广泛应用到故障诊断领域,但这些方法通常需要大样本数据进行模型训练,而工程实际中通常存在数据不足的情况。因此需要合适的方法进行小样本情况下的故障诊断。深度卷积生成对抗网络能够实现样本生成。它不仅提高了对数据的学习能力,还对网络设定了一连串的限制,增加了网络的稳定性和收敛性。但其存在着训练不稳定和生成样本质量不高的问题。对深度卷积生成对抗网络进行了改进,提出了一种改进的深度卷积生成对抗网络(Improved-deep Convolutional Generative Adversarial Networks,简称IDCGAN)然后运用到滚动轴承故障诊断中。实验信号分析结果表明了该方法的有效性。

Effect of wave shaper on reactive materials jet formation and its penetration performance

Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge(RLSC)are investigated by experiments and simulations.The reactive materials liner with a density of2.3 g/cm^3 is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380℃.Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of0.5,1.0,and 1.5 CD(charge diameter),respectively.The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff,while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff.To understand the unusual experimental results,numerical simulations based on AUTODYN-2 D code are conducted to discuss the wave shaper effect,including the propagation behavior of detonation wave,the velocity and temperature distribution of reactive jet,and penetration depth of reactive jet.The simulations indicate that,compared with RLSC without wave shaper,there is a higher temperature produced inside reactive jet with wave shaper.This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline,which results in significantly decreasing its penetration performance.

Enhanced ignition behavior of reactive material projectiles impacting fuel-filled tank

Reactive material projectiles can be an extremely efficient lethality enhancement technology that incorporates the defeat mechanisms of chemical energy and kinetic energy.This paper presents such a research on the enhanced ignition behavior of reactive material projectiles impacting a fuel-filled tank.Firstly,the ignition process description of the fuel-filled tank impacted by inert metal and reactive material projectiles is presented.Secondly,ballistic impact experiments are performed to investigate the ignition effects of the fuel-filled tank impacted by reactive material versus tungsten alloy projectiles with mass matched.The fuel tank used for the experiments is a cylindrical steel casing structure filled with aviation kerosene and sealed with aluminum cover plates on both ends using screw bolts.The experimental results indicate that,compared with impacts from tungsten alloy projectiles,there is dramatically enhanced structural damage to the fuel-filled tank and an enhanced ignition effect caused by reactive material projectile impacts.Finally,an analytical model is developed,by which the effects of the aluminum cover plate thickness on critical structural failure energy of the fuel-filled tank and the total energy of the reactive material projectile deposited into the fuel-filled tank are discussed.The analysis shows a good agreement with the experiments.

Force chains based mesoscale simulation on the dynamic response of Al-PTFE granular composites

Force chains based mesoscale simulation is conducted to investigate the response behavior of aluminumpolytetrafluoroethylene(Al-PTFE)granular composites under a low-velocity impact.A two-dimensional model followed the randomly normal distribution of real Al particles size is developed.The dynamic compressive process of Al-PTFE composites with varied Al mass fraction is simulated and validated against the experiments.The results indicate that,force chains behavior governed by the number and the size of agglomerated Al particles,significantly affects the impact response of the material.The failure mode of the material evolves from shear failure of matrix to debonding failure of particles with increasing density.A high crack area of the material is critical mechanism to arouse the initiation reaction.The damage maintained by force chains during large plastic strain builds up more local stresses concentration to enhance a possible reaction performance.In addition,simulation is performed with identical mass fraction but various Al size distribution to explore the effects of size centralization and dispersion on the mechanical properties of materials.It is found that smaller sized Al particle of composites are more preferred than its bulky material in ultimate strength.Increasing dispersed degree is facilitated to create stable force chains in samples with comparable particle number.The simulation studies provide further insights into the plastic deformation,failure mechanism,and possible energy release capacity for Al-PTFE composites,which is helpful for further design and application of reactive materials.

