Abstract
This paper presents localization of contact-type failure based on frequency down-conversion of elastic vibration by measurement of structural intensity. It is required to detect contact-type failure such as fatigue cracks and peeling in a structure. When two ultrasonic vibrations with different frequencies are input to the test object with contact-type failure, the contact condition of the failure interface fluctuates by ultrasonic vibrations. In this situation, a difference frequency component is generated in the test object. This phenomenon is called frequency down-conversion. In this paper, since difference frequency component is caused by local non-linearity, we consider that contact-type failure can be regarded as the excitation point of the difference frequency component. Using measurement of structural intensity as a method to estimate the excitation point, we propose a localization method of contact-type failure. By measuring structural intensity, the excitation point can be estimated as a source of vibration power flow. As a basic study, we performed localization of contact-type failure in a uniform beam structure. Furthermore, we clarified the relationship between the vibration mode of the difference frequency component and the detection accuracy of the failure location.
