Steady State Shift Damage Localization: a super-element approach

The steady state shift damage localization (S3DL) method localizes structural deterioration, manifested as either a mass or stiffness perturbation, by interrogating the damage-induced change in the steady state vibration response with damage patterns cast from a theoretical model. Damage is, thus, localized when a postulated damage distribution, under ideal conditions, yields a perfect mapping to the experimental feature. Obviously, this approach poses a constraint on the accuracy of the theoretical model, which, typically, is obtained through finite element (FE) modelling. In order to achieve the required accuracy when examining complex structures, an extensive amount of degrees of freedom (DOF) must often be utilized. Since the interrogation matrix for each damage pattern depends on the size of the system matrices constituting the FE-model, the computational time quickly becomes of first-order importance. The present paper investigates two sub-structuring approaches, in which the idea is to employ Craig-Bampton super-elements to reduce the amount of interrogation distributions while still providing an acceptable localization resolution. The first approach operates on a strict super-element level, while the second combines super-elements and shell elements. The applicability of the proposed approaches is tested in an experimental procedure with a residential-sized wind turbine blade introduced, alternately, to failure of the trailing edge and a modification of the mass.