颗粒固体弹性势能的声波性质

基于大量静止颗粒堆积而成的物体属于非线性弹性体的观点,计算了其弹性势能的声速表达式(考虑圆柱对称和沿主应力方向传播的平面波情形).通过与己报道的一些实验数据的对比,认为精密的声学方法能够测定势能中的所有材料参数,因此是研究这类材料非线性弹性行为细节的一个重要观测手段,但需要对样品的所有应力、密度和均匀程度进行全面仔细的监控.     

Stress distribution and surface instability of an inclined granular layer

Static granular materials may avalanche suddenly under continuous quasi-static drives. This phenomenon, which is important in many engineering applications, can be explained by analyzing the stability of the elastic solutions. We show this for a granular layer driven by its inclination angle in gravity, where the elastic problem can be solved generally and analytically. It is found that a loss of stability may occur only at the free surface of the layer. This result is considered to be relevant for understanding surface avalanches and the flows observed experimentally.     

Properties of surface waves in granular media under gravity

Acoustical waves propagating along the free surface of granular media under gravity are investigated in the framework of elasticity theory. The influence of stress on a surface wave is analyzed. The results have shown that two types of surface waves, namely sagittal and transverse modes exist depending on initial stress states, which may have some influence on the dispersion relations of surface waves, but the influence is not great. Considering that the present experimental accuracy is far from distinguishing this detail, the validity of elasticity theory on the surface waves propagating in granular media can still be maintained.     

Couette颗粒系统中静态应力和侧压力系数的非线性弹性理论分析

经典弹性理论能否适用于静态颗粒物质是颗粒物理的一个基本问题.报道了非线性颗粒弹性方程对环柱几何(或称Couette几何)状样品中应力分布的计算结果.由于这些结果大都可在今后用实验直接测量,因而可将它们用于进一步判断这些弹性方程对颗粒材料的适用性以及澄清这个基本问题.另外,这些结果还可用于分析计算工程中的侧压力系数. 关键词： 颗粒物质 侧压力系数 非线性弹性理论     

一种颗粒底部压力不趋向饱和的粮仓系统

随着深度的增加竖直圆筒容器中的颗粒物质会把自己的重量逐渐转移到容器的侧墙壁上,使容器底部的压力出现不随筒中颗粒材料高度的增加而增加的饱和现象.但值得注意的是,圆筒中的颗粒柱体并不总是表现为这个称为粮仓效应的力学状态.例如当改变侧墙壁的力学环境使其无法承担颗粒的重量时,柱底部的压力显然将随其高度的增加而线性地增加.本文分析讨论了Janssen模型假设对这类处于静力平衡下,但违反粮仓效应的颗粒系统的行为预测. 关键词： 颗粒物质 粮仓 静摩擦 应力