| Horizontally Reversible Plow(HRP)is an important kind of high-speed mold-board ploughs.Plough-breast and plough-share of HRP take the greatest responsibility for tillage.High-speed soil rheology during HRP tillage generally has adverse effects on the plow surface,especially on either the plow-shank or plow-tip zones.This strongly affected the tillage performance of HRP and eventually shortens the tool’s service life.With the increase of tillage speed,the flow rate of soil on the plough surface would be increased.which,in turn,enhances the tool-soil interaction,increases the tillage temperature at both plough-shank and share-point zones,and,hence,results in thermal fatigue.At this time,The HRP works in an environment of multi-physics fields coupled by fluid,thermal and structure.Therefore,we should consider the effect of cutting temperature of HRP when determining the damage of plow-shank and plow-tip zones,so that the results obtained should be more consistent with the actual tillage condition of HRP.However,to the author’s knowledge,so far there is no literature available in literature.In this thesis,I am focused on the following aspects:1.According to the characteristics of commuting tillage of HRP,To take an example,we measured the temperature of the interface between plough-share and soil by setting up a temperature measuring test platform;Then,we established the three-dimensional heat transfer model of the HRP,and the heat partition coefficient between HRP and soil during the tillage process was obtained with the reverse heat transfer method.The results show that the average heat partition coefficient between HRP and soil under different tillage conditions is between 0.72 and 0.79,and the overall trend of the heat partition coefficient between HRP and soil is increased with operating depth and tillage speed,and the variation in heat partition coefficient is less than 10%.2.Thermal-fluid-structure coupling analysis of plough-breast and soil under high speed commuting tillage of Horizontally Reversible Plow.The pressure,temperature and coupling stress distribution of plough-breast under different tillage conditions were studied with the thermal-fluid-structure coupling method,and also the effects of the thermal-fluid-structure coupling between plough-breast and soil on the tool were investigated;then compare the thermal-fluid-structure coupling results with CFD results and wear of plough-shank measured by SEM.The results show that the pressure on the plough-shank is the greatest and increased with the operating depth and tillage speed;and that the maximum tillage temperature and maximum coupling stress of HRP are also appear in the plough-shank,and consistent with the wear position of plough-shank measured by SEM.Moreover,the maximum tool coupling stress does not reach the yield strength of the material,too high stress makes the HRP easily reach the fatigue strength of the material during the HRP tillage process,which will lead to severe wear and shorter tool life.3.Thermal-fluid-structure coupling analysis of ploughshare and soil under high speed commuting tillage of Horizontally Reversible Plow.The pressure,temperature and coupling stress distribution of plough-share under different tillage conditions were studied with the thermal-fluid-structure coupling method,and also the effects of the thermal-fluid-structure coupling between plough-share and soil on the tool were investigated;then compare the thermal-fluid-structure coupling results with CFD results and wear of share-point measured by SEM.The results show that the pressure on the share-point is the greatest and increased with the operating depth and tillage speed;and that the maximum tillage temperature and maximum coupling stress of HRP are also appear in the share-point,and consistent with the wear position of share-point measured by SEM.Moreover,the maximum tool coupling stress exceeds the yield strength of the material,which will lead to severe wear and shorter tool life during the HRP tillage process. |
PDF Full Text Request