基于SPH算法的立式小型深耕机刀具设计优化与试验研究

发布时间：2018-01-21 00:03

本文关键词： 立式旋耕刀 SPH 有限元土壤切削性能优化　出处：《西南大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前丘陵山地主要使用微耕机进行耕地作业,其实际耕深一般只有10~15cm,长期浅耕已经带来了犁底层加厚、土壤板结、保肥保墒能力下降、蓄水保水能力逐年弱化及病虫害增加等严重问题,农户亟需丘陵山地适用的小型深耕机。立式铣削作业是小型深耕机可采用的有效作业模式之一,立式旋耕刀结构参数和运动参数的取值将直接影响立式深耕机的作业质量好坏和功耗大小。本文根据切削理论和土壤动力学理论,对立式旋耕刀线型进行了设计和仿真分析,以选定范围内的最小整机功耗为目的,对立式旋耕刀具的结构参数和运动参数进行了优化和试验研究。(1)根据土壤动力学、切削学基本理论及经验公式初步设计立式旋耕刀的线型,推导了螺旋刀具的线型方程,并选定立式旋耕刀的结构参数;(2)分析了刀具的运动轨迹,其轨迹为摆线;由土壤动力学和切削学理论分析了立式旋耕模式下土壤粒子的运动轨迹和受力状态,并得到立式旋耕刀的临界角速度关系方程;分别从宏观和微观角度分析了旋耕刀切削土壤的功率消耗情况,其主要影响因素有前进速度、结构参数和旋转速度;(3)采用SPH算法构建符合实际特征的土壤本构模型,并对单个旋耕刀进行动态仿真模拟,分析了旋耕刀切削阻力和功率消耗的变化规律及土壤粒子的运动状态;验证了悬臂梁刀具安装的可行性;进行耕作部件的动态仿真,检验了刀具的排列方式、数量和刀盘的设计;通过作业功率测试实验验证了仿真模型的可行性。仿真分析和实验结果表明:1)针对本文所设计的旋耕刀,其前进速度为0.3m/s,旋转速度为240r/min,经切削阻力的分析,单个刀片的切削阻力稳定在1000N左右;2)立式旋耕刀在作业过程中,分别选取三个不同深度的土壤粒子做出运动轨迹,分析土壤粒子的位移、速度和加速度曲线图,得出了刀具对土壤有提升运输作用,基本实现了上翻下松的目的。3)通过刀具的仿真分析,得到其切削功率为3.3kW,大小约为单个旋耕刀的3倍,且功率值波动稳定;说明各个刀片的受力均匀,选择的刀片排列方式切实可行,能达到预期旋耕效果。4)通过测试平台对仿真模型的单个刀具进行验证实验,其实测功率值与仿真结果误差为8.68%。(4)以旋耕刀的前进速度、旋转速度和结构参数为试验因子,功耗为试验指标制定虚拟正交试验,并采用软件SPSS建立功耗与各因子的一次回归方程,设定目标函数和约束条件运用软件MATLAB对其一次线性回归方程进行优化,得到立式旋耕刀具最小功耗值和与之对应的最优运动参数和结构参数为:最小功耗为2.43kW,此时前进速度为0.28m/s,旋转速度为20.78rad/s,螺旋圈数为1.35。(5)进行实验验证。测试优化后旋耕刀具实验功耗平均值为2.64kW,与仿真结果误差为8.64%,验证理论分析和仿真模型的正确性。同时,通过平台实验的测得小型深耕机平台的耕深合格率为91.17%、碎土率为72.54%和耕后地表平整度为2cm,各项耕作性能指标均达标。
[Abstract]:At present, the main use of Hilly and mountainous micro cultivator for farmland operation, the actual depth of only 10~15cm, long-term tillage has brought plough layer thickening, soil compaction, decreased fertilizer holding capacity, water holding ability gradually weakening and serious pest problems increased, farmers need small deep plowing machine for hilly vertical. Milling is one of the effective operation mode of small deep plowing machine can be used, the value of vertical rotary blade structure parameters and motion parameters will directly affect the operation quality and the power consumption of the size of vertical deep plowing machine. Based on the cutting theory and soil dynamics theory, the vertical type of rotary blade design and simulation analysis, in the selected range the minimum power consumption for the purpose of structure parameters and motion parameters on vertical rotary cutting tools were optimized and experimental research. (1) according to the soil dynamics, cutting theory Linear vertical rotary blade preliminary design of the basic theory and empirical formula, linear equation of spiral cutter is deduced, and the selected vertical structure parameters of the rotary blade; (2) analysis of the tool path, the path for cycloid; theoretical analysis and stress state of soil particle trajectory model under vertical rotary tillage by Soil Science the dynamics and cutting, and get the critical angular velocity equation of vertical rotary blade; respectively from the perspective of macro and micro analysis of the power consumption of rotary blade cutting, the main influence factors of forward speed, structure parameters and rotational speed; (3) building accords with the actual characteristics of the soil constitutive model using SPH algorithm. And a single rotary blade were simulated, analyzed the motion variation and soil particle rotary blade cutting resistance and power consumption; to verify the feasibility of cantilever installation tool; Dynamic simulation of tillage parts, inspection tool arrangement, design number and cutter; through the operation power test to prove the feasibility of the simulation model. The simulation analysis and experimental results show that: 1) for the design of the rotary blade, the forward speed is 0.3m/s, the rotation speed is 240r/min, through the analysis of cutting the resistance of the single blade cutting resistance is stable at about 1000N; 2) vertical rotary blade in the process of operation, and selects three different depths of the soil particle motion trajectory, displacement analysis of soil particle, velocity and acceleration curve, the cutter lifting transportation effect on soil, the basic realization of the up and down the purpose of pine.3) by cutting simulation, the cutting power is 3.3kW, the size is about 3 times of a single rotary blade, fluctuation of stability and power; description of each blade of uniform stress, selection The arrangement of the blade is feasible, can achieve the desired effect of rotary.4) test platform through a single tool of the simulation model is verified experimentally, the measured power value error and simulation results for 8.68%. (4) to the rotary blade speed, rotating speed and structure parameters as experimental factors, power of making virtual orthogonal test as test indexes. Using a regression equation was established with SPSS software and the power factor, setting the objective function and constraints using the software MATLAB on the linear regression equation was optimized, by vertical rotary cutting tools the minimum power consumption value and the optimal motion and structure parameters corresponding to the minimum power consumption of 2.43kW, the forward speed is 0.28m/s, the rotating speed is 20.78rad/s, the number of spiral 1.35. (5) experiment. The optimized experimental test of rotary cutting tools the average power consumption value is 2.64kW, and the simulation results of error For 8.64%, verify the correctness of theoretical analysis and simulation model. Meanwhile, through platform experiment, the qualified rate of plough depth of small deep tillage machine platform is 91.17%, the rate of broken soil is 72.54%, and the surface evenness of cultivated land is 2cm, all the indicators of tillage performance are all up to standard.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S222

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