| The collision between potato and rod lifting chain during harvest is the main source of potato damage.In this study,the collision damage between potato and rod was studied and the working parameters of lifting chain were optimized.Hertz contact theory is used to analyze the contact stress of potato and rod when they collide,and the bruise mechanism of potato is obtained through experimental research;With the help of finite element analysis software,the oblique collision simulation is carried out,and the safe friction threshold of potato is obtained combined with the analysis of test results;Based on the analysis of the working principle of the rod lifting chain and the motion characteristics of the shaking device,the rod lifting chain test-bed is designed,and the working parameters of the rod lifting chain are optimized and verified.This study has a certain reference value for reducing the damage of potato in the transportation link.The main research contents and conclusions are as follows:(1)Acquisition of physical parameters and mechanical properties of potato.The potato variety helan15 was selected in this study.The average values of triaxial dimension and mass are 95.70 mm,59.00 mm,49.92 mm and 166.26 g;The density of helan15 potato in harvest was 1.12 g/mm3 measured by drainage method;The static friction coefficients between helan15 potato and 65 Mn steel and rubber are 0.551 and 0.819 respectively;The elastic modulus of helan15 potato on the day of seedling killing,the fifth day after seedling killing and the tenth day after seedling killing were 6.59 MPa,6.3 MPa and 6.21 MPa respectively.The results showed that the elastic modulus of potato after seedling killing continued to decrease within ten days.(2)Study on bruise mechanism of potato rod falling forward collision.Based on Hertz contact theory,it is concluded that the influencing factors of positive impact bruise are potato tuber quality,relative velocity during impact,elastic modulus of potato and contact material,rod diameter;Taking the damage volume and impact energy loss as evaluation indexes,the potato rod drop forward impact single factor test was carried out;The experimental results show that the degree of potato drop bruise is directly proportional to the drop height,potato quality and potato elastic modulus,inversely proportional to the thickness of rubber tube,and is highly linearly correlated with the impact energy loss in normal collision.The fitting linear regression equation is;According to the regression equation,the theoretical impact energy loss threshold of bruise is 0.46 J;By analyzing the contact stress distribution characteristics of pressure sensitive film,it is found that the positive contact surface between potato and rod is oval,and the contact area increases with the increase of drop height,potato quality and rubber tube thickness.The larger the damage volume is,the larger the high stress distribution area is.(3)Study on the mechanism of potato rod falling oblique impact scratch.The mechanical analysis of the oblique contact between potato and rod was carried out.The results showed that the main reason for the oblique contact scratch of potato was the friction of the contact surface;In order to obtain the safe friction threshold of potato oblique impact,a potato rod drop oblique impact test system was built.Through the drop oblique impact test,it was found that the safe drop height of potato was 150 mm when the inclination angle was 45 °;With the help of finite element simulation software ABAQUS,the falling oblique collision simulation of potato under 45 ° is carried out,and the safe friction threshold of helan15 potato is 70.45 n;At the same time,the safe drop height of potato with an inclination angle of 30 ° and 60 ° is75 mm and 275 mm respectively.(4)Optimization of working parameters of rod lifting chain.By analyzing the working principle and motion of the bar lifting chain,it is concluded that the factors affecting the operation quality of the lifting chain are the inclination of the lifting chain,the trajectory radius of the shaking wheel and the rotation speed of the shaking shaft;A bar lifting chain test-bed was built.Taking the damage rate and passing time as the response index,the three factor and three-level orthogonal combination test is designed.Through the analysis of the test results,it is obtained that the optimal working parameters of the rod lifting chain are the lifting chain inclination angle of 21 °,the moving track radius of the shaking wheel of 90 mm and the rotating speed of the shaking axis of 140 r / min.the verification test is carried out.The damage rate of potato is 1.41% by wrapping 4mm rubber tube on the rod,and the passing time is 0.86 s,which meets the design requirements of the rod lifting chain. |
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