Formation and impact-induced separation of tandem EFPs

The formation and separation behaviors of tandem EFPs are studied by the combination of experiments and simulations.The results show that different formation and separation processes can be obtained by adjusting the double-layer liners,and simulations agree with experiments well.Then,the interaction process between the two liners is discussed in details,and the formation and separation mechanism are revealed.It can be found that there are four phases in the formation and separation processes,including impact phase,propulsion phase,slide phase and free flight phase.During the impact phase,the velocities of two liners rise in turns with kinetic energy exchange.In the propulsion phase,the axial impact becomes insignificant,but the radial interaction between two liners influences the appearance of tandem EFPs.Meanwhile,it should be mentioned that the inner surface of foregoing EFP remains to be in contact with the outer surface of following EFP in the propulsion phase,and the following one would continue to push the foregoing one for about 10μ to 20 μs,causing the velocities of following and foregoing EFPs gradually decreasing and increasing respectively.In the slide phase,an obvious relative movement occurs between the two EFPs,and there would be barely kinetic energy exchange.Then,the two EFPs separate gradually and get into the phase of free flight.Generally,if the outer and inner liners have the same thickness,the outer copper-inner copper liners form two long EFPs,the outer copper-inner steel liners become a foregoing short steel EFP and a following long copper EFP,and the outer steel-inner copper liners produce a foregoing long copper EFP and a following conical steel EFP.In addition,thickness match also has an important impact on formation appearance and separation process for both outer copperinner copper liners and outer steel-inner copper liners.With the thickness ratio of outer liner to inner liner decreasing,the length and length-diameter ratio of both foregoing and following EFPs increase gradually.

Establishment of NOD/SCID mouse models of human hepatocellular carcinoma via subcutaneous transplantation of histologically intact tumor tissue

Hepatocellular carcinoma （HCC） is one of the most deadly human cancers, but it is very difficult to establish an animal model by using surgical specimens. In the present experiment, histologically intact fresh surgical specimens of HCC were subcutaneously transplanted in non-obese diabetic/severe combined immunodeficienccy （NOD/SCID） mice. The biological characteristics of the original and the corresponding transplanted tumors and cell lines were investigated. The results showed that 5 new animal models and 2 primary cell lines were successfully established f^om surgical specimens. Hematoxylin-eosin staining showed that xenografts retained major histological features of the original surgical specimens. The two new cell lines had been cultivated for 3 years and successively passaged for more than 100 passages in vitro. The morphological characteristics and biologic features of the two cell lines were genetically similar to the original tumor. The subcutaneous transplant animal models with histologically intact tumor tissue and primary cell lines could be useful for in vivo and in vitro testing of anti-cancer drugs and be ideal models to study various biologic features of HCC.

NaOH/Urea Swelling Treatment and Hydrothermal Degradation of Waste Cotton Fiber

In this study,waste cotton fabric was used as cellulose raw material and pretreated in aqueous NaOH/urea solution system to investigate the effect of NaOH/urea pretreatment solution on the hydrolysis of cotton fiber.The cotton fiber was pretreated with different conditions of aqueous NaOH/urea solution,and the pretreated cotton fiber was hydrolyzed under the same conditions as the original cotton fiber.The results of characterization analysis showed that water retention value of pretreated cotton fiber was higher than that of unpretreated sample.Moreover,the cotton fiber presented both a convoluted structure and a coarser surface,XRD results suggested that the crystallinity degree of cellulose decreased dramatically,more cellulose II appeared,and the hydrogen bond is broken.Among the different pretreatment conditions,the pretreatment effect was the best when the reaction temperature was 0°C,the solid-liquid ratio was 2:50,and the NaOH/urea ratio was 7:12.The hydrolysis experiments of pretreated and unpretreated cotton fibers showed that when the hydrothermal temperature was 230°C,the heat preservation was 2 h,and the hydrochloric acid concentration was 5 wt.%,the glucose yield reached 29.99%.H+could catalyze the hydrolysis of cotton fiber more effectively due to damage to crystal structure and hydrogen bonds.

Shock-induced reaction behaviors of functionally graded reactive material

In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.

