Nondestructive detection of fatigue crack using amplitude change of ultrasonic wave in local vibration

Abstract

This study investigated the property of transmitted ultrasonic waves when the crack face is subjected to dynamically changing stress conditions. Here, we measured the peak amplitude of the transmitted wave's fundamental frequency when a specimen was locally vibrating. Since a fatigue crack was made in the center of the specimen of this study, the first bending resonance mode was chosen to generate the crack face's partial compression/tension. The ultrasonic waves were excited with the time difference to transmit through the crack face at different phases of stress in the resonance vibration. It was shown that the instant change of the peak amplitude value at the fundamental frequency of the transmitted wave increased when the vibration motion became substantial.