A lifetime prediction method based on Cumulative Flaw Length Theory

Ultrasonic pulse velocity testing (UPVT) was carried out to perform non-destructive quality control of refractory plates. Used in conjunction with fracture mechanics, ultrasonic velocity measurements have proved a powerful technique for detecting, positioning and sizing internal voids and cracks in the samples, originated from the manufacturing process. Two cordierite-mullite refractory compositions exhibiting different microstructure and crack propagation behaviour were characterized through their lifetime during which they were subjected to thermal shock loading. In this paper, a new statistical method is proposed which allows to estimate the lifetime when the stress state that will be applied in service (loading) and the scattering of the ultrasonic velocity data in the as-received state are known. Since this lifetime prediction method is based on a non-destructive technique, it could be implemented into a code in an automatic quality control device for continuous lifetime estimation. The correlation between crack propagation behaviour and thermal shock resistance is discussed and semi-empirical models were developed to predict the service life of refractory plates from the measured values of ultrasonic velocities on as-received samples.