It is important to measure the powder bulk density distribution formed in particulate processes, from the point of view of the design method based on powder properties. However, measurements have not yet been sufficiently developed. In this paper, the radiograph method, by which the powder bulk density distribution in a cell can be considered to be measured qualitatively and quantitatively, was noticed. The initial powder bulk density distributions in a cell were systematically radiographed for five kinds of industrial powders, and the clearness of each X-ray picture was discussed. The result was that the optimum region of the radiographing conditions (X-ray pipe voltage and X-ray radiating time) was pointed out to exist for each powder.

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The problems of predicting the bulk density and the principal stress direction in a high-rate charge from a high position, which is one of the latest methods, are investigated experimentally. The results obtained show that the effects of rate of charge on the static wall pressures in a vertically-sided silo are not very large, but that in the convergent hopper they are sufficiently large to be taken into account for design purposes.
Different stress states in the convergent hopper of previous works have been proposed in the theoretical prediction based on the measurements of wall pressure. That is the major principal stress direction with cohesionless bulk solids, 2ε, attains to be zero deg. in the high-rate charge, which is vertical to the hopper wall.

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