1. What percent reduction of the elastic modulus of alumina would be caused by 1% porosity?
2. Pottery is generally ?red at a high temperature; then it is cooled and a glaze is applied. On reheating, the glaze melts and spreads over the surface. On cooling again, residual stresses may develop in the glaze. To ensure that these are compres- sive, what relation is necessary between the properties of the body of the ceramic and of the glaze?
3. Why is there so little concern about thermal shock in metals and polymers, whereas there is much concern with ceramics? Why aren't the parameters R1 = σ f (1 - 2u)/(Eα) and R2 = KIc/(Eα) useful in predicting fracture in metals?