Program Load Spectrum Compilation for Accelerated Life Test of Parabolic Leaf Spring

Abstract

A method of program load spectrum compilation suitable for ALT (accelerated life test) of parabolic leaf spring was presented. In order to shorten the design and test period, road test is conducted on proving ground roads. The displacement spectrum of shock absorber connecting the point of the parabolic leaf spring seat on a commercial vehicle exposed to roads was obtained. The FEA (finite element analysis) method was used to obtain stress spectrum of hot spots on leaf spring by the displacement spectrum, and the fatigue life of the leaf spring is predicted using Palmgren-Miner’s rule. Statistical characteristics of the amplitudes and means of the displacement spectrum is investigated. The amplitudes and means of displacement spectrum found in experiment obey Weibull distribution and normal distribution respectively, and the distributions of amplitudes and means are independent. 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. Follow the theory of equal damage, the program load spectrum is compiled suitable for bench test of fatigue life of leaf spring. The method of program load spectrum compilation can provide reference for fatigue life test and life prediction of parabolic leaf spring assembly.