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以间苯二酚-甲醛为原料,结合自制活动式微模具成型工艺制备不同厚度和密度的碳气凝胶薄片,采用密度为10 mg·cm-3的SiO2溶胶为“粘合剂”,获得单元薄片厚度在100~580 μm,密度在50~400 mg·cm-3范围内变化的5层密度渐变碳气凝胶靶型。重点研究了该特殊靶型内部C/SiO2气凝胶层间界面情况。采用场发射扫描电镜(FESEM),X射线相衬成像仪等对靶型整体结构及碳气凝胶单元薄片表面和内部微观结构进行了表征。结果表明:胶粘层SiO2气凝胶厚度约为15 μm,厚度一致,远小于碳气凝胶层厚度且与碳气凝胶薄片的胶粘程度较好,界面平整,靶结构均匀。 相似文献
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Abstract A method for plate-impact dynamic compaction of copper powder has been developped. The optimization of the experimental set-up (impedance adjustments, tensile wave traps, relative thickness of impactor and target,…) is presented. 2D axisymetrical numerical simulations have been performed with a Lagrangian finite element code. Geometrical characteristics of the experimental set-up as well as the dynamic response of the powder (Reaugh equation of state) and of the material of the set-up have been taken into account. These simulations show that, due to the difference in shock velocities in the container and in the powder, the powder is submitted to 2D loading waves. As a matter of fact the powder may be loaded by a non-planar shock wave propagating in the as-expected direction, as well as by a sweeping wave initiated at the bottom of the powder container, and propagating obliquely from the bottom-up. This second wave loads the bottom of the powder first. The influence of the impactor thickness as well as its material on the shock front shape and on the shock density-pressure history of the material has been studied. 1D simulations are shown not to evaluate properly the stress history and the energy deposition in the powder sample. Metallographic observations as well as X-ray tomography experiments have been performed on consolidated samples. A very good agreement has been found between results of 2D numerical simulations and the observed final shape and density maps of the samples. The shape of deformed powder particles are also in agreement with the expected shock history. 相似文献
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采用一维弹塑性流体动力学计算方法,通过对LLNL(Lawrence Livermore National Laboratory)Mg-Cu体系密度梯度飞片冲击加载-准等熵加载实验过程数值计算和比较,验证了流体动力学计算方法、不同材料体系混合模型以及计算程序的正确性和实用性。考虑到在飞片材料制备中,单层厚度最小值为0.2 mm和Mg-W最大阻抗混合质量分数的致密条件限制,开展了对新的Mg-W体系密度梯度飞片实现冲击加载-准等熵加载过程计算设计,给出了满足加载要求的飞片结构特征;从计算给出的粒子速度波剖面可见,密度梯度飞片波阻抗分布对加载过程和加载强度非常敏感,通过精心设计准连续型变阻抗的梯度飞片,可以进行不同复杂加/卸载过程的物理模型设计和实验研究。 相似文献
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根据鱼雷对舰船毁伤的特点,建立了多介质水下爆炸数值模型,提出了交界面处理及广义光滑长度计算方法,编制了多介质水下爆炸计算程序,并对水下爆炸空气隔层衰减冲击波的性能进行了定量分析。结果表明:无论是接触爆炸还是非接触爆炸,空气隔层均可有效衰减冲击波,并且接触爆炸中空气隔层衰减冲击波的效果更好,最大可使冲击压力峰值降低约55%;空气隔层厚度与爆炸厚度之比为1时便可达到较好的衰减冲击波效果,继续增加空气隔层厚度对衰减冲击波效果影响不大。研究结果可为舰船结构防护及防雷舱的结构设计提供参考。 相似文献
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基于修正的Rayleigh气泡脉动方程对水下等离子体声源放电产生的 强声冲击波的传播过程进行了分析; 利用Euler方程作为控制方程组, 建立了水下等离子体声源的聚束声场模型, 通过仿真计算获得的传播云图对冲击波负压的形成机理进行了直观的理论分析. 结果表明: 经过聚能反射罩反射汇聚得到的聚束波在反射稀疏波和水的惯性作用下, 聚束波周围水域产生了拉伸, 形成负压区, 如果拉伸力大于水的抗拉上限, 就会使得水中形成不连续现象, 即出现空化气泡; 此外聚能罩边缘处产生的衍射波进一步加剧了负压的产生, 边缘衍射波最终与拉伸波叠加, 使冲击波负压达到最大值; 通过对比仿真波形和实验波形, 从而验证和进一步揭示了冲击波负压的形成原因. 研究结果对认识水下冲击波的传播规律和进一步改进等离子体声源的设计具有指导意义.
