Research on Compilation Method of Multi-Axial Loading Spectrum for Cylindrical Shock Absorber

Abstract

The main failure mode of cylindrical shock absorbers (CSAs) used by taxis in China’s Zhejiang Province is oil leakage because of a large horizontal force loaded on the cylinder wall by a questionnaire survey. The previous CSA durability bench test methods, which do not involve the interaction between horizontal load and vertical load and do not consider the user road spectrum, cannot simulate the real fatigue phenomena of it. In order to preferably reproduce the failure mode and accurately to predict the failure time of the CSA used in the area, a compilation method of multi-axial loading spectrum is proposed based on the road spectrum. The vertical loading spectrum is compiled by using the way of sine on sine, in which high frequency (HF) signal superimposed on low frequency (LF) signal. The LF is determined by the half-power bandwidth theory, which can reflect the power spectral density distribution of the random road spectrum. The HF is determined by the maximum line velocity principle to effectively reduce test time. The loading cycles and amplitudes of them are determined by using the rain-flow counting method. In addition, the horizontal loading force is taken into consideration in the multi-axial loading spectrum. To prove the validation and efficiency of the method described in this paper, the compiled multi-axial loading spectrum was used to conduct the durability bench test. The results show that the mean failure mileage of specimens is close to the mean mileage time of field samples. The failure modes of the specimens are the same as those of field samples. Thus the proposed method can be used as a reference for durability bench test of CSA. The test data can also be used to accurately study the reliability of CSA.