The Physical And Mechanical Property Research Of Corn Ears And Simulated Analysis Of Corn Threshing Progress

In this paper, the physical and mechanical property of corn ears is researched, and thediscrete element method （DEM） is adopted to simulated analyze the corn threshing process.There is a review of the research status of corn threshers, the physical and mechanicalproperty of corn ears and the application of DEM in the field of particle breakage. Weselected two varieties of corn ears and one drum–type corn thresher as the research objecttested the physical properties and threshing mechanical properties of the corn ears,established the connection mechanics model between corn kernels and corncob, which wasverified by experimental results afterward. At the same time, the fracture criterion of theconnection between corn kernels and corncob was set up, which was also verified byexperimental results. At last, we carried out a bench test and simulated the corn threshingprogress using three-dimensional DEM analysis software which is researched independentlyby our group. The feasibility and effectiveness of the method of studying the corn threshingprogress by DEM was confirmed by the comparison of simulation results and experimentalresults. Thus we have put forward a novel method for the research of the corn threshingprogress. The main work and results of this paper are as follows.（1） The physical properties of the corn ears of xianfeng8and xianyu335were tested.First of all, the corn ears were divided into sections according to the morphological feature,the size of each section was tested. Secondly, the dimension of corn kernels was received bycalculation and also by tested, thus the feasibility of the modeling method of the corn earswas confirmed by the comparison of the calculated and measured values. In the final, thedensity and the moisture content of corn kernels and corncob were tested, which helps tosupply parameter data for the analysis of corn threshing progress by DEM.（2） The mechanical property of the two varieties of corn ears was studied. Theconnection mechanics model between corn kernels and corncob was set up. TheMohr-Coulomb failure criterion was used as the threshing criterion in this paper. The workand results are as follows.①The load along three axes were applied to single corn kernels attached to the cornears, influence of the load speed, variety and the corn ears’ position on the connectionmechanical property between corn kernels and corncob along three axes were studied at thesame time. The experimental results indicated that, load speed has no obvious effect on the connection mechanical property between corn kernels and corncob of the mesomere ofxianyu335at the load speed of5mm/min²00mm/min under axial load. When the loadspeed is5mm/min, the connection stiffness coefficient and fracture force between cornkernels and corncob of the mesomere under the compression force along y-axis arecomparably different between different varieties but basically identical in the test alongx-axis and z-axis. The corn ears’ position of xianyu335has little influence on the resultsunder axial force at the load speed of5mm/min.②Theconnection mechanical model between corn kernels and corncob wasestablished and the parameter selection method was also studied. Based on the theoreticalanalyses of the mechanical model, we designed compaction and shear tests in differentdirection in XY plane, studied the connection stiffness coefficient, the fracture force and thefracture displacement between corn kernels and corncob. The results indicated that when theangle between the force direction and negative x-axis axle is0°⁹0°in XY plane, the forcedirection has significant impact on stiffness coefficient and fracture force between cornkernels and corncob of the mesomere of xianyu335, but that on fracture displacement islittle. The results primarily validated the feasibility to calculate the connection force betweencorn kernels and corncob with setting the connection stiffness coefficient under axial forcesas that under space forces.③The Mohr-Coulomb failure criteria was proposed to apply as the corn kernels’ fallingoff criteria. We got the component in x-axis (F_弹X) and the one in y-axis (F_弹Y) of theconnection force between corn kernels and corncob by plugging the test results into themechanical model mentioned in②, we can verify the applicability of the criterion byjudging the location of points (F_弹Y，F_弹X) in the judgment regions. The result shows that, thepoints (F_弹Y，F_弹X) were largely sitting on the sidelines of the judgment regions ofMohr-Coulomb criterion, it is preliminarily proved applicative to apply the criterion as thejudgment condition of the corn kernels’ falling off.（3） The bench test and the simulated analysis of the threshing progress of xianfeng8corn ears were carried out using a drum–type corn thresher and the simulation analysissoftware of three-dimensional DEM developed by our group. The influence of differentexperimental factors such as rotating speed of the drum, feed quantities of corn ears andpositions of ear in maize on the threshing rate and the distribution of the renegade kernelsalong the drum shaft were analyzed. At last, the simulation results were compared with theexperimental results. The result shows that at the rotating speed of the drum of 122.70r/min³17.15r/min, when the feed quantity is10and the position is mesomere, withthe rotating speed of the drum increased, the simulate and experimental threshing rateincreases and change correspondingly. The renegadekernels decreased along the drum axleand the simulate and experimental rangeability of axial separation curve changecorrespondingly. At the rotating speed of the drum of252.10r/min, when the feed quantity is5²0and the position is mesomere, with the rotating speed of the drum increased, thesimulate and experimental threshing rate increases and change correspondingly, with amaximum relatively error of3.37%. The simulate and experimental rangeability of axialseparation curve change correspondingly. At the rotating speed of the drum of252.10r/min,when the feed quantity is10and the positions are epimere, mesomere and hypomererespectively, the positions of ear in maize on the threshing rate and the distribution of the renegadekernels along the drum shaft was little, the simulate and experimental rangeability of axialseparation curve change correspondingly. The results verify it feasible to study the cornthreshing progress using DEM.