ABSTRACT
This chapter describes the porosity dependence of tensile strength, with attention also given to the very limited data on porosity effects on reliability at 22°C. It shows that a family of models is necessary and that MSA models are better for general porosity. The chapter demonstrates that major variations occur due to: grain size increases with decreasing P, porosity heterogeneity constraining lengths of normally elongated machining flaws, and especially individual and clustered pores acting as fracture origins approximately consistent with mechanistic models, but with important material-related and other deviations, especially pores as blunter flaws in glasses. It presents the overall P-dependence of strength is closer to that of E than of KIC, mainly due to crack branching and bridging having much less impact on strength since flaw sizes are often too small relative to the microstructure. The chapter shows how strengths decrease rapidly initially, then more slowly, with increasing contents of preexisting microcracks.
