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脆性材料的抗压强度大于抗拉强度,但究竟大多少,它们之间有没有近似的定量关系,这个问题引起不少人的兴趣。Griffith从讨论裂纹的角度得到抗压强度σ_c是抗拉强度σ_b的8倍(即σ_c/σ_b=8)的结论,McClintock等从Griffith裂纹有摩擦力的角度得到σ_c/σ_b=10。显然,这些结论过于绝对,与实际情况很不符合。σ_c/σ_b的比值对于不同的材料应该是不同的。本文就某些脆性材料的抗压强度与抗拉强度之间的关系提出一个近似公式。为此,我们首先对第二强度理论进行适当的修正,它是我们提出的近似公式的来源和理论根据。
Compressive strength of brittle materials is greater than the tensile strength, but how many, whether there is an approximate quantitative relationship between them, this issue has aroused much interest. Griffith concluded that the compressive strength σ_c is eight times the tensile strength σ_b (ie, σ_c / σ_b = 8) from the point of view of cracking, and McClintock et al. Obtained σ_c / σ_b = 10 from the point of Griffith crack friction. Obviously, these conclusions are too absolute and not in accordance with the actual situation. The ratio of σ_c / σ_b should be different for different materials. This paper presents an approximate formula for the relationship between compressive strength and tensile strength of some brittle materials. For this reason, we first make a proper revision of the second strength theory, which is the source and theoretical basis of the approximate formula we proposed.