| With the growing of population and improving of living standards, the world takes more and more attention to agriculture, production efficiency of agricultural directly affects the people's standard of living. The rapid development of industry has promoted the modernization and mechanization of agricultural production, greatly enhanced the efficiency of agricultural production. At present, the development of new agricultural machinery products need to prototype design, prototype, test, modify the design and repeat the tedious process of trial and experimentation, this process need to take a long time to shape products and put into production.With the rapid development of the computer technology and numerical simulation methods,American scholar, Cundall Professor, presented a numerical simulation method of Analysis of discrete process of physical movement– DEM, in 1971, providing a new solution to study the dynamic complex behavior of objects. As the superiority of DEM in the analysis of discrete physical, it has become a numerical simulation method in an efficient, rich in prospects for the development to solve the problem of non-continuous medium mechanics, in recent years. DEM is widely used in mining engineering, structural engineering, geotechnical engineering, material flow, materials, mechanics and engineering geology and other fields. After the nineties, with the rapid development in foreign countries of DEM, a variety of discrete element commercial software has emerged. U.S. ITASCA developed and refined the UDEC and 3DEC procedures based on the irregular shaped block unit, and the PFC2D and PFC3D software based on the disc-shaped and spherical discrete units. In particular, PFC2D and PFC3D software, A result of a neighbor cell search fast and efficient simulation of large deformation, etc., has been widely applied in many areas, so that DEM in engineering a major step forward.If the DEM and the design of agricultural machinery was combined, we can make the design of agricultural machinery have a work-in-process simulation, this can solve the agricultural machinery design, prototype, test, modify the design of the cumbersome process, save a lot of manpower, material and financial resources, for the promoting the early realization of China's agricultural mechanization, it has positive significance.The corn is China's second largest grain varieties, having extensive use of the value of involving the planting, breeding, food, chemical, pharmaceutical and other industries. Therefore, researching corn particle model has important significance for agricultural production. At present the research about the corn particles DEM modeling at home and abroad is relatively small. In 2009, coetzee set up the corn particle DEM analysis model of corn particle using balls combinations method. The corn model ,using two different radius of the ball through a fixed position as a whole, represents a three-dimensional model of corn . This methods can be roughly expressed corn particles, but there are some disadvantages,such as deviation and poor flexibility. One of the main work of this paper is to build a relatively precision and flexibility DEM corn model。Combination particle model method provides a technology to simulate irregular particles or irregular blocks. The basic idea is that a number of particles form a particle unit through a combination of a fixed spatial structure. In this article, three-dimensional corn grain is modeled by using combination particle model method. Three-dimensional geometric modeling of corn grain is detailedly described by graphics and algorithms and the corn grain generation method is discussed. The generation conditions in the discharge port are analyzed to make sure that corn grains have been generated are correct. The implementations of several important functions of the simulation software are introduced. The neighbor search of corn grain,valuation distribution, the normal distribution and uniform distribution of the particle sizes,the simulation process between a corn and another corn, a corn and a boundary, the method of how to save the results of simulation are included. It also introduces several important functions of demonstration and performance analysis module in the DEM software of the three-dimensional corn grain, such as normal presentation, showing the number and the speed of a particle, tracking a particle, showing the sports curves about various physical quantities of tracked particles in a period of time or in the whole simulation process.Based on the research of DEM algorithms about three-dimensional combination corn, the writer uses object-oriented modeling to analyses three-dimensional DEM simulation software, including system requirements analysis, the function modules, architecture design and the specific processes ,gives the system's class diagram and flow chart ,having laid the foundation for the DEM simulation software aboutthree-dimensional combination corn . The advantages of the particle model the expressed by super-ball equation as (f x y z =∑= axε? =can simulate the particle shape of more than 60% of natural existence Approximately. To study the super-sphere particle model discrete element method, it will be have a certain significance of the development of DEM. In view of the well-form of the procedure and simulation results of Three-dimensional combination of corn particles, this paper adopts the method of combination of ball particles to achieve the super-ball particles in discrete element method simulation. First, display the super-ball contour model in a powerful mapping tool for PRO / E with the marking key points of methods, then, set the position of each combination ball in the ultra-ball contour model by using the PRO / E; Finally store the parameters information of the super-ball and the information for each combination of balls in the database. When the three-dimensional discrete element simulation software requires super-particle model, the calculation on the discrete element simulation can be done only by reading the data from the database.Using a combination of black box testing and white box testing methods, this paper has been done the test of system, include modules of the corn grain front module test, particulate calculation module test, simulation module testing, performance analysis module test . During the process of testing, Problems was discovered continuously, procedure was also optimized continuously .This paper proves the reasonable of the software simulation, based on the three-dimensional discrete element simulation software simulation of corn particle model, by comparing and verifying the way of through the test of the simulation results, the kinds of odd and even row of the rate of seed tilt angle, seed and other aspects.In summary, on the basis of the developed three-dimensional discrete element simulation software by the research group, this article adds two important functional modules of three-dimensional combination of corn grain and super-ball, and expands the scope of application of the discrete element of the development, which is essential in the promoting of DEM and the realization of China's agricultural mechanization especially. |
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