Comparative study of vibration measuring techniques applied to aluminum beams with localized damage

Abstract

When a structural damage changes the characteristics of stiffness and mass of a mechanical system, the dynamic behavior of this beam will also change. Only a few studies about the correlation between damage and the effect caused in dynamic behavior can be found. Based on this, this study will analyze the behavior of the natural frequencies and damping ratios of four aluminum beams, with and without damages. This work aims to determine the error between the two methods of data acquisition and the effects of the damage inflicted on the shape modes, natural frequencies and damping ratios for each beam. To achieve the purposes, initially, a numerical FEM simulation will be performed, followed by experimental impact tests, aiming to obtain the estimated natural frequencies and damping ratios. After this, damages will be made on these beams and the impact tests will be repeated for each beam. The FEM analysis will be performed using Ansys. For the impact tests, two data acquirement methods will be used during the impact testing, the first, using accelerometers to obtain the vibration response, the second using a Brüel & Kjær’s sound level meter. The obtained data will be compared and will be possible to determinate the error between the natural frequencies measured using both methods. The results obtained will be used to correlates the dynamic behavior with the damages inflicted on the beams. This paper allowed analyzing the usage viability of the sound level meter to measure the output of a vibrating system, considering certain limitations. In addition, the damage effects on the natural frequencies of the beams.