IDENTIFICATION OF INHOMOGENEOUS COVER LAYER BY NON-CONTACT ULTRASONICMETHOD – STUDIES FOR MODELMATERIALS

Abstract

The paper is devoted to validation of the method of identi-fication of inhomogeneous cover layer of materials. Theidentification procedure applies non-contact ultrasonictechnique of surface waves with air as the couplingmedium and optimisation method which searches the bestfit of the Thomson-Haskell model of surface waves in lay-ered medium to experimental data. Within the work theexperimental studies were performed for two material sys-tems: PMM (cover layer) over aluminium and the concreteclass C8 (cover layer) over the concrete class C20. Thethickness of the cover layer was from few millimetres tofew centimetres. The experiments were performed overfrequency range from 40 to 250kHz. The cover layer mim-ics the degraded layer of structural materials. The identifi-cation procedure uses dispersion curves of pseudo-Rayleigh waves and the identified parameters are thicknessof the cover layer and velocities of the shear waves in thematerials of layers.