Experimental identification of square flexible plate deflections

This paper presents an experimental methodology for determining deformations of a flexible square plate under distributed loading on its surface using real-time holographic interferometry. A technological sequence for experiment preparation and execution has been developed, ensuring precise compliance with rigid clamping boundary conditions, high-precision stepwise variation of transverse load, and determination of corresponding displacement increments. A systematic experimental study of deformation of a square copper plate (60×60 mm, 300 μm thickness) under hydrostatic pressure with linear distribution along the plate height due to its vertical orientation was conducted. Three base loading levels corresponding to average pressures pavg ≈ 300, 3330, and 6670 Pa were investigated, with series of incremental increases for each level. Thirty high-quality double-exposure holograms containing from 3 to 71 interference fringes were obtained. The effect of geometrical stiffening of the flexible plate at large deflections was experimentally demonstrated: the tangential stiffness at average pressure 6370 Pa exceeds the initial stiffness of the undeformed plate by more than 4 times. The developed methodology provides displacement field determination with spatial resolution up to 70+ fringes over the 60 × 60 mm area and accuracy in normal displacement of λ/2 ≈ 266 nm. The obtained experimental data create the foundation for subsequent quantitative verification of theoretical models of nonlinear thin plate deformation and identification of real mechanical characteristics of the material and boundary condition parameters.