2015. . No. 2(68) - Jun 2015, pp. 27-30
Low-Frequency Acoustic Method Based on Natural Oscillations Frequencies. Testing of the Method Application Possibility for Brick Grade Determination. The Results
Wide variety of bricks with maximum characteristic difference was beforehand picked out of different technological batches; they included both solid and hollow bricks of different types and sizes.
Research procedure is illustrated by measurements of solid red bricks.
In order to find the correlation between acoustic parameters and strength and to determine features of the correlation, the couples of bricks with almost equal natural frequencies (of maximal, minimal and average values by two from the inspected selection) were put to standard destructive strength test.
It has been established that correspondence between natural frequency and ultimate strength is similar for practically all types of bricks with a quite high value of correlation coefficient. It is reasonable to suppose that there is a stable correlation between acoustic and strength properties and accordingly there is a possibility for operational non-destructive strength testing on the basis of natural frequency measurements.
Keywords: free oscillation technique, natural frequency, building bricks, strength, ultimate compressive strength
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