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超声速欠膨胀冲击射流有着重要的实际应用价值,如S/TOVL飞行器、火箭发射、除尘等。其流场结构复杂,包含间断激波、反射激波、马赫盘、滞止泡以及冲击平面传热不同于亚声速冲击射流的特点。为了分析超声速欠膨胀冲击射流流场和传热,采用有限体积法,结合k-l湍流模型以及二阶精度的TVD格式进行数值模拟:对比实验和k-ε湍流模型的努赛尔数,得出k-l湍流模型在传热问题中更具优势;对比阴影图和计算密度云图以及对比冲击平面压力系数的实验值和计算值,验证了k-l湍流模型模拟超声速欠膨胀冲击射流流场的合理性;采用k-l湍流模型研究3种冲击高度(3D,6D,10D),3种压比(2.0,3.4,4.4),3种喷管总温(493 K,591 K,580 K)下,冲击平面温度分布。数值研究结果对分析超声速欠膨胀冲击平面的烧蚀有一定的指导意义。 相似文献
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通过碳纳米管的不同表面官能化,构造其与环氧树脂的不同界面。采用动态机械性能分析研究不同表面官能化碳纳米管对环氧树脂复合材料玻璃化转变温度的影响;采用摆锤冲击试验研究环氧树脂复合材料的韧性。结果表明:与纯环氧树脂相比,氨基化碳纳米管/环氧树脂复合材料的玻璃化转变温度升高,而羧基化碳纳米管/环氧树脂复合材料的玻璃化转变温度反而有所下降;碳纳米管/环氧树脂复合材料的冲击强度相比纯环氧树脂均提高了近一倍。复合材料性能的这些变化规律主要归因于不同表面官能化碳纳米管与环氧树脂基体间形成了不同的界面。 相似文献
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采用一种高效的应力更新算法,运用Fortran语言编写Johnson—Cook本构模型的Vuamt子程序,模拟材料在高速冲击工况下的动态力学性能,研究塑性大应变、高应变率以及温度软化作用对材料力学性能的影响。 相似文献
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《情报指挥控制系统与仿真技术》2011,(6):23-23
如何在不牺牲产品性能的条件下,显著提高产品的可靠性、稳定性,是生产企业面临的挑战。军工存储行业巨头源科公司推出的磐龙V代SSD,在保证军工品质的同时极大提高了产品性能。磐龙V代SSD完全按照军用设备标准进行温度、震动、冲击、盐雾等筛选实验, 相似文献
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利用ABAQUS建立了防暴盾牌受10 kg半球型冲击组件低能量冲击的数值模型研究一种由聚碳酸酯注塑成型的警用防暴盾牌的冲击响应.基于该数值模型分析了不同冲击能量、不同曲率半径以及不同厚度防暴盾牌的冲击动力响应.基于简易的落锤冲击试验机对防暴盾牌进行了低能量冲击试验,并进行了冲击动力响应和冲击能量响应分析,将试验结果与仿... 相似文献
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针对多层侵彻引信的实验室短间隔连续冲击试验技术需求,设计了一种新型的旋转式连续高冲击试验装置,实现了连续冲击过程中冲击幅值和冲击频率同步提升.基于ANSYS/LS-DYNA建立了试验装置主要结构的有限元仿真模型,仿真获得了试验装置关键力学作用结构的应力分布和被冲击机构上的冲击接触力,结合冲击试验对有限元仿真结果进行了验... 相似文献
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《防务技术》2020,16(2):374-380
Micro-TATB particles with different sizes and 3D nanoporous TATB architectures with different specific surface areas were prepared through recrystallization to study short pulse duration shock initiation properties by electric gun technology. For micro-TATB, the initiation threshold significantly decreases with TATB average size ranging from 79.7 μm to 0.5 μm. For 3D nanoporous TATB architecture, the initiation threshold decreases and then increases with specific surface areas increased from 9.6 m2/g to 36.2 m2/g. The lowest initiation thresholds are obtained for the micro-TATB with average sizes of 1.3 μm and 0.5 μm, and 3D nanoporous TATB architecture with specific surface area of 22.4 m2/g. The shock initiation thresholds of micro-TATB and 3D nanoporous TATB architectures show significantly decreases with the porosity increased. The decomposition reaction and thermal conductivity properties were further investigated to understand the initial response mechanism. High porosity provides more collapse sites to generate high temperature for formation of hot spots. The low thermal conductivity and decomposition temperature could enhance the formation and ignition of the hot spots, and initial decomposition reaction of TATB. The effect of the decomposition temperature is higher than that of the thermal conductivity on the shock initiation properties. The enhanced decomposition reaction could promote energy release and transfer process from the ignition to the combustion. This work offers a new insight to understand the effects of microstructure on the shock initiation properties and the initial response mechanism of TATB. 相似文献
