A Hybrid Experimental-Numerical Approach for Structural Health Monitoring Using Sem and Measured FRF

Khaled M.  Ahmida Al-ashouri

doi:10.66411/jer.v41i1.138

Authors

Khaled M. Ahmida Al-ashouri Department of Mechanical and Industrial Engineering, Faculty of Engineering, University of Tripoli Author

DOI:

https://doi.org/10.66411/jer.v41i1.138

Keywords:

Structural damage, Vibration-based methods, Spectral element method, wave propagation in structures, hybrid approach

Abstract

Vibration-based damage detection methods have gained significant attention due to their non-destructive nature in what is referred to as Structural Health Monitoring (SHM). The SHM is essential for ensuring safety, reliability, and long-term performance of engineered systems; non‑destructive vibration-based techniques are particularly valuable because they allow early detection of damage without interrupting service. Many approaches require information about the stiffness matrices of the structure, as in Modal Strain Energy (MSE) method, which becomes somehow difficult to obtain in real structures. This paper proposes a new hybrid computational approach for SHM, based on calculating the potential energies from the measured Frequency Response Functions (FRFs), due to elastic deformations in the structure. This study aims to develop and validate a hybrid, frequency-domain method that identifies and localizes damage by comparing potential energies computed from measured FRFs collected at multiple points before and after the damage. The proposed method uses Spectral Element Method (SEM) formulations for 3D frame waveguides (rod, shaft, and beam) to compute the potential energies from FRFs. Therefore, avoiding the need for explicit stiffness matrices as required by other approaches. Numerical simulations across several damage percentages demonstrate that changes in the computed potential energy reliably indicate damage occurrence and location. Two damage localization indices were used; an overall index; and a resonance-based index. The proposed methodology successfully identified damages as low as 5%. Noise-contaminated FRFs are used, by incorporating a white Gaussian noise. This is done by introducing a signal-to-noise ratio (SNR) of 25 dB into the FRFS to simulate experimental noise. This 25dB is usually considered the minimally acceptable SNR in FRF measurements. The main findings show that the method is simple to implement, as it only requires FRF measurements, and yields notable accuracy in damage detection and localization, supporting broader application of SEM-based techniques in practical SHM.

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