【作者】 张清珠；

【导师】 佟金； 陈东辉；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2014， 博士

【摘要】 镇压辊是农业机械中典型的滚动触土部件，用于压实土壤。适当的压实可以减少土壤中的大孔隙，使种子与土壤紧密接触，加强毛细管作用，提高作物产量。传统镇压辊材料多为石材、铸铁或钢材，触土表面在宏观上是普通光滑的，其作业过程中容易粘附土壤，不但增加能耗，降低作业效率，而且使土壤失墒严重，影响种子发芽。此外，传统镇压辊作业过程中会将一部分土壤推到镇压辊前方，形成波浪状凸起，即“拖堆壅土”现象，不但使镇压辊达不到镇压的目的，还要多消耗功，而且会导致种子间距分布不均，造成作物减产。镇压力的合理选择与土壤墒情有关。本研究通过压板下陷试验获得含水量分别为20%d.b.和28%d.b.的土壤在不同镇压力下的土壤容重和下陷量。采用Bailey三参数模型描述应力-容重关系，通过Matlab最小二乘法对试验数据进行拟合，得到2种土壤含水量对应的应力-容重方程。将适宜玉米生长的容重带入方程，并经过换算，得到土壤含水量分别为20%d.b.和28%d.b.时，适宜的镇压力范围为25.25kg~88.48kg和13.95kg~70.26kg，为后续土槽试验和田间试验提供了依据，并且不同镇压力对应的下陷量可以用来验证有限元的模拟结果。土壤洞穴动物臭蜣螂和穿山甲在粘湿土壤环境中行动自如，且身体表面不粘土。研究表明其体表的几何结构是其防粘减阻的原因之一。本研究根据臭蜣螂(Coprisochus Motschulsky)腹侧面的几何结构，设计了9种仿生肋条型几何结构镇压辊，其中仿生肋条结构采用超高分子量聚乙烯(UHMWPE)材料，通过螺纹紧固方式固定在镇压辊基体上，镇压辊基体采用Q235钢。用正交试验方案在室内土槽进行试验研究，以粘附土壤量、牵引阻力、种子粒距变化率和土壤容重为试验指标，考察土壤含水量分别为20%d.b.和28%d.b.时，仿生肋条结构的底面宽度、高宽比(仿生肋条结构的断面高度/底面宽度)、载荷和面积比(仿生肋条结构在柱面上投影面积之和与镇压辊表面积之比)对仿生肋条型几何结构镇压辊作业性能的影响；根据穿山甲(Manis Pentadactyla)体表的鳞片结构，设计出3种仿生多面体型几何结构镇压辊，其材料与传统镇压辊一样，均是Q235钢，对比传统镇压辊与3种仿生多面体型几何结构镇压辊在3种载荷和2种土壤含水量下的作业效果。通过优化得出效果最佳的仿生肋条型几何结构镇压辊和仿生多面体型几何结构镇压辊，将Q235钢、UHMWPE材料和搪瓷涂层材料应用到优化后的仿生肋条型几何结构和仿生多面体型几何结构上，考察材料对两种类型仿生几何结构镇压辊防粘减阻的影响。采用有限元软件ABAQUS建立传统镇压辊及土槽试验优化得到的采用UHMWPE材料的仿生肋条型几何结构镇压辊和采用Q235钢的仿生多面体型几何结构镇压辊与土壤相互作用的模型。模拟结果中伪应变能约占内能的0.1%，证明沙漏模式对计算结果的影响可以忽略，传统镇压辊以及两种类型仿生几何结构镇压辊的牵引阻力和下陷量的模拟值与试验值吻合很好，从而验证了所创建有限元模型的可靠性。从Mises应力云图、镇压辊与土壤的接触面积和X、Y、Z方向的位移云图三方面对比3种镇压辊的模拟结果，分析了仿生几何结构镇压辊防粘减阻、防壅土的机理。本研究进行了田间试验，以牵引阻力、土壤容重、种床土壤含水量的变化趋势、株距变化率和出苗率为试验指标，考察了使用3种材料的仿生肋条型几何结构镇压辊和仿生多面体型几何结构镇压辊在3种载荷和2种作业速度下的田间作业效果，并与传统镇压辊对比，同时考察了仿生几何结构材料、仿生几何结构镇压辊类型、作业速度和载荷对仿生几何结构镇压辊作业性能的影响。更多还原

