抄録
A new tapping system has been developed to measure bulk densities of powdery materials and to study their compaction characteristics. The new tapping system has an electronic monitor of impact acceleration to observe the peak value of impact acceleration, that is, the intensity of tapping action. The impact acceleration of a conventional tapping machine is not monitored quantitatively and generally higher than 200 G. The adjustable range of the new tapping system is from 3 to 500 G. Tapping height adjustment of a conventional tapping machine is done without any appropriate change of colliding materials. Such an adjustment causes very ambiguous covariation of tapping intensity and tapping energy quantity. Some confusions of these different factors have been making it difficult to analyse and discuss the effects of tapping height. The peak value of impact acceleration and the tapping energy quantity of the new tapping system can be varied independently through the combination of tapping height adjustment and cushioning material selection.
Four limestone powders, five white alundum powders and two Kanto loam powders were used as testing powders. Their specific surfaces, SW , were measured by an air permeability method. Tapping tests were done for each powder under various tapping conditions.
Higher tapping energy in the sense of quantity causes faster compaction process but does not affect the terminal tapping density, ρ∞, which varies widely with SW and tapping acceleration, A. The terminal tapping density of finer powder is lower than that of coarser powder. Higher impact acceleration causes higher terminal density, but the effect of A seems to be saturated when A becomes sufficiently high. The density difference owing to the size difference becomes smaller with an increase in A. Tapping tests with lower impact acceleration are much more informative than those with higher acceleration.
