METHODOLOGY TO PREDICT DELAYED FAILURE DUE TO SLOW CRACK-GROWTH IN CERAMIC TUBULAR COMPONENTS USING DATA FROM SIMPLE SPECIMENS

The methodology to predict the liftime of sintered a-silicon carbide (SASC) tubes subjected to slow crack growth (SCG) conditions involved the experimental determination of the SCG parameters of that material and the scaling analysis to project the stress rupture data from small specimens to large components. Dynamic fatigue testing, taking into account the effect of threshold stress intensity factor, of 0-ring and compressed C-ring specimens was used to obtain the SCG parameters. These SCG parameters were in excellent agreement with those published in the literature and extracted from stress rupture tests of tensile and bend specimens. Two methods were used to predict the lifetimes of internally heated and pressurized SASC tubes. The first is a fracture mechanics approach that is well known in the literature. The second method used a scaling analysis in which the stress rupture distribution (lifetime) of any specimen configuration can be predicted from stress rupture data of another.