| The stalk chopping device is a crucial component of the stalk turnover of a corn harvester,and its performance significantly impacts the operational quality and efficiency of the machine.However,traditional stalk chopping devices are limited by low instantaneous stalk grasping capacity,unsatisfactory cutting quality,high energy consumption,and severe tool wear,all of which significantly decrease the operation speed of the corn harvester and affect the overall efficiency and quality of the machine.To address these issues and achieve high-quality,high-efficiency,and low-power operation of the stalk chopping device of the corn harvester,this study proposes a longitudinal arrangement of cutter by combining the theoretical analysis,virtual simulation,and experimental research methods.The study also explores the longitudinal cutter-stalk interaction mechanism while fully considering the structures and cutting characteristics of the corn stalk.The cutting-sawing mechanism of ant mouthparts was analyzed and proposes a bionic design for the stalk-cutting blade.Moreover,the study elucidates the bionic cutter-stalk cutting mechanism,optimizes the blade parameters of the bionic cutter,and experimentally studies the performance of the longitudinal stalk chopping device and the bionic cutter.The main contents and findings of the study,which aims to increase the operation quality and efficiency of the stalk-chopping device of the corn harvester.The main content and conclusion are as follows:(1)This study analyzed the physical characteristics of the corn stalk and experimentally studied its cutting characteristics.A correlation model was established between the key physical parameters of the corn stalk,and the tissue structures of corn stalk internodes and stalk nodes were compared and analyzed.This study also established a regression equation between the cross-sectional area and the maximum cutting force at corn stalk internodes and stalk nodes.Through testing the cutting characteristics of the corn stalk,the significant factors influencing the maximum cutting force at the internodes and stalk nodes were determined to be the stalk cross-sectional area,loading speed,and mis-cut angle.These findings provide a theoretical basis for the optimization of the design of key components and simulation experimental research.(2)The study also investigated the longitudinal cutter-stalk interaction mechanism and kinetic analysis.The longitudinal stalk chopping device was used to analyze the longitudinal cutter-stalk interaction mechanism,and a mechanical model of the longitudinal cutter and a mathematical model of the blade motion trajectory were established.The study established a kinetic model of longitudinal cutter-stalk to analyze the critical conditions of stalk fracture during the operation of the longitudinal cutter and longitudinal chopper.Accordingly,the study determined the structural parameters of the cutter that affect the cutting of stalk and the working parameters of the longitudinal chopping device.The mathematical calculation models of the stalk cutting angle and stalk section length were established.(3)The cutting mechanism of ant mouthparts was investigated and a bionic blade was designed.The biological characteristics of ants were analyzed,and the movement characteristics of the upper jaw of ant were studied using high-speed photography technology to investigate the cutting-sawing mechanism of the maxillary-tooth blade of the arch back ant.The frontal and lateral contour curves of the maxillary teeth of the arch back ant were extracted through image processing technology,and mathematical models of the frontal and lateral contour curves of the maxillary teeth were established.On the mathematical analysis of the frontal contour curve of the palate of the arch-back ant,the 4th tooth structure of the arch back ant was selected as the bionic object for the cutter blade structure.The mapping relationship between the cutting area per unit time of the 4th tooth of the palate and the cutting area per unit time of the stalk cutting blade was established by combining the basic dimensions of the 4th tooth,to complete the design of the bionic cutter and the bionic chopper.(4)In this study,the bionic cutter-stalk interaction mechanism was elucidated,and the parameters were optimized.The finite element method was used to investigate the effects of the blade pitch,angle of inclination,and structural edge angle on the deformation and stress field of the bionic cutter under two conditions: the force acting along the edge direction of the blade and the blade surface direction.The structural design of the bionic cutter blade and the bionic chopper blade was accomplished,and the deformation and stress field of common and bionic knives were compared and studied.The total deformation and maximum equivalent stress values of bionic blade cutting knives were reduced by 2.09% and 0.98%,respectively,compared to those of common chopping knives;the total deformation and maximum equivalent stress values of the bionic chopping knives were reduced by 12.69% and 2.60%,respectively,compared to those of common chopping knives.The order of significance of the operating parameters affecting the equivalent stress on the stalk was obtained through cutting simulations as follows: blade shaft speed > blade mounting angle > travel speed > angle of inclination of blade.Compared to that of common cutting blade and common chopping blade,the maximum equivalent force on stalk when cut using a bionic cutting blade and bionic chopping blade is increased by 8.29% and 8.76%,respectively,indicating that bionic blade are more suitable for cutting corn stalk.(5)An experimental study was conducted on the cutting performance of a longitudinal stalk chopping device.A test bench for a longitudinal stalk chopping device of the corn harvester was built,and the bionic cutter and bionic chopper were produced using metal three-dimensional printing technology.Based on single factor test and four-factor four-level orthogonal combination test,the order of significance of the test factors on the qualification rate of the stalk section length was determined as follows: blade mounting angle,blade type,blade shaft speed,and travel speed.The optimal combination was determined to be a blade shaft speed of 1400 r/min,blade mounting angle of 50°,travel speed of 3.5km/h,and blade type combination of a bionic cutter and a bionic chopper.The order of significance of influence on stalk-cutting power consumption was in the order of the blade mounting angle,blade shaft speed,blade type,and travel speed.The optimal combination of stalk-cutting power consumption was determined to be a blade shaft speed of 1400 r/min,blade mounting angle of 50°,travel speed of 3.0km/h,and blade type combination of a bionic cutter and a bionic chopper.Field trials were conducted to validate the results.The combination of optimal parameters achieveded a qualification rate of 97.31% for the stalk cutting length,stubble height of 70.03 mm,and breakage rate of stalk of 1.02%.These results met the design requirements of corn harvester stalk chopping and returning to the field,as well as other relevant performance indicators and technical requirements of corn harvesting machinery. |
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