金属圆柱壳受大质量低速冲击的屈曲变形

对钢质和铜质金属圆柱壳的轴向冲击动力响应进行了实验研究,记录了两种不同材料圆柱壳在大质量低速冲击下的冲击力时程曲线,得到其屈曲模态。采用高速摄像及模拟技术给出了钢质圆柱壳渐进屈曲的全过程,为理解钢质圆柱壳的屈曲机理提供了直观的结果。黄铜质圆柱壳在大质量低速冲击下, 出现整个壳面滿布屈曲波纹的塑性动力屈曲现象,说明高速冲击不是产生塑性动力屈曲的充要条件。像铜这样具有高密度的韧性材料,在大质量低速冲击下,会在轴向产生持续的压缩塑性流作用而出现塑性动力屈曲现象。     

轴向冲击载荷作用下弹性圆柱壳横向弯曲动态屈曲

研究在轴向冲击载荷下弹性圆柱壳动态屈曲问题.通过构造哈密顿体系,在辛空间中将临界载荷和动态屈曲模态归结为辛本征值和本征解问题.辛本征解反映了局部的压缩屈曲模态和整体的弯曲屈曲模态,特别是在冲击端为自由支承边界时的特殊屈曲方式.数值结果给出了具体的临界载荷和屈曲模态规律.     

辛方法和弹性圆柱壳在内外压和轴向冲击下的动态屈曲

针对有内压或外压的弹性圆柱壳在轴向冲击载荷耦合作用下的动态屈曲问题,构造哈密顿体系,在辛空间中将临界载荷和动态屈曲模态归结为辛本征值和本征解问题,从而形成一种辛方法。该方法直接得到非轴对称的屈曲模态。数值结果给出了圆柱壳问题的临界载荷和屈曲模态以及一些规律。     

圆柱薄壳的动相变屈曲行为

利用MTS809材料试验机对TiNi圆柱薄壳进行了轴向动渐进相变屈曲实验,对轴向冲击下处于伪弹性状态的TiNi合金柱壳的动相变屈曲行为进行了数值模拟研究。结果表明,不同的加载强度将会激发出柱壳不同的动屈曲响应模态。当冲击速度较高时,柱壳两端首先形成轴对称环形相变屈曲波纹,并产生应力平台;随着马氏体含量不断增加,环形相变屈曲波纹逐渐贯穿整个壳体,名义应力缓慢抬升;当名义应变超过一定阈值时,对称环形屈曲模态突变为非轴对称块状屈曲模态,名义应力大幅下降。撞击速度为40 m/s的算例（含10％随机缺陷）与S.Nemat-Nasser等的实验结果很好吻合,说明本文中计算模型、方法和结果的有效性经过了实验的考核。结果还表明,相变耗能是TiNi柱壳吸收冲击能量的主要机制,适合制作可重复使用的高效吸能元件,并给出了相应的理想厚径比。     

受轴向冲击圆柱壳的塑性动力屈曲研究

令屈曲模态同时包含轴向坐标x和环向坐标 ,通过最优模态的分析 ,直接得到各向同性线性强化刚塑性圆柱壳受轴向冲击时发生轴对称屈曲或非轴对称屈曲时的临界速度 ,在此基础上讨论了临界速度与径厚比的关系。     

充满液体的封闭圆柱壳受轴压时屈曲过程的实验研究

报导了对充满水的金属圆柱薄壳在轴向压缩时屈曲性能的实验结果。实验观察表明，充满液体的金属圆柱壳在轴压作用下的屈曲模态呈轴对称型，液体的内压与外部轴压随轴向缩短的变化趋势大致相同。由于壳内液体的存在，同内空的圆柱壳相比只是临界载荷略有提高，屈曲后承载能力并无显著降低，且对初始几何缺陷表现得远不象内空柱壳那样敏感。     

轴压作用下充液圆柱壳屈曲的实验研究

本文从实验及理论两个方面对充满液体的圆柱壳在轴向压力作用下液体内压的变化进行了实际测试及理论定性分析．采用薄壳理论分析了屈曲前液体内压随轴向压力的变化规律，讨论了壳材料、几何参数及边界约束对内压的影响．通过实验实际测定了内压随轴向压力的变化规律．通过实验手段测定了充满液体的圆柱壳临界载荷、屈曲模态，讨论了充满液体的圆柱壳的承载能力等问题．     

充满液体弹塑性圆柱壳轴向冲击屈曲的数值模拟

基于对充满液体的弹塑性圆柱壳轴向冲击屈曲的实验观察 ,建立了相应的计算模型 ,借用 LS-DYNA软件包 ,在 HP-C36 0工作站上完成了数值模拟 ,得到了动画显示 ,给出的屈曲模态及一些特征量的时程曲线与实验结果相当一致。文中对壳的几何、物理参数对屈曲性能的影响进行了较详细的讨论     

轴向冲击下圆柱壳非轴对称屈曲耗散能分析

主要研究受轴向冲击圆柱壳非对称屈曲耗能,从轴向屈曲变形、环向屈曲变形和轴向压 缩变形3个角度进行理论推导. 结果表明: 环向屈曲变形能随屈曲折叠边数增加有减小 趋势, 且占总耗能比例很小,可知圆柱壳受轴向冲击屈曲过程中外力做功主要转变为轴向变形 能,环向屈曲变形消耗外力功很少.     

