Hiroshi Tsunakawa

Measurements of the failure properties of granular materials and cohesive powders

Abstract A direct shear tester equipped with a press loading system has been employed to measure the failure properties of granular materials and cohesive powders. An advantage of this tester is that a yield locus for such materials can be obtained from one shear test by a continuous line. The yield locus for granular materials has been directly drawn as a straight line on an X-Y recorder chart having the normal stress as the abscissa and the shear stress as the ordinate. Yield loci for cohesive powders have also been drawn as convex curves on the recorder chart, having reduced shear and reduced normal stress axes. They are therefore reduced yield loci. The shapes of the loci obtained for a range of initial consolidation stresses of 10 to 350 g/cm2 are satisfactorily described by the Warren Spring equation. When this equation is rewritten with reduced stresses, it can be expressed in terms of three dimensionless parameters. The values of these parameters, which are determined from the measured loci, seem to depend on the bulk density of the sample.

The vertical force of bulk solids on objects in bins

The vertical force exerted on discs, spheres and horizontal square bars in test bins was measured during gravity flow of bulk solids. Approximate methods for estimating the vertical force on such objects were developed from the equation which expressed the stress in a conical mass flow hopper. With three adjustable parameters, good agreement was obtained between experimental and computed results for discs, provided the disc diameter was more that five times as large as the particle diameter. Identical parameters for a given material were found to be applicable in analyses for spheres and horizontal square bars.

The Flow Rate Equation of Granular Materials from Pyramidal Hoppers

An investigation of the flow of granular materials from pyramidal hoppers under the influence of gravity has been carried out and the influence of the hopper angle, outlet area and its shape on the flow rate has been studied.Consequently, it was found that the flow rate measured was proportional to 1.33 power of the effective discharge area, and the influence of hopper angles was different for each material. But, it is generally able to be expressed that the flow rate is proportional to (tanθ/2)-n. For spherical materials n=0.33. For irregular shape materials n=0.33 or 0.50, but there exists a critical hopper angle. For hopper angles greater than the critical hopper angle, the flow rate is independent of hopper angles. The critical hopper angle of granular materials is approximately correlated with its surface kinetic angle.It was found that the discharge coefficient of pyramidal hoppers with the square discharge outlet was approximately correlated with the surface kinetic angle of granular materials, more exactly it was considered that the discharge coefficient was determined with a particle size and shape.Also, it was found that the discharge coefficient of pyramidal hoppers with the rectangular discharge outlet was smaller than that of the square, and correlated with the effective hydrolic diameter ratio.

Flow Rate of Granular Materials in Water through Holes perforated In a Plate

水中における粒体の多孔板からの流出速度を測定した。流出速度は孔の数に比例しては増加せず, ある限界流出速度に近づくことがわかった。流出速度は, 先に求められた単一孔オリ7イスの場合と同様な方法で計算が可能である。