| The leaf spring is a common elastic component in the car suspension,which is widely used in trucks and some non-independent suspension on the bus.When vehicle exposed to random road,the force condition of leaf spring is very complicated which leads to a great challenge for its durability.A method of load spectrum compilation suitable for fatigue reliability analysis of nonlinear leaf spring with varying stiffness was presented according to the durability problem happened during road test.A finite element model of leaf spring with consideration of nonlinear contact was established with ANSYS.Model parameters were identified by using bench test method.Base on the model,the nonlinear relation between stress and deformation at any point was obtained.Arc height signal of leaf assembly on intensify road was obtained by acceleration signal acquisition and processing.Base on the relation between stress and deformation signal,accurate stress spectrum of hot spots is calculated.Fatigue reliability analysis using compiled load spectrum counted by rain-flow counting method was carried out and the result coincide well with road test.Then,based on the stress spectrum,a method of program load spectrum compilation suitable for ALT(accelerated life test)of nonlinear leaf spring was presented.Based on rain-flow counting result.The amplitude of stress was found to obey Weibull distribution,but the mean of stress is not distributed as normal or Weibull like other automotive parts.On the basis of the extrapolated spectrum,Conover method was used to convert stress spectrum to two-dimensional load spectrum.Besides,method of one-dimensional load spectrum compilation and realization for bench test was studied.Compared to the result of road test,the compiled ALT program load spectrum is in accordance with the road test.Finally,the method proposed in the paper for leaf spring fatigue analysis was packed and a software platform was built by secondary development based on VC6.0. |
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