Study On The Mechanical Properties Of Corncob And Corn Kernel Carpopodium

Corn is one of the three major grain crops in China.Corn threshing is one of the key aspects in the process of corn harvesting,and the corn thresher is widely used in China.In order to improve the performance of corn threshing machinery,the mechanical properties of corncob and corn kernel carpopodium need to be studied.The research status of the mechanical properties of corncob and corn kernel carpopodium is reviewed in this paper.The mechanical properties of corncob are studied by discrete element method,and our research team developed DEM-based software which can simulate the process of corncob crushing.By the comparison of the simulation results with the experimental results,the feasibility and effectiveness of the corncob's modelling method are verified.Two varieties of corn ears(Gaoyu and Fuyou)are selected as the research objects.The mechanical properties of the corn kernel carpopodium are measured by a WDW-20 computer controlled electronic universal testing machine.The main work and conclusions of this paper are as follows.(1)The modelling method of corn cob is proposed,and the method of combination of particles is used to model the corn cob.The mechanical model of corn cob is established.The parameters in bonding model and contact model are selected.(2)The crushing of corn cob is carried out by simulation.The effects of diameter and length on the mechanical properties of corn cobs are studied.?The stiffness coefficient of corncob decreases with the increase of the length of corn cob,and the simulation results are consistent with the test results.The disruption displacement of corncob increases with the increase of the length of corn cob,and the simulation results are consistent with the test results.?When the corn cob height is 20,40 and 60 mm respectively,the relative error between the simulation value and the test value in the stiffness coefficient is 8.74%,9.34% and 1.78% respectively.?With the increase of the diameter of corn cob,the stiffness coefficient of corn cob has rising trend.The results show that the modeling method of corn cob proposed in this paper is effective and feasible.(3)The mechanical properties of the corn kernel carpopodium is measured and analyzed through four kinds of loading ways(the radial tensile,radial compression,axial shear and tangential shear).The effects of two factors(varieties and moisture content)on the damping force of corn kernel carpopodium are analyzed.?The effects of variety of corn on the mechanical properties of corn kernel carpopodium is studied.The results show that different varieties of corn kernel carpopodium have different mechanical properties.?The effects of different moisture content on the mechanical properties of corn kernel carpopodium is studied.With the increase of moisture content,the variation trends of the damping force of the first ring area and the second ring area are the same.With the increase of moisture content,the damping force of corn kernel carpopodium measured through three kinds of loading ways(the radial tensile,radial compression and axial shearing)decreases first and then increases,but the damping force of corn kernel carpopodium measured through the tangential shearing decreases.?It is studied that the effects of different loading ways on the mechanical properties of corn kernel carpopodium are studied.The damping force of the corn kernel carpopodium has the largest value in radial compression,and the damping force of the corn kernel carpopodium has the second largest value in radial tensile.The damping force of the corn kernel carpopodium has the minimum value either in axial shearing or tangential shearing.