Technology Research On Calculating Hardpoints's Forces And Moments In Suspension System

About the analysis of strength and durability on control arms,steering links and bushings,etc,the Hardpoints's forces and moments in suspension system are necessary inputs,and that the treatment of boundary conditions is very important to the exactitude of those analysis results.At present,in engineering practice,the Hardpoints's loads are obtained through establishing the multi-body dynamic model of suspension by ADAMS.This way that to obtain the loads is relatively complex and single.Now,there is no Specific software for calculating the loads of the Hardpoints's in China and abroad.Always getting the bushing stiffness are difficult and considering the design costs,only the linear stiffnesses of bushings are taken into account when calculating the joints forces and moments in suspension mechanisms.So there may be a bigger error between the calculate results and the actual results.Taking the front and rear suspensions of a certain vehicle as the research object,some researches,as follows,were done for accurately calculating the Hardpoints's loads in the suspensions mechanisms.To begin with the rubber material,the common constitutive models for rubber materials are discussed.The common constitutive models for rubber materials are chosen to fit the stress strain relationships,based on the tests of rubber materials.According to the comparison results of fitting curves and test curves,one constitutive model for rubber materials,which can accurately match the rubber material for rubber bushes,is selected to describe rubber material.Combining with finite element analysis technology and parameters reverse technology,the omni-direction stiffness information of the rubber bushes were recombined,based on the existing rubber bushings stiffness data.Then using the recombined stiffness data to calculate the joints forces an d moments in suspension systems.Secondly,taking a Macpherson front suspension and a two-link rear suspension as the object of the research,mathematical models about the two kinds of suspensions were established.The nonlinear equations,using to calculating the joints loads in front and rear suspension mechanisms,were proposed.And the Newton Iteration Method were applied to solve those nonlinear equations by MATLAB.The mathematical models and nonlinear equations,proposed in this paper,were used to analysis the joints loads under several kinds of typical driving conditions.The multi-body dynamic models of the front and rear suspensions,considering the nonlinear stiffness characteristics of bushings,are established by ADAMS.The joints loads were calculated by the multi-body dynamic models of suspensions at the same typical driving conditions.The validity and accuracy of the calculation method was verified by comparing the calculation results in one of two ways.The applied research of calculating the joints forces and moments in suspensions systems was done in the end of paper.The joints loads,obtained by the calculating method,were used to analyze the strength of the knuckle under several kinds of driving conditions.And then a software,specialized in calculating the joints loads in suspensions,was developed by the software of MATLAB.