关于各向间性材料的泊松比的下限问题,已经争论了许多年。多数人认为是 0_。少数人认为是-1,但他们在理论推导上往往出错,而且一直找不到泊松比为负的实物。本文对这个问题作了理论上的分析,得出的结论是:体弹性模量小于剪切弹性模量的三分之二的材料,泊松比为负。在这种理论的指导下,笔者第一次找到了泊松比为负的材料--泡沫塑料。 The issue of the lower limit of Poisson’s ratio for interspinous materials has been debated for many years. Most people think it is 0_. A few people think that it is -1, but they often make mistakes in theoretical derivation, and they have never found a Poisson’s ratio negative. This paper makes a theoretical analysis of this problem and concludes that the bulk modulus is less than two-thirds of the shear elastic modulus and the Poisson’s ratio is negative. Under the guidance of this theory, the author found for the first time that the Poisson’s ratio is negative material--foam plastic.