关键词:
等离子体声源
冲击波负压
聚束声场模型
气泡 相似文献
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通过开展装药沉底爆炸原理性实验研究,得到了不同水底条件对装药沉底爆炸气泡运动和冲击波压力的影响规律:沉底装药水下爆炸气泡通常呈半球形,依附在水底并同时急剧膨胀达到最大半径,随后气泡做收缩运动并连带水底介质颗粒迅速上浮,同时形状发生显著变化,如在石底和泥底时气泡在水底射流的作用下呈蘑菇状上浮,砂底时气泡则呈现出柱状上浮、未出现明显脉动运动即已坍塌破裂;沉底爆炸与水底介质发生强烈耦合作用而形成不同程度的反射波,通常水下石底的反射冲击波较泥底和砂底更强烈,且一般迭加后的冲击波峰值压力高于入射波阵面压力;不同水底介质条件下,装药与水底发生的强烈耦合作用均对水底造成强冲击破坏。 相似文献
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基于拉格朗日描述,建立了水中金属丝电爆炸的单温磁流体动力学模型,并给出一种高阶混合有限元离散求解方法。拉氏可压缩流体方程组中,速度定义在H1连续有限元空间,内能定义在L2间断有限元空间实现物质界面的精确捕捉,存在激波的区域引入张量人工粘性抑制数值振荡。磁扩散方程仅考虑周向磁通量密度,简化为标量方程,使用H1连续有限元方法离散求解。焦耳热和洛伦兹力作为源项引入实现磁流体方程的耦合。数值算例表明:磁扩散求解器能够求解存在不同电导率的多介质磁扩散问题;拉氏流体求解器能够精确追踪物质界面,具有较好的激波分辨能力;耦合RLC电路的磁流体求解器能够复现水中金属丝电爆炸加热相变、冲击波的产生与传播、放电模式转变等物理过程。 相似文献
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通过理论计算和水下爆炸实验,初步研究了MgH2敏化储氢型乳化炸药的爆炸特性和爆轰反应机理。结果表明:与玻璃微球敏化的乳化炸药相比,MgH2敏化的乳化炸药水下爆炸的冲击波超压、比冲量、比冲击波能、比气泡能及水下爆炸比总能量显著增加,其中冲击波超压和水下爆炸总能量分别增加了20.5%和31.0%。MgH2储氢型乳化炸药的爆轰机理与玻璃微球敏化乳化炸药不同,MgH2在乳化炸药中起到了敏化剂和含能材料的双重作用,即MgH2在乳化基质中水解产生均匀分布的氢气泡,起到了敏化作用,同时氢气参与爆炸反应,提高了炸药的爆炸能量和做功能力。 相似文献
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The preparation and evaluation of graded multilayer ta-C films deposited by FCVA method 总被引:1,自引:0,他引:1
Gui-Gen Wang Hua-Yu ZhangWen-Yan Li Fang-Xu YangLin Cui Hong-Bo ZuoJie-Cai Han 《Applied Surface Science》2011,257(11):5064-5069
In this study, a series of graded multilayer ta-C films were investigated by varying their sublayer thickness ratios, in which each film sublayer was prepared at different substrate bias by filtered cathode vacuum arc (FCVA) method. The experimental results show that the graded multilayer film structure can effectively decrease the internal stress level of deposited ta-C film, and meanwhile the graded multilayer ta-C films still have high sp3 fractions. The applied substrate bias voltage and sublayer thickness ratio can apparently influence the microstructure characteristics and internal stress of the graded multilayer ta-C films. The graded multilayer ta-C film has larger sp3 fraction when applying a larger negative substrate bias voltage and having a thicker outer sublayer during the film deposition process. However, the internal stress in the as-deposited film also increases with larger thickness of the outer sublayer, and the optimal ratio of sublayer thicknesses is 1:1:1:1 for graded ta-C film with four sublayers. 相似文献
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《中国物理C(英文版)》2018,(11)
It is known that in supernova explosions, there might be a reverse shock wave in addition to the forward shock wave during the explosion phase, when the mass of supernova is in a certain range. In this paper, we propose to add the reverse shock wave to the previous supernova model, in which only the forward shock wave was included,and thus obtain a new model. By analyzing the resonance condition as well as the density jump in the new model and using the Landau-Zener method, an expression for the crossing probability in high density matter(PH) is given.We proceed to study how PH varies with time and with neutrino energy when both the reverse shock wave and the forward shock wave are considered. From comparison with the previous results, where only the effects of the forward shock wave were considered, it is clear that the reverse shock wave brings significant changes to PH. 相似文献
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The effect of shock sterilization on marine Vibrio sp. is investigated by carrying out a bio-experiment based on a bubble-shockwave interaction. In the experiments, underwater shock waves with different strength and frequencies are produced by a high-voltage power supply in a cylindrical water chamber. The bio-experimental results show marine Vibrio sp. is completely inactivated in a short time by a 1.0-Hz electric discharge. However, a high sterilization effect requires a strong and high frequency of the bubble motion, and it also depends on the lifetime of the bubble. Subsequently, by an experiment with an air gap to prevent the underwater shock waves entering the cell suspension, it is found that the introduction of a strong shock pressure is not entirely required to obtain the effective sterilization. On the other hand, the direct effect of the sterilization by rebound shock wave resulting from the bubble-shock wave interaction is examined in the experiments. The results suggest that free radicals mainly contribute to killing marine bacteria, and direct mechanical effects of the bubble motion are not responsible. In addition, the creation of the OH radical is indirectly confirmed by measuring the H2O2 concentration. Finally, the Herring equation is solved to investigate the condition of free radical generation when considering the effect of thermal conductivity at the bubble interface. As a result, the effective sterilization conditions based on the bubble-shock wave interaction are clearly obtained. 相似文献
