Time- and Velocity-Dependent Properties of Powders Effecting Slip-Stick Oscillations

摘要

Slip-stick behavior of powders is a phenomenon characterized by self-excited, pulsating flow, i.e., the powder starts and stops flowing intermittently. If slip-stick friction occurs in a silo, the resulting vibrations are called silo quaking (low frequencies; periods up to several hours) or silo noise (higher, audible frequencies) [1]. Slip-stick can also occur at the measurement of powder properties with shear testers, where it often causes a sawtooth-like course of the shear stress. Slip-stick friction has been observed both within flowing powders (internal friction) and at powders flowing along rigid walls (wall friction).