The Research Of A Method For Representing Boundaries Of 3D DEM Based On The Software Of AutoCAD

There are lots of granular materials in the nature, and the traditional continuummechanics method (CMM), which is applied to research the interaction betweengranular materials and related mechanical parts, can only consider the granular colonyas a whole, and it is unable to analyze the movement course of each granular particleand the interaction among the colony. As a result, it cannot resolve the problem verywell. Recently when designing the related mechanical parts, the experience andexperimentation methods are depended on mostly, and it takes both time and staminaa lot and cannot achieve the expected designing purpose. It is estimated that theabrasion loss of related equipments during the carrying course of granular materialscosts 40%, and the demand of optimized design and energy saving is far away fromsatisfaction.In seventies of the 20th century, Cundall et al. put forward the DEM primarily.The basic thought is to simplify granular colony as a set of particles with a certainkind of shape and mass, and endues the particle-particle and particle-boundaryrelationship with a certain kind of contact mechanics model and some parameters.The DEM is applied to research the contact effects, which influence theparticle-particle and particle-boundary relationship, and the different physical andmechanical characteristics between particle and contacted boundary. The dynamiclaxity method, the Newton's Second Law and time step iteration are introduced inDEM to calculate the movement and displacement of each particle, and thus it isespecially compatible to resolve the nonlinear problem. Because of these virtuesmentioned above, DEM has become a popular method on studying the kineticproblem of granular colony, and it is widely applied in the field of rock engineeringand sands flowing;the transportation, mixing, classification of granular materials;theagglomeration and collision of granular materials;the interaction between granularmaterials and related mechanical parts;the equipment of chemical industry and mineengineering.With the extensive application of DEM, it becomes an emphasis and difficulty inthe research of boundary modeling of DEM and the development of the software ofDEM that how to build up an analysis of boundary model of DEM with thecomplicated structure and the style of movement. This paper is based on the presentstatus of the research of DEM and the summary of the current boundary modeling ofDEM. I put forward a method of building up an analysis of boundary model ofDEM from the CAD model of 3D mechanical. Also it can implement the integrationof the software of AutoCAD and the software of 3D DEM analysis and simulation,thereby we develop the general system of the design of structure and the analysis ofperformance in the integrated analysis and design of mechanical. We also proved thefeasibility of the method through lots of calculation and simulation experiment ofDEM.The modeling of 3D entity in AutoCAD is based on Boundary Representationswhich separately represent the topology and geometric information. In the process ofidentify model information of 3D mechanical, we need not only identify the type oftopology, but we also need obtain the geometric information of the correspondingtopology. According to this method, first we need decompose the complicatedstructure 3D mechanical according to the topology and make them to be basicprimitive that can be calculated in DEM. We also need abstract the geometricinformation of the basic primitive. Second, we need combine the type of movement,and set the information of movement and material up to the 3D mechanical. Then, wetransfer the information of topology, geometry, movement and material to externaldatabase. The software of 3D DEM analysis and simulation obtain the primitiverecord, including the geometric information of boundary (type of primitive topology,feature parameter of boundary), the information of movement (movement attributeparameter of primitive), the information of material (material parameter of primitive).It need build up the instance of the class of primitive of DEM, and then store all theprimitive instance. These can be provided in the process of the calculation andsimulation of DEM. As a result, it builds up an analysis of boundary model of DEM,including the model of topology and geometry of 3D boundary, the model ofmovement and the attribute of material.The advantage of building up an analysis of boundary model of DEM from theCAD model of 3D mechanical: ①In the process of design of mechanical, modifyingthe design of CAD, we can build up an analysis of boundary model of DEM withthe different structure, size and the different style of movement. Also we can makethe analysis of structure and the evaluation of performance through the calculationand simulation of DEM. This can optimize the structure and size of mechanical;②Inthe process of the simulation of DEM of mechanical, making analysis of operationalprinciple, with the help of expertise and heuristic rule, we can invent the mechanicalbased on new principle. Gathering the design and evaluation in the whole body, thiscan not be realized in the current merchandise software of 3D DEM.