Model-based SHM: Demonstration of identification of a crack in a thin plate using free vibration data

In this paper a model-based approach to identifying a single crack in a thin, clamped plate undergoing free vibration is described and demonstrated experimentally. Data are gathered from only three resistive strain gages, placed at arbitrary orientations and locations far from the crack. The time series response of the gages to a single impact excitation are then used to estimate the crack parameters that characterize the damage using an efficient finite-element model of the plate. The approach is demonstrated effective in identifying crack location, orientation and length, as well as credible intervals for each. The results show that even with limited, noisy vibration data valuable information regarding the damage state can be successfully estimated.

► The four parameters of a single crack in a thin plate can be accurately identified.
► A Bayesian method is used so that rigorous confidence intervals can be found.
► The effectiveness of the technique is demonstrated with experimental data.
► No reference data is needed, but users must be able to model the system accurately.
► Only a single free response is needed, and only three foil strain gages are used.