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AUSM+-up格式是近年来发展的AUSM类格式,通过在对流通量中引入压力耗散,同时在压力通量中引入速度耗散,使之在各种马赫数下均有良好的收敛性和稳定性。然而,通过对格式的分析,我们发现当马赫数为零时,在压力间断位置会出现质量通量无穷大的非物理现象。为了克服这一缺陷,采用特征线法获得了压力间断问题的解析解;以此为基础,对对流通量中的压力耗散项进行修正,发展出新的AUSM+-up格式。以新的格式对不同速度驱动下的冲击波发展、不同强度压力间断问题和激波衍射问题进行了仿真,计算结果与理论解吻合得较好。 相似文献
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提出一种水平方向、光学波导中原子干涉的加速度测量方案。详细介绍了光路结构、原子团制备以及光学波导的绝热装载等。通过实验手段对测量方案进行验证,首先将~(87)Rb原子团冷却至50 nK的玻色爱因斯坦凝聚态,随后对超冷原子团施加布拉格光进行分束、合束,完成原子干涉过程。实验结果显示,所提干涉测量系统能够实现单轴加速度测量,对未来高精度多轴加速度测量系统的研制具有指导借鉴意义。 相似文献
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《防务技术》2019,15(3):319-325
Nanothermites (metal oxide/metal) can offer tremendously exothermic self sustained reactions. CuO is one of the most effective oxidizers for naonothermite applications. This study reports on two prospectives for the manufacture of CuO nanoparticles. Colloidal CuO particles of 15 nm particle size were developed using hydrothermal synthesis technique. Multiwalled carbon nanotubes (MWCNTs) with surface are 700 m2/g was employed as a substrate for synthesis of CuO-coated MWCNTs using electroless plating. On the other hand, aluminium particles with combustion heat of 32000 J/g is of interest as high energy density material. The impact of stoichiometric nanothermite particles (CuO/Al & Cuo-coated MWCNTs/Al) on shock wave strength of Al/TNT nanocomposite was evaluated using ballistic mortar test. While CuO-coated MWCNTs decreased the shock wave strength by 15%; colloidal CuO enhanced the shock wave strength by 30%. The superior performance of colloidal CuO particles was correlated to their steric stabilization with employed organic solvent. This is the first time ever to report on fabrication, isolation, and integration of stablilized colloidal nanothermite particles into energetic matrix where intimate mixing between oxidizer and metal fuel could be achieved. 相似文献
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Dror Zuckerman 《海军后勤学研究》1986,33(3):469-477
A system receives shocks at random points of time. Each shock causes a random amount of damage which accumulates over time. The system fails when the accumulated damage exceeds a fixed threshold. Upon failure the system is replaced by a new one. The damage process is controlled by means of a maintenance policy. There are M possible maintenance actions. Given that a maintenance action m is employed, then the cumulative damage decreases at rate rm. Replacement costs and maintenance costs are considered. The objective is to determine an optimal maintenance policy under the following optimality criteria: (1) long-run average cost; (2) total expected discounted cost over an infinite horizon. For a diffusion approximation, we show that the optimal maintenance expenditure rate is monotonically increasing in the cumulative damage level. 相似文献