Id4 promotes cell proliferation in hepatocellular carcinoma

Background: Hepatocellular carcinoma(HCC) is a common malignant tumor in the world, especially in China. As a member of the inhibitor of differentiation(Id) family, Id4 has been reported to function in many cancer types, but relatively little is known about its role in HCC. The purpose of this study was to investigate the potential relationship between Id4 and HCC development and the underlying mechanism involving the function of Id4 in HCC.Methods: We used quantitative real?time polymerase chain reaction and Western blotting to examine the RNA and protein expression of Id4. In addition, we used Cell Counting Kit?8 assay and colony formation assay to identify the function of Id4 in the regulation of cell proliferation in human HCC.Results: We found that the expression of Id4 protein was up?regulated in tumor tissues from HCC patients. Over?expression of Id4 promoted HCC cell proliferation, clonogenicity in vitro, and tumorigenicity in vivo. Id4 knockdown experiments showed that silencing Id4 blocked the proliferation and colony formation ability of HCC cells in vitro. Furthermore, overexpression of CCAAT/enhancer?binding protein β inhibited Id4 expression in HCC cells.Conclusion: Id4 may be developed as a potent therapeutic agent for the treatment of HCC, but more details about the underlying mechanisms of action are needed.

朝戈

范迪安(中国美术家协会主席、中央美术学院院长):每一个画家都有他自己关于“最好的艺术”的理解与追求,朝戈的绘画历程就伴随着他对“绘画到底是什么”的深层追问,这也正是一个学者型画家使命感的体现。他的艺术观可以说是“社会心理学”型的,他要做的是让绘画“与人的心理生活、心理活动及最深刻的社会存在”发生联系。

Polarization-dependent ultrafast carrier dynamics in GaAs with anisotropic response

The transient dynamics of anisotropic properties of Ga As was systematically studied by polarization-dependent ultrafast time-resolved transient absorption.Our findings revealed that the anisotropy of reflectivity was enhanced in both pump-induced and probe-induced processes,suggesting an extraordinary resonance absorption of photon-phonon coupling(PPC)with intrinsic anisotropic characteristic in carrier relaxation,regardless of the concrete crystallinity and orientation of GaAs sample.The results,delivering in-depth cognition about the polarization-dependent ultrafast carrier dynamics,also proved the paramount importance of interaction between polarized laser and semiconductor.

论“新旧分离”模式下历史城区的保护——基于韩城老城区的观察

在老城区外另设新城区、双中心并驾齐驱的“新旧分离”城市发展模式,一度被视为具有文化遗产保护作用的城市发展方针。进入20世纪后,随着城镇化进程的发展,新旧城区之间的差距日益拉大,老城区发展停滞,日趋衰朽,逐渐沦为边缘化的城市区块,保护形势十分严峻。主流观点认为,“新旧分离”是造成当前状况的肇因,改善方法是培育新型城市功能即旅游业。然而,对韩城老城区的实地调查研究可以发现,“新旧分离”并非罪魁祸首,阻碍老城区保护与发展的症结在于其固有居住功能的退化,而管理体制的混乱加剧了这一问题,同时任何改善现状的尝试都面临无法可依的窘境。要改变这种局面,仅依靠旅游业无异于舍本逐末,只有在指导思想上注重新旧城区平衡发展,通过遏止破坏、修复肌理、有机更新等手段分步进行,并以风貌建筑的保护更新为抓手,方可最终实现“以人为本的城镇化”。

守正创新:新时代油画艺术的成就与展望

结合9月22日全国美术作品展览油画展区开幕,由中国美术家协会主办,中国美协理论委员会、重庆市美术家协会、四川美术学院共同承办的"守正创新:新时代油画艺术的成就与展望"学术研讨会同步举行。研讨会以第十三届全国美术作品展览与中国当代油画为主题,邀请了理论名家、艺术创作与教育名家,发表主题演讲并展开圆桌讨论,大家一道聚焦"新时段",立足"新现场",构建"新话语",讴歌"新时代"。