Discrete element parameter calibration and wear characteristics analysis of soil-rotary tillage blade in gneiss mountainous area

Abstract

Aiming at the problems of fast wear and short service life of rotary tillage blade in gneiss mountainous area, and the lack of accurate and reliable discrete element simulation parameters for exploring the interaction mechanism between soil and rotary tillage blade, taking the typical gneiss sandy loam in Taihang Mountain as the research objects, the relevant simulation parameters were calibrated and the wear characteristics of rotary tillage blade were analyzed. Firstly, the contact parameters between soil particles were calibrated. Taking the simulated accumulation angle of soil particles as the response value, the significance of the influencing factors was screened based on the Placket-Burman test in the Design-Expert software. Through the steepest climbing test and Box-Behnken test, the regression model of soil accumulation angle was determined. Through model optimization, the JKR surface energy, collision recovery coefficient, static friction coefficient and rolling friction coefficient are 4.85 J/m2,0.24,0.1 and 0.25, respectively. At this time, the simulated value of soil accumulation angle is 42.21°, and the relative error between the simulated value and the measured value is 3.8%. Secondly, the contact parameters between soil and 65 Mn steel were calibrated,and the static friction coefficient, rolling friction coefficient and collision recovery coefficient between soil and 65Mn steel were obtained through static friction, inclined plane and inclined plate collision tests. Taking the sliding friction angle of soil on 65Mn steel plate as the response value, the regression model of soil sliding friction angle was obtained based on Box Behnken method. By optimizing the model, the static friction coefficient, rolling friction coefficient and collision recovery coefficient between soil and 65 Mn steel are 0.49,0.13 and 0.32 respectively. At this time, the simulation value of static sliding friction angle is 19.90°, and the relative error with the measured value is 5.7%. Finally, the calibration parameters are verified to be accurate and reliable by soil disturbance test. Through the wear test and wear law analysis, it is concluded that the serious wear parts of the rotary tillage blade are mainly concentrated in the blade part and the tail of the tangential blade.,in which the tangent blade and side cutting blade wear more, and the wear at the transition between tangent blade and side cutting blade is relatively small.When the rotational speed of the rotary tillage blade is 160 ~ 200 r/min, the wear amount is not much different ; when the speed is greater than 200 r /min, the wear amount increases obviously. With the increase of rotational speed, the wear rate of rotary tillage blade increases. When the rotational speed is 160 ~ 200 r/min, the wear rate of rotary tillage blade is slower, while when the rotational speed is 220 ~ 240 r/min, the wear rate of rotary tillage blade is faster. When the rotational speed is 260 ~ 300 r/min, the wear rate of rotary tillage blade is the fastest. In addition, with the increase of tillage depth and forward speed, the wear amount and wear rate of rotary tillage blade also increase.