| One of the main grain crops is corn in China,accounting for more than 23.57% of total world production.As a major grain crops in Yunnan region,corn occupies the largest planting area.Therefore,it is a main source of income for farmers in mountainous areas.However,the efficiency of corn production in Yunnan Guizhou Plateau is low,as a result of it,human labor is largely wasted.It is caused by the fact that the mechanization seeding of corn is less than 5% in Yunnan because there are heavy soil and relatively small farmland.Moreover,there are problems with the existing planters in operations such as low passing frequency and poor sowing quality.Based on the experimental study on the stretch and cutting of maize roots,a new type of maize no tillage planter sowing machine is designed.According to the principle of active disc cutter cutting,twice ditching,fertilizing and seeding.The machine is driven by a type of micro tillage with a disc cutter,which can do operations of stubble,ditching,fertilizing and seeding at the same time,the field test was carried out before putting into practice.This study was based on the Yunnan provincial science and Technology Department(2015FB125)project "Research on the mechanism and machinery of no tillage sowing and anti-blocking of Maize in rocky desertification area".Detail research content and conclusions are as follows:(1)This study sets on corn planting environment and Agronomy in Yunnan,the maize cultivar "Liyu 168" pot breeding shows that its growth period was 118 days,176 cm in plant height,85 cm ear height,13.4 cm for ear length,4.9 cm ear diameter,14~16 rows per ear,the seeds are closely arranged,and seed rate reaches more than 85%.The weight of 1000 grains is 353.17 g and the germination rate reaches more than 95%.Through in-depth study on the mechanical properties maize root and the physical and mechanical properties of soil,the overall structure of maize no tillage planter is finally determined by the application of disc cutter and the depth limited wheel walking device with stubble trenching depth limit anti-skid function,and so do the structure of maize no tillage planter stubble device finally determined.(2)Dealing with the problems of present no tillage planters,it is necessary to develop key devices.The design of stubble depth wheel attempts to ensure a high speed cutting and good grip performance.Cutting off the stubble through a rotating and sliding circular knife,as well as opening the ditch again in the narrow channel by a double disc,which can realize two processes of seeding and fertilizing in a vertical ditch.(3)A tensile and shear tests of corn stubble are done,the results shows that: The maximum tensile force and stubble is proportional to the diameter of root stalk,while the tensile strength is negatively related.The limit of three different standard distance of the stubble shall is 6.8 MPa,5.9 MPa and 5 MPa.The higher the root diameter,the more changes of the tensile strength.When the moisture content is low,the elongation rate increases with the increasing length of diameter,while the moisture content is high,the opposite result can be attained.The ultimate shear stress of stubble increases with the increase of root diameter,but when it is more than 4mm,it reaches its maximum at 70% moisture content.Through the shear performance test of root soil composite,it is known that moisture content is the most critical factor affecting the ultimate shear stress,and the largest force is the corrugated disc cutter.(4)Through Solidworks/Simulation,static analysis is carried out on the structural strength of three different types of disc knives.The maximum stress and displacement of the notched disc knife,respectively were 97.68 MPa,0.286 mm.Therefore,a conclusion can be drawn that the test results meet the requirements,and the design is reasonable.Through applying the ANSYS/LS-DYNA to display dynamic analysis,the results show that the corrugated circular knife force is 747.18 N,the gap and the plane disc were 406.99 N and 351.18 N.According to the stress distribution of disc cutter cutting soil model,it is known that there are no stress concentration on X,Y,Z of three types of disc cutter,which indicates that the design of cutting tools is reasonable.At the same time,through the analysis of the direction of the three shape variables we can know that the depth of ditch is respectively in 92.7 ~ 96.4 mm when the three types of disc cutter are in operations.(5)According to the field tests carried out by corn no tillage planter machine,the results show that the new type no tillage planter with plane disc cutter has the following features: the soil disturbance,corrugated fuel consumption and gap disc are respectively lower 4.03%,1.15% and 14.6%,7.5%;traction resistance at 0.54 m/s 1.2 kN.By using the three types of disk cutter,fertilizer use depth pass rate reaches more than 85%,the qualified index of the grain distance is 90.3% and the main technical parameters are qualified. |
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