Structural damage identification in laminated structures using FRF data

A damage identification technique based on frequency response functions (FRF) sensitivities is presented. This technique leads to a set of linear equations, which is solved using an algorithm that constrains the solution to be physically admissible. Damage simulation and identification on a laminated rectangular plate is performed. The influence of the number of natural frequencies and mode shapes used on the FRF computation, as well as the frequency range, the excitation location and the number of measured degrees of freedom (m-DOF) is studied. Numerical tests show that the best accuracy is obtained when using the dynamic expansion of the m-DOF. It is also demonstrated that for small damage the errors are the main influence, whereas for large damage the model incompleteness becomes the most important factor in the results. A procedure for weighting and deletion of equations is used to obtain better identification results. The results of the technique presented in this paper versus those obtained by a technique based on modal data is also discussed.