Failure Analysis And Optimization Design Of Corn Harvester Frame

With the continuous improvement of agricultural modernization level in China,higher requirements for safety and reliability of agricultural machinery equipment are put forward.Corn harvester,as a large agricultural machinery with complex structures,has been developing to the direction of high-speed,multi-functional and large Feed Quantity in recent years.As the core component of the harvester,the frame bears more impact load,so it can affect the quality and performance of the whole vehicle directly.Therefore,it is of great significance to optimize the frame’s structure and improve its fatigue durability.In this paper,the corn harvester frame is taken as the research object.Based on the static analysis and dynamic stress analysis,the structure of the frame is optimized and its fatigue life is estimated.The main research contents are as follows:First of all,the finite element model of corn harvester frame is established.According to the actual working environment,the loading mode and boundary conditions are determined.Static analysis under full load bending and torsion conditions is carried out.According to the stress distribution,the location of stress concentration is obtained,and the causes are analyzed.Then,the dangerous points’ load spectrum is measured by test system when the harvester passes the testing ground.Then,the multi-body dynamic model of corn harvester is established,and the accuracy and validity of the model are verified by the measured load spectrum of testing ground.The dynamic stress analysis of the frame is carried out when it passes through the road of different heights at different speeds,and the critical damage work conditions of the frame is obtained when it is impacted by the load.Secondly,according to the location of stress concentration,the optimization area of the frame is determined.Based on the variable density method,topological optimization to the structure is carried out,and the final topological structure is formed under multiple work conditions.After topological optimization to the frame,size optimization is carried out which based on response surface method and multi-objective genetic algorithm.Then the optimal thickness of the design variable is obtained.Finally,static analysis and dynamic stress analysis to the new frame are carried out again It is proved that optimization method not only reduces the frame’s mass,but also greatly improves its strength.Finally,based on the harmonic superposition method,the mathematical model of random road surface roughness is derived,and the three-dimensional random road surface which can be used for dynamic simulation is compiled based on triangle grid method.Then the force load spectrum of corn harvester frame’s each connection point is obtained.Based on the simulation load spectrum and combined with the finite element calculation results and material S-N curve,the fatigue durability analysis of the frame is carried out to estimate its fatigue life.