Research On Structural Reliability Of Bus Frame Based On Roughness Of The Road

Nowadays,the environmental problems aroused people's attention.People prefer traveling by public transportation.Thus,the safety,economy,comfort of buses is gaining more and more attention.Bus body frame is the main bearing structure.Body frame strength,stiffness and fatigue properties have a direct impact on the life of the body frame,safety,handling and stability.At present,the vibration fatigue analysis of the body is generally based on the empirical formula.Otherwise,real vehicle test need to be carried out in laboratory or test field to predict the fatigue life.In this paper,the professional fatigue analysis software will be used to study the finite element fatigue reliability of the skeleton,which can forecast the vehicle life and dangerous position in the design stage,reduce the design cycle of the bus and reduce the design cost.With the research object of a certain type of full-load bus body skeleton,the three-dimensional data model will be simplified,which means ignoring some of the unimportant structures for analysis.Then the finite element model of passenger car body structure was established with Hypermesh.And the thesis choose four kinds of typical working condition of buses during daily driving to carry on a static characteristic analysis.Finite element static analysis is carried out on the bus body frame structure,stress distribution and deformation of bus body is obtained under various working conditions,which checks stress and strain of dangerous position.This thesis calculate the body frame of the free modal analysis,received the body's natural frequency and corresponding vibration modes,avoiding the resonance phenomenon.According to the road grading standard of GB7031-87 for mechanical vibration-road surface profiles-reporting measured data,the road roughness power spectrum density can be simulated in the MATLAB.Based on the Fourier inversion,power spectrum density in frequency domain can be simulated.Then stochastic vibration analysis was carried out by inputting road power spectrum density into the FE model to obtain the displacement,velocity and acceleration responses on the critical locations of the frame.Finally,the random load and the SN curve of the material are applied to the skeleton and the static load in the static analysis is replaced with the random load.Then the fatigue life of the skeleton is obtained,the reliability of the vibration of the passenger car can be evaluated.In this paper,the fatigue reliability of car body skeleton based on simulated road surface motions is studied.It provides a method for predicting the fatigue life of bus body skeleton during the actual design process,which is of great significance to shorten the development cycle and reduce the cost.