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21.
利用球形空腔膨胀理论的响应函数对靶板在弹体撞击下的侵彻进行分析,并基于量纲理论建立了侵彻相似律的一般形式.通过对侵彻混凝土靶的已有实验数据进行分析,得到了不同缩比因子下,无量纲侵彻深度曲线随侵彻速度不同而发生偏转和偏移.考虑到材料的应变率效应和损伤演化,认为几何相似律对混凝土等脆性材料在抗侵彻时不成立,有必要引入材料应变率效应和损伤演化对几何相似律的修正. 相似文献
22.
This paper investigates the noise sources in a pneumatic nail gun. The study combines two complementary experimental approaches. The first uses simultaneous data observation, with sound, acceleration and air pressure signals simultaneously recorded in conjunction with a nail gun motion high speed video. This strategy allows the identification of the physical processes involved in the operation of the machine at different time instants, as well as the associated noise generation mechanisms. However, since multiple noise sources radiate at the same time, this observation technique is not sufficient for noise source identification and ranking. Thus, a second approach introduces a selective wrapping procedure, and the strategy assures a reliable classification of the noise sources. The investigation considers the following noise origins: the air exhaust, the machine body and the workpiece/worktable. 相似文献
23.
Raman spectroscopy has become a versatile tool for the in vivo characterization of skin. Here we describe use of Raman spectroscopy for high resolution optical cross sectioning to resolve skin constituents and administered drugs at the cellular level. Percutaneous penetration is typically studied using permeation cells with biopsies of animals or human skin. Although this technique provides valuable clinical data, little insight is gained in the microstructure of drug penetration (intercellular or transcellular) or in the mode of action of applied vehicles or penetration enhancers. Therefore, a Raman microspectroscopic method was combined with a confocal scanning setup to image the microstructure of commercially available skin models (SkinEthic®) and the spatial distribution of penetrated actives. The models’ microstructure was scanned without any special treatment or environment such as cutting, staining, freezing, or application of vacuum. The non-invasive Raman images reveal the layered structure of stratum corneum. This in particular for lipids while water tends to be more evenly distributed. When penetration of the hydrophilic active glycerol and the lipophilic octyl methoxycinnamate, OMC, was studied, a strong correlation between the local distribution of skin constituents and the hydrophilic/lipophilic character of the active was observed. 相似文献
24.
为研究高硬度钢板抗不同着角钨球的侵彻性能及破坏模式,通过弹道枪进行了?8 mm、?11 mm钨合金球形破片以0°、20°、40°着角撞击厚度为6 mm、8 mm的高硬度钢板试验,得到了极限贯穿速度v50;分析了钨球轴向径向变形及靶板失效模式与撞击速度的关系,发现高硬度钢板失效模式主要为压缩开坑破坏和沿厚度方向剪切破坏。采用有限元方法对试验进行了模拟,验证了数值模型及参数的合理性,并运用数值模拟方法研究了撞击着角对靶板吸能模式影响,结合试验数据,修正已有极限贯穿速度计算公式。结果表明:随侵彻着角增大,极限贯穿速度提高,且着角越大,极限贯穿速度增长越快;随着角增大,靶板吸能模式逐渐由压缩开坑向剪切冲塞过渡,且着角大于50°时,剪切冲塞耗能将超过压缩开坑耗能;修正后极限贯穿速度计算公式适用范围更广、精度更高,具有较好工程应用价值。 相似文献
25.
Based on the equations which describe the dynamic behavior of material under high-velocity and high-pressure shock, corresponding equations at shock front whose surface is general space curve surface were established. For concrete material, a normal expansion theory was proposed by which some deceleration about time history of the projectile can be analytically given. This normal expansion theory is not only suitable for spherical and cylindrical-nose projectile, but also suitable for other general nose projectile, for example conical nose or ogive-nose. And it is not only suitable for perpendicular shock but also for oblique shock. 相似文献
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叠层靶板弹击实验及弹道侵彻机理的数值模拟研究 总被引:3,自引:0,他引:3
为了提高军盔等防护装备的防弹性能,采用非线性动态显式有限元分析软件ANSYS/LS DYNA5.6.1模拟了几种复合材料防弹靶板的抗弹道侵彻过程,弹头采用标准1.1g模拟弹片。结合v50弹击实验分析了靶板在此类弹击下的破坏机理和吸能方式,对靶板的选材、铺层顺序、层数和制造工艺等提出合理化建议,主要是沿靶板厚向应采用非均匀的三段式结构和工艺。 相似文献
28.
In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s. 相似文献
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