Internal Friction Factors and Normal Stress Distribution of Fine Powder by Constant Vertical Shear Load Test

The shearing stresses were measured by a shearing tester for the packed bed of several kinds of fine powder. The normal stress distribution aboe and below the shearing plane were also measured.The characteristics of fine powders were classified in terms of the trend of the shearing process and normal stress distributions.The internal friction factor (μm, s) was calculated from the steady state value of the measured shearing stress(τx, s) The flowability of powder was discuss in terms of μm, s.The findings are as follows:(1) The less the flowability is, the greater the normal stress distribution is. The normal stress (σz, m) averaged over the plane was smaller than the applied normal stress (σz, w). This implied that a part of the applied force may be consumed in the powder bed.(2) Satisfying Coulomb's law, the σz, m is exactly proportional to the τx, s. The relationship between σz, w and τx, s however slightly deviate of from Coulomb's law.(3) The relationship between σz, m and τx, s is independent of both the initial voidage and the height of upper powder bed. The internal friction factor μm, s can be explained in terms of the flowability depending on the normal stress distribution.