Which One Has More Influence on Fracture Strength of Ceramics: Pressure or Strain Rate?

Abstract

Both strain rate and confinement pressure have been known to have a strong influence on the failure strength of ceramics. However, the debate about which one has more influence has never been resolved. This manuscript aims to conclusively prove that confinement pressure has significantly higher influence than strain rate on the compressive strength of a ceramic. Normalized shear stress versus hydrostatic pressure plot on a variety of ceramics shows that the quasi-static and dynamic strength of brittle solids is a strong function of applied pressure and not the strain rate. The plots also revealed that despite the differences in material properties, test methods, and strain rate the data on failure strength fall in a narrow range and therefore a unified model, that extends the traditional Mohr-Coulomb criteria by adding an exponential term, can capture the overall deformation behavior of structural ceramics at high pressures.