Abstract

Electronic speckle pattern interferometry combined with phase-shifting techniques for vibration analysis of logs is presented. Changes in the vibration pattern were followed on a television monitor at the video rate. We determined resonant vibrations by scanning through the frequency range of interest and by changing the point of excitation. We observed bending and torsional modes of vibration by changing the support and point of excitation. The vibrational modes reflect the structural properties of the material. The longitudinal modulus of elasticity and the shear modulus were calculated, giving valuable information for the strength grading of logs.

© 1997 Optical Society of America

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