稻麦秸秆旋耕作业中受力与位移分析

Stress and Displacement Analyses of Rice and Wheat Straws in Rotary Tillage Process

摘要:

常见稻麦秸秆在实际作业过程中与刀具作用发生2种变形：挤压秸秆发生弯曲变形和剪切秸秆发生剪切变形，根据2种变形设置弯曲试验和剪切试验，分别测试15~30mm/min加载速率下弯曲强度和剪切强度。试验结果表明，小麦秸秆抗弯强度随着加载速率增加而减小；水稻秸秆抗弯强度随着转速增加，表现为先增加后减小。小麦秸秆剪切强度随着加载速率增加，表现为先增加后减小；水稻秸秆剪切强度随着加载速率增加而增加。其次在田间试验中，根据2种变形设置横纵向秸秆以及180~280r/min的刀轴转速，并对其反旋作业。采用同位素示踪法，即根据标记秸秆前后坐标变化值来代替机具在幅宽范围内纵横向秸秆的位移变化，将得到的标记点坐标在三维坐标系中用Matlab绘制成曲线，该曲线形状与旋耕刀片在刀轴上排列相似。耕作后位移和坐标结果表明：水稻秸秆位移大于小麦秸秆位移，水稻秸秆标记点位移变化较小麦秸秆标记点位移变化均匀；2种秸秆排列方式对应2种分布情况：纵向标记秸秆坐标在X轴上以零点对称分布，横向标记秸秆坐标在X、Z轴上两侧对称分布。基于以上因素考虑，实际作业中，选择刀轴转速230r/min以及改变秸秆在田间排列方式，以使秸秆还田效果达到更佳。

Abstract:

Because of two kinds of deformation with tool under general process of tillage, i.e., bending deformation with straw extrusion and shear deformation with straw shear, at loading speeds of 15~30mm/min, and also on two different positions of straw for measuring the displacement in the soil, which was horizontal and vertical with down-rotary speeds of 180~280r/min with the help of color straw labeled and arranged in lines and paralleled to the rotor axial. The original and final positions of straw tracers were drawn with Matlab software. It was found that the shape of final positions was similar to the arrangement of rotary blades attached to the rotor. The results revealed that the bending strength of wheat straw was decreased with increase of loading speed, and that of rice straw was increased at initial stage and then decreased with the increase of loading speed. It was obvious that the shear strength of rice straw was increased, and for wheat straw it was also increased at initial stage and then decreased with the increase of loading speed. The comparisons and conclusions of experiment were drawn as follows: the displacement and fluctuation of rice straw were greater compared with those of wheat straw, and the straw arrangement mode was corresponding through two types of straw distribution, the coordinate position of vertical straw and horizontal straw was symmetrically distributed on the X axis and X and Z axes, respectively. Based on these findings, the rotational speed of 230r/min can be chosen，meanwhile，adjusting the operation type and straw arrangement in the field can help to achieve a good effect of straw returning to field.