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ON THE DIAGNOSIS OF HURDIS CEILING SLABS USING NON- LINEAR ULTRASONIC SPECTROSCOPY METHODS

The paper is focused to possibility of utilization of the non-linear phenomena arising in connection with the propagation of ultrasonic waves in solids to diagnostic ceiling slabs Hurdis. Breakdowns of ceiling structures made of Hurdis slabs have be problem in building industry of today. Since the early 90’ several thousands of buildings with these ceilings were constructed. As a result of this failures may appear again in the following years. Therefore it is necessary to develop and check suitable methods enabling the testing of endangered ceiling structures and considering their static reliability. Non-lineary ultrasonic spectroscopy methods are based on the fact that a crack induced non-linearity makes an extremely sensitive material impairment indicator. Due to the presence of defects, the atom potential energy ceases to be exactly harmonic. Second and third harmonic frequencies signals arise. The intact material region generates almost zero non-linearity. Another important benefit results from the higher sensitivity in relation to the defect size and the system immunity to the measuring of smaller signal reflections, as the sample edges lack any non-linear properties and consequently, there are no narrow-band signals arising from these reflections. Non-linear ultrasound spectroscopy methods due to their supposed higher sensibility and more exact characterization of material quality and reliability appear as perspective for both aims.