共查询到20条相似文献,搜索用时 84 毫秒
1.
2.
3.
4.
5.
6.
研究地下爆炸弹性区的震动特性,关键是获得场地介质与爆炸能量耦合作用下辐射弹性波的实验参数。对于不易加工成大尺寸模型的砂土岩,为研究其填实爆炸下辐射弹性波的特征,采用0.125 g TNT微型炸药球作为爆炸源,以塑性区可置换的?1 370 mm×1 200 mm黄土样品作为提供应力波传播路径的载体,用波阻抗近似相等的重塑黄土和砂土岩样品分别作为源区介质,对比分析了两种介质中微药量填实爆炸辐射的弹性波传播特征。实验结果表明:在测试范围内,两种介质中填实爆炸激发的弹性应力波粒子速度(位移)峰值的衰减规律、波形的主频变化规律一致;砂土岩中爆炸辐射的弹性波粒子速度(位移)峰值整体高于黄土、粒子速度波形的半高宽和主频低于黄土;砂土岩中爆炸耦合的向外传播的弹性波能量比黄土大。实测结果反映,黄土和砂土岩中填实爆炸弹性波能量耦合强度的差别。 相似文献
7.
8.
为了在较低压力下获得较小粒径的细水雾,降低喷雾抑爆系统的运行成本,提高系统的适用性和抑爆效率,自行搭建了尺寸为120 mm×120 mm×840 mm的透明有机玻璃瓦斯爆炸管道实验平台。采用双流体喷嘴将N2和细水雾送入试验管道,通过调节喷雾压力和喷雾时间开展了双流体细水雾抑制瓦斯爆炸实验研究,从火焰速度、瓦斯爆炸超压2个方面探讨双流体细水雾的抑爆有效性。实验结果表明:N2双流体细水雾抑爆效果明显,可以减小瓦斯爆炸强度;随着喷雾时间的延长,爆炸火焰的速度峰值逐渐下降,爆炸超压峰值逐渐下降,平均升压速率逐渐降低;当N2压力为0.4 MPa、喷雾时间为3 s时,速度峰值比不喷雾时下降60.39%,爆炸超压峰值下降37.76%。 相似文献
9.
膨胀环实验技术主要包括爆炸膨胀环实验技术和电磁膨胀环实验技术,实验过程中膨胀环的加载应变率在达到峰值后会随着圆环的膨胀而迅速降低,给研究应变率敏感材料的拉伸碎裂带来极大的不便。在前期提出的液压膨胀环实验技术的基础上,发展了一种恒应变率加载技术。首先,从理论上获得了实现金属圆环恒应变率膨胀所需的液压加载曲线的近似表达式;然后,采用有限元流固耦合数值模拟了液压膨胀环装置中1060-O铝环的膨胀碎裂过程,在给定液压加载曲线下,膨胀环的环向应变率在应变率稳定阶段上下波动范围最大不超过20%;并进一步研究了加载曲线对碎裂过程中应变率的影响规律。在液压膨胀环实验装置上对1060-O铝环开展了膨胀环实验,验证了恒应变率加载技术的可行性。 相似文献
10.
分析了目前膨胀环实验技术的研究现状,介绍了本课题组搭建的电磁膨胀环和爆炸膨胀环实验平台,着重介绍了其原理和主要性能参数。爆炸膨胀环实验中提出了一种新的爆炸丝起爆方式,电磁膨胀环平台中使用了一种先进的三电极开关实现电流截断。膨胀环的传统研究方向为材料的断裂行为、破片的统计规律、材料的动态拉伸本构等,本课题组将其拓展到材料在冲击拉伸加载下的损伤演化规律、裂纹的扩展速度等研究领域。本文对膨胀环平台的主要应用研究进行了一个较全面系统的总结概括,并指出今后膨胀环平台应用研究的主要方向。 相似文献
11.
