Dr. Salvinder Singh, Senior Lecturer at the University of Kebangsaan Malaysia who specializes in fatigue life assessment and reliability engineering, will give a seminar at the Institute of Risk and Reliability in Hannover in mid October 2023 on two topics:
- Assessing Fatigue Life Characteristics of API X65 Steel under the Effects of Corrosion in Deep-Sea Environment
- Strain-based running-reliability characterisation in time-domain for risk monitoring under various load conditions.
The seminar session will take place in the institutes library, room 116, on Friday, October 20, 2023. Start is at 9:00 a.m. The seminar will also be available via Webex online meeting. If you want to participate online please contact Torsten Ilsemann.
Assessing Fatigue Life Characteristics of API X65 Steel under the Effects of Corrosion in Deep-Sea Environment
M.A. Khan1, S.S.K. Singh1,*, S. Abdullah1, M. Bashir2
1Department of Mechanical and Manufacturing Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia.
2 School of Engineering, Faculty of Engineering and Technology, Liverpool John Moores University, Liverpool, United Kingdom
Keywords: Fatigue, Stress-Life, Durability.
Abstract: In the oil and gas industry, assessing the pipeline failure caused by corrosion is important especially when dealing with crack growth that is induced by internal and external cyclic loads. The aim of this study is to assess the fatigue life characteristics based on the effects of corrosion for API X65 steel under deep-sea environment. Likewise, the strength of offshore pipelines is affected by the presence of cracks due to the variation of loads, material properties and the corrosive effects due to salinity and pH values. During the service life of subsea pipelines, corrosion fatigue crack growth is a common occurrence that often results in a decrease in their strength and loss of asset integrity which frequently leads to pipeline cracking. Therefore, evaluating the durability of pipelines is essential because of the interdependence between corrosion fatigue, pipeline material properties, crack dimensions, geometric design and load ratios. Tensile test is carried out for welded and non-welded specimens that were not submerged and submerged for 48 hours in sea water condition. This is based on the salinity and pH test values of the seawater condition sourced from the coastal area of Port Dickson, Malaysia. In addition, the microscopic features and chemical composition were examined through FESEM and EDX on the fractured surface of the pipeline material. A fatigue stress-life (S-N) curve is plotted using the Basquin equation based on values obtained from the UTS/mechanical testing. Finite element modelling for the compact tension was carried out for three different load ratios (0.1, 0.4, and 0.7). The finite element analysis of the pre-cracked CT specimen shows that the stress intensity factor is proportionally linear with the length of crack and load ratio. Hence, providing a relevant alternative approach for fatigue life estimation of API X65 steel using crack growth as a function of corrosion fatigue mechanism.
Strain-based running-reliability characterisation in time-domain for risk monitoring under various load conditions
L. Abdullah, S.S.K. Singh*, S. Abdullah, A.K. Ariffin
Department of Mechanical and Manufacturing Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM 43600, Bangi, Selangor, Malaysia.
Abstract
This aim of this study is to characterise the strain-based fatigue life data in time-domain using the newly modelled running-reliability technique that considers the load sequence effect. This is because the current established conventional strain life models do not consider the dependence on either low or high amplitudes that will occur first in the load history for fatigue reliability, especially for the automotive suspension system. Finite element analysis is carried out to ensure that time-domain strain signals are captured at the most critical region during road test at various conditions, i.e. highway, rural and campus. The fatigue life with the mean cycle to failure is predicted by considering the cycle sequence effect using cycle-counting method and inverse damage accumulation law. In addition, the newly modelled running-reliability technique is formulated to extract the features of high amplitude excitation obtained from the time-domain strain signals for characterising the fatigue reliability features under load sequence effect. Hence, providing the reliability-hazard rate relationship for fatigue reliability feature characterisation of strain-based fatigue life assessment in time-domain using the proposed running-reliability technique.
