Détection de fissures dans les poutres d'acier : une nouvelle approche par balayage de mesures de vibrations

Abstract

In the last few years, the techniques of detection and identification of damage in structures benefited from important research efforts. Several methods of non-destructive damage detection, such as techniques based on modal analysis, were developed in addition to the traditional methods. The difficulties encountered by these techniques are their low performance, considering the industrial requirements to detect cracks as early as possible.In this work, a retrospective of the principal modal parameters is done, in order to discuss their sensibility for identifying precociously a transverse crack in a steel beam (shaft, tube, bars, etc.), and if possible to find more sensitive properties or techniques. Our preliminary experimental results, as predicted by a bibliographical study, showed that the parameters used have a low sensitivity due to their dependence on measurement errors and to the low variation of the total stiffness rate. In fact, although testing has covered a broad range of modes, results remained always below our hopes to detect early cracks. However, it turned out, according to the theory, that local flexibility is significantly affected in the case of small cracks. Investigating other parameters that have good local characteristics seems to be the best way to improve the sensitivity of techniques allowing one to detect cracks at an early stage. Parameters such as local stiffness were used. A comparison of results concerning the sensitivity of various properties as well as of the introduced parameters is presented and discussed in this article.