Abstract
Summary The purpose of this paper was to study the effect of vibration for the fluidity of slurry such as dental stones and investments.The fluidity was defined by the speed of slurry flowing down the semicircular trough of diameter20 mm with inclination angle 20°.Other parameters were frequency(20〜200Hz), peak-to-peak amplitude(150〜3000μm)and wave shape(sine or rectangular).Results were as follows.1)Frequency and amplitude of vibration were closely related to the fluidity.As these were respectively increased, the fluidity was increased.But, there was limitation of increase, and beyond the limitation, the fluidity was rather decreased.In case of rectangular wave, the fluidity increased a little.2)As the water-powder ratio was decreased, the fluidity of slurry was decreased.Using the same kind of powder, the effect of vibration for the fluidity showed almost same tendency.3)There were various forms of fluidity curve caused by the difference of powder under the same vibration.4)The fluidity of slurry mixed with colloidal silica was decreased, especially fluidity showed more decrease between 15 and 30wt% SiO2.5)Under stronger vibration, some kinds of slurry didn't flow but slid down in a mass, in this condition bubbles were easily produced.
