Discrete element model calibration for industrial raw material simulations

The use of computational fluid dynamics in continuous operation industries have become more prominent in recent times. Proposed system improvements through geometric changes or control strategies can be evaluated within a relatively shorter timeframe. Applications for discrete element methods (DEMs) in real life simulations, however, require validated material-calibration-methods. In this paper, the V-model methodology in combination with direct and bulk calibration approaches were followed to determine material model parameters, to simulate real life occurrences. For the bulk calibration approach a test rig with a containment hopper, deflection plate and settling zone was used. Screened material drains from the hopper, interacts with the deflection plate, and then settles at the material angle of repose. A high-speed camera captured material interaction with the rig, where footage was used during simulation validation. The direct measuring approach was used to determine particle size, shape and density, while confirming friction and restitution coefficients determined in the bulk calibration method. The test was repeated and validated for various geometrical changes. Three categories of validation were established, namely particle speed assessment, -trajectory assessment and -plate interaction assessment. In conclusion, the combination of direct and bulk calibration approaches was significant in calibrating the required material model parameters.

Comparison of the Two Formulations of w-u-v and w-F in Nonlinear Plate Analysis

In a moderately large deflection plate theory of von Karman and Chu-Herrmann, one may consider thin-plate equations of either the transverse and in-plane displacements, w-u-v formulation, or the transverse displacement and Airy function, w-F formulation. Under the Galerkin procedure, we examine if the modal equations of two plate formulations preserve the Hamiltonian property which demands energy conservation in the conservative limit of no damping and forcing. In the w-F formulation, we have shown that modal equations are Hamiltonian for the first four symmetric modes of a simply-supported plate. In contrast, the corresponding modal equations of w-u-v formulation do not exhibit the Hamiltonian property when a finite number of sine terms are included in the in-plane displacement expansions.

Dynamic Elastic/Viscoplastic Response of Hull Plating Subjected to Hydrodynamic Wave Impact

A numerical simulation of the response of a flat plate subjected to hydrodynamic wave impact is presented. The formulation is based on a time domain solution of the large deflection plate equations using a finite difference mesh. The material behavior is elastic/viscoplastic, following the classical Perzyna model, and the procedure is validated against a series of model collision experiments. The correlation results were found to be good and the procedure was subsequently used to predict the response of plating subjected to wave impact loads, characterized by a steep rise to a maximum pressure followed by an exponential decay. A comparison with an analytical model was conducted and following this a parametric study of the characteristics of the pressure pulse was carried out. The paper concludes with a study of the effect of multiple wave impacts. It was found that, even though individual impacts may not cause rupture, a small number of these may lead to rupture of the plating, provided the maximum pressure is large enough.

Hydroelastic Instability of Infinite Strips Under Shearing Load on an Elastic Foundation

The paper examines the hydroelastic instability of an infinitely long plate subjected to shearing load with two different boundary conditions, one side of which is exposed to an incompressible inviscid flow, and the other side supported on an elastic foundation. The analysis is based on the small deflection plate theory and the classical linearized potential flow theory. The Galerkin method and Fourier transforms are used. It is found that the effects of the shearing load and the elastic foundation on the divergence velocity can be illustrated by a single curve for both clamped and simply supported cases.