Abstract
An experimental theorem (1) is proposed for conversion of the curve representing powder bed compression by tapping into a straight line. The theorem was found to apply to a variety of particulate solids : εe=-b log a+k (1)where εe is the porosity of the powder bed at a stable state for specific acceleration levels, a is the acceleration caused by tapping at constant height differences (Δh), and b and k are constnts.If the speed of pouring the powder bed with the sample was high, two continuous straight lines (lines 1 and 2) were obtained. Line 1 was thought to represent the porosity primarily due to the interaction between the particles and the walls of the container, in addition to the porosity at a table state for the mostly loosely filled sample. Line 2 was considered to represent the maximum porosity under a constant acceleration when there is no interaction between the container and sample.The two lines could be approximated by line 3 at low filling speeds. This straight line is believed to represent the porosity for the most dense packing under a constant acceleration. The three straight lines tend to converge into a single line as the particle size is reduced. A correlation was also found between the slope of line 3 and the particle size.
