| There are lots of flows of granular materials (such as rock, coal, soil, silt, particleagricultural product and granulated fertilizer, etc.) and actions between granularmaterials and working parts of machinery in industrial and agricultural production.One good performance design of machinery's working parts should make flow ofgranular materials in accord with the way that it is expected, reduce the unnecessarydamage in flow, save mechanical motive force to consume, Therefore, it is must beconsidered the action between granular materials and working parts of machinery anddynamic matter of granular materials.The traditional continuum mechanics method (CMM), which is applied toresearch the interaction between granular materials and related mechanical parts, canonly consider the granular materials as a whole, and it is unable to analyze themovement course of each particle and the interaction among the colony. As a result, itcannot resolve the problem very well. Recently when designing the relatedmechanical parts, the experience and experimentation methods are depended onmostly, and it takes both time and stamina a lot and cannot achieve the expecteddesigning purpose. It is estimated that the abrasion loss of related equipments duringthe carrying course of granular materials costs 40%, and the demand of optimizeddesign and energy saving is far away from satisfaction.In seventies of the 20th century, Cundall et al. put forward the DEM primarily.The basic thought is to simplify granular materials as a set of particles with a certainkind of shape and mass, and endue 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 intoDEM to calculate the movement and displacement of each particle, and thus it isespecially compatible to resolve the nonlinear problem. It can analyze particlelumping, destruction of the whole material, flowing heterogeneously, chemicalreaction and heat transfer, when adopting different dynamics equations. It cananalyze not only the interaction between various granular materials and differentborder but also the influence on the motion of granular materials, according tochanging the model of particle, the model of border, dynamics equations andparameters in Discrete Element Method. Because of these virtues mentioned above,DEM has become a popular method on studying the kinetic problem of granularmaterials, and it is widely applied in the fields of rock engineering and sands flowing,the transportation, mixing, classification of granular materials, the agglomeration andcollision of granular materials, the interaction between granular materials and relatedmechanical parts, the equipment of chemical industry and mine engineering.Therefore, related the characteristics and design requirements of working parts ofmachinery, this paper presents a novel method to establish a three-dimension DiscreteElement Method (DEM) to analyze model of machine's parts based on their CADmodel. And then implements the integration of CAD software and the DEManalyzing software by self-development for analyzing the performance of machine'sparts which are contacted with granular materiel at working, thereby establishes anovel universal digital design method and integrated software for designing andanalyzing the machine's parts. The software will offer a new method and new tool foroptimal design of the machine's parts.During the development processing of software, a new method on the basis ofpicture element (such as plane, sphere, ellipse sphere, cylinder and conical surface) isadopted for border modeling. It also presents conception of virtual and real borderin this paper, in order to represent the deletion of picture element.This paper takes spheroid particle for example, presents the thought of modelingDEM computing courses. The DEM computing model is composed of the contactingmodel, dynamic equation, searching algorithm and methodology and theory of DEMcomputing.Based on the methodology and theory above, the code of Discrete ElementMethod is developed with WINDOWS platform. OpenGL graphics library isintroduced to draw graphics. It introduces the framework, function of the softwareand the key techniques to realize the software, includes generating particles,establishing the three-dimension DEM analyzing model of the boundary (machine'sparts) based on the CAD model, detecting method for the contact of particles and theboundary, the computational process of DEM, description of object classes, theintegration of CAD software and the DEM analyzing software, etc.The virtues of this competitive design-analysis software are: ①It can establishthe DAM based on the CAD model of related mechanism directly, and then canimplement the integration between CAD software and the DEM analysis software,thereby can integrate the CAD design and DEM performance analysis of relatedmechanism. ②It can analyze and evaluate the performance of boundary withdifferent structure and accessional parameters through modifying the CAD model indesigning period, and can realize the optimization of structure scheme and sizeparameter of related mechanism. ③It can carry through a dynamic simulation for theworking process of mechanical parts based on the CAD model, therefore can analyzethe working mechanism and invent the mechanical parts with new mechanism. Thesecannot be implemented by current design methods and technique of mechanical partsthat are relative to granular materials. |
PDF Full Text Request