セラミックスおよび複合材料の高温弾性定数の衝撃音による計測

抄録

A simple instrumentation system is developed to determine the elastic moduli of engineering ceramics and their composites from the sound produced by the impact of a sphere on a specimen which is suspended by thin metallic wires or ceramic threads in a furnace. The natural frequencies of the flexural and torsional vibration modes are measured from the impact noise using a fast Fourier transform analyzer. Elastic moduli are then computed from these frequencies using Timoshenko's beam theory and also Saint-Venant's torsion theory. The validity of the measurement method is demonstrated by room temperature tests on ceramic and metallic specimens of known elastic moduli. Sialon and Al-Al₂O₃ composites are tested at elevated temperatures up to 800°C. It is shown that Young's and the shear moduli of the materials tested decrease with an increase in temperature, while Poisson's ratio remains almost constant.