Model updating improves the correlation between the response of the real structure and the response of the finite-element (FE) model; however, the selection of the updating parameters ...(parametrization) is crucial for its success. Using full-field modal shapes, a large number of parameters can be updated, e.g., the Young’s moduli of all the finite elements; however, the structural response is not necessarily sensitive to an arbitrary parameter, making the optimization problem ill-conditioned. Additionally, the computation of the full sensitivity matrix is not feasible for relatively large FE models. Not all locations are equally important for model updating; at locations of the highest mechanical loads, more focus is required. In this research, the updating parameters are based on the curvature of the 3D full-field experimental shape, where locations with high curvature are associated with high sensitivity. The assumption is initially researched with the Euler–Bernoulli beam elements and second-order tetrahedrons. The proposed method is investigated on numerical and real experiments, where successful updating was confirmed. With the proposed parametrization and updating approach, a geometrically complex structure is parametrized and the parameters updated without significant user input, generalizing the model-updating procedure.
•3D full-field modal shapes are identified using the frequency-domain triangulation.•The numerical model is parametrized based on each measured full-field modal shape curvature.•Interior Point Method (IPM) is used to update the numerical model.•Anomaly on the structure is successfully identified on the numerical and real experiments.
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•The Spectral Optical Flow Imaging method is extended for multiview measurements.•3D operating deflection shapes are measured using a single still-frame camera.•The effects of ...multiple-view triangulation on measurement precision are observed.•Compared to DIC, image data sizes are reduced by two orders of magnitudes.•Compared to DIC, processing times are reduced by four orders of magnitude.
To measure high-frequency 3D vibrations, multi-camera, high-speed imaging hardware is normally required. An alternative using still-frame cameras was recently introduced with the Spectral Optical Flow Imaging (SOFI) method. In this research, the SOFI method is extended to multiview measurements of spatial operating deflection shapes. This is achieved by utilizing harmonically controlled illumination to perform an analogue Fourier transform on image-intensity data in multiple camera views. The obtained multiview displacement spectra are combined with geometrical data to perform frequency-domain triangulation and reconstruct spatial deflection shapes. By introducing additional camera views into the image-based measurement, its field of view is extended and the signal-to-noise ratio of the final result is increased. For linear, time-invariant mechanical structures under stationary excitation, full-field 3D measurements of high-frequency vibrations can be performed using a single still-frame monochrome camera. The proposed method identifies displacements in the frequency domain directly on the camera sensor, resulting in orders-of-magnitude smaller data sizes and post-processing times compared with conventional multiview image-based methods.
