Influence factor analysis of mechanical damage on corn ear picking

Abstract: In order to study the damage and mechanism of corn during corn ear picking, this paper analyzed the force of corn ear when picking corn ear, and then found that there were 3 kinds of forces working on corn ear, which were the reacting force, the frictional forces of stripping roller and the force of stripping roller rib, and caused the corn ear damage with different forms. This paper made the mathematical model of forces, and analyzed their change law and their influence on the damage of corn ear. With the rising of corn ear diameter, the reacting force, the frictional forces of stripping roller and the seed loss increased. The experiments of corn ear picking were carried out on test bed. The results showed that the damage of corn seed increased as the length of corn ear was greater than 175 mm. Because with the increase of the corn ear, the center of gravity for corn ears was upward and the corn ear swing increased when it was picked, the probability of collision increased. The rate of corn damage descended as the rotating speed of stripping roller changed from 650 to 800 r/min. When the rotating speed of stripping roller was more than 800 r/min, the corn damage increased significantly. When the rotation of stripping roller became faster, the down velocity of corn ears became bigger, the impact between corn ear and stripping roller increased, and the corn damage rose. Besides, the reduction of friction between the maize straw and stripping roller was another reason for the increasing of corn damage. The corn seed loss rate decreased and then increased as the rotating speed of stripping roller changed from 650 to 750 r/min, and the corn seed loss rate decreased again as the rotating speed of stripping roller changed from 750 to 850 r/min. Because when the rotation of stripping roller became faster, the corn ear down speed became bigger, the impact between the corn ear and stripping roller increased. The corn damage and seed loss decreased and then increased as the stripping roller clearance changed from 8 to 15 mm. The corn damage and seed loss were the minimum when the stripping roller clearance was 10 mm, and then with the clearance of stripping roller increasing, the corn damage and seed loss ascended, which was consistent with the result of theoretical analysis. And the mechanical damage form of corn usually included corn nibbled, corn impacted, corn extruded and broken corn ear. The process of corn ear picking was recorded with the high-speed camera and the movement of corn ear was analyzed. The results indicated that the moving velocity of corn ear had no effect on corn damage. It was also observed from the record that the moving state of corn ear picking had 3 types: first, corn ear was picked smoothly and entered the conveyer device; second, corn ear bounced; third, corn ear picking became difficult or corn ear contacting stripping roller for a long time. And the corn ear damage became more serious with the increasing of the contacting time between corn ear and stripping roller.