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| | Abstract | | We applied a laser Doppler vibrometer, LDV, system for detecting fractures in a concrete block. LDV has an advantage that it can detect ultrasonic vibration of the concrete in a noncontact method. Using two LDV equipments, we can measure surface particle velocities in the vertical and radial directions and can distinguish surface waves. Ultrasonic waves near a fracture are characterized by stronger low-frequency components, compared with the waves in crack-free areas. |
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