| There are lots of flows of granular materials and actions between granular materials and working parts of machinery in industrial and agricultural production. when sowing seeds, this course has the seed, the fertilizer and soil flowing; when farming the land, this course has the soil flowing; agricultural product harvest, transportation, graduation, processing, packing and so on, they also have the flows of granular materials.The flows of granular materials have the relation with not only itself mechanical properties but also the farm machinery's working part structural style, size parameter, movement parameter and so on. One good performance design of machinery's working parts should make flow of granular materials in accord with the way that it is expected, reduce the unnecessary damage in flow, save mechanical motive force to consume, Therefore, it is must be considered the action between granular materials and working parts of machinery and dynamic matter of granular materials.Granular materials have the property between the solid and the fliud, and although their structure are simple, but they have the complex mechanics characteristic. 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. Recently when designing the related mechanical parts, the experience and experimentation methods are depended on mostly, and it takes both time and stamina a lot and cannot achieve the expected designing purpose. It is estimated that the abrasion loss of related equipments during the carrying course of granular materials costs 40%, and the demand of optimized design 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 certain kind of shape and mass, and endue the particle-particle and particle-boundary relationship with a certain kind of contact mechanics model and some parameters. The DEM is applied to research the contact effects, which influence the particle-particle and particle-boundary relationship, and the different physical and mechanical characteristics between particle and contacted boundary. The dynamic laxity method, the Newton's Second Law and time step iteration are introduced into DEM to calculate the movement and displacement of each particle, and thus it is especially compatible to resolve the nonlinear problem. It can analyze particle lumping, destruction of the whole material, flowing heterogeneously, chemical reaction and heat transfer and so on, when adopting different dynamics equations. It can analyze not only the interaction between various granular materials and different border but also the influence on the motion of granular materials, according to changing the model of particle, the model of border, dynamics equations and parameters in Discrete Element Method. Because of these virtues mentioned above, DEM has become a popular method on studying the kinetic problem of granular materials, and it is widely applied in the fields of rock engineering and sands flowing, the transportation, mixing, classification of granular materials, the agglomeration and collision of granular materials, the interaction between granular materials and related mechanical parts, the equipment of chemical industry and mine engineering.Therefore, related the characteristics and design requirements of working parts of machinery, topic group presents a novel method to establish a three-dimension Discrete Element Method (DEM) to analyze model of machine's parts based on their CAD model. And then implements the integration of CAD software and the DEM analyzing software by self-development for analyzing the performance of machine's parts which are contacted with granular materiel at working, thereby establishes a novel universal digital design method and integrated software for designing and analyzing the machine's parts, The software will offer a new method and new tool for optimal design of the machine's parts.The virtues of this competitive design-analysis software are: ?It can establish the DAM based on the CAD model of related mechanism directly, and then can implement the integration between CAD software and the DEM analysis software, thereby can integrate the CAD design and DEM performance analysis of related mechanism. (2) It can analyze and evaluate the performance of boundary with different structure and accessional parameters through modifying the CAD model in designing period, and can realize the optimization of structure scheme and size parameter of related mechanism. (3)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. These cannot be implemented by current design methods and technique of mechanical parts that are relative to granular materials.In the independent research of the three-dimension DEM analysis software, this paper uses a boundary modeling method based on graphic element. Now one existing problem is that the surface of some spare parts is not an integrated graphic element, such as one cylinder surface drills a circular hole and one cone surface opens a trench. In order to remove these flaw parts when analyzes the boundary modeling and three-dimension DEM, this paper presents concepts of virtual and real boundaries. Real boundary expresses surfaces which actually exist in mechanical parts, these surfaces produce contact strength when they contact with the granular materials. Virtual boundary expresses the flaw parts of the real boundary, and it doesn't produce contact strength when contacts with the granular materials, so the granular materials can pass through the virtual boundary. According to the analysis, the methods to define the virtual and real boundary, may solve the relative problems among different graphic elements.Based on the methodology and theory above, this paper establishes the contacting detection, the contact point calculation and the contact overlap calculation of spheral particles and the virtual circle surface, virtual cylinder surface, and also establishes the contacting detection, the contact point calculation and the contact overlap calculation of spheral particles and real polygon surface, real arc surface, real cone surface. With Visual C++ 6.0 development environment and object-oriented techniques, this paper realizes the algorithm above, and the simulated results by adopting the basic cartography function, illumination and the double buffer technology of OpenGL, and as a result consummates the function of the three-dimension DEM calculation-simulation software which is researched by topic group.Adopting the perfected three-dimension DEM calculation-simulation software, proceed in simulated analysis to the contact collision and movement process of spheroid particles with several simple boundaries, movement boundaries, combination graphic element boundaries and intersection graphic element boundaries. According to the observation of the simulated result, the movement process of particles is very similar to the actual situation, and therefore validates the correctness and efficiency of the method established in this paper with instances.This paper has much positive sense to the consummation of the integrated design analysis software and the establishment of general digitized design method to the relative mechanical parts. |
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