A Modal Method for Structural Health Monitoring.

Abstract

Among the new perspectives opened by the recent developments in the field of adptive structures is an interesting future for structural health monitoring. A structure with embedded actuators and sensors represents the best environment for an integrity assessment device based on the monitoring of the systems's vibrational behavior. For this purpose, an algorithm is needed that is able to extract reliable information from vibration measurements about the position and extent of damage in a structural system. This idea is not new; many contributions can be found in the literature. Nevertheless, until now no approach has established itself as the way to be followed. On the contrary, the opinion has become more and more popular that damage detection by modal techniques would be possible only with extremely accurate measurement results. The techniques examined in this paper give confidence to the possiblility of realizing a reliable modal damage diagnosis under normal measurement conditions and also when a small amount of measured modal data is available. A recently proposed detection approach, based on the measured eigenmodes, is completed here by a new method which supplies an independent diagnosis only on the basis of the measured eigenfrequencies. Both approaches require the availability of a reliable mathematical model of the undamaged structure. Numerically and experimentally tested on a cantilever beam, the approaches are virtually able to operate on all structurtes for which a modelization with the Finite Element is possible. The damage localization is supplied with a resolution that is correlated with the element dimensions in the model. Some of the results are presented in the paper; the information on.