以WELDOX 700E钢为研究对象,研究了8 mm钢在6 kg球形TNT空爆载荷、12 mm钢在10 kg球形TNT空爆载荷下的抗爆轰变形行为,结合ABAQUS模拟计算软件建立了WELDOX 700E钢抗爆轰变形模拟计算模型。结果表明:材料强度是影响WELDOX 700E钢抗爆轰变形行为的关键因素之一,高强度WELDOX 700E钢在球形TNT空爆载荷条件下呈现均匀的拱形变形。在6 kg球形TNT空爆载荷下,8 mm WELDOX 700E钢板中点的最大动态位移为144 mm,永久挠度为124 mm,回弹为21 mm;在10 kg球形TNT空爆载荷下,12 mm WELDOX 700E钢板中点的最大动态位移为166 mm,永久挠度为143 mm,回弹为23 mm。在不考虑实验工装整体偏移的条件下,球形TNT空爆载荷下钢的抗爆轰变形模拟计算结果可准确反映WELDOX 700E钢的抗爆轰变形行为。WELDOX 700E钢在抗爆轰形变过程中存在显著的厚度减薄现象并伴随一定的应变硬化行为,应变硬化行为主要为WELDOX 700E钢马氏体晶粒内部位错増殖的表现,8 mm和12 mm WELDO... 相似文献
12.
R. E. Kelly 《Applied Scientific Research》1968,19(1):34-59
Summary The effects of superposing streamwise vorticity, periodic in the lateral direction, upon two-dimensional asymptotic suction flow are analyzed. Such vorticity, generated by prescribing a spanwise variation in the suction velocity, is known to play an important role in unstable and turbulent boundary layers. The flow induced by the variation has been obtained for a freestream velocity which (i) is steady, (ii) oscillates periodically in time, (iii) changes impulsively from rest. For the oscillatory case it is shown that a frequency can exist which maximizes the induced, unsteady wall shear stress for a given spanwise period. For steady flow the heat transfer to, or from a wall at constant temperature has also been computed.Nomenclature (x, y, z)
spatial coordinates
- (u, v, w)
corresponding components of velocity
- (, , )
corresponding components of vorticity
-
t
time
-
stream function for v and w
-
v
w
mean wall suction velocity
-
nondimensional amplitude of variation in wall suction velocity
-
characteristic wavenumber for variation in direction of z
-
T
temperature
-
P
pressure
-
density
-
coefficient of kinematic viscosity
-
coefficient of thermal diffusivity
-
(/v
w)2
-
frequency of oscillation of freestream velocity
-
nondimensional amplitude of freestream oscillation
-
/v
w
2
-
z
z
-
y
–v
w
y/
-
v
w
2
t/4
-
/v
w
-
U
0
characteristic freestream velocity
-
u/U
0
-
coefficient of viscosity
-
w
wall shear stress
-
Prandtl number (/)
-
q
heat transfer to wall
-
T
w
wall temperature
-
T
(T
w–T)/(T
w–) 相似文献
13.
14.
The flow patterns and heat transfer coefficients of R-22 and R-134a during evaporation in small diameter tubes were investigated
experimentally. The evaporation flow patterns of R-22 and R-134a were observed in Pyrex sight glass tubes with 2 and 8 mm
diameter tube, and heat transfer coefficients were measured in smooth and horizontal copper tubes with 1.77, 3.36 and 5.35 mm
diameter tube, respectively. In the flow patterns during evaporation process, the annular flows in 2 mm glass tube occurred
at a relatively lower vapor quality compared to 8 mm glass tube. The flow patterns in 2 mm glass tube did not agree with the
Mandhane’s flow pattern maps. The evaporation heat transfer coefficients in the small diameter tubes (d
i
< 6 mm) were observed to be strongly affected by tube diameters, and to differ from those in the large diameter tubes. The
heat transfer coefficients of 1.77 mm tube were higher than those of 3.36 mm and 5.35 mm tube. Most of the existing correlations
failed to predict the evaporation heat transfer coefficient in small diameter tubes. Therefore, based on the experimental
data, the new correlation is proposed to predict the evaporation heat transfer coefficients of R-22 and R-134a in small diameter
tubes. 相似文献
15.
