| Guizhou has special topography and soil conditions,most of which are hilly and mountainous areas with heavy clay.At present,the tillage depth of Micro tiller widely used is shallow,which can not break the tillage pan,resulting in deterioration of soil properties.A field investigations were conducted in Guizhou tobacco planting areas in order to get the exactly tillage depth data.A new small chain deep tiller was developed and the factors affecting the stability of deep tillage depth of small chain deep tiller were analyzed in order to replace the Micro tillers.On the basis of relevant design theory and virtual simulation method,several chain deep tillage blades were designed and their structural parameters were optimized.The main work and research are as follows:（1）For the first time,the present situation of soil tillage depth in Guizhou was investigated.Soil tillage depth and cultivable soil layer of 492 fields were surveyed in Bijie districts.Results showed that the utilization rate of Micro tiller was 63%in Bijie tobacco planting area.Only 50%of area are up to 25cm in tilling depth while 95%of area aremore than 30cm in cultivable soil layer.It is urgent to popularize the use of small chain deep tillers,so as to improve the tillage depth and meet the corresponding production requirements.（2）Based on geographic information system theory and ArcMap software,spatial analysis method and cross validation method of GIS were applied to analyzing the spatial distribution of cultivable soil layer thickness.Ordinary Kriging method was found as a optimal interpolation model to predict the soil thickness of uninvestigated areas.（3）The factors affecting the stability of deep tillage were analyzed for the small chain deep tiller.The chain blades structure,which has a major influence on the stability of the soil depth,were analyzed and designed theoretically.The plane blades,the curved surface blades and bionic curved surface blades were designed to crushing the soil including their straight and curve line.Combined with the different functions of the chain blades and the production requirements of the chain deep tillage device,the arrangement mode of the chain blades was built.（4）Based on Discrete Element Method,EDEM software was used to establish a model for simulating deep tillage soil groove.Cutting resistance as the optimization goal of a orthogonal experiment,the optimal structure parameters for plane blades were?n=50.988°,?=9.221°,?n=10.266°.The circular arc and bionic curved surface of blades were compared and found out that circular arc surface was better in reducing cutting resistance.The optimal structure parameters were?=27.732°,?z 0=35.180°,?z1=47.847°.The chain deep tillage device was simulated in deep tillage soil groove.The chain blades rotary angular velocity was w（28）15.7rad/s,the linear forward velocity was v（28）0.25m/s,the bottom fluctuation of the tillage layer did not exceed 20mm,and the tillage depth was stable.（5）Based on the coupling method of Discrete Element and Finite Element,the stress and strain analysis of the chain deep tillage device was carried out.The stress distribution of the whole device was good,and the maximum equivalent stress was30.878MPa,which was far less than the yield limit of Q235 steel of 235MPa.The maximum displacement of the device was 0.39 mm,which was far less than the allowable maximum deformation,the design requirements met well.（6）A field experiment was carried out to test the tillage depth stability of a small chain deep tillage tiller.The results of deep tillage under two conditions were compared.When the unit forward speed was mv=0.25m/s,the small chain deep tillage tiller was able to achieve the tillage depth of 25cm above and the width of20cm,the tillage depth stability was up to 93.05%.The parameters met the relevant agronomic requirements.In order to solve the problems of shallow surface layer and soil deterioration caused by the extensive using of micro-tillers in guizhou,this paper studied the tillage tillage depth stability of small chain deep tiller.It has practical significance.At present,the new developed optimized small chain deep tiller has been recognized by some agricultural machinery professional cooperatives in Bijie,Guizhou,began to promotion. |
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