Ultrasonic Velocity Technique for Non-Destructive Quantification of Elastic Moduli Degradation during Creep in Silicon Nitride
F Lofaj, Gerald V. Blessing, Sheldon M. Wiederhorn
The ultrasonic velocity technique was used for non-destructive quantification of creep damage during interrupted tensile creep tests at 1400 degrees}C in an advanced silicon nitride, SN 88. The longitudinal and shear wave velocities, Poisson''s ratio, Young''s shear and bulk moduli linearly decreased with strain. Precise density change measurements indicated a linear relationship with a coefficient of proportionality of approximately equal to} 0.7 between the volume fraction of cavities and tensile strain. Cavitation was identified as the main creep mechanism in the studied silicon nitride and the reason for ultrasonic velocity and elastic moduli degradation. The measurement of the longitudinal wave velocity changes is preferred and sufficient for quantification of cavitation during creep. The capability of the ultrasonic velocity technique for simple, sensitive and reliable nondestructive monitoring of creep damage during intermittent creep was demonstrated in silicon nitride.
, Blessing, G.
and Wiederhorn, S.
Ultrasonic Velocity Technique for Non-Destructive Quantification of Elastic Moduli Degradation during Creep in Silicon Nitride, Journal of the American Ceramic Society
(Accessed March 2, 2024)