共查询到20条相似文献,搜索用时 187 毫秒
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采用分子动力学方法,分别模拟完好的和含有缺陷的(7,7)扶手椅型氮化硼纳米管的轴向压缩过程.原子间的相互作用采用Tersoff多体势函数来描述.为验证结果的可靠性,同时针对(7,7)扶手椅型碳纳米管进行对比计算.结果表明,氮化硼纳米管的压缩失效模式同碳纳米管相同,均表现为管壁的局部屈曲.发现纳米管的压缩强度,如临界轴向内力在低温下受温度影响明显,并且和应变率的大小有关.然而,应变率对纳米管的弹性变形没有影响.另外,还发现空位缺陷降低了纳米管的力学性能.与完好的纳米管相比,含有缺陷的纳米管轴向压缩强度对于温度的影响并不敏感. 相似文献
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使用分子动力学方法研究几种不同半径尺寸的单壁碳纳米管组成的双壁碳管,预测了其初始稳定构型;分析了其自由弛豫阶段的特征;并模拟了它们在轴向压缩载荷作用下的屈曲行为;研究了不同层间距导致的范德华力变化对屈曲行为的影响.采用Tersoff-Brenner势描述单壁碳纳米管内原子间作用,Lennard-Jones势描述内外层间的范德华相互作用.计算结果表明:在通常意义下的双壁管间距(约0.34 nm)外还可以存在稳定的双壁碳管构型,并且这些新的稳定构型表现出了不同的力学性质.
关键词:
双壁碳纳米管
分子动力学
屈曲 相似文献
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碳纳米管表面化学修饰是当前研究的一大热点,修饰后由于极性基团的存在,碳纳米管在极性溶液环境中的分散度得到明显改善,这在很大程度上扩展了纳米管研究的应用范围.本文采用C80H20模型来表示(10,0)碳纳米管,基于此模型计算了一系列氮烯、卡宾和氟化的单壁纳米管的结构、偶极矩,以及核磁共振参数.研究表明高精度的密度泛函理论(DFT)计算能够用来预测纳米管的13C化学位移,理论研究的结果揭示了氮烯、卡宾以及1,2和1,4氟化的单壁纳米管的若干13C信号特征化学位移值,为实验NMR谱图的归属提供了一定的依据,并且可通过与实验相结合来监测表面官能化碳纳米管加成反应是否发生以及确认其加成方式. 相似文献
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碳纳米管表面化学修饰是当前研究的一大热点,修饰后由于极性基团的存在,碳纳米管在极性溶液环境中的分散度得到明显改善,这在很大程度上扩展了纳米管研究的应用范围. 本文采用C80 H20模型来表示(10,0)碳纳米管,基于此模型计算了一系列氮烯、卡宾和氟化的单壁纳米管的结构、偶极矩,以及核磁共振参数. 研究表明高精度的密度泛函理论(DFT)计算能够用来预测纳米管的13C化学位移,理论研究的结果揭示了氮烯、卡宾以及1,2和1,4氟化的单壁纳米管的若干13C信号特征化学位移值,为实验NMR谱图的归属提供了一定的依据,并且可通过与实验相结合来监测表面官能化碳纳米管加成反应是否发生以及确认其加成方式. 相似文献
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《Physics letters. A》2006,349(5):370-376
A nonlocal multiple-shell model is developed for the elastic buckling of multi-walled carbon nanotubes under uniform external radial pressure on the basis of theory of nonlocal elasticity. The effect of small length scale is incorporated in the formulation. An explicit expression is derived for the critical buckling pressure for a double-walled carbon nanotube. The influence of the small length scale on the buckling pressure is examined. It is concluded that the critical buckling pressure for a carbon nanotube could be overestimated by the classic (local) shell model due to ignoring the effect of small length scale. 相似文献
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Based on theory of thermal elasticity mechanics, an elastic multiple column model is developed for column buckling of MWNTs with large aspect ratios under axial compression coupling with temperature change. In this model, each of the nested concentric tubes is regarded as an individual column and the deflection of all the columns is coupled together through the van der Waals interactions between adjacent tubes. The thermal effect is incorporated in the formulation. Following this model, an explicit expression is derived for the critical buckling strain for a double-walled carbon nanotube. The influence of temperature change on the buckling strain is investigated. It is concluded that the effect of temperature change on the buckling strain is dependent on the temperature changes, the aspect ratios, and the buckling modes of carbon nanotubes. 相似文献
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A.R. Ranjbartoreh A. Ghorbanpour B. Soltani 《Physica E: Low-dimensional Systems and Nanostructures》2007,39(2):230-239
In this paper, the buckling behavior and critical axial pressure of double-walled carbon nanotubes (DWCNTs) with surrounding elastic medium are investigated. A double-shell (circular cylindrical shell) model is presented and the effects of surrounding elastic medium on the outer tube and the van der Waals forces between two adjacent tubes are taken into account. The analysis and the numerical solution method are based on the classical theory of plates and shells and the Galerkin method. Equations are derived for the critical axial forces and pressures of DWCNTs; the critical axial forces and pressures are calculated for different axial half sine wavenumbers and circumferential sine wavenumbers and compared with those for single-walled carbon nanotubes (SWCNTs).Results indicate that the critical axial force of a DWCNT is higher than that of an SWCNT, but the critical axial pressure of a DWCNT is lower than the critical axial pressure of a SWCNT. Although the critical axial force of a DWCNT decreases as the axial half sine wavenumbers increase, it rises as the circumferential sine wavenumbers increase. 相似文献
