Objective:Research was conducted to determine the minimum squeezing force that caused damage to corn kernels during the mechanical threshing process ,as well as the minimum axial and radial shear forces required to separate the corn kernels from the cob.Methods:Three kinds of ears of different periods were picked before and after ,the extrusion and shearing tests of the ears were carried out by using a universal tensile and compression testing machine.Results:The extrusion test results showed that the grain of the ear would go through three stages ,namely ,deformation ,breakage and burst.During the different picking periods ,the mean value of moisture content was 71.51％ ± 2.00％, 64.96％ ± 2.00％,50.21％ ± 2.00％ respectively.The average value of the test force corresponding to the critical point of grain damage was 81.7 ,644.5 ,960.4 N respectively.The results of the axial shear tests showed that when the average of the axial cutting force on the spike at 25.3 ,60.8 ,234.1 N ,the first and second rows of grains were completely removed.The results of the radial shear test showed that the mean test force for radial resection of single grain ears was 20.5 , 12.1 , 6.8 N ,respectively.Conclusion:The important physical and mechanical parameters obtained in this study could provide theoretical basis and reference for the design of key components of fresh corn thresher.
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