Discrete-element method simulation of agricultural particles' motion in variable-amplitude screen box

Cleaning and screening of agricultural materials is an important process in agricultural production. Many researchers have carried out important works in this area based on mechanism, parameter optimization, and particles' motion. In this paper, both advantages and disadvantages of the traditional reciprocating screen widely used in combine harvester were analyzed. Furthermore, a variable-amplitude screening mechanism developed from classical swing bar type reciprocating screens in Adams software was studied, and the trajectories of 11 marker points on the screen under different conditions were obtained. After transforming the motion of a variable-amplitude screen to 3 DOF (degree-of-freedom) motions (two translations and one rotation, 2T-1R), DEM (discrete-element method) simulations of agricultural particles (grain and stalk) in a variable-amplitude screen box were performed based on the Hertz-Mindlin contact model in an EDEM software environment. The results show that the variable-amplitude screen could make the agricultural particles at the front of the screen be quickly thrown up and moved back but could not favor their segregation and separation at the screen front. This variable-amplitude screening method can provide reference for solving the retention problem of agricultural materials at the screen front. (C) 2015 Elsevier B.V. All rights reserved.