| 摘要 |
The non-destructive testing of materials, particularly coarse grain materials such as the carbonaceous materials used in the anodes and cathodes of an aluminium smelting furnace, using longitudinal compression waves employs a waveguide to apply the waves to a specimen, the and specimen having a cross-sectional dimension Dg of between 3 and 5 times the material average grain size Dg. Alternatively, or in addition, the waves used preferably are of effective wavelength from about 30Ds to 50Ds. Alternatively, or in addition, the effective wavelength of the waves is preferred to be approximately equal to the length of the sample; the necessary very long samples may be obtained by connecting a plurality of smaller elementary samples end-to-end. The apparatus may include a controllable furnace for cycling the sample to determine the change with temperature of the physical characteristic that is being measured. The methods and apparatus employ relatively low frequencies, in the sonic range, and high powers; although particularly suited for measurements with coarse grain materials they are also very effective with more usual fine grain materials, such as ceramics.
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