Abstract
The rheological properties of various powders have been measured by four different methods in order to examine the effect of particle characteristics on the flow phenomena of powder.
There are many methods available to estimate the rheological behaviour of powder. In the present experiments, the following four methods were used:
(a) Measurement of the rate of effusion of powder from an orifice,
(b) Measurement of the fluidity of powder in a vibrating state with the rotating cylinder viscometer,
(c) Measurement of the ratio of bulky density to final packing density, ρmax/ρmin,
(d) Measurement of the angle of repose of heaped powder.
The relation between the rate of effusion of powder and orifice diameter showed reasonable lineality in the log-log plotting. The slopes of these lines correlated with the values of ρmax/ρmin. Sample materials have revealed that graphs of effusion rate vs. particle size exhibit a maximum. The position of the maximum depends on the properties of the particle, such as rugosity and shape. The shear diagram obtained from the rotational cylinder viscometer under a vibrating state exhibits plastic flow. The magnitude of shear stress of the powder bed is caused by interparticle force and void ratio of the bed, but their effects are not independent from each other.
The influence of these particle characteristics on the flow behaviour of powder differs among different phenomena. Therefore, calibration is needed to obtain the apparatus constants and the correlation between the results of different methods. Some calibration data of flow characteristics of various powders have been obtained by comparing their effusion rates with that of the standard glass beads powder.
