| The area of China’s paddy field accounts for about 1/4 of the country’s arable land,of which the area of the deep muddy paddy field exceeds 2 million hm2.The complex foot conditions of the soil make the traditional tractors such as wheeled tractors and tractors unable to work well.The ship type tractor using the "floating principle" can avoid sliding down and adapt to the paddy field operation with different depth of mud feet.However,there are still many problems with the boat-type tractor such as large rolling resistance,low power utilization rate and poor running straightness.The lack of research on rheological properties of paddy soil also makes boat-type tractor under the condition of lack of reliable theoretical guidance.Therefore,to improve the performance of the tractor,it is necessary to study the rheological properties of the paddy soil and boat-type tractor.On the basis of the research on the rheological characteristics of the boat-type tractors and soil at home and abroad,on the basis of the soil mechanics characteristics and numerical simulation analysis of the paddy field,the structure and working parameters of the paddy soil tractor and the performance test are studied.The main conclusions are as follows:1.The physical and mechanical properties of soil samples from the paddy field in the new Jia Zhuang village,Fuyang District,Hangzhou,were measured.The results showed that the soil samples were silt loam soil,the initial water content was 15.10%,the saturated water content was 51.04%,the plastic limit was 22.50%,the liquid limit was 42.50%,the plastic index number was 20%,the internal friction angle was 31.0059 degrees and the cohesive force is 25.879kPa.2.The interaction process of the paddy field tractor model and the soil is simulated by using the ANSYS/LS-DYNA software,and the regression analysis and the corresponding surface analysis are carried out with the drag resistance and the subsidence depth as the response values.The influence of interaction factors on response value was studied by orthogonal test with three factors and five levels.The results show that the contribution rate of each factor to the sliding resistance from high to low is the angle of grounding,the speed of advance and the radius of curvature,and the contribution rate of each factor to the subsidence depth is the advancing speed,the radius of curvature and the ground angle from high to low.The relationship between the sliding resistance and the advancing speed,the radius of curvature and the ground angle are all concave curves.When the ground angle is 29.4 degrees,the radius of curvature is 418.4mm,and the advancing speed is 0.58m/s,the drag resistance is 139.2N,139.2N and 139.7N,respectively.The relationship between the subsidence depth and the ground angle and the forward velocity are both concave curve and half curvature.The influence of the diameter on the depth of subsidence is not significant.When the grounding angle is 30 degrees and the advancing speed is 0.64m/s,the subsidence depth reaches the minimum value of 8.1cm and 8.0cm respectively.When the bow angle is 29.4 degrees,the radius of curvature of the first port is 417.8mm and the speed of advance is 0.57m/s,the subsidence depth is 7.0cm,and the optimum value of the test index sliding resistance is 138.1N.The test results show that the relative error of the sliding resistance is 7.45%compared with the measured value of the soil trough traction test,and the relative error of the simulated subsidence depth and the soil trough traction test is 11.24%.The simulation results are in good agreement with the measured values,which proves that the simulation methods adopted in this study are consistent with reality.3.A traction test rig for paddy field hull model is designed and built,which is mainly composed of paddy soil trough,traction device,detection system and hull model.On the basis of the pre experiment,a formal test design method is used on the basis of the soil trough test platform,with the influence factor of ground specific pressure,traction speed,ground angle,curvature radius and surface water depth,and the traction resistance and the subsidence depth are the response values,and the difference analysis and analysis of variance are carried out to explore the subsidence depth and traction resistance of each factor.The structural parameters and working parameters of ship tractor are optimized and calculated.The results show that the order of the factors affecting the drag and subsidence depth are:ground specific pressure>ground angle>traction speed>surface water depth>starboard radius of curvature.The factor level of minimization of traction resistance is A1B3C4D4E2,and the factor level of minimum subsidence depth is A1B4C5D3E2.According to the analysis of variance,the effect of ground specific pressure on traction resistance is very significant.The influence of traction force,ground angle and surface water depth on traction resistance is significant,and the influence of the radius of curvature on traction resistance is not significant;the influence of ground specific pressure on the subsidence depth is very significant,and the shadow of ground angle and traction speed on the subsidence depth The influence of surface water depth and curvature radius of the bow side on the depth of subsidence is not significant. |
