Damage Detection in Structural Systems: A Modal Approach.

Kurzfassung

The dynamic behavior of a structural system is influenced by damage to the structure. Extraction of reliable information about the position and extent of damage from vibration measurement results would transform modal analysis into an attractive tool for non-destructive assessment of structural integrity. The advantages of a modal approach for structural health monitoring would be remarkable for a wide range of applications: aircraft, space structures, off-shore platforms, and basically all systems characterized by limited accessibility and high inspection costs. Therefore, it is no wonder that in the last few decades much research has been done in this field. In spite of the simplicity of the basic idea, until now no approach has established itself as the way to be followed. On the contrary, the opinion that damage detection by modal techniques would be possible only with extremely accurate measurement results has become more and more popular. The new technique proposed in this paper performs the damage detection on the basis of measured modal properties of the structure, with the prerequisite that a reliable mathematical model of the undamaged structure is available. The method is virtually able to operate on all structures for which a modelization with the finite element method is possible. The damage localization is supplied with a resolution which is correlated with the element dimensions in the model. The quality of the detection is influenced by the accuracy of the measured modal parameters, as well as by the amount of available data. In order to verify the proposed method, some numerical simulations and experimental tests were performed on a cantilever beam. This paper presents some of the results. Not only large zones of stiffness degradation, but also small cracks are successfully detected in the test structure.