Lifetime prediction of internally pressurized siliconized SiC tubes subjected to creep rupture loading

The main objective of this research was to develop an experimental and analytical methodology to predict the lifetime of internally pressurized SiC tubes from the lifetimes of simple specimens subjected to similar delayed failure modes. Finite element analysis was used to determine the strain rate distribution in a thick-wall tube subjected to sustained internal pressure. This analysis was used along with the Monkman-Grant creep rupture criterion (obtained from creep testing of tensile specimens) to predict the lifetime of SCRB210 tubes. Results showed a large difference between experimental and predicted lifetimes. This difference was due to the existence of severe defects in the SCRB210 tubes which failed at low stresses. These tubes failed in crack growth mode rather than creep mode. This result leads to the conclusion that creep rupture criteria obtained from testing simple specimens cannot be projected to predict the lifetimes of large and more complex components.