Damage Evaluation of Free-Free Beam Based on Vibration Testing

Abstract

Damage can be detected by vibration responses of a structure. Damage changes the modal properties such as natural frequencies, mode shapes, and damping ratios. Natural frequency is one of the most frequently used damage indicators. In this paper, the natural frequency is used to monitor damage in a free-free beam. The modal properties of the intact free-free beam are identified based on a setup of 15 accelerometers. A finite element model is used to model the free-free beam. Three models are considered: beam (1D), shell (2D), and solid (3D). The numerical models are updated based on the first five bending natural frequencies. The free-free beam is damaged by a rectangle cut. The experiment is re-setup and the model properties of the damaged beam are re-identified. The cuttings are modeled in the numerical simulations. The first five numerical bending natural frequencies of the damaged beam are compared with the experimental ones. The results showed that the 1D beam element model has the highest errors, while the 2D and 3D models have approximately the same results. Therefore, the 2D representation can be used to model the damaged beam for fast computation.

Damage detection in steel plates using feed-forward neural network coupled with hybrid particle swarm optimization and gravitational search algorithm

“…In (Nguyen et al, 2020a), types of elements, e.g. beam element, shell element, and solid element, were used to investigate the variation of mesh size of the FE model.…”

“…This guaranteed good accuracy of the FE results. Details of the convergence study are given by Nguyen et al (2020a).…”

“…It is easy to obtain natural frequencies by using the dynamic response of structures. A simple excitation induced by a hammer blow or under ambient load (Ho et al, 2019;Nguyen et al, 2020a) can provide values of natural frequency, and mode shapes of laboratory beams with high accuracy. Ho et al (2020) used piezoelectric sensors to obtain the vibration frequencies of cables of a real cable-stayed bridge under ambient load.…”

Characterizing the Frequency Response of Compliant Materials by Laser Döppler Vibrometry Coupled Acoustic Excitation

“…According to Figure 5a, boundary conditions were introduced by fixing the lateral sides of the half-cane sample in its length direction. Meshing was optimized by discretizing the model with 0.1 × 0.5 mm 2 SHELL181 elements, as shown in Figure 5b, as Nguyen et al [25] showed that 2D elements are suited for this type of simulation. According to Figure 5a, boundary conditions were introduced by fixing the lateral sides of the half-cane sample in its length direction.…”