| Soil-tool interaction is one of the major studies for the tillage process, and soil-tool interaction has a critical impaction on reducing cutting resistance and the energy efficiency. Many methods can be used in analysis the soil-tool contact process, such as theories analysis, experiment analysis and numerical simulation. However, numerical simulation has certain advantages in soil-tool contact analysis because of ensuring simulation results, saving time and saving labour and material resources.This paper established the soil-tool interaction model based on extended finite element method, discrete element method and the basic physical and mechanical parameters of Yunnan red soil. The cutting resistance was studied by numerical simulation and orthogonal design on different rake angle, depth of soil and the coefficient of friction between soil and farming tools. The extended forms of soil cracks in the cutting process were also investigated in this paper. Numerical simulation results are:(1) When the rake angle is fixed, the crack length increases and flattens with the increase of the tillage depth and coefficient friction; when the coefficient friction changes, with the fixed rake angle and tillage depth, the forms of soil cracks vary.(2) With the rake angle of20°, tillage depth0-10cm, and the friction coefficient of0.45, the cutting resistance is small, while the cutting resistance is large with the rake angle of25°, tillage depth11-20cm, and the friction coefficient of0.7.The simulation results in this paper have a good correlation with the experiment data obtained by O.B Aluko. The conclusions from soil cracks extended forms and the cutting resistance are:(1) The forms of soil cracks and the cutting resistance force are different with different factors and levels.(2) The rake angle, tillage depth, and the coefficient friction between soil and tools are have major effections on cutting resistance in soil cultivation and the interaction among these factors should not be ignored.(3) Analysis of variance results showed that, rank angle is the main impact factor in tillage process, the following factors are the interaction between rake angle and the coefficient of friction between soil and farming tools, tillage depth, coefficient of friction between soil and farming tools, the interaction between rake angle and tillage depth. Intuitive analysis results showed that, rank angle is the main impact factor in tillage process, the following factors are the interaction between rake angle and the coefficient of friction between soil and farming tools, coefficient of friction between soil and farming tools, tillage depth, the interaction between rake angle and tillage depth.(4) Intuitive analysis results indicated that:the cutting resistance is smallest on15°of the rake angle, while the cutting resistance is largest on25°; the cutting resistance is smallest on0-10cm of the tillage depth, while the cutting resistance is largest on21-30cm; the cutting resistance is smallest on0.6of the friction coefficient, while the cutting resistance is largest on0.7;(5) The optimal solution in this study is the rake angle of15°, tillage depth0-10cm, and the friction coefficient of0.6by the smallest cutting force,.The results obtained in this paper can helpful for future theoretical and practical study of soil-tillage interaction problem. |
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