In this paper the dynamic torsional buckling of multi-walled carbon nanotubes （MWNTs） embedded in an elastic medium is studied by using a continuum mechanics model. By introducing initial imperfections for MWNTs and applying the preferred mode analytical method, a buckling condition is derived for the buckling load and associated buckling mode. In particular, explicit expressions are obtained for embedded double-walled carbon nanotubes （DWNTs）. Numerical results show that, for both the DWNTs and embedded DWNTs, the buckling form shifts from the lower buckling mode to the higher buckling mode with increasing the buckling load, but the buckling mode is invari- able for a certain domain of the buckling load. It is also indicated that, the surrounding elastic medium generally has effect on the lower buckling mode of DWNTs only when compared with the corresponding one for individual DWNTs.
By applying the integral transform method and the inverse transformation technique based upon the two types of integration, the present paper has successfully obtained an exact algebraic solution for a two-dimensional Lamb＇s problem due to a strip impulse loading for the first time. With the algebraic result, the excitation and propagation processes of stress waves, including the longitudinal wave, the transverse wave, and Rayleigh-wave, are discussed in detail. A few new conclusions have been drawn from currently available integral results or computational results.
采用改进的高精度时-空守恒元解元算法(the space-time conservation element and solution element meth-od,CE/SE method)和考虑组分的二阶段化学反应模型(Sichel的二步模型)对气相爆轰问题的数值模拟进行了分析。分析发现采用Sichel的二步模型得到的数值结果虽然比早期二阶段化学反应模型(旧二步模型)更接近实验值,但是仍然不能得到爆轰过程准确气体动力学参数。为此通过修改组分的质量分数分布形式对Sichel的二步模型进行了改造,然后采用新的二步模型对平面爆轰波进行了数值模拟。数值结果表明采用新的二步模型计算得到气体动力学参数更接近于实验值和基元反应模型的计算值,在计算精度上有较大提高。
