Experimental damage localization in beam by using natural frequency distribution and modal strain energy change ratio based methods

Abstract

Two methods for a beam like structures damage identification using frequencies distribution and Modal Strain Energy Change Rate (MSECR) are presented in this paper. Firstly, the measured frequencies sensitivity is improved, and the frequency distribution is used to determine the suspected damage location. Secondly, the change of modal strain energy before and after the occurrence of damage is employed to locate the damage location. To conduct these studies, an experimental modal analysis program was carried out on a cantilever Bernoulli-Euler beams subjected to a controlled crack levels and the first seven modes (natural frequencies and mode shapes) were extracted and used to localize the damage. The effect of crack sizing in the local stiffness and in the frequency fluctuation was evaluated. The localization magnitude of the damage by the frequency distribution was predicted within an acceptable error range. The experimental MSECR was computed and the location of the damage was accurately identified especially for crack sizing as small as 10 % of the beam height. Finally, finite elements models were built and validated, MSECR method was applied and the results demonstrate that the method is capable of localizing damage for beam structure