Location of the corrosion damage in rectangular plates

The presence of corrosion influences the dynamic behaviour of plates, by modifying its natural frequencies and mode shapes. Many methods to assess damages in structural elements are known, but they mainly address to the geometric discontinuities, where mass loss is insignificant. In some of the prior research, we have got success in achieving a mathematical relation between damage geometry and frequency shifts. Since the mass decrease is also associated with numerous corrosion mechanisms, the idea of this paper is to establish the influence of mass changes in the natural frequencies of plates and including this information in a baseline, to apply it in processes for corrosion assessment. Thus, by research the evaluation of frequency changes due to mass loss and stiffness decrease has been followed. The finite element analysis was performed, considering corroded area as being simulated by a constantly decreasing plate thickness. In this way, is highlighted the correlation between frequency changes in the transversal vibration modes and mass loss. The dependency between mass loss and frequencies is accomplished, as a mathematical relation as well. This relation is associated with another relation, who predicts the frequency decreases due to stiffness reduction, in order to find the curves of frequency shifts and promote them as a baseline for corrosion assessment. Also, a corrosion assessment method, based on the contrived frequency shift curves, has been developed and proved as reliable and easily applicable.