Ide tifi rs: Crystal dislocations. Extensive research on factors influencing the behavior of brittle non-metallic ceramics was undertaken. General information on the forms of Al2O3 and MgO studied and preliminary work on the effect of porosity on the fracture strength of Lucalox (Al2O3) are presented. Individual problem areas were attacked on separate task programs: (1) Effect of structural size (the zero strength); (2) Effects of strain rate; (3) Effect of non-uniform stress fields; (4) Effect of microstructure; (5) Internal friction measurements; (6) Surface energy on brittle behavior; (7) Fracture mechanisms; (8) Impurity influences; (9) Static fatigue (delayed fracture); (10) Effect of thermal-mechanical history; and (11) Surface active environments.