Abstract
The measurement of tensile strength of the powder bed having various water contents has been carried out, using fine powder with its specific surface diameter below 10μ, and the effect of the water content on the adhesion force among the particles discussed.
The adhesion force caused by the pendular rings of the water at the points of contact increases as the water content increases. It is considered that the pendular ring of the water formed at every contact point of the particles is of uniform size at relatively high void fraction. In this case, the relationship between the non-dimentional adhesion force of one contact point and the water content is to be expressed by the equation fc/πdpT=Kwc1.4. On the other hand, it is considered that at low void Fraction the pendular rings of the water blend into one another, or form a sort of bridges between the nearby particles. The adhesion force is considerably influenced by the true void of the powder bed.
The present experimental result does not agree with the theoretical analyses of the two spheres of equal size hitherto reported by many investigators.
