Plenary Lecture

Wavelet Based Fatigue Data Editing: Application for Accelerated Fatigue Tests of Steel Specimens under Spectrum Loadings

Associate Professor Shahrum Abdullah
Department of Mechanical and Materials Engineering
Faculty of Engineering and Built Environment
Universiti Kebangsaan Malaysia
43600 UKM Bangi, Selangor
MALAYSIA
Email: shahrum@eng.ukm.my; shahrum1@gmail.com

Abstract: Many experimental loadings measured on both roads and test tracks generate variable amplitude (VA) load time histories contain transient or high amplitude. The presence of large amplitude cycles is common in time histories of ground vehicle vibration and fatigue damage. When a vehicle is moving over the irregular road surface, high amplitude features (or bump segments) can be observed in the time histories. Therefore, the need to reduce development time and improving confidence in the fatigue road load analysis means that it is an interest to investigate the issue of fatigue loading compression. This method, which is known as fatigue data editing, is used to produce a shortened loading containing large amplitude cycles. Accelerated fatigue tests can then be performed in the laboratory using these loadings, which has shorter time length and equivalent fatigue damage potential when compared to the original loading. Without editing VA loadings, the testing time and cost become prohibitive. Hence, this work describes the accelerated fatigue tests of BS 080A42 steel specimens using shortened VA loadings. Practically, a VA strain loading which was measured on the lower suspension arm of a vehicle while driven over a pavé road surface was used. This loading was summarised using Wavelet Bump Extraction (WBE), for which WBE was developed based on the idea of bump identification and extraction in order to produce a shortened loading using the orthogonal wavelet transform approach. The aim of this study is to demonstrate the applicability of the WBE mission loadings for laboratory accelerated fatigue tests using notched specimens. The WBE shortened loading was also validated based on the fatigue life comparison to the original loading using four strain-life fatigue damage models. Experimental fatigue tests were performed using a cylindrical shape of notched specimens made from the BS 080A42 steel. The experimental findings showed that the fatigue tests were accelerated from 99 hours to 36 hours, and 78.8 hours to 32.5 hours for smooth and notched specimens, respectively. The results indicate that the WBE algorithm gave an alternative solution for the accelerated fatigue tests, particularly in the durability and automotive research.



Brief Biography of the Speaker:
Dr. Shahrum Abdullah is the lecturer in Department of Mechanical and Materials Engineering, Universiti Kebangsaan Malaysia. He obtained his first degree in Mechanical Engineering at Universiti Kebangsaan Malaysia in 1995. In 1997, he obtained his MSc (Engineering Design) degree from Loughborough University of United Kingdom. In 2005, Finally, he was awarded the Ph.D. degree in Mechanical Engineering at the University of Sheffield, United Kingdom. His PhD thesis is within the scope of fatigue data analysis using the signal processing method, particularly the wavelet transform, which are the core research activities in his current days. Dr. Shahrum Abdullah authored many papers related to his specialization (engineering design and fatigue life assessment) in many international journals and proceedings.