油菜籽粒点面接触碰撞中恢复系数的测定及分析

Measurement and analysis of rapeseeds' restitution coefficient in point-to-plate collision model

为建立油菜籽粒与播种、收获等机具相关重要工作部件间发生碰撞时的碰撞模型,该文基于运动学方程构造了油菜籽粒恢复系数的测定装置,并针对油菜籽粒的弹性特性进行了试验测定和分析。针对华双4号油菜品种,采用L8(41×24)混合正交试验方案研究了碰撞材料、碰撞材料厚度、自由下落高度和含水率等因素对油菜籽粒恢复系数的影响,然后针对碰撞材料、下落高度和碰撞材料厚度等重要因素进行了单因素试验,并进一步获得下落高度和碰撞材料厚度2个因素对恢复系数的影响规律及回归方程。试验结果表明,影响油菜籽粒恢复系数的因素主次顺序为:碰撞材料、自由下落高度、碰撞材料厚度和含水率。油菜籽粒与Q235、铝合金、有机玻璃、橡胶等碰撞材料之间恢复系数依次减小,并且随着下落高度的增加而减小,随着碰撞材料厚度的增加而增大。在碰撞材料为厚1 mm的Q235和籽粒含水率8.06%条件下,恢复系数随下落高度变化的回归方程决定系数R2=0.9979;在碰撞材料为Q235、籽粒含水率8.06%和下落高度420 mm条件下,恢复系数随材料厚度变化的回归方程决定系数R2=0.9872。该文结果可为油菜精密播种及高性能收获机具中相关工作部件的设计提供依据。

The restitution coefficient is an important elementary physical data of the grain related to the research and development of farm machinery. In order to build a collision model between oil rapeseeds and key parts of seeding or harvesting equipment, a restitution coefficient measuring device based on kinematics was designed in this paper, and the restitution coefficient of oil rapeseeds was measured and analyzed by experiment. Research on the collision materials, the thickness of collision materials, the falling height, and the moisture content of oil rapeseed＇s effect on the restitution coefficient of the ‘Huashuang 4＇ oil rapeseed was conducted by a mixed orthogonal experiment based on the scheme of L8（4^1×2^4）. Then, single factor tests for factors including the falling height, the material thickness, and the moisture content of oil rapeseeds were carried out and the corresponding regression equations were obtained by analysis. During the experiment, selected rapeseeds were soaked in pure water for about 3 hours and then air-dried in the shade for 2 hours. After that, an ‘MB45 Moisture Analyzer＇（made by Ohaus） was used to control the moisture content of rapeseeds by drying them in different times, determining it by drying them until the weight did not vary. An existing camera tripod was used to control the falling height and four kinds of materials, including Q235 steel, rubber, aluminum and Plexiglass, in different thicknesses were used as well. For each test, oil rapeseeds were dropped from the same height, rebounded after collision with an inclined plane at a fixed angle, and then received and fixed by two groups of sponge plates covered with lithium grease in different levels. Two groups of different placement data were measured, with which the restitution coefficient can be deduced according to the related formulas. 15 to 25 oil rapeseeds with diameters from 1.80 mm to 1.95 mm were selected manually, which should be in good sphericity（if any of which were wizened, not full, or elongated would be ruled out）. When the placement data was being determined, the measurement point was required to be the center of a circle which should embrace most of the oil rapeseeds（more than 90%）. Experimental results show that the most significant factor is the collision material, followed by the falling height, then the thickness of collision material; the moisture content of oil rapeseeds is the most insignificant factor. Furthermore, the restitution coefficient of oil rapeseeds ascends steadily at first and then more slowly with the increasing of the thickness of collision material, but the restitution coefficient decreases along with the declining of the falling height. Under the condition that the oil rapeseeds＇ moisture content is 8.06% and the thickness of Q235 steel as the collision material is 1mm, determination coefficient R^2 of the regression equation for the curve of the oil rapeseeds＇ restitution coefficient with the falling height is 0.9979. Under the condition that the oil rapeseeds＇ moisture content is 8.06%, the falling height is 420 mm, and the collision material is Q235 steel, determination coefficient R^2 of the regression equation for the curve of the oil rapeseeds＇ restitution coefficient with the material thickness is 0.9872. Those results above can be an important reference in the designing and developing of high performance rapeseeds seeding or harvesting equipments.