Analysis of sensor placement in beams for crack identification

Abstract

A previous study has shown that the mode shapes of a beam are more sensitive to damage than other vibrational parameters, thus making them better suited for crack identification purposes. However, they have the disadvantage of being more difficult to be measured. To overcome this difficulty, an interesting idea is to monitor changes produced by cracks on the mode shapes only in a few strategic points, instead of performing a complete experimental modal analysis. Considering this possibility, the aim of the present work was to determine the most appropriate locations for installing sensors in beams in order to identify and characterize structural damages. The effect of different locations of cracks on the mode shapes of beams was studied through a numerical computational model using the finite element model. The results were plotted in 3D graphs relating the relative nodal displacement of damaged and intact beams with the crack position and the location of the point analyzed. Through the analysis of these graphs, it was possible to point out the most adequate sites for placing sensors aiming at identifying cracks in a beam in fixed-free and fixed-fixed boundary conditions. Aiming at testing the results, an optimization problem for crack identification was proposed and solved through genetic algorithm GA. The cracks were identified with an accuracy that is appropriate for engineering applications, showing that the proposed method is effective and could be used in Structural Health Monitoring SHM issues. Limitations on its use were also discussed.

Preface to the special issue of the International Symposium on Solid Mechanics (MecSol 2017)

“…• X-FEM, G-FEM, and BEM: crack propagation and X-FEM modelling (Angelo et al, 2018); G-FEM modelling (Sato et al, 2018) and dynamic analysis (Weinhardt et al, 2018); BEM analysis of buckling of anisotropic plates (Monteiro and Daros, 2018), and 3D frictional contact (Ubessi and Marczak, 2018). • Structural Reliability Methods and Reliability-Based Design Optimization: Multi-objective optimization (Passos and Luersen, 2018) and experimental crack identification (Oliveira Filho et al, 2018). • Multiaxial and Fretting Fatigue: identification of fatigue limits and continuum damage mechanics (Castro and Bemfica, 2018), stress-life curves for alloy steels (Duran et al, 2018) and assessment of fatigue limits (Bandeira et al, 2018).…”

A Novel Low-Velocity Impact Region Identification Method for Cantilever Beams Using a Support Vector Machine

“…Vibration mode changes are more correlated with structural damage; however, since high-order modes are di cult to measure accurately, Vafaei and Alih [1] proposed a damage identi cation method based on the arti cial neural network and the rst-order mode. To overcome the disadvantage of mode shapes being more di cult to be measured, Oliveira Filho et al [2] performed some work to study the optimization of the sensor installation position on beam structures. Ghannadi and Kourehli [3] proposed a modal test analysis model to estimate unmeasured mode shapes for damage assessment of the cantilever beam.…”