The Transitional Behavior of the Mechanical Properties of a Powder Bed Prepared by Various Compressive Histories

Abstract

As was reported by the authors, it was recognized that the tensile strength of a powder bed prepared by compressive creep was increasing with time. This phenomenon is important in practical operations such as the storeage of powder.
In the present work, to more quantitatively analyze this phenomenon, the transitional behavior of the tensile strength and stress-deformation curve are measured. The powder beds are prepared by three kinds of compressive histories, that is, creep, recovery of creep, and relaxation. In order to consider the mechanism of this phenomenon, the bottom stress distribution is measured during compressive histories. Materials used are Kanto loam, fused alumina, lactose and limestone powder.
As results, it is recognized that the transitional processes of the tensile strength the depend on the preparations. In the case of creep and the recovery of creep and unlikely relaxation, the tensile strength is increasing with time. On the other hand, it is found that the bottom stress distribution tends slightly to become homogeneous for creep and recovery. From these results, the mechanism of increasing tensile strength with time is explained qualitatively by the homogenization of the bottom stress distribution.