Regularised Finite-Element Model Updating of a Thin-Walled Cylinder Based on Non-Contact Experimental Modal Analysis

Material removal changes the dynamics of thin-walled parts during machining, making an accurate pre-machining baseline essential for subsequent prediction. This study integrates non-contact testing, scan-based reconstruction and material-property updating into a free-state modelling workflow: laser vibrometry identifies the target frequencies, vision-based measurement extracts the end-face circumferential shapes, and three-dimensional scan data are reconstructed into editable CAD geometry. With geometry and Poisson’s ratio fixed, Young’s modulus E and density ρ are updated using a mean-square relative-frequency-error objective with Tikhonov regularisation, the weight being chosen by a discrete L-curve. Free-state frequencies identify the ratio E/ρ; regularisation selects a representative material-parameter pair under the specified prior and weight, while mode shapes provide morphological checks. In the case study on a thin-walled steel cylinder, the reconstructed model has a median absolute radial deviation of 0.0362 mm (about 1% of the mean wall thickness); the relative RMSE of the three target modes decreases from 1.71% to 1.00%, and that of the non-target modes excluded from the fit decreases from 0.68% to 0.65%, indicating comparable sub-percent aggregate errors with a small decrease for the examined free-state non-target modes. At a fixed weight, runs from two opposite initial directions converge to nearly identical material parameters, showing similar endpoints for the two examined runs under their respective search settings. Geometric, measurement and fitting errors are distinguished. Experimental assessment addresses the free state, complemented by a numerical demonstration under prescribed clamping conditions.