共查询到18条相似文献，搜索用时 218 毫秒
1.
城市地下过街通道是城市重要的交通系统组成部分,也经常会成为恐怖分子爆炸袭击的对象。为了更好的了解爆炸冲击波在地下过街通道中的传播规律,本文通过数值模拟分析了13KG炸药在通道爆炸后冲击波的传播。分析过程中分别考虑了炸药起爆位置及通道顶盖对冲击波传播的影响。分析结果表明当TNT在通道内起爆后,通道顶部的角落将受到更大的冲击波压力作用,当冲击波从出口向外传播时将发生明显的射流现象;当通道出口有顶盖时,炸药在出口的起爆将明显加强通道内部及出口梯道的压力峰值。 相似文献
2.
声音在传播过程中遇到障碍物时，就会象光的反射一样改变传播方向．这种现象称为声音的反射，反射回来的声音叫做回声．回声时时有，声声皆入耳，但是为什么有些回声我们清晰可辨，有些回声我们却听而不闻呢？原来呀，人耳的分辨能力是有限的，只有当两次南响的时差在0．l秒以上时人耳才能分辨．就是说，只有当回声到达人耳比原声晚0．1秒以上时，人耳才能把回声与原声分开．已知声音在空气中的速度是34O米／秒，在0．1秒内声音将走过34米．因此，要想听到回声，我们离开障碍物的距离必须大于（或等于）17米．如果小于这个距离，回声和原声… 相似文献
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《中国科教创新导刊》2004,(10)
□子弹追踪器“听声辨位”●《简氏防务周刊》加拿大陆军最近采购了一种子弹追踪器,该系统全称为“雪貂”轻武器探测和定位系统,可以实现“听声辨位”。在一般情况下,轻武器射击时会发出两种冲击波,一种是超音速子弹产生的冲击波,另一种是推进火药产生的枪嘴冲击波。在较短距离内,通过两种冲击波的到达方向和时间就能精确判断出枪手的位置;如果距离较远,则需要考虑子弹的弹道和冲击波参数,例如通过冲击波产生的压力和周期可以判断子弹的型号。“雪貂”就是利用上述原理工作的。“雪貂”轻武器探测和定位系统主要由麦克风、压力传感器以及控… 相似文献
4.
晓平 《初中生世界(初三物理版)》2004,(32)
声波遇到障碍物时,将在界发生反射。遇到障碍物被反射回的声音叫做回声。人站在山谷中大声喊话时,以听见几次回声。这是声音在传过程中遇到障碍物时会发生反射缘故。由于声音遇到了远近不同障碍物被反射,且反射回来的时间先后不同,所以往往可听到几次回声。回声的形成具有一定的实际意义。如利用回声测定距离,利用回声求车速等。例1拍手后0.5秒听到对面墙壁反射回来回回声,求人与壁间的距离。[思路分析]拍手发出声,经0.5秒听到声,表明声音在这段墙、再由墙反射传到人与墙壁间距离的明当时空气的温度,[解]设人与墙℃时空气的传声速播时间t=0.… 相似文献
5.
赵长海 《陕西师范大学继续教育学报》2006,23(4):106-107
由于电磁波以光速传播,所以它不可能有静止质量。电磁波具有能量,所以它就具有动量。电磁波在物体表面反射或吸收时,会对表面有压力作用,称为辐射压,或者光压。通过对电磁波动量密度的讨论,得出电磁波的辐射压力,并由光压了解辐射压力的作用。 相似文献
6.
高原地区进行的水下爆破工程,因水体表面气压随海拔的升高而线性降低,其装药爆炸后的特征参数是否发生变化,对爆破施工有重要意义;采用密闭的高压爆炸容器,模拟高原气压条件,对雷管水下爆炸参数进行了实验研究,研究结果表明：在海拔0---4500m范围内随着气压降低,冲击波峰值压力大小与气压无关。冲击波衰减时间却有一定增长,导致比冲击波能微小增大;气泡脉动周期按二阶多项式规律显著增大,仍由于气压随海拔升高丽变小,装药深度处的总静水压力随之降低,使比气泡能微量减小,而爆炸总能量基本不变。 相似文献
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陈国平 《初中生世界(初三物理版)》2009,(Z5)
江西省弋阳县圭峰国家风景名胜区有一个有趣的景点——四声谷.一声我——来——了!,片刻便收到了三声回应.环山而来的袅袅余音,加上自己的发声,不多不少正好四声.当我们发声时,声音在空气中传播到崖壁时一部分被反射,声波反射到另外一个崖壁,这种声波的连续反射,就形成了回音,由于距离的前后不同,也就产生了声音的前后到达. 相似文献
10.
