Study On Mechanical Damage Characteristics Of Apple And Design Of Harvesting Test Platform

Apple is a typical seasonal and annual fruit with high nutritional value and storage resistance.However,Apple may be damaged in harvest,transportation,storage and grading.In China,fruit harvesting mainly depends on labor,and the labor demand and intensity in harvesting are high.Fruit industry must reduce the labor demand through mechanized operation.Facing the problem of high fruit damage rate in mechanized operation,the key to solve the problem is to study a new harvesting platform and its conveying device.By studying the apple mechanical characteristics and damage principle in the conveying process after picking,this paper provides a theoretical basis for the design of new harvesting platform to improve the mechanized harvesting level of apples.The research contents of this paper are as follows:(1)Study on mechanical properties of appleThe material characteristics of apple were measured,and the axial size,radial size,moisture content,density,fruit weight and other parameters were measured.The elastic modulus of apple pulp,peel and core were measured by compression and tensile tests and the damage stress was measured as well.Through the finite element simulation analysis,apples were loaded.When the axial loading force was 5N,10 N and 15 N,the maximum stress corresponding to the apple peel was 0.0835 MPa,0.1669 MPa and 0.2504 MPa respectively,apples would not be damaged.When the loading force was 20 N,the stress of the pulp was0.3199 MPa,which was greater than its failure stress of 0.31 MPa.When the radial loading force was 5N,the maximum stress corresponding to apple peel was 0.3093 MPa,and the stress of peel,pulp and core were less than its failure stress,and there was no mechanical damage.When the loading force was 10 N,15N and 20 N,the stress of apple peel and pulp began to be greater than its own failure stress,and apples began to suffer varying degrees of mechanical damage.Through three factors and three levels orthogonal test,the relationship between apple drop height,apple single fruit quality and buffer material and apple collision damage volume was analyzed.The significance was ranked as drop height H > Apple buffer material P >Apple Quality M from high to low.The process of apple impact damage was simulated by finite element simulation,and the relationship between drop height,drop angle and drop direction was obtained.(2)Structural design and mechanical analysis of apple harvesting test platformA multi station harvesting test platform was designed,and the distance between the medium and high stations and the ground was determined.Complete the design of conveyor,chassis wheel set and picking workbench of the test platform and the selection of electrical components.Determine the length of main conveyor was 2100 mm,width was 640 mm,inclination was 20 °,the length of sub conveyor was 1050 mm,width was 190 mm,installation angle was 30°and could be adjusted freely.The finite element analysis and strength check of the key parts of the test platform were carried out.The analysis showed that the maximum stress on chassis was 241.2MPa,the maximum deformation was 1.286 mm,the maximum stress on axle was 34.28 MPa,the maximum deformation was 0.055 mm,and the stress on picking workbench under two working conditions were 15 MPa and 9Mpa respectively,and the maximum deformation were 0.439 mm and 0.025 mm.The modal analysis of the workbench was carried out to determine that there was no resonance on the workbench,and the above components all met the strength requirements.The simulation analysis of apple conveying process showed that the better placement mode and the belt speed range of sub conveyor after picking apples were 0.02 ～ 0.04m/s.(3)Processing and transportation test of harvesting test platformThe apple harvesting test platform was processed,the parameters and dimensions of the test platform were measured and compared with the design value.The test platform basically met the working requirements,and then the apple conveying test was carried out.Hanfu apple as the research object,belt speed of conveying device as the factor and the conveying efficiency and apple damage rate as the evaluation index,the influence law of sub conveyor belt speed and main conveyor belt speed on conveying efficiency and apple damage rate were determined,and the value range of sub conveyor belt speed were determined,so as to achieve better conveying effect and reduce apple damage rate under the condition of ensuring conveying efficiency.