水稻根茬-土壤复合体剪切特性试验

Shear Characteristics of Rice Root-Soil Composite

为了降低稻茬地少耕免耕过程中的阻力,提高作业质量,同时为破茬开沟装置提供设计依据,采用自制的剪切试验装置在万能材料试验机上对水稻根茬-土壤复合体进行了剪切试验,对根茬-土壤复合体含水率、土壤容重、根茬-土壤复合体的当量直径、剪切位置、剪切速度、切刃刃角、切刀刃口形状7个因素进行了单因素试验。在单因素试验的基础上选取根茬-土壤复合体含水率、剪切速度、切刃刃角3个因素进行了正交试验。单因素试验结果显示:极限剪切应力与复合体的含水率呈二次多项式函数关系,与土壤容重呈幂函数关系,与根茬-土壤复合体直径呈二次多项式函数关系,与剪切速度呈对数函数关系,剪切位置距离根茬中心越远极限剪应力越小,切刃刃角越小极限剪切应力也越小;在4种形状的刃口切刀中,凹圆弧切刃的极限剪切应力最小。正交试验结果表明:切割速度450 mm/min、含水率25%、切刃刃角15°时,极限剪切应力最小。

In order to reduce the rice stubble of minimum tillage and no tillage resistance in the process,improve the quality of work,and provide basis for the design of stubble breaking ditching device,the shear experiments on the universal material testing machine was tested on rice stubble and soil complex.Soil moisture content,soil bulk density,complex stubble soil composite equivalent diameter,cutting position,cutting speed,cutting edge angle and blade shape were tested by single factor test. Based on single factor experiment,the orthogonal experiment was carried out on three factors,including soil moisture content,shear rate and cutting edge angle. The results of single factor test showed that the relationship of ultimate shear force and water complex rate was two-order polynomial function,a power function relationship with soil bulk density,a two order polynomial function relationship with stubble and soil complex diameter, logarithmic relationship with shear velocity. The ultimate shear stress was decreased with the increase of shear distance from stubble,and it was also decreased with the decrease of cutting edge angle; among the four shapes of cutter blade,the ultimate shear stress of concave arc cutting blade was the least. The results of orthogonal test showed that the ultimate shear stress was the minimum when the cutting speed was 450 mm/min,the moisture content was 25% and the cutting edge angle was 15°.