FRACTURE-RESISTANCE MEASUREMENT METHOD FOR IN-SITU OBSERVATION OF CRACK MECHANISMS

A special test fixture has been developed for fracture mechanical test ing of brittle materials inside an environmental scanning electron mic roscope. The fixture loads a double cantilever beam specimen with pure bending moments and provides stable crack growth. Crack growth is det ected by in situ observation and acoustic emission, As an example, cra ck growth in a cubic-phase yttria-stabilized zirconia is detected easi ly by in situ observation of the crack-tip region, Many fracture tough ness measurements are obtained for each specimen, giving high confiden ce in the measured fracture toughness value, In situ observation is us eful for the study of toughening mechanisms and subcritical crack-grow th behavior and to sort out erroneous measurements (e.g., due to crack branching).