Mechanical properties of single-walled carbon nanotube bundles as bulk materials

Single-walled carbon nanotubes (SWNTs) in crystalline bundles may exhibit a transition in which the cross-sections of tubes turn from perfectly circular to hexagonal, depending upon the tube diameter and externally applied pressure, and this structural instability leads to an abrupt change in the bulk elastic properties of SWNT bundles. This paper presents a hybrid atom/continuum model to study the bulk elastic properties of SWNT bundles, and the predicted characteristics of this structural instability agree well with the experimental observations available in the literature. Linearized bulk elastic properties of SWNT bundles with respect to a stable configuration are transversely isotropic and hence can be characterized by five independent elastic moduli. A complete set of these five moduli is predicted for the first time. It is found that the deformability of tube cross-sections play a dominant role in characterizing the transverse moduli.     

轴向瞬间阶梯载荷下圆柱壳动力屈曲的双特征参数分析

对于轴向瞬间阶梯载荷下圆柱壳的弹性非轴对称动力屈曲问题，将临界应力和屈曲惯性项指数参数作为双特征参数求解。由能量转换和守恒准则，导出压缩波阵面上的屈曲变形附加约束条件。失稳控制方程、边界条件和波阵面上的连续条件，连同此附加约束条件构成求解两个特征参数和动力失稳模态的完备定解条件。由伽辽金法得出求解双特征参数问题的数值方法。     

Two-dimensional stability problem for two interacting short fibers in a composite: In-line arrangement

A solution is found to a plane problem for a composite material reinforced with two in-line fibers and subjected to longitudinal compression. The problem formulation is based on the piecewise-homogeneous model and the three-dimensional theory of stability. The dependence of the critical strain and buckling mode on the distance between the fibers is studied for various mechanical and geometrical characteristics of the composite components.Translated from Prikladnaya Mekhanika, Vol. 40, No. 9, pp. 65–74, September 2004.     

不连续岩石梁的失稳解析

本文根据不连续岩石梁的物理力学特性提出了无拉力岩石梁的力学解析模型。根据Ｆｒｅｅｂｏｄｙ法及Ｃａｓｔｉｇｌｉａｎｏ定量导出了不连续梁各物理量的求解方程式。进而采用挠度增量δｍａｘ＾ｉ＋１＝δｍａｘ＾ｉ＋Δδ↑－的逐次解析方法，求解了不连续梁的失稳问题，得出了与Ｆ．Ｄ．Ｗｒｉｇｈｔ的试验值相吻合的结果。探讨了不连续岩石梁在不同荷载条件下的失稳特性。     

Motion of a system of seismic sources over ice on a body of water under the action of a pulse

The vertical motion of a system of two identical seismic sources and a spring truck tractor on ice under the action of a shock pulse from the seismic sources is studied to estimate the strength of ice. It is shown that during the pulse time, the interaction of the masses of the seismic sources and the tractor is small and the compressibility effect of the liquid can be ignored. Calculations show that for the seismic sources, the dynamic load far exceeds the static load and for the tractor, the static load is maximal. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 147–155, March–April, 2007.     

高耸异型烟囱结构风压和风振系数试验研究

本文在模拟的大气边界层中,对某一发电厂高耸异型烟囱的刚性模型进行了测压试验研究,得到了这一结构的平均风压系数、最大和最小风压系数分布,以及该结构的风荷载体型系数;结果表明在烟囱外形明显变化的局部区域,风压绝对值较大,与理论分析一致。同时,对动态测力试验模型进行了高频动态天平测力试验研究,详细介绍了试验及数据处理方法,根据试验结果计算得到了该烟囱在风作用下的动力响应和风振系数;根据试验结果计算所得的风振系数值大于按规范公式估算值。这些结果不仅为结构的风荷载计算提供了依据,也有助于进一步认识该类异性烟囱结构的风荷载和风振特性。     

临界空穴扩张比准则的适用性

用新研制成的DE36平台钢制的轴对称和平面应变试样,进一步考察了临界空穴扩张比V_(Gi)准则[1]、[2]、[3]的适用性。实验和大应变有限元理论计算结果表明,V_(Gi)准则适用于所研究材料。文中指出,按V_(Gi)准则可根据试样或构件材料中V_G的发展变化来预起裂位置。     

投影云纹法在研究加劲板后屈曲平衡路径及后屈曲模态转化过程的应用

本文应用投影云纹法研究受压加劲板的大挠度非线性问题。用投影云纹法测量加劲板后屈曲平衡路径,记录了随着载荷的增加,加劲板后屈曲模态变化的全过程。将云纹图输入微型计算机处理,获得了加劲板的全场位移和全场应力的分布情况。用投影云纹法所测得的结果同理论计算值基本吻合。     

爆炸载荷作用下地下拱形结构动态分析

应用有限元方法分析了爆炸载荷作用下地下拱形结构与土介质的动力相互作用问题。结构与介质均假定为弹塑性，并用Ｍｉｓｅｓ屈服准则描述，且考虑其几何非线性的影响。使用了人为阻尼边界，并使计算模型的几何尺寸满足限制性条件，从而大大提高了计算精度。还对几种解进行了比较，对影响结构应力场的因素也进行了讨论。     

ELASTIC PULSE BUCKLING OF CYLINDRICAL SHELLS UNDER RADIAL IMPULSIVE LOADING

ＥＬＡＳＴＩＣＰＵＬＳＥＢＵＣＫＬＩＮＧＯＦＣＹＬＩＮＤＲＩＣＡＬＳＨＥＬＬＳＵＮＤＥＲＲＡＤＩＡＬＩＭＰＵＬＳＩＶＥＬＯＡＤＩＮＧＨｕａｎｇＣｈｅｎｇｙｉ（黄承义）ＬｉｕＴｕｇｕａｎｇ（刘土光）ＺｈｅｎｇＪｉｊｉａ（郑际嘉）（Ｄｅｐａｒｔｍｅｎｔｏ...