This paper describes an apparatus based on a novel use of a powder bed, whereby the relationship between consolidation stress, tensile strength, and free volume of fine powder is measured. The powder to be tested is first initialized to a reproducible state. The initialized powder is next consolidated either beyond its own weight or below its own weight by means of a controlled flow of gas. An ultrasonic device measures the height of the bed, thus providing an average value of the powder free volume. Next the consolidated bed of powder is subjected to a slowly increasing gas flow, so directed as to put the powder under tension. The overpressure causing the powder to break provides a measure of the tensile strength of the powder, which in turn is a function of the consolidation and free volume. The relationship between consolidation stress, tensile strength, and free volume is related to powder flowability.
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