电爆阀启动过程的响应特性与活塞撞击变形分析

对航天飞行器上的高压常闭式电爆阀启动过程的动态响应特性进行仿真,并通过试验验证两者基本吻合。在此基础上,对电爆阀启动过程活塞撞击变形情况进行分析。采用Abaqus软件对活塞与壳体碰撞行为进行显式非线性动态分析,研究了电爆管、材料性能以及电爆阀出口压力条件对活塞撞击变形量的影响。结果表明,电爆阀出口压力条件对活塞与壳体撞击变形量影响最大,出口压力增大对应变形量急剧减小,电爆阀工作的可靠性随之降低。

汽车罐车撞击变形后的应力分析及安全等级评定

本文针对汽车罐车撞击变形后的应力分析及安全等级评定问题进行分析,采用模型的建立分析,对应力分析及安全等级评定与变形特点及其影响因素进行研究,希望通过笔者的研究能为相关人员提供一定的借鉴。

基于LS-DYNA的爆炸碎片撞击圆筒形储罐的数值模拟

金属容器爆炸产生的碎片对石化园区储罐等设备将产生严重的安全隐患。因此,对储罐受碎片撞击的规律研究具有十分重要的工程意义。作为石化园区常见的储罐结构之一,建立了碎片撞击立式圆筒形储罐的分析模型,采用ANSYS/LS-DYNA有限元分析软件对碎片撞击储罐的过程及变形进行了数值模拟,研究了立方体碎片材料、碎片与储罐碰撞接触面积、碎片初始速度、储罐容积以及储罐内压等因素对碎片撞击储罐的影响及破坏规律。结果表明:立方体碎片撞击圆筒形储罐的接触面积越大,对储罐的危害越小;储罐受撞击产生的变形随碎片初始速度的增大逐渐增大;与Q345R材料相比,铅黄铜材质碎片撞击储罐将产生更大的变形;同等条件下,大容积的储罐受撞击产生的变形更大;储罐内压能够减缓撞击变形的作用。

孙吴陨石雨的建造原理

阐述了孙吴陨石的主要特征和孙吴陨石雨的建造原理。通过对孙吴撞击熔融陨石的仔细观察和深入研究发现,孙吴陨石的前身流星体在太空中运行时经常遭到砾石雨和砂尘暴撞击。一般来说,当它遭到砾石撞击以后,在高温高压作用下就会产生熔融变质现象,并且建造出一层熔壳包裹着砾石嵌入到流星体内。也有的砾石与流星体撞击以后,又被弹回了太空,但它却在流星体上留下了一个撞击熔壳。有的岩矿撞入到流星体内以后,在高温高压作用下变成了粉末状态,这种太空撞击粉末化现象属于首次发现,意义重大。通过对孙吴陨石的研究,还发现许多流星体多次遭到砾石雨或砂尘暴猛烈撞击以后产生了压缩变形、拉伸变形、扩张变形、扭曲变形和分裂成为碎块等形变建造。

Analysis of Dynamic Failure of Plastic Spherical Shells Under Local Impact

Aim To study the dynamic failure of the plastic spherical shell impacted by a missile. Methods The deformation mode of spherical shells was given by introducing isometric transformation. The governing equation of motion of the rigid plastic spherical shell was given by energy balance. This equation was solved by using Runge Kutta method. Results The relationships between the impact force, dimple radius, central point deflection and time were obtained. The response time initial velocity, the maximal impact force permanent initial velocity, the central point deflection initial velocity and the dimple radius initial velocity characteristics were respectively plotted. Conclusion A comparison made between the theoretical results and the experimental ones indicates that the two groups of results are in conformity with each other.

Efficient energy absorption of functionally-graded metallic foam-filled tubes under impact loading

The deformation behavior and crashworthiness of functionally-graded foam-filled tubes(FGFTs)under drop-weight impact loading were investigated.Closed cell aluminum,A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations.The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components,and then propagates in the high-strength components through the gradual increment of stress.The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption(SEA)for the graded structures,whereas the high-strength zinc foam has no positive effect on the crash performance.The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions.However,the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition.The Al−A356 foam-filled tubes with a combination of the highest SEA(10 J/g)and the lowest initial peak stress(σmax of 10.2 MPa)are considered as the best lightweight crashworthy structures.

