The failure criteria that were developed for brittle solids were the maximum stress / strain criteria. The maximum stress criterion assumes that a material fails when the maximum principal stress σ σ 1 in a material element exceeds the uniaxial tensile strength of the material. Alternatively, the material will fail if the minimum principal stress σ σ 3 is less than the uniaxial compressive strength of the material. If the uniaxial tensile strength of the material is σ σ t and the uniaxial compressive strength is σ σ c , then the safe region for the material is assumed to be