Abstract
Structural health monitoring (SHM) methods based on the cumulative second harmonic Lamb waves show attractive advantages. An ideal nonlinear parameter should allow precise characterization of the cumulative effects of the distributed nonlinear sources such as the material nonlinearity of a plate (MNP), in the presence of other unavoidable localized nonlinear components. While highlighting the deficiencies of the traditional nonlinear parameter (TNP) in the nonplanar cases, a refined nonlinear parameter (RNP) is proposed. Through compensations for the wave attenuation associated with the wave divergence, the new parameter entails a better characterization and differentiation of the cumulative MNP and other noncumulative localized nonlinear sources. Theoretical findings are ascertained by both finite element (FE) simulations and experiments, through tactically adjusting the dominance level of different nonlinear sources in the system. Results confirm the appealing features of the proposed RNP for SHM applications.
Highlights
The nonlinear-Lamb-wave-based structural health monitoring (NL-SHM), a technology combining the advantages of both Lamb-wave-based inspections and nonlinear ultrasonics, has been gaining popularity in recent years
Compared with the commonly used high-frequency mode pairs, the use of the S0 mode Lamb waves in the low-frequency range is attractive for the structural health monitoring (SHM) applications in terms of the flexibility it offers in choosing the excitation frequencies and the lower demand for the measuring equipment
A clear cumulative effect can be observed from the results
Summary
The nonlinear-Lamb-wave-based structural health monitoring (NL-SHM), a technology combining the advantages of both Lamb-wave-based inspections and nonlinear ultrasonics, has been gaining popularity in recent years. Taking Lamb waves as the information carrier, it is possible to interrogate a large area of a thin-walled structure with a sparse sensor array for the realtime and online monitoring of its health status [1,2,3] Owing to their high sensitivity to microstructural changes, nonlinear Lamb waves allow the early detection of the structural damage or even material degradations, facilitating the further maintenance decisions [4,5]. Compared with the commonly used high-frequency mode pairs, the use of the S0 mode Lamb waves in the low-frequency range is attractive for the structural health monitoring (SHM) applications in terms of the flexibility it offers in choosing the excitation frequencies and the lower demand for the measuring equipment Localized nonlinear sources, such as the instrumental nonlinearity, adhesive nonlinearity (AN) [18] and so on, are often considered as typical non-damagerelated nonlinear sources. AN is chosen as a typical example of the localized nonlinear sources, to be investigated in this paper
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