Numerical Simulation for Progressive Collapse of Continuous Girder Bridge Subjected to Ship Impact

The three-stage simulation method based on LS-DYNA was introduced in this study to simulate the progressive collapse of a continuous girder bridge after a ship-bridge collision. The pile-soil dynamic interaction and the initial stress and deformation of the whole bridge before the collision were considered. By analyzing the damage, deformation, stress distribution and collapse process of the whole bridge, the results show that the displacement response of the cap beam lags behind the pile cap. The response order of the whole bridge's components depends on their distances from the collision region. The plastic deformation of soil around piles has a positive effect on delaying the further increase in the displacement of piles. The impacted pier's losing stability and its superstructure's excessive deformation are the main reasons leading to the progressive collapse of the continuous girder bridge.

针栓式喷注单元膜束撞击雾化混合过程数值模拟

为了全面认识针栓式喷注器喷雾场结构,基于自适应网格加密技术和分三相计算的PLIC VOF(Piecewise Linear Interface Calculation Volume of Fluid)方法对针栓式喷注单元膜束撞击雾化混合过程进行了仿真分析,通过对两路推进剂分别进行界面追踪,获得了膜束撞击雾化混合过程的详细结构特征,与高速摄影试验结果定性定量对比均吻合较好,验证了数值方法的准确性。以此为基础对膜束撞击的喷雾场结构、撞击变形过程、流场涡结构、雾化破碎典型特征及破碎后的雾化混合分布特征进行了识别分析,结果表明:膜束撞击形成了液束未穿透液膜和液束穿透液膜2种不同的喷雾扇结构。膜束撞击形成的喷雾扇呈"Ω"形,膜束同时发生弯曲变形和横截面变形。另外,膜束撞击同时受到正压和剪切应力作用,导致了一系列复杂涡流现象,使得相互作用增强,雾化混合均增强,这也是膜束撞击喷注构型优于膜膜撞击的本质原因。最后,还发现膜束撞击喷雾场液滴分布呈现分区结构特征,分别是液束控制主导的上雾化区、液膜控制主导的下雾化区及夹在中间的混合区,实际中应兼顾雾化特性和混合特性,选取中等动量比膜束撞击,这可为针栓式喷注器的理论研究和工程设计提供重要参考。

针栓式喷注器液膜下漏率预估模型

为了对针栓式喷注器液膜下漏率进行准确预测,基于针栓式喷注单元喷雾场结构分析,结合理论推导、数值仿真及试验研究3种方法建立了液膜液束各自变形的相对变形量模型;在考虑液膜液束变形的基础上,引入相互影响系数表征多喷注单元间相互影响,建立了实际阻塞率和实际下漏率模型。通过数值仿真及试验结果的多参数充分验证,结果表明:理论预估模型与数值仿真及试验结果一致性较好。液膜液束相互作用下,液膜绕液束流动和液束根部横截面前后缘位置移动不同步导致的展向变宽分别是液膜和液束发生变形的主因,且有效动量比越大,液膜相对变形越大,液束相对变形越小。对于一定阻塞率的几何结构,结果表明:下漏率随着有效动量比的增大而增大,增大趋势呈先快后缓,且实际下漏率均小于几何下漏率,这是由膜束变形导致的实际阻塞率比几何阻塞率更大造成的。另外,发现液膜下漏率仅与表征流场结构(有效动量比)及几何结构的无量纲参数(液膜厚度与液束直径之比和阻塞率)有关,与喷射速度的绝对值无关,并给出了模型中的常系数供工程设计预估使用,对从设计初期就考虑针栓头的热防护问题具有重要的指导意义。

气液针栓喷注单元雾化角模型

为了准确预测气液针栓喷注单元的雾化角,基于动量守恒建立了液束撞击气膜的雾化角理论模型,通过试验结果获得变形因子,并分析了结构参数和工况参数对雾化角的影响规律。结果表明:局部动量比对雾化角影响最大,其他结构参数和工况参数都是通过影响局部动量比而进一步决定雾化角;随着局部动量比增大,液束变形程度减小,液束变形导致有效撞击动量比小于几何动量比。根据试验结果分段给出了变形因子,当局部动量比范围为0~3时,变形因子推荐值为0.61,当局部动量比范围为3~4.5时,变形因子推荐值为0.70,当局部动量比范围为4.5~7.2时,变形因子推荐值为0.75,引入变形因子的理论预测值与试验结果吻合很好,该模型可为气液针栓喷注器的理论研究和工程设计提供参考。