In this paper diagnostic methods are applied is order to study the behaviour of the structure as they are being excited and response to the exciting reasons.
For this purpose, measurements are taken on the field of time and form the, using spectrum analysis., spectra of frequency are taken for studying to the amplitude of the frequencies or to the position of each frequencies or to the position of each frequency of the field of frequencies. It is obvious there is a connection between the condition of stress and strain of the structure between the condition of stress and strain of the. structure and the position and the amplitude of frequencies that are taken form the analysis of the measurements.
So controlling the frequencies for some kind of measurments it is easy to control the condition of the structure.
Otherwise using simulation and optimization methods it is possible first to build a model and after to examine this model for several types of fatigue.
Taking always the spectra of measurements and comparing them by themselves it is possible to find the optimal model and taken to apply the conclusions to the structure.
Finally it could be said that this work can be applied during the stage of design of the structures as it helps by control. The simulating models in order to find the optimal structure.