Working Model for Porosity Effects on the Uniaxial Strength of Ceramics

Abstract

A working model for the effects of porosity on the uniaxial strength of ceramics at low temperatures is developed, validated physically in limiting cases, and tested successfully against experimental data for polycrystals and glass. Other existing models are in apparent conflict with quantitative features of the experimental and physical evidence. The model (1) confirms the Duckworth equation as an approximation but shows that its linearity is significantly in error as P→0; (2) confirms the approximations for glass and for polycrystals, with the same reservation; (3) describes radical values of β in terms of pore type and shape in polycrystals and in terms of pore control of the Griffith crack length, c̄ p , in glass; and (4) conforms to several less obvious features of strength‐porosity data.