ISSN:
1573-9139
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Conclusions High-porosity graphite contains two regions in which the speed of the USO varies with the pore size. When the pores are small relative to the ultrasonic wavelength, the USO speed increases within increase in the pore diameter to about 400μ (ratio of the USO wavelength to the mean pore diameterλ/¯D=3–4) and then decreases. The experimental results do not conflict with the analytically predicted relations between the USO speed on the one hand and the overall porosity, pore diameter variance, and Poisson's ratio for the intervening material on the other. The theoretical relation was calculated on the basis of MacKenzie's model of a porous material from the equations of the effective elastic moduli. An analysis was made of the relation between the resistivity of the specimens and the size of the pores. The resistivity data obtained confirms, together with the known thermal conductivity data, the validity of the above hypothesis about the variation of the speed of the USO. The results of this investigation can be used for a more precise determination of variations in the density and strength of graphite products.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01284158
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