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采用分子动力学方法模拟了氮化硼纳米管在轴压和扭转复合荷载作用下的屈曲和后屈曲行为.在各加载比例下,给出了初始线性变形阶段和后屈曲阶段原子间相互作用力的变化,确定了屈曲临界荷载关系.通过对屈曲模态的细致研究,从微观变形机理上分析了纳米管对不同外荷载力学响应的差异.研究结果表明,扶手型和锯齿型纳米管均呈现出非线性的屈曲临界荷载关系,复合加载下的屈曲行为具有强烈的尺寸依赖性.温度升高将导致屈曲临界荷载的下降,且温度的影响随加载比例的变化而变化.无论在简单加载或复合加载中,同尺寸的碳纳米管均比氮化硼纳米管具有更强地抵抗屈曲荷载的能力. 相似文献
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The present study has theoretically investigated the combined torsional buckling of double-walled carbon nanotubes (DWCNTs) with axial load in the multi-field coupled condition. The effects of torsion, axial load, thermal-electrical change, surrounding elastic medium and the Van der Waals forces are all taken into consideration. The governing equation of buckling for CNTs subjected to thermo-electro-mechanical loadings has been established based on an elastic shell model of continuum mechanics. Reasonable s... 相似文献
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Using molecular dynamic simulation (MDS), effects of chirality and Van der Waals interaction on Young's modulus, elastic compressive modulus, bending, tensile, and compressive stiffness, and critical axial force of double-walled carbon nanotube (DWCNT) and its inner and outer tubes are considered. Achieving the highest safety factor, mechanical properties have been investigated under applied load on both inner and outer tubes simultaneously and on each one of them separately. Results indicate that as a compressive element, DWCNT is more beneficial than single-walled carbon nanotube (SWCNT) since it carries two times higher compression before buckling. Except critical axial pressure and tensile stiffness, in other parameters zigzag DWCNT shows higher amounts than armchair type. Outer tube has lower strength than inner tube; therefore, most reliable design of nanostructures can be attained if the mechanical properties of outer tube taken as the properties of DWCNT. 相似文献
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In this Letter, the thermal buckling properties of carbon nanotube with small scale effects are studied. Based on the nonlocal continuum theory and the Timoshenko beam model, the governing equation is derived and the nondimensional critical buckling temperature is presented. The influences of the scale coefficients, the ratio of the length to the diameter, the transverse shear deformation and rotary inertia are discussed. It can be observed that the small scale effects are significant and should be considered for thermal analysis of carbon nanotube. The nondimensional critical buckling temperature becomes higher with the ratio of length to diameter increasing. Furthermore, for smaller ratios of the length to the diameter and higher mode numbers, the transverse shear deformation and rotary inertia have remarkable influences on the thermal buckling behaviors. 相似文献
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R. Ansari R. Gholami S. Sahmani 《Applied Physics A: Materials Science & Processing》2013,113(1):145-153
In the present investigation, the axial buckling and post-buckling configurations of single-walled carbon nanotubes (SWCNTs) are studied including the thermal environment effect. For this purpose, Eringen’s nonlocal elasticity continuum theory is implemented into the classical Euler–Bernoulli beam theory to represent the SWCNTs as a nonlocal elastic beam model. A closed-form analytical solution is carried out to analyze the static response of SWCNTs in their post-buckling state in which the axial buckling load is assumed to be beyond the critical axial buckling load. Common sets of boundary conditions, named simply supported–simply supported (SS–SS), clamped–clamped (C–C), and clamped–simply supported (C–SS), are considered in the investigation. Selected numerical results are given to represent the variation of the carbon nanotube’s mid-span deflection with the applied axial load corresponding to various nonlocal parameters, length-to-diameter aspect ratios, temperature changes, and end supports. Moreover, a comparison between the post-buckling behaviors of SWCNTs at low- and high-temperature environments is presented. It is found that the size effect leads to a decrease of the axial buckling load especially for SWCNTs with C–C boundary conditions. Also, it is revealed that the value of the temperature change plays different roles in the post-buckling response of SWCNTs at low- and high-temperature environments. 相似文献