张志良 《数理天地(高中版)》2008,(2):46-46
会钻牛角尖的声音由于声音遇到障碍物会发生反射,所以当声音遇到如图所示的"牛角尖"时就会发生连续不断的反射,从而钻进牛角尖.雪后特别安静就是这个道理.人们利用这种现象制成了吸声器. 相似文献
11.
The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave over-pressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure. 相似文献
12.
Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load 总被引：4，自引：0，他引：4
The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA. The multi-material Eulerian and Lagrangian coupling algorithm was adopted. A flu-id-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground, multiple ALE element for simulating air and TNT explosive material. Numerical simulations of the blast pressure wave propagation, struc-tural dynamic responses and deformation, and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed. The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure. The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation. The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic defor-mation subjected to intensive blast waves, and columns lost carrying capacity, subsequently lead-ing to the collapse of the whole structure. The approach coupling influence between struc-tural deformation and fluid load well simulated the progressive collapse process of structures, and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load. 相似文献
13.
The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA.The multi-material Eulerian and Lagrangian coupling algorithm was adopted.A fluid-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground,multiple ALE element for simulating air and TNT explosive material.Numerical simulations of the blast pressure wave propagation,structural dynamic responses and deformation,and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed.The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure.The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation.The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic deformation subjected to intensive blast waves,and columns lost carrying capacity,subsequently leading to the collapse of the whole structure.The approach coupling influence between structural deformation and fluid load well simulated the progressive collapse process of structures,and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load. 相似文献
14.
The loads of shock wave effect on fabricated anti-blast wall and distribution law around the wall were investigated by using near surface explosion test method and FEM.The pressure-time histories and variety law on the foreside and backside of the anti-blast wall were adopted in the tests of variety of different explosion distances and dynamites,as well as in the comparison between the test and numerical calculation.The test results show that the loads of shock wave effect on the anti-blast wall were essen-tially consistent with calculation results using criterion under surface explosion when explosion distances exceed 2 m,the distribution of overpressure behind wall was gained according to variety law based on small-large-small.It is also demonstrated that the peak overpressure behind wall had commonly appeared in wall height by 1.5--2.5 multiples,and the peak overpressures of protective building behind wall could be reduced effectively by using the fabricated anti-blast wall. 相似文献
15.
Mesh size effect in numerical simulation of blast wave propagation and interaction with structures 总被引：3，自引：0，他引：3
Numerical method is popular in analysing the blast wave propagation and interaction with structures.However,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical results.Therefore,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures. 相似文献
16.
气泡对声传播影响的研究 总被引：1，自引：0，他引：1
姚文苇 《陕西教育学院学报》2008,24(1):107-109
以气泡壁处声压和径向振动速度为边界条件,研究气泡对声传播的影响;给出了含气泡介质内声速的表达式,得到了声速随气泡体积分数及声波频率的变化图。表明：声波频率一定时,声速随着气泡体积分数增大而减小;气泡体积分数一定时,频率增大对声速的影响较小。 相似文献
17.
Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, including explosion cratering, scabbing of the backside, radial cracking induced failure and circumferential cracking induced failure. It also illustrates that the foam material sandwiched in the multi-layered media has an important effect on damage patterns. The phenomena encountered have been analyzed by the calculation with ALE method. Meanwhile, the optimal analysis of foam material thickness and position in the sandwich panel were performed in terms of experimental and numerical analysis. The proper thickness proportion of the soft layer is about 20% to the thickness of sandwich panel and the thickness of the upper hard layer and lower hard layer is in the ratio of 7 to 3 under the condition in this paper when the total thickness of soft layer remains constant. 相似文献
18.
吴伟 《淮南职业技术学院学报》2014,(4):5-8
台阶式爆破主要针对大断面掘进巷道而使用的爆破工艺,可以很好地解决大药量同时起爆产生的强冲击波致使巷道成型变差以及瓦斯释放量的增加的问题;通过实践对比,台阶式爆破很好地解决了超挖和欠挖的现象,提高了爆破效果和巷道成型质量,降低了围岩和瓦斯的危害。 相似文献