液肥穴施肥机扎穴针体与土壤互作仿真分析及试验

Simulation Analysis and Test of Interaction between Pricking Hole Needle Body of Liquid Fertilizer Hole Applicator and Soil

针对液肥穴施肥机斜置式扎穴机构扎穴时,触土部件-针体所受三向阻力变化规律以及土壤动态行为特性难以直接通过试验获取问题,通过采用Drucker-Prager屈服准则构建穴施土壤有限元模型,运用ADAMS运动学分析模块获得扎穴机构喷肥针扎穴轨迹,利用ANSYS/LS-DYNA显示动力学软件建立喷肥针与土壤互作仿真模型。以Z轴方向针体所受最大压力(均指绝对值)为测量指标,工作参数为影响因素,进行喷肥针单向受力虚拟和台架对比试验。结果表明,压力皆随前进速度和扎穴机构转速的增大先增大后减小,仿真和试验数据接近,变化趋势基本相同。以喷肥针前进速度0.62 m/s、扎穴机构转速70 r/min及斜置角20°为仿真工作参数,对针体进行三向阻力以及土壤动态行为仿真分析,可知喷肥针在3个方向的阻力先增大后减小。0~0.189 s内即喷肥针入土过程,针体在X轴方向阻力缓慢上升,说明喷肥针对前进方向土壤扰动较小;针体在Z轴方向上阻力增大较快,说明喷肥针冲击土壤作用较强,土壤受到针尖剪切致使应力主要集中在此方向上,在0.189 s阻力达到最大值21.69 N;针体在Y轴方向上阻力较小,说明喷肥针挤压土壤作用较弱,在0.189 s阻力达到最大值8.56 N。0.189~0.214 s内即喷肥针原位置自身摆动过程,针体在X轴方向阻力增大趋势变快,说明喷肥针对前进方向土壤产生较大扰动;其他两个方向阻力基本保持不变。0.214~0.350 s内即喷肥针出土过程,喷肥针在Z轴和Y轴方向阻力逐渐减小直至变为0;其中在0.214~0.238 s内,针体在X轴方向阻力瞬间增大,说明喷肥针对前进方向土壤产生强烈挤压,0.238 s达到最大值31.87 N。在整个扎穴过程中,穴口形成是喷肥针出土过程自身的摆动姿态与前进方向土壤扰动引起的,因此针体沿X轴方向阻力影响显著,符合实际扎穴规律。

Aiming at the problem that it is difficult to directly obtain the three-dimensional resistance variation law and soil dynamic behavior characteristics of the soil contact component-needle body through experiments when the liquid fertilizer hole applicator is pricked with the inclined pricking hole mechanism. By adopting the Drucker-Prager yield criterion to construct the finite element model of hole application soil,the ADAMS kinematics analysis module was applied to obtain the pricking hole track of fertilizer spraying needle of pricking hole mechanism,and ANSYS/LS-DYNA display dynamics software was used to establish the interaction simulation model between fertilizer spraying needle and soil. Taking the maximum pressure on the needle body in the Z-axis direction as the measurement index and the working parameters as the influencing factors,the virtual and bench comparative tests of single way stress on the fertilizer spraying needle were carried out. The results revealed that the pressure was increased first and then decreased with the increase of the advancing speed and the rotation of puncture speed. The simulation and test data were close in size and the change trend was basically the same. Taking the advance speed of the fertilizer spraying needle( 0. 62 m/s),the rotation speed of the puncture hole( 70 r/min) and the inclined angle( 20°) as the simulation working parameters,the three-dimensional resistance of the needle body and the dynamic behavior of the soil were simulated and analyzed. The analysis disclosed that the resistance of the fertilizer spraying needle in the three directions was increased first and then decreased. Within 0 ~ 0. 189 s,the process of the fertilizer spraying needle entering the soil,the resistance of the needle body was changed slowly in the X-axis direction,indicating that the fertilizer spraying disturbed less to the soil in the advancing direction. The resistance of the needle body was increased rapidly in the Z-axis direction,which indicated that the fertilizer spraying needle had a strong impact on the soil. The stress of the soil was mainly concentrated in this direction due to the shear of the needle tip,and the resistance reached the maximum value of 21. 69 N at 0. 189 s. The resistance of the needle body in the Y-axis direction was small,which indicated that the squeezing effect of the fertilizer spraying needle on the soil was weak,and the resistance reached the maximum value of 8. 56 N at 0. 189 s. Within 0. 189 ~ 0. 214 s,the original position of the fertilizer spraying needle swung itself,the resistance of the needle body was increased rapidly in the X-axis direction,which indicated that fertilizer spraying needle triggered great disturbance to the soil in the advancing direction. The resistance values in the other two directions remained basically unchanged. Within 0. 214 ~ 0. 350 s,the excavation of the fertilizer spraying needle,the resistance of the needle in the Z-axis and Y-axis directions were gradually decreased until it became zero. Among them,within 0. 214 ~ 0. 238 s,the resistance of the needle body in the X-axis direction was increased instantly,indicating that fertilizer spraying produced strong extrusion on the soil in the forward direction,reaching the maximum value of 31. 87 N at 0. 238 s.During the whole pricking process,the formation of the puncture opening was mainly caused by the swing posture of the fertilizer spraying needle itself and the soil disturbance in the forward direction during the excavation process. Therefore,the resistance of the needle body along the X-axis direction was influenced significantly,which conformed to the actual pricking hole law. The simulation method of needle-soil interaction provided can be a reference for the optimization design of fertilizer spraying needle and the research of clay characteristics.