Damage identification in rectangular plates using spectral strain energy distribution

Abstract

In this paper, a vibration-based damage detection method designed for thin plates is proposed. The method bases on the relation existing between the strain energy stored in the plate in several vibration modes and the respective natural frequencies. For any mode, the strain energy results as sum of the energies stored in all plate elements in that mode. It depends on the square of the mode shape curvature achieved in each element location for the given vibration mode. As a result, the energy distribution along the plate is different for each mode. By reducing the rigidity of one plate element due to a damage, the frequencies will drop in a different manner, depending on the damaged element location. This permits to define patterns that characterize the dynamic behavior of the plated for any damage location. Actually, the patterns are derived from the normalized frequency shifts attained by numerical simulations. Herein the patterns that characterize a centrally located damage of different extent are consequently derived by means of the finite element analysis and used as a benchmark in the damage detection process. These patterns are successfully used to recognize, localize and quantify damages from measurements on in real plates.