Random Vibration Fatigue Life Estimation Of A Tractor Frame

Tractor is the main vehicle type in logistics transportation,and the frame of tractor is its main loaded parts.Considering various loads of the tractor will be passed to the frame eventually,thus the performance of the vehicle frame is directly related to the effects of vehicle design.The basic properties of the frame include safety,comfort,stability and service life.What's more,making a Static and dynamic characteristics analysis of frame and random vibration fatigue life estimation by CAE has an important position in the automobile product development,which has a very engineering significance.In this thesis,the 6x4 tractor frame was chosen as the research object.Firstly,a finite element model of frame was established by HyperMesh,and the static analysis of frame towards bend,torsion,brake and swerve was carried out to calculate the stress and displacement of frame by Radioss.Secondly,the free mode analysis of frame and vehicle model was carried out to analyze the resonance characteristic of frame.The frequency response of frame in vehicle environment was analyzed by the modal method to obtain frequency response function of frame under the excitation of six wheels.Based on the displacement power spectrum density of road roughness,the vibration response characteristics of frame had been obtained by analyzing the random vibration of whole vehicles.Finally,based on the frame frequency response function and frequency domain model of road roughness and combined the frame material S-N curve,the location of fatigue damage can be determined and the fatigue life of dangerous parts can be estimated by simulating with fatigue analysis software--MSC.fatigue.Matlab program is used to estimate the random vibration fatigue life of frame dangerous joints.By comparing the calculation results with simulation,the accuracy of fatigue life estimation result can be verified.The structure of hazardous part was improved based on fatigue analysis results.The result shows that the improved frame has good anti-fatigue ability.The vibration fatigue analysis method based on frequency domain can estimate the random vibration fatigue life of frame quickly and efficiently,which provide theoretical basis and analysis method for frame design and improvement.