【Abstract】 Press roller, as a typical rolling soil-engaging component, was used to compactagricultural soil. Appropriate compaction of soil could decrease soil porosity, provide bettersoil-seed contact, strengthen the capillary action and increase crop yield. Conventional pressrollers were mainly made of stone, cast iron or low carbon steel. The surface of conventionalpress rollers was smooth with macroscopic scale. Soil has a tendency to adhere to the surfaceof conventional rollers during the process of tillage. Not only resulted in high energyconsumption and low work efficiency, but also consuming soil moisture and affecting thegermination. Besides, soil was pushed to the front of conventional press rollers in thecompaction process, hence an upheaval was formed, i.e., the hilling phenomenon. Not onlyresulted in uncompacted, but also consumed more energy, made the distance between seedsbecame non-uniform and, as a result, crop yield decreased.Reasonable compacting pressure was dependent upon soil moisture content. In thiswork, pressure-sinkage tests were carried out to get soil bulk density and sinkagecorresponding to different pressures for soil moisture content of20%d.b. and28%d.b.. Athree-parameter multiplicative model of soil compaction proposed by Bailey was used todescribe the relationship between stress and bulk density. Using Matlab nonlinear leastsquares method to fit experimental data, the equations of stress and bulk densitycorresponding to the two kinds of soil moisture content were obtained. The requiredoptimum bulk density for corn was introduced into the equation. The results showed that theappropriate pressure was25.25kg~88.48kg and13.95kg~70.26kg by conversion,corresponding with soil moisture content that were20%d.b. and28%d.b. respectively. Andthe sinkage could be used to validate the finite element simulation results.It was found that soil-burrowing animals, such as dung beetle and pangolin, could gothrough soil easily and had very little soil sticking to their bodies. The geometric structure ofthe cuticle surface of these soil-burrowing animals was one of the main reasons why theseanimals exhibited very low adhesion and friction against soil. Nine bionic press rollers with bionically ridged structures were designed learning from the geometric structure of theventral cuticle surface of dung beetle (Copris ochus Motschulsky). Bionically ridgedstructures made of ultra high molecular weight polyethylene (UHMWPE) were modeled byscrew on the substrate of press rollers, and the substrate was made of steel Q235. Orthogonaltests were performed in an indoor soil bin with soil moisture content of20%d.b. and28%d.b.respectively, and soil adhesion, tractive resistance, percent change of seed spacing and soilbulk density were taken as test indexes. The effects of the bottom width of bionically ridgedgeometrically structure, the ratio of section height to bottom width, loads and the area ratioof the projection of bionically ridged structures to the cylindrical roller surface on theoperating performance of bionically ridged geometrically structured press rollers weredetermined. According to the scale structure of the cuticle surface of pangolin (ManisPentadactyla), three bionically polyhedral geometrically structured press rollers weredesigned using steel Q235, which was the same with the conventional press roller. Theoperating performance of the conventional press roller and three bionically polyhedralgeometrically structured press rollers were compared under three kinds of normal loads andtwo kinds of soil moisture content. Bionically ridged geometrically structured press rollerand bionically polyhedral geometrically structured press roller with the best performancewere obtained by optimizing. Steel Q235, UHMWPE and enamel coating were applied to theoptimized bionically ridged geometrically structure and bionically polyhedral geometricallystructure. The effects of material on reducing adhesion and resistance for two kinds ofbionically geometrically structured press rollers were explored.The finite element software ABAQUS was used to model a three-dimensional soilcompaction process. The behavior of the soil-bionically ridged geometrically structuredpress roller and soil-bionically polyhedral geometrically structured press roller interfacewere investigated and compared with a conventional press roller. Simulation results showedthat the artificial strain energy was approximately0.1%of the internal energy, indicating thathourglassing had negligible influence on simulation results. For conventional press roller andtwo kinds of bionically geometrically structured press rollers, simulation results of resistanceand sinkage agreed well with the experimental results. It proved that the finite elementmodel was reliable. The Mises stress nephogram, contact area between soil and press rollerand displacement nephogram in X, Y and Z direction were adopted to compare the simulation results of the three press rollers. The mechanism of reducing adhesion and resistance forbionically geometrically structured press rollers was analyzed.Field tests were run under three kinds of weights and two kinds of velocities. Tractiveresistance, soil bulk density, the trend of bed soil moisture content, percent change of plantspacing and emergence rate were taken as test indexes, and the working quality of fieldoperations of the bionically ridged geometrically structured press roller and the bionicallypolyhedral geometrically structured press roller made of three kinds of materials wasexamined, and compared with the conventional press roller. Meanwhile, the effects ofmaterials of bionically geometrically structure, types of bionically geometrically structuredpress roller, velocities and loads on the operating performance of the bionicallygeometrically structured press rollers were examined.更多还原