粉体食品の内部摩擦角
1962 年 31 巻 4 号 p. 286-293
詳細
1962 年 31 巻 4 号 p. 286-293
By means of direct shear test, the angle of internal friction for eight kinds of powdered food-skimmed milk powder, whole milk powder, lactose powder, butter milk powder, flour, starch and ice cream mix powder-was determined.
The coefficients of internal friction of these kinds of powdered food are found to lie in the range of 0, 23 to 0.70. Especially, the whole milk powder and ice cream mix powder which contain a large amount of fat possess the cohesive force of about 40 g/cm2.
The stress under shearing increases in pulsatile steps with increasing shearing displacement and saturates gradually. Vertical strain increases linearly with the logarithmic increase of shearing strain. When the normal stress increases over 0.3 kg./cm2., however, the slope of the straight line suddenly rises up and the variation of the slope tells clearly the formation of the slip layer including the shearing plane.
The vertical height of packed powder generally decreases with the increase of shearing displacement but the powder composed of cubical particles like sugar expands its volume during shearing. This is a kind of dilatancy.
The internal friction of the powder is remarkably affected by the shape and size of shear box and by the density of powder that filled the shear box.
By photographic observation of flow pattern, an irregular flow is found along the inner edge of shear box and on the shearing plane during the shearing.
