1998 Volume 24 Issue 6 Pages 918-922
The shearing and friction characteristics of a powder bed consisting of porous particles under conditions of various liquid content have been evaluated by means of the apparent viscosity coefficient ηa. In the present case, Rumpf's model has been applied to estimate the shearing force H at the contact point between two particles measured by the intrusion method. According to the tendency to change inηaand H with the ratio of liquid to powder weight w, the states of the powder can be classified into thethree regions. In the region I (0≤w≤0.89) ηa and H have similar values in the dry state, respectively, i. e. no change in surface condition due to absorption of the liquid into the pore spaces of the particles. In the region II (0.89≤w≤1.50), the powder property changes from the pendular to the funicular state, so ηa and H increase with increasing w, and H does not change in the void fraction ε. In the region III (w≥1.50), the powders are in the capillary states, ηa and H decrease with increasing w, and H increases with decreasing ε.
