Lifetime prediction of ceramic components after proof testing

Failure times and fracture stresses of an electrical porcelain were measured on samples which survived a preceding proof test. The data were compared with predictions made by combining the model of time–dependent strength of ceramics with proof–testing theory. The close coincidence showed that the proof–testing procedure employed was able to eliminate the weak samples without affecting the strength of the survivors. All measured data of failure time and fracture stress of proof–tested samples exceeded the minimum values predicted by the model. It was concluded that proof testing is a suitable means to provide a lower limit of the material's performance, even under service conditions where subcritical growth of the strength–controlling flaws occurs.