充满水的金属圆柱壳经受轴向撞击时屈曲过程的实验研究

本文报道了五种规格充满水的圆柱壳经受大质量低速度轴向撞击作用时屈曲过程的实验结果。研究表明由于液体的存在，圆柱壳的屈曲模态呈轴对称型的环带波纹，整个撞击过程可以明显地分为振荡的动力加载、平稳发展的后屈曲和迅速下降的弹性卸载三个阶段。并讨论了试件壁厚和高度等几何参数对其屈曲性能的影响。     

EXPERIMENTAL INVESTIGATION AND COMPUTER SIMULATION ON DYNAMIC BUCKLING BEHAVIOR OF LIQUID-FILLED CYLINDRICAL SHELLS UNDER AXIAL IMPACT

This article reports an experimental investigation on the axial impact buckling of thin metallic cylindrical shells fully filled with water. Low velocity impact tests are carried out by DHR-9401 drop hammer rig. The whole process of dynamic buckling is simulated using LS-DYNA computer code. The consistency between experimental observation and numerical simulation is quite satisfactory. The investigation indicates that quite high internal hydrodynamic pressure occurs inside the shell during the impact process. Under the combined action of the high internal pressure and axial compression plastic buckling occurs easily in the thin-walled shells and buckling modes take on regular and axisymmetric wrinkles. This project is supported by the National Natural Science Foundation of China(19672039) and the Shanxi Foundation for Returned Scholars from Abroad.     

圆柱形薄壳冲击扭转屈曲的实验研究

本文对受冲击扭矩作用下的圆柱形簿壳扭转屈曲进行了实验研究，利用Ｈｏｐｋｉｎｓｏｎ扭杆使圆柱受阶跃扭矩作用，分析所得到的应变－时间曲线，得到了不同几何参数的圆柱壳的冲击临界扭矩Ｍｄｅｒ和屈曲波数ｎ及几条定性结论，同时找出了圆柱壳静力扭转屈曲行为和冲击扭转屈曲行为之间的异同。     

Axially compressed buckling of pressured multiwall carbon nanotubes

This paper studies axially compressed buckling of an individual multiwall carbon nanotube subjected to an internal or external radial pressure. The emphasis is placed on new physical phenomena due to combined axial stress and radial pressure. According to the radius-to-thickness ratio, multiwall carbon nanotubes discussed here are classified into three types: thin, thick, and (almost) solid. The critical axial stress and the buckling mode are calculated for various radial pressures, with detailed comparison to the classic results of singlelayer elastic shells under combined loadings. It is shown that the buckling mode associated with the minimum axial stress is determined uniquely for multiwall carbon nanotubes under combined axial stress and radial pressure, while it is not unique under pure axial stress. In particular, a thin N-wall nanotube (defined by the radius-to-thickness ratio larger than 5) is shown to be approximately equivalent to a single layer elastic shell whose effective bending stiffness and thickness are N times the effective bending stiffness and thickness of singlewall carbon nanotubes. Based on this result, an approximate method is suggested to substitute a multiwall nanotube of many layers by a multilayer elastic shell of fewer layers with acceptable relative errors. Especially, the present results show that the predicted increase of the critical axial stress due to an internal radial pressure appears to be in qualitative agreement with some known results for filled singlewall carbon nanotubes obtained by molecular dynamics simulations.     

外压对环肋圆柱壳轴向弹塑性动力屈曲的影响

采用增量理论,借助增量数值解法研究了复合加载（轴向流－固冲击载荷＋径向均匀外压）条件下环肋圆柱壳的弹塑性动力屈曲,采用类似B－R准则和Southwell方法来确定临界载荷,讨论了径向均匀外压对结构动力性态及抗轴冲击能力的影响。     

静力预加载环向加筋圆柱壳的轴向流-固冲击屈曲

将初缺陷放大准则应用于静力预加载环向加筋圆柱壳结构受轴向流-固冲击加载作用时的几何非线性动力屈曲研究中。运用Galerkin方法推导出壳体-肋骨系统的动力屈曲控制方程,并且采用Runge-Kutta法进行数值求解。着重分析了静力预加载荷对结构屈曲性态及抗轴向冲击能力的影响。     

轴向冲击圆柱壳非弹性响应

简要论述承受轴向冲击载荷圆柱壳非弹性动屈曲响应的研究进展。采用Ｋａｒｍａｎ－Ｄｏｎｎｅｌｌ运动方程研究轴向流固冲击载荷作用下的圆柱壳轴对称弹塑性动屈曲问题。本构关系采用增量理论，借助增量数值方法求解动力方程组。研究不同边界条件对屈曲的影响，以及径向外压力在不同边界条件下对屈曲的影响。     

An experimental study on the static and impact torsional buckling of cylindrical shells

In this paper, experimental studies are carried out on the buckling of circular cylindrical thin shells under impact torque. Experiments of impact buckling are made on a Hopkinson torsional bar. The torsional bar gives a step torque on the shells. Through an analysis of the strain-time curve obtained in experiment, the dynamic buckling critical torqueM _er and buckling waves numbern of the shell with different geometric data and some qualitative results are obtained. The buckling behavior of circular cylindrical thin shells under static and impact torque is compared.     

Buckling of unstiffened conical shells under combined loading

An experimental program was conducted in order to determine the family of interaction curves for the buckling of unstiffened conical shells under combined axial compression, torsion, and external or internal pressure. Careful experimental technique permitted many repeated buckling tests on the same aluminumalloy shell without noticeable damage and yielded reliable interaction curves. Results of combined-loading tests are presented and compared with linear theory. Test results show that the interaction curve for compression-torsion-pressure loading is defined by superposition of compression-pressure, torsion-pressure and compression-torsion behavior.