(741a) Stick/Slip in Bulk Solids Flow

Jacob, K., The Dow Chemical Company
Fan, Y., The Dow Chemical Company

Stick/slip behavior unpredictably shows up frequently during the powder and powder/wall testing of bulk solids.  This behavior can have adverse effects on the flow of bulk solids at full scale as evidenced by silo vibrations, quaking and potentially silo collapse. In this preliminary study, the stick/slip behavior of corn starch and other materials is examined in a Schulze ring shear tester and the wall friction of these materials is examined using a Jenike shear tester. Specifically, the frequency and amplitude of the stick/slip phenomena as function of major principal stress is analyzed.  In turn, this analysis is used to predict silo designs according to the method set out by Jenike in Bulletin 123.