| Wheat is one of the largest food crops in the world, it is also an important source of food in people’s daily lives. In the process of threshing, the grain’s loss rate is very huge. So it is necessary to study how we can reduce the rate of loss in the threshing process. If we can computationally simulate the process of wheat threshing, we can make it easy to optimize the design of wheat thresher according to the simulation results. In order to simulate the process of wheat threshing,we need to build the physical and mechanical model of wheat plants.In this paper, firstly, The wheat plants physical modeling method is researched.Then,the morphological characteristics of the wheat plants were observed and measured to obtain the relationship between morphological parameters, position, species, moisture content influence on the breaking force of wheat panicle, stiffness coefficient is studied, a method of wheat plants physical model was introduced. The main specific work as follows:(1) Morphology, structure, characteristics of Taixue No. 12 and Hengguan No. 25 wheats plants are observed, stem, leaf sheath, leaf, panicle were measured, samples of a series of morphological parameters was obtained. Through analysis to find out the various relations between morphological parameters: inter-section between the section number and length of wheat a quadratic polynomial relationship, wheat equivalent diameter node number and node of a quadratic polynomial relationship between the thickness of the inter-section and section number was a linear relationship, wheat equivalent section between the diameter and section number showed a quadratic polynomial. Blade length between wheat and section number was near quadratic polynomial relationship between the length of the sheath section number approximately linear relationship between the length of the blade at the bottom of the section number is nearly linear relationship between the length of the sheath at the bottom section number is approximately linear relationship.Wheat total length is approximately normal distribution, there is no obvious relationship between the spike length and the number of spikelets of wheat.(2) This junctions are tested in the Universal Testing Machine-the junction between the the spike branches and spindle. And position, species and moisture content are considered to influence the breaking force and stiffness coefficient. The main conclusions are as follows:(1) Position on the physical and mechanical properties of a small portion of the wheats.(1) At the same species and the same moisture content, the average tensile stiffness coefficient becomes larger as the position coefficient becomes larger as tensile stiffness changes in the size of: the upper ear <the middle ear <spike lower portion.(2) At the same species and the same water content, tensile force increases as the position of the average coefficient becomes large tensile force that is the size of the changes: the upper ear <the middle ear <spike lower portion.(3) At the same species and the same moisture content,there is not between compression coefficient and stiffness coefficient of a unified position of the law, its upper, middle and lower stiffness coefficient similar.(4) At the same species and the same moisture content, there is no uniform law of force between the pressure off the maximum coefficient position under the same moisture content, its upper,middle and lower part of the pressure off almost the same force.(2)Species on physical and mechanical properties of small portions of the wheats.(1) At the same moisture content and the same location parameters, the average tensile stiffness of the size: Hengguan No. 25> Taixue No. 12(2) At the same moisture content and the same location parameters, dropdown breaking strength average size: Hengguan No.25> Taixue No. 12(3) At the same moisture content and the same location parameters, when the position of an upper compression,stiffness coefficient of average size: Hengguan No.25> Taixue No. 12. When the wheat is in central position coefficient, compression stiffness coefficient average size is Lower: Hengguan No. 25 <Taixue No. 12.(4) At the same moisture content and the same location parameters, pressure off the maximum size of the force: Hengguan No. 25 <Taixue No. 12(3) Moisture content on physical and mechanical properties of small portions of the wheats.(1) Taixue No. 12 tensile stiffness coefficient and moisture is related, with the increasing of moisture content,the tensile stiffness coefficient firstly decreases then increases; Hengguan No. 2 tensile stiffness coefficient and moisture is related, with the increasing of moisture content, tensile stiffness firstly increases and then decreases.(2) At the same species and the same position, there is no uniform rule between the changes in tensile force and the changes in moisture content.(3) At the same species and the same position,with the increase of moisture content,the compression stiffness firstly mean increases then decreases(4) At the same species and the same position, there is no uniform rule between the changes in compressive force and the changes in moisture content.(4) The tensile stiffness coefficient of wheats was significantly greater than thecompression stiffness coefficient; tensile force is also significantly greater than the value of the pressure off the force.3)A method of wheats plants physical model was introduced. The geometric model of internode is build with frustum of a cone or ball combination method, so the geometry model of stem is the combination of several internode geometric models. The geometric model of leaf sheath is build with a cylinder which is part left. Distribute several balls on the skeletons which are in the cylinder. Leaf edge curve and leaf vein curve are built with Bezier curves which several balls are distribute on. Spike branches are built with ball combination method while grains are built with ellipsoid. The panicle of the wheats is assembled with spike branches and grains. Stem and panicle mechanical model is linear viscoelastic mechanical model, leaf and leaf sheaths mechanical model is particle-spring model. when the connection force is bigger than the maximum connection force which is tested, the connection breaks. |
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