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制作了铽镝铁保偏光纤换能器,建立了全保偏马赫—曾德尔光纤干涉仪系统,采用工作点控制方法解调信号,实现了光纤磁场传感。该全保偏光纤干涉系统结构简单、抗干扰,有效解决了偏振不稳定问题。实验检测了系统对磁场幅度变化的响应特性,最小可测交流磁场信号为3×10-10T。 相似文献
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冲击波的聚焦可以在聚焦区域形成局部较高的压力.基于能产生较强冲击波的水中脉冲放电声源和具有会聚作用的旋转椭球面反射罩建立了水下冲击波聚焦系统,开展了水下冲击波聚焦的实验研究,分析了水下冲击波的聚焦过程.对压力历史、轴线上的压力分布及峰值压力进行了分析,研究了旋转椭球面反射罩的聚焦特性.实验发现聚焦区域会产生负压,并导致局部空化.基于冲击动力学理论对这一现象进行了分析.实验结果表明,水下冲击波聚焦系统具有显著的聚焦效果. 相似文献
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为探索一种减弱扫掠激波/边界层干扰强度的侧压方式,采用数值计算方法研究两道同侧扫掠激波作用下形成的三维平板边界层。对三维边界层的流动机理进行研究,并与相同气流偏转角的一道扫掠激波作用下形成的三维边界层进行定量比较。研究表明,存在两道同侧扫掠激波时,第一道扫掠激波使侧壁附近边界层变薄,进而使第二道扫掠激波与再附形成的边界层的相互作用减弱,从而总的效果是两道扫掠激波与边界层的相互作用强度比一道扫掠激波的弱;两道扫掠激波的气流总偏转角与一道扫掠激波的相同,相交后汇聚成的激波强度与一道扫掠激波的基本相同,之前被两道扫掠激波"扫"起来的边界层在汇聚激波作用下还呈现锥形流动,分离线和来流的夹角也与一道扫掠激波的基本相同。 相似文献
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钢丝绳隔振器冲击特性试验研究 总被引:4,自引:0,他引:4
采用气缸式冲击模拟台对钢丝绳隔振器进行了冲击特性试验研究,介绍了试验系统及测量方法。在比较符合舰船实际冲击环境的情况下,获得了钢丝绳隔振器压缩和拉伸方向完整的特性曲线。试验结果分析表明,钢丝绳隔振器表现出明显的冲击软化现象,其冲击刚度特性小于静刚度和动刚度,而且它具有大阻尼耗能特性,是比较理想的抗冲元件。 相似文献
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The present study focuses on the mitigation of shock wave using novel geometric passages in the flow field. The strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstruction, which in turn is expected to reduce the shock wave strength at the target location. In the present study the interaction of a plane shock front (generated from a shock tube) with various geometric designs such as, 1) zig-zag geometric passage, 2) staggered cylindrical obstructions and 3) zig-zag passage with cylindrical obstructions have been investigated using computational technique. It is seen from the numerical simulation that, among the various designs, the maximum shock attenuation is produced by the zig-zag passage with cylindrical obstructions which is then followed by zig-zag passage and staggered cylindrical obstructions. A comprehensive investigation on the shock wave reflection and diffraction phenomena happening in the proposed complex passages have also been carried out. In the new zig-zag design, the initial shock wave undergoes shock wave reflection and diffraction process which swaps alternatively as the shock front moves from one turn to the other turn. This cyclic shock reflection and diffraction process helps in diffusing the shock wave energy with practically no obstruction to the flow field. It is found that by combining the shock attenuation ability of zig-zag passage (using shock reflection and diffraction) with the shock attenuation ability of cylindrical blocks (by flow obstruction), a drastic attenuation in shock strength can be achieved with moderate level of flow blocking. 相似文献