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《Current Applied Physics》2015,15(9):977-986
This paper presents a simulation model for the generation of strong pressure wave by means of pulsed spark discharge in water and its application to well cleaning. In the simulation model, one-dimensional time-dependent magnetohydrodynamic equations are coupled to a capacitive discharge circuit equation. A cylindrical conducting spark channel formed by electrical breakdown of water gap between a pair of electrodes is treated as a load of which resistance and inductance are allowed to change with time. For describing the spark channel properties accurately, precise calculations on thermodynamic properties and electrical conductivity are included in the simulation model. The simulation results show an excellent agreement with the experimentally measured shock pressure as well as the current and voltage waveforms. The simulation reveals that Joule heating of the spark channel during the very early phase of electrical discharge plays a key role in the formation of shock wave in water. The voltage on a capacitor at breakdown, the circuit inductance, and the resistance of the spark channel are found to be the most important parameters for the shock wave formation. With this technique, a pilot test for the cleaning of a clogged well has been performed in a water well which was constructed as a test-bed for riverbank filtration near the Anseong-cheon (river) in Korea. Well treatments have been carried out with an electrical energy of 510 J stored on a pulsed power system, at which the maximum shock pressure is measured to be around 7 MPa at the position of the well screen, i.e. 0.1 m away from the spark gap. A slug test shows 2.9 times improvement in the hydraulic conductivity of the well, which, combined with a visual inspection inside the well using an underwater camera, clearly demonstrates that the strong pressure wave generated by underwater spark discharge can effectively remove almost all incrustations formed in the well screen and thus improve well performance. Operating parameters for controlling the strength of shock pressure are discussed using the simulation model for extensive applications of the present technique to various types of water wells. 相似文献
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Shun-ichiro KARATO 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2014,90(3):97-103
One of the difficulties of the current giant impact model for the origin of the Moon is to explain the marked similarity in the isotopic compositions and the substantial differences in the major element chemistry. Physics of shock heating is analyzed to show that the degree of heating is asymmetric between the impactor and the target, if the target (the proto-Earth) had a magma-ocean but the impactor did not. The magma ocean is heated much more than the solid impactor and the vapor-rich jets come mainly from the magma-ocean from which the Moon might have been formed. In this scenario, the similarity and differences in the composition between the Moon and Earth would be explained as a natural consequence of a collision in the later stage of planetary formation. Including the asymmetry in shock heating is the first step toward explaining the chemical composition of the Moon. 相似文献
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Marcelo G. Honnicke Jeffrey W. Keister Raymond Conley Konstantine Kaznatcheev Peter Z. Takacs David Scott Coburn Leo Reffi Yong Q. Cai 《Journal of synchrotron radiation》2011,18(6):862-870
Characterization and testing of an L‐shaped laterally graded multilayer mirror are presented. This mirror is designed as a two‐dimensional collimating optics for the analyzer system of the ultra‐high‐resolution inelastic X‐ray scattering (IXS) spectrometer at National Synchrotron Light Source II (NSLS‐II). The characterization includes point‐to‐point reflectivity measurements, lattice parameter determination and mirror metrology (figure, slope error and roughness). The synchrotron X‐ray test of the mirror was carried out reversely as a focusing device. The results show that the L‐shaped laterally graded multilayer mirror is suitable to be used, with high efficiency, for the analyzer system of the IXS spectrometer at NSLS‐II. 相似文献