【作者】 翟力欣；

【导师】 姬长英；

【作者基本信息】 南京农业大学 ， 农业电气化与自动化， 2011， 博士

【摘要】 耕作阻力大,能耗高是耕作的主要特征。提高耕作机械或土壤加工机械的能源利用效率或者说在满足农业生产对土壤加工要求的前提下,降低土壤耕作或土壤加工机械的能源消耗,是人们普遍关注的问题。对于占我国耕地面积比例很大的水田而言,由于尚缺乏水田土壤和机械相互作用规律的深刻认识,水田土壤耕作部件的设计很少有理论上的依据,这使得能源无法得到有效合理的利用。为了寻求水田土壤耕作部件设计理论的依据,探讨水田土壤的流变性质对耕作部件的影响,本论文分析研究了耕作部件在不同土壤条件、工作参数及几何结构参数下的耕作阻力。以耕作部件的耕作阻力最低作为研究目标,通过对影响耕作部件工作性能的因素进行深入研究,找出了其中的影响规律,为耕作部件的设计提供了理论依据。这对于降低我国农业生产能耗,节省生产资源,增加农民收入,促进社会主义新农村的建设均具有重要的实用价值。本课题以耕作机械中的重要部件犁体为研究对象,以犁体的工作功率最低为目标,借助运动学分析、数值模拟技术及优化设计方法,具体开展以下研究工作：1、对犁体与土壤相互作用进行分析。以二面楔和三面楔的工作原理为理论基础,将其应用到犁体的受力分析,建立了犁体牵引阻力的数学模型。2、对犁体进行三维建模。利用三坐标测量机来采集现有犁体曲面上的点数据,采用逆向工程技术,在Pro/E中将点数据进行三维重构得到犁体曲面的计算机模型。并以此实物模型为样本,对其进行了参数化设计。3、流变参数的转换。对试验土壤的机械参数进行了测量,并将纳入试验因素研究的流变参数进行了Prony级数的转化。4、建立犁体-土体有限元模型,并进行数值模拟分析。利用ANSYS软件建立了犁体和土壤相接触的有限元模型,并进行了三维动态模拟分析,获得了整个切削过程中,犁体阻力的实时动态变化情况。通过模拟不同的切削速度分析了切削阻力变化规律,并与土槽试验进行对比分析,其误差控制在10%以内,验证了数值模拟的可行性。5、进行土槽试验以分析不同耕作条件对比阻的影响。借助土槽试验,对犁体的模型、耕作速度、耕作深度以及土壤流变参数进行了四因素三水平的正交试验,并对各试验因素对试验指标的影响进行了分析。同时,对试验结果进行回归分析得出耕作土壤时单位切削面积上的耕作阻力(即比阻)与犁体的模型、耕作速度、耕作深度和流变参数的相互影响关系。试验证明,耕作深度、犁体模型以及耕作速度都对比阻有显著影响,并得到了试验因素的优组合。此外,以犁体在同一耕作深度为前提,通过物理试验分别应用双目摄像机与压力传感器对土壤表层的位移场与内部的应力场进行了测试。6、通过数值模拟分析犁体不同结构参数对比阻的影响。利用数值模拟试验,在犁体最优组合的工作参数前提下,对犁体的推土角、起土角、覆土角以及犁体高度进行了四因素三水平的正交试验,通过分析得到犁体覆土角对耕作比阻的影响较小,可忽略。故对比阻与推土角、起土角以及犁体高度进行回归分析并得出回归方程。7、对犁体的结构参数进行优化设计。借助数值模拟研究,以比阻最低为目标函数,建立了犁体主要结构参数的优化设计数学模型；并运用MATLAB工具中的约束非线性fmincon函数开展了犁体比阻的优化分析。得出了影响犁体比阻的三个主要的独立可变参数推土角、起土角以及犁体高度的最佳匹配组合。试验结果表明优化设计后的犁体比阻较之前犁体最高减小26.60%,最低也减少了6.77%。8、对优化犁体进行性能检测。依据翻垡原理,在ANSYS数值模拟软件中,对优化后的犁体进行了翻垡性能检测。检测结果表明,优化犁体的翻垡效果良好。更多还原

