Using a fatigue data editing approach for analysing cycle sequence effects in variable amplitude road loadings

Abstract

This paper presents the analysis of cycle sequence effects using variable amplitude (VA) fatigue loadings extracted from a wavelet-based fatigue data editing algorithm, known as Wavelet Bump Extraction (WBE). This algorithm was used to produce a shortened mission signal by extracting fatigue damaging events from the original signal. In relation to the fatigue life prediction, current industrial practice uses the Palmgren-Miner linear damage rule which lacks load interaction accountability in VA loadings. Considering the importance of cycle sequence effects in VA loadings, a suitable fatigue life prediction approach was identified, i.e. the Effective Strain Damage (ESD) model. In this study, the cycle sequence effects were analytically and experimentally analysed using VA fatigue loadings. Uniaxial fatigue tests of the WBE extracted loadings were performed and the results were compared with predicted results using four strain-life models, i.e. Coffin-Manson, Morrow, Smith-Watson- Topper (SWT) and ESD. The smallest and acceptable difference of about 19% between the experiment and prediction was found using the ESD model. Finally, to note that it is important to retain the original cycle sequence in order to properly determine fatigue life under VA loadings.