TV Holography As A Possible Tool For Measuring Transverse Vibration of Logs: A Pilot Study
Keywords:Nondestructive evaluation, vibration analysis, TV holography, laser interferometry
AbstractVibration analysis on a short spruce log was performed by using TV holography, which is a laser interferometry technique applying video recording. This is a non-contact vibration measurements method capable of detecting amplitude of the scale of nanometers. It also allows for real-time inspection of vibrations and full-field measurements. The log was put into vibration by a periodic force acting on a point on the log surface. Resonant vibrations were found by varying the excitation frequency and running the TV holographic system in a phase modulation mode. Several bending modes, familiar from classical beam theory, were identified during the experiments. In addition, another type of vibration was discovered, in which the primary motion was in the transverse plane of the log, causing deformation of the cross-sectional shape. The results show that the method is suitable for measuring vibration patterns on logs. This information may be used for nondestructively predicting interior structural properties.
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