Research And Development Of Two-dimensional DEM Simulation System Based On Disc Model

It is estimated that the abrasion loss of related equipments during the carrying course of granular materials costs 40% in our county, for 5 hundred million tons grain that we produce every year, the damage in the reaping and transport reaches about 5%, the consumption of energy used to plough the field of our country is huge. So the designing of the related mechanical parts which cost less energy and make less damage has high benefit in economy and society.The traditional method depends on the experience and experimentation in designing the related mechanical parts, and it takes both time and stamina a lot and cannot achieve the expected purpose. For the advantages of computer emulation, such as no constrains, stability, no waste, it has been applied to design the related mechanical parts, and becomes a primary method. The actions between granular materials and working parts and dynamic matter of granular materials are frequent during the course of designing, so it is must be considered.The traditional continuum mechanics method (CMM), which is applied to research the interaction between granular materials and related mechanical parts, can only consider the granular materials as a whole, and it is unable to analyze the movement course of each particle and the interaction among the colony. As a result, it cannot resolve the problem very well.In 1971, the Discrete Element Method (DEM), which Cundall et al. put forward primarily to analyze the mechanical property of granular materials, can be applied in all related problem. Its basic thought is to simplify granular materials as a set of particles with a certain kind of shape and mass, to consider the interactions between granular materials and working parts by giving the contact mechanics model, to do iterative computation by splitting time, to compute the function and movement of every particle using the dynamic laxity method, the Newton's Second Law and mediam interplation. DEM can be used to analyze the interactions between granular particles and mechanical parts, the agglomeration of granular particles, the destruction of materials (the smashing and the cutting), medical actions and heat conduction. It is fit to resolve the non-linear problem, and has become a popular method on studying the kinetic problem of granular materials.This article simply introduces the production, development, situation and problem of DEM. It discusses the basis of the DEM, so is the contact mechanical model and particle model, and then lists the contact mechanical model and particle model in common. It points out the problem of DEM, including generating particles, detecting the contacts, computing the congruence, computing contact functions, computing speed, confirming the position, and etc, then gives out the resolving.It simply introduces the technology of computer emulation, points out the major problems that are modeling and simulation. It analyzes the DEM simulation system, finds out the three elements, modeling the system. Take the two-dimensional disc model as example, the simulation model is designed, and so do the complex boundary analysis model and the mechanical analysis model and the disc analysis model. It designes the flow of the DEM system based on the disc model, and give out the diagam of flow. The two-dimensional DEM software under Windows platform is developed with VC++6.0, and then a current and digital system is organized by unifing the AutoCAD boundary modeling program developed by our group. It introduces the basis of the test theory, designes the testcase for the 2D DEM system, and the lightness is confirmed by running thees test-cases. Steptime, number of particle and running time influence the speed of DEM system, and the influenct is discussed in this paper under the performation test.A new method that is an improvement of the Brensenham algorithm in graphics is put forward primarily to confirm the grids of shape by using the character of the shape. It is applied to line, arc and eclipse, and achieves the optimization by using this algorithm.The two-dimensional DEM software based the disc model which is designed in this paper can not only uses with the AutoCAD, but also uses separately to do emulation. The virtues of this competitive design-analysis software are:①simplify and convenient: It can modify the boundary model by redrawing the AutoCAD graph in the period of designing, so it avoids the entering command lines in traditional method.②Uses and : It can carry through a dynamic simulation for the working process of mechanical parts based on the CAD model, therefore can analyze the working mechanism and invent the mechanical parts with new mechanism.