The Measurement of the Impact Time to Evaluate the Plate Thickness

The present study proposes a simple and low-cost indirect method for estimating the thickness of plates by measuring the contact time (TC) generated by the impact of a freefalling sphere. The theoretical model has been developed on Tsai approximation of Zener’s theory, which describes the dynamic interaction between the sphere and the plate taking in account the propagation of flexural waves. The methodology was validated through FEM simulations and through an extensive experimental campaign, where the contact times were measured using a simple electrical circuit. The results show excellent agreements between predicted and actual thicknesses, with relative errors below 3% for λ < 1.5 (where λ is the inelasticity parameter). For very thin plates and highly deformable materials, the above accuracy decreases due to flexibility and plastic deformation. We believe the proposed approach to be particularly promising in non-destructive testing applications within several scenarios, where speed, cost-effectiveness, and safety are essential requirements.