Measurement of the apparent density of green ceramic tiles by a non-contact ultrasonic method

Autores: Revel, G.M.
Fuente: Experimental mechanics
47 (5), 637-648

This paper discusses the problem of the measurement of the apparent density of green ceramic tiles during production. This is a fundamental parameter for the quality of the final product. In fact, the apparent density determines the entity of the dimensional shrinkage of the ceramic body during the firing of tiles, and it is proportional to the final mechanical resistance. Currently, non-destructive systems for the on-line measurement of this parameter are not available. The work presents an innovative method for non-intrusive measurement of the apparent density of green ceramic tiles during the production stage. This method uses non-contact ultrasonic probes. The time of flight of ultrasonic waves is measured during the transmission through the tile. From the time of flight, with the distance between probes known, the propagation velocity can be achieved, which is proportional to the apparent density. The conversion factor between velocity and apparent density is determi! ned by a calibration procedure with a reference method of known uncertainty, e.g. based on a hydrostatic weighing in a mercury bath. This experimental procedure is extensively validated in the work and supported by a theoretical model. The paper presents the theory on which this measurement method lays and the instrumental apparatus, and discusses in detail the analysis of uncertainty. In the end, the paper presents the results of an on-line application.

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