Localization and quantification of damage by frequency based methods : Numerical and Experimental applications on bending vibration beams
Résumé
The sudden growth of damages can cause catastrophic failure of structures or mechanisms that lead to un- planned shutdowns of machines and production lines. If a damage remains undetected and reaches a critical size, sudden collapses and failures can happen. To overcome these problems, it is essential to detect these damages before they reach their critical state. The presence of damages can alter the structure which reduces the bending stiffness and modify the modal parameters and the natural frequencies. One of the most suitable monitoring methods to define the presence of damage and assess the structure is vibration based structure health monitoring (VBSHM). The objective of the work is to localize and quantify the damages with the considera- tion of eigenfrequencies of healthy and tested structures. Hence, a methodology for damage identification in structure using frequency shift coefficient (FSC) is presented. Numerical finite element models (2D and 3D) are performed and correlated to obtain a damage library for the cantilever beam structure. Based on the cost function, Young’s modulus of 2D and 3D models are iteratively updated to closely match the frequencies of the reference beam. The approach also quantified geometry damage with vibration measurements on cantilever beams, which is related to an equivalent bending stiffness reduction by the use of FSC. The effect of severity of the damage is considered. Finally, the result is validated numerically through the identification of geometry damage.
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