飞行器液压导管受接头和卡箍等约束,在使用的振动环境中,会因弯曲应力而导致破裂,影响到飞行安全.本文对飞行器液压系统通用的不锈钢导管的裂纹萌生寿命进行了试验研究.首先在对8 mm、12 mm无缺陷导管和含U型缺口8 mm导管的疲劳试验和有限元分析的基础上,得到了导管的最大拉应变-裂纹萌生寿命数据.然后采用基于强度极限和弹性模量估算法的Manson-Coffin公式来预测导管裂纹萌生寿命.最后引入加载类型修正系数、表面质量修正系数、试样尺寸修正系数、应力集中敏感系数和有效应力集中系数,使修正后的公式对三种类型的导管均有较好的裂纹萌生寿命预测精度. 相似文献
16.
通过对实验室中几何尺寸为80×80mm钢制管道内部加装高度分别为4mm、8mm、12mm、16mm的四种螺旋环,模拟巷道支护结构对瓦斯爆炸火焰传播速度的影响。采用高精度动态数据采集分析系统,测量爆炸过程中的火焰传播速度,研究了不同高度的螺旋环对火焰传播速度的影响。结果表明:在螺旋环其他条件相同的情况下,管内瓦斯爆炸火焰传播速度随螺旋环高度、圈数增加而增加。并从理论上进行了分析,其主要原因为螺旋环高度越大、圈数越多,产生湍流度的程度亦愈大,对瓦斯爆炸火焰加速亦愈明显。试验结果对巷道支护的选择有指导意义。 相似文献
17.
Flexible solid-state battery has several unique characteristics including high flexibility, easy portability, and high safety, which may have broad application prospects in new technology products such as rollup displays, power implantable medical devices, and wearable equipments. The interfacial mechanical and electrochemical problems caused by bending deformation, resulting in the battery damage and failure, are particularly interesting. Herein, a fully coupled electro-chemo-mechanical model i... 相似文献
18.
Toshio Aihara Professor
Shigenao Maruyama
Mitsuo Hongoh Research AssociatesSunao Aya
Engineer 《Experimental Thermal and Fluid Science》1988,1(4):315-323A novel gas fluidized-bed heat exchanger with a very small static bed height has been developed for a heat-exchanging system using a low-pressure fan. This fluidized bed is composed of a multislit distributor, a single row of 8 mm diameter tubes, and glass beads 48–195 μm in diameter. The measured performance of heat transfer is excellent and that of fluidization is satisfactory, in spite of the static bed height being as small as 13 mm. In the best case, the test fluidized bed exhibited a heat transfer performance comparable to that of a conventional fluidized bed with a perforated plate distributor and a static bed height of 150 mm, and showed one-fourteenth the pressure loss. 相似文献
19.
20.
Experimental investigations were conducted to examine the behavior of concrete sandwich composites under compressive and tensile loads. The sandwich cores were composed of nonpermeated, expanded aluminum honeycomb and the facings consisted of concrete mortar. Appropriate theories that predict the behavior of such composites were presented and compared with experimental data. All specimens had facing thicknesses of 1 in. (25.4 mm), core thicknesses of 1, 2 and 3 in. (25.4, 50.8 and 76.2 mm); core-cell size of 1/8 and 3/8 in. (3.2 and 9.5 mm); while four different core foil gages were considered for each size. The facings were either plain concrete mortar or reinforced with steel wires. The large-core-cell-size specimen displayed better bond characteristics and produced more consistent experimental data. The ultimate strengths of both compressive and tensile specimens were not affected by the core-cell size, core thickness, or core density. Axial compressive loads were carried by the facing area while tensile loads were by the reinforcements in the facings. The buckling waves were developed due to the wrinkling of the facings. The buckling waves in the two facings were independent of each other and the overall wave pattern was antisymmetrical. 相似文献