Analysis of bulk -solid pressures in silos by explicit finite element method
Abstract
The purpose of the current study is to determine the pressures on the walls of a silo caused by stored bulk materials during two operational states: storing (static) and discharging (dynamic). There has been no complete and simple method for pressure estimation which takes into account all the effects and phenomena in the silos. Specifically, the flow of bulk materials during discharging is not usually considered. The wall pressures are inaccurately predicted and the failure of the silo structure frequently occurs. Therefore, the current study determines the wall pressures by a simple finite element formulation that considers the necessary features of a bulk material during both the static and dynamic phases. In the current study, an explicit finite element method based on an incremental displacement formulation is used. The bulk solid mesh is described in a Lagrangian coordinate system. The rigid body motion of an element is eliminated at each time step using an updated co-rotation formulation. Additionally, small strain theory is assumed for the incremental strain even though the total accumulated strain for the entire analysis is large. The silo model is assumed to be a rectangular plane strain silo with a wedge shaped hopper connected below. The bulk material is assumed to be a linear-elastic-perfectly-plastic material. Hooke's law is used to model a linear elastic material. Drucker-Prager yield criterion as well as von Mises condition as a nonassociated flow rule is implemented for a plastic material. The interactions between the stored bulk material and the silo walls are modeled by a roller boundary condition with Coulomb friction. A bulk solid element is eliminated from the analysis when it moves out from the silo. Both static and dynamic wall pressures are determined and compared to the results from analytical models and experiment. Additionally, the various numerical results such as the deformation, stress, and velocity of the bulk material are obtained and discussed. Parametric studies of the effect of the bulk material parameters on the numerical results such as normal wall pressure and velocity are also conducted. Recommendations for the use of the model are given.
Degree
Ph.D.
Advisors
Jeong, Purdue University.
Subject Area
Civil engineering
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