Estimation of damaged part in a beam structure based on nonlinear wave modulation

Abstract

This paper proposes a damage localization method for a beam structure, which can discriminate a specific part of the structure involving contact-type damages such as cracks, delamination and loose bolt failures. When the structure is subjected to a low-frequency excitation, the scatter characteristics of high-frequency waves in the vicinity of the damage location may fluctuate in synchronization with the low-frequency vibration due to the contact acoustic nonlinearity. Thus, a high-frequency sinusoidal probe wave going through the damaged part undergo amplitude and phase modulation, and as a consequence, sideband-frequency waves emerge accompanied with the the probe wave. In this paper, it is derived that the damaged structural part can be discriminated by measuring in-coming and out-going wave components separately by a sensor array and evaluating the amplitude ratio between those components at the sideband frequency. Experiments using a beam specimen with a simulated damage is conducted to examine the validity of the proposed method.