Assessing multiple cracks in beams by a method based on the damage location coefficients

Gilbert-Rainer Gillich,Alexandra Teodora Aman,Codruta Oana Hamat,Dorian Nedelcu,Tiberiu Manescu

doi:10.21595/vp.2019.20661

Gilbert-Rainer Gillich, Alexandra Teodora Aman + Show 3 more

Open Access

https://doi.org/10.21595/vp.2019.20661

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Abstract

In this paper, we analyze the case of structural integrity assessment when the beams have several cracks. The relationship between the location and the severity of one crack and the resulting frequency shift is known. That is why we can design databases containing many defects for which we can calculate precisely the frequency changes and the subsequent damage location coefficients. When the natural frequency evolution of several vibration modes is monitored, we can find alteration due to the crack. Comparing the results of the measurements with the values contained in the database, for instance by involving a bin-by-bin dissimilarity estimator, we can find the location and severity of the crack. For multiple cracks, this approach was not investigated. In this study, we design a database for two cracks affecting at the same time the beam. For these cracks, which have various severities and locations, we calculated the frequency changes by applying the superposition principle. Afterward, we find the frequency shifts for a test structure by means of the finite element method. The comparison between the damage location coefficients in the database and the signature of the damages achieved by simulation is made by the software we have developed in Visual Basic for Application in Excel. We succeed to find the severity and the location of the two cracks for all considered crack configurations.

Highlights

The evaluation of structural integrity based on vibration analysis is a major concern of the researchers
If more vibration modes are involved, the comparison is made by using dissimilarity estimators that perform a bin-by-bin evaluation [10,11,12]
We propose in this paper an algorithm to find the location of multiple cracks and show how it ISSN PRINT 2345-0533, ISSN ONLINE 2538-8479, KAUNAS, LITHUANIA

Summary

Introduction

The evaluation of structural integrity based on vibration analysis is a major concern of the researchers In this regard, numerous techniques that permit assessing the size and position of a crack in the beam exist. Numerous techniques that permit assessing the size and position of a crack in the beam exist They consider either the change in the natural frequencies, mode shapes, modal curvatures or modal damping [1,2,3,4]. The mathematical relationship between the damage parameters, i.e. the location and severity, and the frequency decrease is presented in the papers [5,6,7]. ASSESSING MULTIPLE CRACKS IN BEAMS BY A METHOD BASED ON THE DAMAGE LOCATION COEFFICIENTS. The functionality of the algorithm is tested for the frequencies obtained by means of the finite element method (FEM) for the healthy beam and a series of simulated damages

Theoretical background

The proposed algorithm

Findings

Conclusions