Abstract
This paper presents a concept of nonlinear ultrasonic-based damage detection method that may not require high-rate data sampling as well as baseline data in the healthy state. Recently, because of a serious problem that most of Japanese infrastructures become deteriorated in near future, efficient and non-labor-intensive inspection methodologies are eagerly required. In this study, we propose a method that utilizes a frequency mixture phenomenon referred to as "frequency down-conversion" which is induced by a contact acoustic nonlinearity associated with contact-type damages involved in the structure. Because of this nonlinearity, when an amplitude-modulated wave is input to the structure, a low frequency component which has the same frequency as the modulation signal is excited. The result of a preliminary experiment using a steel beam specimen shows the excitation of the low frequency component when the specimen has a simulated damage, and the dependency of the magnitude of that component on the modulation frequency.
