Linear and Nonlinear Damage Detection Using a Scanning Laser Vibrometer

Because a Scanning Laser Vibrometer (SLV) can perform vibration measurements with a high spatial resolution, it is an ideal instrument to accurately locate damage in a structure. Unfortunately, the use of linear damage detection features, as for instance FRFs or modal parameters, does not always lead to a successful identification of the damage location. Measurement noise and nonlinear distortions can make the damage detection procedure difficult. In this article, a combined linear-nonlinear strategy to detect and locate damage in a structure with the aid of a SLV, will be proposed. To minimize the effect of noise, the modal parameters will be estimated using a Maximum Likelihood Estimator (MLE). Both noise and nonlinear distortion levels are extracted using the residuals of a two-dimensional spline fit. The validation of the technique will be performed on SLV measurements of a delaminated composite plate