The flowability of a cohesive powder was represented by a ratio of the unconfined yield stress to the unit weight of a bulk solid. An expression of the flowability was studied on the basis of a power function which was assumed between an applied force and a cohesive force at the contact of particles adjacent to each other.
The expression was supported by the results of shear tests for 17 kinds of dry cohesive powders which had a range of 2 to 40μm in the specific surface diameter. It's diameter ratio of 1.4 to 5.5. The flowability was expressed in terms of the specific surface diameter of the powder, the major consolidation stress and two experimental coefficients. The coefficients seemed to be proper for the powder material.
