Ultrasonic Measurement of Applied Stresses in Wood by Acoustoelastic Birefringent Method
Sasaki, Yasutoshi Assoc.Professor Hasegawa, Masumi Graduate Student Graduate School of Bioagricultural Sciences Nagoya University, Nagoya 464-8601, Japan
The velocity changes of ultrasonic shear waves propagating transverse to the direction of the applied stress in wood were investigated experimentally. Their direction of oscillation was parallel and normal to the direction of uniaxially applied stress. Additionally, bending stress distributions in wood beam specimen were estimated by measuring ultrasonic shear wave velocities, that is, by the acoustoelastic birefringent method. The investigation showed that the ultrasonic waves changed speed a little due to the applied stress and the velocity of the shear waves propagating transverse to the direction of the stress was dependent on whether its direction of oscillation was parallel or normal to the direction of the stress. The relative differences of the ultrasonic velocities were given as functions of applied stress and the acoustoelastic constants for texture- and stress-induced birefringences were obtained. By using these constants and ultrasonic velocities of shear waves polarized parallel and normal to the direction of principal stresses, the difference of the principal stresses can be obtained and this is called the acoustoelastic birefringent method for the determination of the stress states. According to this acoustoelastic technique, bending stress distributions in wood beam specimen were tried to determine, and the stress states estimated agreed well with the stress values obtained by strain gauge method and mechanical calculation. The acoustoelastic birefringent phenomena can be applied to determine stress conditions of wood.
Publication Source: Proceedings of the 12th International Symposium on Nondestructive Testing of Wood University of Western Hungary, Sopron, 13-15 September 2000, ISBN 963 7180 88 5 Publisher: University of Western Hungary, H 9400 Sopron, P.O.Box 132, FAX: +36 99 311 103
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