Vibration Effect Of Multi-source Excitation On Plate And Shell Structure Of Combine Harvester Threshing Frame And Structure Optimization

As one of the three major components of the combine harvester,the plate and shell structure accounts for more than 55%,and the quality of its structural performance will greatly affect the performance of the whole machine.The combine harvester has many excitation sources and quite complex vibration environment.After the coupling and superposition of different vibration signals on the plate and shell,the working parts on the machine body are seriously affected,and the reliability of the whole machine is not high.Therefore,it is urgent to carry out research on the vibration mechanism and structural optimization of the plate-shell structure on the combine harvester.This paper mainly adopts a combination of theoretical calculation,experimental verification and numerical simulation to systematically analyze the vibration mechanism of the upper plate structure of the harvester,and obtain the inherent characteristics of the upper plate of the combine harvester and the vibration mechanism in the multi-source excitation vibration environment.,and the structural optimization design was carried out according to its vibration response characteristics under multi-source excitation.This research provides a theoretical basis and method for the design and structural optimization of the combine harvester’s plate and shell structure,and is of great significance to improve the comprehensive performance of the domestic combine harvester.The research work of this paper mainly consists of the following four parts:(1)The plate-shell structure on the combine harvester is classified based on the connection method between the plate and the frame,and the welding plate and the bolt connection plate,which account for a large proportion,are deeply studied.To highlight the difference in connection methods,the welded and bolted plates were numerically modeled using the Hypermesh preprocessing function,and their natural frequencies and natural mode shapes were then solved by modal simulation.In addition,the actual mode shapes and frequencies of the panels of the same scale are tested by modal tests.Comparing the simulation modal and experimental modal results of the welded plate and the bolted plate to determine the influence of the connection method on the natural vibration characteristics of the plate and shell,studies have shown that the difference in the connection method does affect the vibration characteristics of the panel.Bolted plates have higher inherent vibration characteristics than welded plates.(2)For the welded plate and bolted plate on the combine harvester,it is simplified to four-side fixed plate and four-side simply supported plate,and the dynamic modeling is carried out.For the four-sided simply supported plate and four-sided fixed plate,dynamic models under natural vibration and forced vibration are established.The modal superposition method is used to establish the natural vibration dynamic model of the simply supported plate with four sides,and the natural vibration dynamic model of the four-sided fixed plate is established by the multi-component combination method of beam function.At the same time,the forced vibration models of four-sided simply supported plate and four-sided fixed plate under the action of concentrated simple harmonic force are established.The results obtained by the analytical method are compared with those obtained by the simulation to verify the accuracy of the model.The establishment of the dynamic model of the upper plate and shell structure of the combine harvester provides the basis for the design of the plate and shell structure of the combine harvester.(3)The excitation sources on the combine harvester were tested by order tracking experiments.The influence of the intrinsic structural parameters of the upper plate and shell structure of the combine harvester on its natural vibration and forced vibration response is studied.By means of simulation,the effects of the parameters related to stiffened plates,holes and edge stiffening on the natural and forced vibrations of four-side simply supported and four-side fixed plates are analyzed.And through the orthogonal experiment,the influence degree of each structural parameter on the vibration characteristics of the plate is determined.(4)According to the internal structural characteristic parameters of the plate and shell structure of the combine harvester,the structure is optimized from the perspective of natural vibration characteristics and forced vibration response,so as to improve the vibration performance of the plate.In order to choose a reasonable plate structure optimization method,this paper designs the steps of the experimental design scheme,the approximate model selection,and the structure optimization algorithm selection in the structure optimization.Finally,through the Workbench platform,using the optimization method based on the proxy model,the structure of the board parts of the threshing device on the combine harvester is optimized.The optimized plate is processed,and the natural vibration response and forced vibration response of the optimized front and rear plates are tested by bench test.The natural vibration characteristics and forced vibration characteristics of the plate before and after optimization are compared to verify the feasibility of structural optimization,thus verifying the feasibility and accuracy of the optimization scheme in this paper.