Evaluation of damage for alumina/graphite refractory using apparent sonic velocity measurement

Damage evaluation for alumina/graphite refractory was conducted under uni-axial compressive loading. Apparent sonic velocity during a loading-unloading cycle was measured by ultrasonic method. Quasi-elastic-plastic behavior was observed in the stress-strain curve for each cycle. However, it is difficult to detect damage from the stress-strain curve during each loading- unloading cycle. On the other hand, using the result of change in apparent sonic velocity during a loading-unloading cycle, it is possible to estimate damage to some extent. The apparent sonic velocity kept approximately constant during the first loading process, but it decreased remarkably during the first unloading one. In the subsequent loading-unloading cycles, it increased in the loading process and decreased in the unloading one. Consequently, it is concluded that damage mechanism during the first loading-unloading cycle is different from that during the subsequent loading- unloading cycles for alumina/graphite refractory.