Research On Mechanical Model And Compression Molding Equipment Of Corn Straw

Under the background of development in the biomass compression technology, the mechanical model of the corn and the compression molding equipment is studied detailly in this thesis. It provides technical support to the biomass industry. This study also belongs to "the key technology and equipment of straw collection and compression" in advanced manufacturing technology, which is the National High Technology Research and Development Program (863 Program). The main conclutions are in the following:(1) Corn stalk is mainly composed of skin, core and sections. Every part of the corn stalk has its physical and mechanical properties. In this paper, corn stalk is the research object, which can be abstracted to the shaft structure with skin, core and sections. All the three parts are transversely isotropic material, so the corn stalks are composed of three different transversely isotropic materials. With the mechanics theory of the composite materials and the mechanics model of the transversely isotropic materials, we can obtain the displacement equilibrium equations, which is considered as the linear partial differential equations. There are three methods in solving the partial differential quations, but among them the Finite Element Method is the best.(2) By the mechanics theory of the composite materials, the skin,core,sections and the corn stalk are tested through three traditional methods: Tensile test, compression test, bending test. We can obtain their load-displacement curve. With the help of data processing software, we can get many elastic parameters of the skin,core,sections and the corn stalk,such as the tensile elastic modulus, compressive elastic modulus, bending elastic modulus, the maximum tensile strength, the maximum compressive strength, the maximum bending elastic modulus and so on. There are many elastic parameters of the transversely isotropic materials. Some of them can not be obtained by the test. By comparing with the characteristics and parameters of other biological materials, all the elastic parameters can be obtained at last.(3) The corn core FEM model is established with the average geometric model, it adopts the ANSYS software to simulate the corn core with the horizontal uniform load. We can obtain the stress and the displacement in it. The conclusion is following:the stress of the whole corn core is the same everywhere. It is also the same as the stress in the isotropic material. This proves that the transversely isotropic material's properties has the same mechanical properties with the isotropic material in the isotropic surface. So the elastic theory is applicable to both the transversely isotropic material and the isotropic material. Along the radial direction from the inside to the outside, strain increases. The outest is the most, the inner is zero.The corn skin FEM model is established with the average geometry model. It also can be simplified to the static contact problems and large deformation finite element analysis. We can obtain the stress and the displacement with the horizontal uniform compression load. The conclusion is as follows:the maximum stress is between the skin and core of corn stalks. The stress on the corn core is essentially the same, and it has a change in the junction of corn skin and core. Along the radial direction from the inside to the outside, the strain decreases. The strain of the corn stalk increases from the inside to the outside at the radial direction. The maximum strain occurs at the skin near the junction of the corn core and the skin.(4) According to the production conditions, processing requirements and associated technical indicators, we can analysis the system function and design the overall structure. The new straw molding machine is one of the hydraulic piston molding machine when the straw does not nees to be grinded, just need to be cut. The stress of the critical components and materials in the compression molding process has been analysised. According to the straw of different states in the molding process, the compression zone can be divided into four regions: the feeding zone, compression zone, molding zone and the keeping-type zone. Corresponding to that, the compression molding curve can be divided into four phases:loose phase, transition phase, compression phase and transition phase. Also, the macro and micro stress of the molding die is analysised. After that, the molding die of the new compression molding machine is designed. The bigger radius is 100mm, the smaller radius is 70mm, the forming angle is 6°, the total length is 280mm, the length of the keeping-type die is 200mm. By rapidly re-grinding replaceable tool of carbide material, it can greatly raise the life of the cutting tool and reduce energy consumption and unit costs. At last, the hydraulic system is designed, and its schematic diagram is drawed. Also, the components of the hydraulic system is calculated and selected.