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Technique for Detecting Voids in Porous Materials

IP.com Disclosure Number: IPCOM000099501D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 33K

Publishing Venue

IBM

Related People

Batchelder, JS: AUTHOR

Abstract

Measuring the density of a solid material is a proven technique for detecting the existence of defects, such as voids in the material; the density in material with voids is lower than in pure material. Typically, such density measurements are made by weighing the material immersed in two different fluids (e.g., air and water).

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Technique for Detecting Voids in Porous Materials

       Measuring the density of a solid material is a proven
technique for detecting the existence of defects, such as voids in
the material; the density in material with voids is lower than in
pure material.  Typically, such density measurements are made by
weighing the material immersed in two different fluids (e.g., air and
water).

      There is a class of porous materials in which the act of
immersing the material in fluids changes its density; the fluid fills
pores and voids that the measurement should detect.  Alternatively,
there are materials that are damaged by immersion in convenient
fluids, or that are physically awkward to immerse.  In these cases a
density measurement can be made by weighing the material in a single
fluid (e.g., air) at two different densities.  This can be achieved
by changing the temperature of the fluid surrounding the material.

      For example, there is a buoyant force on an object in air given
by the volume of the object times the density of air (typically about
0.001 grams per milliliter at room temperature).  Changing the air
temperature some 15 degrees centigrade changes the air density about
5%, which changes the buoyant force on the object from the air by the
same amount.  If the weight of the object is measured to a precision
of 6 digits, the density can be determined to a few percent (assuming
that the density of the object is around 3).