Vibration Analysis And Structure Improvement Of The Head Of Rape Combine Harvester

Rape is one of the most important oil crops in China,with the largest annual planting area and output in the world.The harvest of rapeseed with mechanical tools is a key process in the whole mechanization of rapeseed cultivation.At present,the rapeseed combine harvester applied in the domestic market is modified on the basis of the rice and wheat combine harvester which has the process of whole feeding,and the problems such as its structure,reducing power consumption,slowing down vibration and noise,and reducing loss rates are also have to be considered.As a key component of the rape harvester,the header is not only affected by external loads such as engine,cutter drive system,field working conditions,reel and other interactions with crops,but also subjected to the movement of rotating parts such as stirrers,threshing drums,and inertial load excitation.These loads will cause seriously vibration of the header and the high failure rate.Therefore,it is necessary to study the vibration characteristics and the influence law of the header,which is very important for the vibration reduction,noise reduction,dynamic design and optimization of the combine harvester.This paper is based on the analysis of the vibration characteristics and structural optimization of the rapeseed combine harvester header at home and abroad.The main research contents are as follows:(1)Analysis of vibration characteristics of rapeseed headers.The 3D model of the rape harvester header was built by Solidworks,then it was imported into Ansys workbench in parasolid format file,and the middle surface of the produced finite element model was extracted in DM and the surface imprint was added.Then,selected material,divided the mesh,supposed the boundary conditions,etc.By solving and post-processing,the static characters and modal analysis results are analyzed,the total deformation,strain,stress,and mode shape are obtained.At the same time,the maximum deformation,maximum equivalent stress,stress concentration,and first 20 modal frequencies are also given.The excitation frequency of the main rotating parts of the combine harvester and the natural frequency of the canola header was compared,the results showed that to avoid resonance and provide effective theoretical guidance for the later improvement.(2)Vibration test of rapeseed header.In order to find out the maximum vibration source that affects the vibration of the header,the field and non-field experiments were conducted.The CoCo-80 dynamic signal analyzer and the three-axis acceleration sensor are used to respectively collect the acceleration signals of the corresponding measuring points of the header in different working conditions.The non-field test mainly measured the acceleration at idle speed(1500r/min),medium speed(2000r/min)and high speed(2500r/min)under the conditions of engine work,engine and cutter working together.Signal,while the experiments in the field was to collect the signal under normal working conditions,then the signal was imported into the engineering data management software EDM for spectral transformation(FFT)and the corresponding spectrum signals were obtained.Finally,the signals of the measurement points of the header vibration were analyzed,including the ime domain and spectrum signals,the parts with large vibration,the excitation frequency and the excitation source were found,which provides practical guidance for the later structural improvement.(3)Comparative analysis between finite element theory analysis and vibration test.A strong excitation source for the header was obtained,in order to better understand the vibration characteristics of the header,and provide theoretical guidance for the structural optimization of the later header.The local structure with large stress and deformation is improved.(4)Improvement of the structure of the rapeseed header.Compare and analyze the results of finite element analysis and vibration test results,find out the relatively weak links of the design,apply local optimization,and optimize the header finally by adding support and reinforcement.Compare and analyze the optimization effects between different improvement schemes,and select a better improvement scheme.The finite element analysis of the improved header structure again shows that the new structure not only meets the strength design requirements,but also raises the first natural frequency from 7.87 Hz to 11.55 Hz,which avoids the cutter,chain conveyor and the drum excitation range,and also avoids resonance.