Direct Shear Test of Powder Beds

Interrelations among shearing stress, applied vertical stress (by external load), actual vertical stress at shearing plane, vertical displacement (powder bed expansion or contraction) and shearing displacement have been extensively investigated for a number of powders under various test conditions such as the method of preconsolidation, the shearing cell diameter, the initial void fraction of powder beds and so on, by utilizing a simple shear tester capable of testing under both constant-load and constant-volume conditions and of measuring the actual vertical stresses (6 points) in the vicinity of shearing plane, the shearing stress and the vertical displacement of a powder bed simultaneously. It has been concluded that; if the internal friction factor having a universal validity and fairly independent of the test conditions is to be obtained, it is essential to measure the mean actual vertical stress in the vicinity of shearing plane, or it is indispensable otherwise to measure at least the vertical displacement of powder beds along with the shearing displacement and to make sure that the vertical displacement is being kept as small as possible during a course of shearing.