共查询到19条相似文献,搜索用时 64 毫秒
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双层碳纳米管在扭矩作用下的屈曲 总被引:2,自引:2,他引:0
考虑双层碳纳米管层间范德华力的作用,利用连续介质力学的壳体理论,建立了扭矩作用下碳纳米管屈曲问题的双层弹性壳体模型,给出了相应的临界屈曲扭矩,分析了双层碳纳米管层间范德华力对临界屈曲扭矩的影响。 相似文献
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本文分析了具有不同面内边界条件的矩形板,面内受到常位移梯度偏心加载和常荷载偏心距加载的条件下的屈曲后性能和极限荷载.计算中同时考虑了板初曲和残余应力的影响,成功地将线性有线条理论推广应用于解决板的大挠度弹塑性稳定问题.这一方法与目前研究此类问题的其它方法相比较,在同等精度下计算工作量小得多. 相似文献
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考虑范德华力曲率效应的双壁碳纳米管外压屈曲 总被引:1,自引:0,他引:1
针对双壁碳纳米管外压屈曲问题,研究了层间范德华力的曲率效应对临界外压的影响。应用弹性双层圆柱壳模型,考虑层间范德华力不仅与层间距有关而且与挠度曲率的变化有关,导出了外压屈曲临界压力解析公式。计算得出在不同半径、不同长细比下,外压屈曲临界压力的数值结果,并与经典壳的结果和忽略范德华力曲率效应的结果做了比较。结果显示,对于小半径的双壁碳纳米管曲率效应对外压屈曲有效明显的影响。 相似文献
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本文讨论考虑横向剪切变形的各向同性、正交各向异性矩形板的屈曲和后屈曲性态。应用Reissner理论,采用文[1]提供的摄动方法,给出了完善和非完善各向同性、正交各向异性矩形板的后屈曲平衡路径,并与薄板理论结果作了比较。 相似文献
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弹性直杆动态屈曲与后屈曲的实验研究 总被引:7,自引:0,他引:7
对传统的霍普金森压杆装置(SHPB)进行改进,用于研究弹性直杆的动态屈曲与后屈曲,并且分析了影响实验精度的因素。实验结果表明,在轴向应力波作用下弹性直杆的动态屈曲临界载荷明显高于静态的,并且在屈曲发生后,在直杆中有弯曲波产生,其波速大约为弹性剪切波的波速。 相似文献
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由于层间距和手性的耦合影响,非公度双壁碳纳米管的层间摩擦行为比较复杂,其规律至今仍不清楚.论文采用分子动力学模拟方法,研究了非公度双壁碳纳米管的层间摩擦特性.总体来说,层间距较小或层间手性角差较小时,层间摩擦力较大.当层间手性角差在10°以上时,层间接触接近非公度接触,层间摩擦力几乎不受层间手性影响;此时在层间平衡位置附近(0.34±0.02 nm),层间摩擦力与层间距之间近似呈线性关系.无论层间手性如何匹配,边界原子所受摩擦力总是大于内部原子所受摩擦力,显示边界效应是纳尺度摩擦中的一个普遍现象. 相似文献
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WangLifeng HuHaiyan GuoWanlin 《Acta Mechanica Solida Sinica》2005,18(2):123-129
This study focuses on the postbuckling and the nonlinear behavior of single-walled carbon nanotubes subject to a cyclic axial compressive load through the use of molecular dynamic simulation based on the Tersoff-Brenner potential. It reveals the bifurcation behavior in the buckling process simulated with very fine time steps. In the whole cycle of nonlinear deformation, the carbon nanotubes exhibit the profound hysteretic behavior and the energy absorption ability. The molecular dynamics simulation indicates that the carbon nanotube behaves approximately as an ideal plastic spring when the cyclic strain is applied within the same postbuckling mode. In comparison, the theory of continuum mechanics gives a good prediction about the critical buckling strength, but only provides a rough estimation for the post-buckling behaviors. 相似文献
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Buckling and postbuckling behaviors of perfect and imperfect,stringer andorthotropically stiffened cylindrical shells have been studied under axial compression.Based on the boundary layer theory for the buckling of thin elastic shells suggested in ref.[1],a theoretical analysis is presented.The effects of material properties of stiffeners andskin,which are made of different materials,on the buckling load and postbuckling behaviorof stiffened cylindrical shells have also been discussed. 相似文献
