Study On Fatigue Analysis And Bench Test Load Spectrum Compilation Method Of Leaf Springs With Heavy Duty Vehicle

With the rapid development of the transportation industry,heavy duty vehicle is playing a significant role in this process.The parabolic leaf spring and balanced suspension leaf spring are a common elastic component in the triaxial heavy commercial vehicle.When vehicle exposed to random road,the force condition of leaf spring assembly is very complicated which leads to a great challenge for its durability.A method of constant fatigue life suitable for fatigue reliability analysis of taper leaf spring is presented.Based on the Timoshenko beam theory,a simplified model was presented,which can be applied to rapidly solve the bending stress of curved leaf spring and straight leaf spring under different load conditions.The result of FEA with ANSYS is in accordance with the analytical model.The fatigue life prediction of the leaf spring is carried out with the nominal stress method and Miner damage accumulation theory.The suggested model can be used to generate fatigue life diagram that predicts the required mean and alternating load values for a desired fatigue life.Firstly,the parabolic leaf spring and balanced suspension leaf spring of a certain heavy duty vehicles was employed as research object,and a method of fatigue reliability analysis based on road and virtual prototype simulation is presented.The finite element model of parabolic leaf spring and balanced suspension leaf spring with consideration of geometry and contact were established with ANSYS.Based on the model,the relation between stress and deformation at any point was obtained.The displacement spectrum of shock absorber connecting the point of the parabolic leaf spring seat on a commercial vehicle exposed to roads was obtained.In addition,the displacement spectrums of front and rear of balanced suspension leaf spring were also obtained.The equivalent method for load Spectrum and state judgment method of balanced suspension leaf spring are presented.The FEA method was used to obtain stress spectrum of hot spots on two types of leaf spring by the displacement spectrum,and the fatigue life of the leaf spring is predicted using Palmgren-Miner's rule.At the second stage,statistical characteristics of the amplitudes and means of the displacement spectrum is investigated.The amplitudes and means of displacement spectrum of the parabolic leaf spring were found in experiment obey Weibull distribution and normal distribution respectively,the distributions of amplitudes and means are independent.The distribution function of amplitudes and means is evaluated via parameter estimation.Meanwhile,the amplitudes and means of stress spectrum of the balanced suspension leaf spring was found obey Weibull distribution,but the mean was not distributed as normal or Weibull.The Kernel density estimation method was used to estimation probability density function.Finally,based on the Conover principle,the two-dimensional spectrum with eight levels is established by applying the cycle extrapolation method,and then it is converted into one-dimensional spectrum with the variable mean method.The program load spectrum is compiled suitable for bench test of fatigue life of leaf spring by using the theory of equal damage.This dissertation provides a reference for fatigue life test and life prediction of parabolic leaf spring and balanced suspension leaf spring assembly.