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Title:	High temperature fatigue of AA6061 aluminium alloy
Authors:	Fahad Hussain (P74254)
Supervisor:	Shahrum Abdullah, Prof. Ir. Dr.
Keywords:	Aluminum
Issue Date:	25-May-2018
Description:	This study focuses on the load sequence effect of fatigue life at high temperatures. The study of fatigue life under variable amplitude loadings is an important as most of automotive engine components, such as engine block, cylinder head, piston, engine oil pans, and heat exchangers are under the combine effect of temperature and fatigue loading. The objective of this study is to develop an improved method to characterise the fatigue life and the load sequence effect at high temperatures. Aluminium alloy AA6061 was used as liable material for this study due to its broad application in automotive and engineering components. The fatigue life analysis was performed at room and high temperatures. At room temperature a simulation based method was used to study the fatigue life behaviour of the material by stress-life (S-N) approach. The results from simulation were compared with the experimental results using different statistical techniques. The linear regression analysis results for a value of 0.95 of the coefficient of determination, and data scatter of 83% around 1:1 correlation line with a range of factors 2 indicated a strong correlation between the experiment and simulation. Fatigue life tests were performed according to ASTM E466 under constant amplitude loading with a stress ratio of -1. Two types of loading sequence were obtained from the constant amplitude loading namely: low-to-high and high-to-low loading. Cyclic test was performed at room temperature using constant, low-to-high and high-to-low loadings. The similar loadings were used for cyclic testing at the increased temperatures of 50 °C, 100 °C, 150 °C, 200 °C, 250 °C and 300 °C. The maximum temperature was chosen on the basis of the half of the melting point of aluminium alloy AA6061 and based on the peak temperature of a piston head of an automotive engine that can be reached in service. The test results for room temperature show the minimum fatigue life under constant amplitude loading followed by high to low, and low to high loading sequences. For high temperatures, the scattered results were obtained for fatigue life due to a small difference of test temperatures. The Weibull reliability analysis was used for the characterisation of fatigue life under different loading sequences. The reliability distributions show that at 90 % of reliability, the fatigue life under constant loading condition was about 16,200 cycles, 30,800 cycles under high to low, and 50,480 cycles under low to high loading sequences. These results indicated that minimum fatigue life is under constant amplitude loading at different levels of high temperatures. The results were validated using the Weibull cumulative probability plot by fitting experimental data within 95 % of confidence intervals. Thus, an improved method for fatigue life characterisation using the probabilistic approach contributed to the prediction of fatigue life under different loading sequences at high temperatures.,Certification of Master's/Doctoral Thesis" is not available
Pages:	122
Call Number:	TN775.H947 2018 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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