| Sugarcane is main sugar crop in China.The growth height of sugarcane reaches 0.8-1 m and grows very fast in its elongation and big cultivation period.It is required that the pass clearance of the cultivator should be more than 1.5 m,so as to reduce the breaking of sugarcane by the cultivator.Wheel spacing of the cultivator should be adjustable for different sugarcane row spacing in different plots.A Rhombic Four Wheel Cultivator developed by our team in early stage basically met those requirements.However,the weight of that prototype was too high.Study on its adaption to hilly fields has no been conducted.In this paper,based on the design of frame structure,combined with prototype test and finite element analysis technology,the stress,strain and modal response of four typical working conditions of sugarcane cultivator were studied.The performance parameters of the prototype,the boundary conditions of the frame finite element analysis and the method of topological optimization design were determined.Studies of this paper could provide support for simulation on light weight design of cultivator frame.The studies and conclusions were as follows:(1)Structural design of cultivator frame.The frame structure of some high clearance vehicles was referred to,and the characteristics of sugarcane and its field was considered.According to the design objectives of the cultivator,driving method was determined.Parts,such as engine,distribution box,hydraulic tank,hydraulic valves,battery,radiator and so on,were laid on the frame.The frame structure and its parts was designed.The 2D and 3D models of the frame were built by AutoCAD and CATIA software.(2)Tests of prototype performance.The maximum speed,minimum turning diameter and maximum ridge height of the prototype were tested.Results showed that its maximum ground speed was 13 km/h,the minimum turning diameter was 7 m,and the maximum ridge height was 160 mm.In addition,the weight of the cultivator measured was 4100 kg.Comparing the test results with the design objectives,the prototype met the design requirements.(3)FEM Modeling of cultivator frame.ANSYS Workbench was used for structural statics and modal analysis.Hyperworks was used for structural topological optimization of the frame.The 3D model of the frame was imported into the Workbench,the model was geometrically cleaned and the material parameters were set,the type of the frame unit was determined,and the frame model was meshed.(4)Static analysis of frame structure.According to the main operating environment of the cultivator,the structural statics analysis was carried out under four working conditions,including frame bending,torsion,machine turning and braking.The position and size of the load were determined.The simulation results showed that the maximum stress of the existing frame reached 255 MPa in torsion.The value exceeded the yield limit of Q235.The frame need be strengthened.(5)Modal analysis of the frame.In this paper,a subspace iterative method was used to extract the frame modes.The first 14 modes of the frame were extracted.Moreover,the excitation frequency of the engine was calculated between 43-50 Hz,and the comparison showed that the 8-order natural frequency of the frame was close to the excitation frequency of the engine,which had the possibility of resonance.(6)Topology optimization design of the frame.A software was used to optimize the topology of the frame,the original closed space was selected as a complete design space,and the optimized condition was determined to be the frame twist.The corresponding material parameters and constraints were set in the Hyperworks software.The optimal response as compliance and volume fraction were determined.The optimized volume fraction was set to 30% of the original volume,and the design goal of minimum compliance was set.After 48 iterations,the corresponding optimization results are obtained.Combined with the original frame and optimization results,the second design of the frame was carried out,and the four working conditions and modes were analyzed.The analysis results showed that the frame mass was reduced 18.9%,and the stress and strain extremes were reduced,which showed the effectiveness of the optimization results. |