【Abstract】 High resistance and energy consumption are the main features of tillage operation. Improving the efficiency of energy utilization of tillage machinery or soil processing machinery or decreasing the energy consumption of the machinery under the condition that the agriculture requirement is satisfied is widely concerned. For paddy fields, a large proportion of total cultivated area in China, since the lack of the profound understanding for the interaction between soil and the machinery. There is little theoretical basis for the design of paddy soil’s mechinary, which makes the energy can not be utilized effectively.In order to seek a theoretical basis of tillage component’s design for paddy soil and to investigate the affect of the rheological properties on the tillage performance, the tillage resistance under different soil conditions, working parameters and structure parameters was analysed in the paper. Aiming at the minimum tillage resistance for operation, the factors effecting tillage performance and the effecting principle were put forward, which has an important significance and practical values for the design of tillage component.Regarding plough as the research object, aiming at the minimum power consumption for operation, with the methods of kinematics analysis, numerical simulation and optimal design, the following research was carried out:1. The interaction between plough and soil was analysed. The force on the plough in the process of tillage was analysed based on the working theory of two-surface and three-surface wedges. And the mathematical model of plough’s resistance was built.2.3D model of plough was built. Based on existing plough, point data of plough’s surface were obtained by three-dimensional measuring machine. With reverse engineering technique,3D reconstruction was conducted with Pro/E in order to attain computational model of plough surface. And parametric design for plough was done with plough’s computational model as a sample.3. The expression method of soil rheological parameters in the simulation processing was studied. The basic mechanical parameters of soil are measured. And the soil’s rheological parameter is one of the facors in the experiment of soil-bin. In the processing of simulation, the rheological parameters were convered into Prony series.4. The finite element model of plough and soil was set up, and the interaction of plough and soil was analysed by the numerical simulation. Utilizing the software ANSYS, the finite element model about the interaction between plough and soil has been developed. Through 3D analyzing, the real-time dynamic change in resistance of plough in the whole tillage process was obtained. With simulating under various tillage speeds, the change rule of the tillage resistance was studied. The error between simulation results and experiment data in soil-bin is within 10%. It shows that the numerical simulation is feasible.5. The affect of different tillage conditions on specific resistance was analysed by soil-bin experiments. Orthogonal tests with four factors, involving model of plough, tillage speed, tillage depth and soil’s rheological parameters, and three levels were carried out on the specific resistance in soil-bin. The affect of experimental factors on experimental index is analyzed. Through regression analyzing, the interaction relationships for tillage specific resistance and model of plough, tillage speed, tillage depth and soil’s rheological parameters were obtained. The test showed that tillage depth, model of plough and tillage speeds have significant impact on the soil tillage specific resistance. The optimal combination among experimental factors was observed. Besides, the displacement field and stress field were measured at premise of the same tillage depth.6. The affect of different structure parameters on specific resistance was analysed by simulation. At premise of the optimal combination among plough’s working parameters, orthogonal tests with four factors, involving pushing angle, rake angle, covering angle and height of plough, and three levels have been carried out on the specific resistance by numerical simulation. The result showed that the affect of covering angle on specific resistance can be ignored. And the regression equation for tillage specific resistance and pushing angle, rake angle and height of plough was obtained.7. The structure parameters of the plough were optimized. By means of the numerical simulation, using the specific resistance as target function, the mathematical model for optimization design for the main structure parameters of the plough was set up. Then the optimization of specific resistance was carried out by using the constrained nonlinear funetions in MATLAB. At last, the optimal combination among the three main stand-alone variable parameters affecting the specific resistance which includes the pushing angle, rake angle and height of plough was obtained. Experiments demonstrated that comparing with the resistance of initial plough, the resistance of optimal plough decreased by 26.60% at most and by 6.77% at least.8. The performance of optimal plough was verified. According to the law of turnning, the turn performance of optimal plough is detected in the ANSYS. The result of detection shows that the performance of optimal plough is satisfactory.更多还原