Measurement And Analysis Of The Physical And Mechanical Properties Of Corn Ears

Corn is one of the most important grain crops in China and also one of the three majorgrain crops in the world. Corn threshing is one of the key aspects in the process of cornharvesting, and corn threshers are widely used in our country. However, technical level ofcurrently available corn threshers is relatively low with poor threshing performance andserious breakage of corn kernels. Measurement of the physical and mechanical properties ofcorn ears can provide a theoretical basis and necessary parameters for the development andoptimization of high-performance corn threshers. It’s a new idea to adopt discrete elementmethod (DEM) to research the corn threshing process, and our team has done a lot of studyon this. When using DEM to research the corn threshing process, it’s necessary to establish arational DEM analysis model of the corn ear. To gain modeling parameters, it’s necessary tomeasure the physical and mechanical properties of corn ears.In this paper, the physical and mechanical properties of corn ears were researched basedon the review of the research status of the physical and mechanical properties of corn kernelsand corn cobs as well as corn ears. Two kinds of corn ears (Xianyu335and Baidan678)were selected as the research objects. Morphological parameters of corn ears were measuredand analyzed statistically. The mechanical properties of the corn carpopodium (which is thejoint between the corn kernel and corn cob) were measured by using WDW-20computer-controlled electronic universal testing machine. The mechanical properties of corncobs were also measured. The main work and conclusions of this paper are as follows.(1) The morphological parameters of two kinds of corn ears were measured andanalyzed statistically, including length of corn ear, number of rows, number of kernels perrow, diameter of corn ear, diameter of corn cob, kernel angle per row. Then the corn ear wasdivided into five sections along the axial direction of corn ear. The morphological parametersof each section of corn ear were measured and analyzed statistically. The statistical resultsshow that lengths and diameters of each section of corn ear and corn cob followed a normaldistribution. The effects of length of corn ear on number of rows, number of kernels per row,average diameter of corn ear, average diameter of corn cob were studied and analyzed. Thetest results show that as the length of corn ear increases, number of kernels per row, averagediameter of corn ear and corn cob increase almost linearly, while number of rows is nearlyinvariable. And the effects of average diameter of corn ear on number of rows, number ofkernels per row, length of corn ear, average diameter of corn cob were also studied andanalyzed. The test results show that as average diameter of corn ear increases, number ofrows, length of corn ear and average diameter of corn cob increase almost linearly, whilenumber of kernels per row is nearly invariable.(2) The mechanical properties of the corn carpopodium, including connection stiffness coefficient, fracture force and fracture deformation, were measured and analyzed throughfour kinds of loading ways (the radial tensile, radial compression, axial shear and tangentialshear). The test results show that loading ways and moisture content have quite significanteffects on the connection force of carpopodium, corn varieties and length of corn ear haverelatively small but still significant effects, and the effect of sections of corn ear is notsignificant. Failure forces of carpopodium under the tangential shear are the smallest, whilefailure forces under the other three loading ways are bigger and have no obvious regularity.Failure deformations of carpopodium under the axial and tangential shear are far greater thanthose under the radial compression and tension. Connection stiffness coefficients ofcarpopodium under the axial and tangential shear are far smaller than those under the radialcompression and tension. Failure forces of carpopodium under the axial shear, radialcompression and tension decrease with the increase of moisture content, while failure forcesof carpopodium under the tangential shear increase firstly then decrease with the increase ofmoisture content. As the moisture content increases, connection stiffness coefficientsdecrease, while failure deformations increase on the whole. Failure forces and connectionstiffness coefficients at low moisture content change more quickly with the change ofmoisture content. With the increase of length of corn ear, failure forces, failure deformationsand connection stiffness coefficients are obviously different, but they have no homogeneousregularity. Tests reveal that tangential shear is the most labor-saving threshing way of corn,while radial compression is the most difficult threshing way of corn because the corn kernelshall be forced into the corn cob.(3) The mechanical properties of the corn cob, including stiffness coefficient, fractureforce and fracture deformation, were measured and analyzed through four kinds of loadingways (the radial compression, axial compression, radial shear and simple bending). Theeffects of corn varieties, moisture content of corn cob, sections of corn cob, length ofspecimen and bending support span were also considered. The measurement results showthat loading ways, moisture content of corn cob, length of specimen and bending supportspan have significant influence on the mechanical properties of the corn cob, while cornvarieties and sections of corn cob have relatively small influence.