Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Patent
1993-11-05
1995-02-07
Raevis, Robert
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
G01N 308
Patent
active
053867319
ABSTRACT:
A method and apparatus for measuring the tensile strength of aggregate material comprising a device in which a layer of dust is applied to a metal electrode, and an electric field is applied in such a way as to induce a charge (negative or positive) on the outer surface of the dust layer. The electric field is then increased until particles break away from the upper surface as a result of the electrostatic force acting on the induced charge. From the balance of forces between the electrostatic (which is easily calculated from the configuration and applied voltage) and the cohesive attraction between the particles, the tensile force of the dust layer is determined. The breakaway point may be observed directly, or it may be detected by a photoelectric device designed to respond to light scattered by the particles as they are lofted from the surface. Alternatively, the breakaway point may be detected by sensing an electric current concomitant with the ejection of surface charge residing in the lofted particles.
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Pontius Duane H.
Snyder Todd R.
Raevis Robert
Southern Research Institute
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