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Experiments were conducted in which multiwalled carbon nanotubes were subjected to uniaxial compression and shell-buckling
loads were measured. A comparison with existing theoretical models shows that the predictions are about 40–50% smaller than
the experimentally measured buckling loads. This is in contrast to the classical elastic shell studies in which the experimental
values were always substantially lower than the predicted values due to imperfection sensitivity. It is proposed that the
discrepancy between the predicted and measured value might be due to imperfections in the multiwalled nanotubes in the form
of sp
3 bonds between the tube walls, which introduce shear coupling between them. An analytical model is presented to estimate the
effect of the shear coupling on the critical buckling strain, which shows that the contribution from shear coupling increases
linearly with the effective shear modulus between the walls. Further, this contribution increases with the number of walls;
the increment from each additional wall progressively decreases. 相似文献
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将Koiter理论和奇异摄动理论中的边界层法相结合处理加筋圆柱壳无因次化非线性边界层型Karman-Donnel方程由分支点和边界层导致的双重奇异性,提出外压加筋圆柱壳总体屈曲Koiter—边界层奇异摄动法。从摄动意义上分析边界条件,前屈曲非线性和初始几何缺陷对外压加筋圆柱壳屈曲载荷的影响。算例表明,本方法具有良好的计算效率和计算精度,与数值解相比更能揭示内在影响规律。 相似文献
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采用分子动力学模拟方法研究了公度、不公度2种情况下碳纳米管在石墨基底上运动的摩擦机制与能量耗散,计算中先使碳纳米管在石墨基底上弛豫平衡,而后施加持续500 fs的固定外力,撤去外力后碳纳米管在基底上减速至相对基底静止.结果表明:在公度条件下,碳纳米管先在石墨基底上滑动,动能降低到一定值后出现翻转、滚动、滑动交替进行的现象.所受侧向力(即摩擦力)在滑动阶段呈现周期性变化,在开始滚动时摩擦力达到负向最大;在不公度条件下,碳纳米管在石墨基底上一直处于滑动状态,侧向力始终为负值;在公度情况下,侧向力对称性的破缺由碳纳米管底部原子与石墨基底原子间的法向趋近与分离引起,并由此而产生摩擦;碳纳米管与石墨基底原子间的相互作用为斥力-碰撞型,黏性摩擦造成了能量耗散. 相似文献
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针对复合材料典型多墙盒段,采用试验和有限元分析相结合的方法,研究了弯扭耦合载荷作用下的稳定性、承载能力及损伤起始、扩展情况.试验采用数字图像相关(Digital Image Correlation, DIC)测量方法捕捉试验件屈曲模态的变化过程,通过载荷-应变曲线获得屈曲和后屈曲破坏载荷.数值仿真基于ABAQUS/Explicit模块,采用Hashin准则结合刚度降的VUSDFLD子程序模拟复合材料的屈曲和后屈曲行为.研究结果表明,多墙盒段在弯扭载荷组合作用下发生屈曲时,扭矩会改变屈曲模态的分布形式和对称性,屈曲鼓包依然保持波峰、波谷交替出现;多墙盒段后屈曲阶段历程较长,屈曲模态由一阶向高阶逐渐发展,直到结构发生过大变形,彻底破坏而失去承载能力. 相似文献
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Buckling and postbuckling behavior of antisymmetrically angle-ply laminated composite plates 总被引:1,自引:0,他引:1
沈惠申 《应用数学和力学(英文版)》1990,11(12):1155-1165
The buckling and postbuckling behaviors of perfect and imperfect antisymmetricallyangle-ply laminated composite plates under uniaxial compression have been studied byperturbation technique which takes deflection as its perturbation parameter.In this paper,the effects of in-plane boundary conditions,angles,total number oflayers and initial geometric imperfection on the postbuckling behavior of laminated plateshave been discussed. 相似文献