Vibration-based damage growth monitoring in beam-like structures

Abstract

Damage growth monitoring plays an important role in providing early warning of structural failure. The existing methods for damage growth monitoring are mainly local inspection methods, such as acoustic emission. These methods need a priori knowledge of accessible damage vicinity, which may not be realized in practice. Hence, vibration-based global approach is adopted to overcome these difficulties. Natural frequency, as a global modal parameter, can be measured easily and is used for vibration-based damage growth monitoring in this study. A concept of damage-induced relative natural frequency change (RNFC) curve is defined first and its relation with mode shape is then derived analytically, giving a good way to approximate RNFC curves. For monitoring damage growth, a damage growth indicator is proposed based on RNFCs between two damaged stages of a beam. The effectiveness of the indicator for damage growth monitoring is proved by both numerical and experimental cases in beam-like structures.

Damage localization in beams based on the analysis of modal parameters

“…Damage-induced RNFC curves in beams are denoted as 𝑔 (𝜁) with 𝑗 being the mode number and 𝜁 being the dimensional coordinate. The RNFC curves of a simply-supported beam can be obtained as [6,7,10]:…”

“…Natural frequencies of a beam before and after damage are known as 𝜔 and 𝜔 . The damage indicator is defined as follows [6,7].…”

“…This requires a prior knowledge of material properties and geometrical dimensions of the inspected structure. The authors developed a damage indicator by combining damage-induced relative natural frequency change (RNFC) curves and the values of RNFCs [6,7]. The indicator was successfully used for damage localization in beam-like structures without knowledge of material properties and geometrical dimensions.…”