青贮玉米仿生切碎刀具优化与试验

    Optimization and testing of characteristic curves of bionic shaped chopping Cutter for silage maize

    • 摘要: 为减小现有青贮玉米切碎刀具作业的切割阻力,降低斜茬率,提高标准草长率,该研究对前期河狸门齿仿生切碎刀具进行优化,确定了刀具结构和动定刀配置参数。采用带几何约束的最小二乘拟合方法对刀具原始轮廓进行非均匀有理 B样条(non unibmn ratinalb splime, NURBS)曲线优化,并分析了凸圆弧曲线刀刃刃倾角、刃斜角与刀刃受力及强度的关系。使用Rocky软件模拟优化前后3种刀具切割的阻力变化,试验结果表明:优化后仿生刀具最大切割阻力为625.05 N,较平板直刀降低13.42%。采用三因素三水平正交试验分析切碎刀刃关键参数对青贮玉米秸秆最大切割阻力的影响,台架试验结果表明,当外滑切角为30°、刃倾角为6°、刃斜角为2°时,切割阻力最小,为536.79 N,比原仿生刀降低14.86%。以作业速度、动定刀间隙、动定刀间距为试验因素,以标准草长率和斜茬率为试验指标,开展二次旋转正交组合试验,试验结果表明:当作业速度1.94 m/s、动定刀间隙0.23 mm、动定刀距离179.39 mm时,标准草长率为93.64%,斜茬率为2.42%;田间收获验证试验结果表明:当作业速度1.94 m/s、动定刀间隙0.2 mm、动定刀距离178 mm时,标准草长率为95.09%,斜茬率为2.50%,试验结果与优化结果相对误差小于5%,较常用平板直刀标准草长率提升了13.56个百分点,斜茬率降低了3.06个百分点。研究结果可为青贮玉米切碎刀具设计提供参考。

       

      Abstract: The study aims to reduce the cutting resistance of the existing silage corn chopping blade operation, in order to reduce the slant rate and improve the standard grass length, the pre-biomimetic beaver incisor profiled chopping blade was used to fit the characteristic curves and optimize the design. A systematic analysis was made to determine the parameters of the blade structure and the movable, as well as the fixed blade configurations. the original profile of the blade with non unibmn ratinalb splime (NURBS) curve was optimized using the least square method (LSM) with geometric constraints. A systematic analysis was made to clarify the relationship among the edge inclination and rake angle of the convex arc curve, as well as the force and strength of the cutting edge. A simulation was carried out using Rocky software. An experiment was then conducted to calculate the resistance changes of the three types of knives when cutting straw before and after optimization. The test results showed that the maximum cutting resistance of the optimized bionic blade was 625.05N, which was 13.42% lower than that of the flat straight blade. The three-factor, three-level orthogonal test was conducted to study the effect of the key parameters of the curved edge of the chopping blade on the maximum cutting resistance of the silage corn stalks, and the results of the bench test showed that the cutting resistance of the blade was the smallest when the angle of the outer sliding cutting was 30°, the tilt angle of the blade was 6°, and the bevel angle of the blade was 2°, and the maximum cutting resistance of the blade under the parameter of the simulation was 536.79N, which was 14.86% lower than that of the original biomimetic shaped blade. The quadratic rotation orthogonal combination test was carried out with the operating speed, the gap between the moving and fixed blade, and the spacing between the moving and fixed blade as the test factors, with the standard grass length rate and the oblique stubble rate as the evaluation indices. The test results show that when the operating speed was 1.94 m/s, the gap between the moving and fixed blade was 0.23 mm, and the spacing between the moving and fixed blade was 179.39 mm, the standard grass length rate was 93.64%, and the oblique stubble rate was 2.42%; the field harvesting results also show that: when the operating speed was 1.94 m/s, the gap between the movable and fixed blade was 0.2 mm, and the spacing between the moving and fixed blade was 178 mm, the standard grass length rate was 95.09%, and the oblique stubble rate was 2.50%, and the relative error between the experimental results and the optimized results was less than 5%, and the standard grass length rate of the commonly used flat straight blades was improved by 13.56%, and the oblique stubble rate was reduced by 3.06%. The results of this study can provide a reference for the design and optimization of silage corn chopping blades.

       

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