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The strength and fatigue performance of 319 aluminum alloy castings

Byczynski, Glenn Edwin (2002)
Ph.D. thesis, University of Birmingham.

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Abstract

Analysis of fatigue samples sectioned from commercial 319 (Al-Si-Cu-Mg) alloy cylinder block castings showed that shrinkage pore networks and oxide films played an important role in fatigue failure.
A reduced pressure technique was employed to study the relationship between porosity and oxide films. Links between oxide films and porosity were made and mechanisms for the inflation of films into porosity networks were established.
Tensile tests performed on samples cast with and without filters showed that the ultimate tensile strengths of the filtered group had a Weibull modulus 2.4 times that of the unfiltered. Samples with abnormally low strengths were found to contain oxide film defects. These films had an approximately 5 times greater damaging effect on strength than that predicted by reduction in cross sectional area. The fracture strengths of these flawed samples were found to obey a linear elastic fracture mechanics model (LEFM).
A LEFM crack growth model was particularly successful in predicting the life of fatigue samples that initiated at oxide films. Having crack-like geometry, and a minute crack tip radius, oxide films effectively acted as preformed cracks. Consequently there was an absence of crack nucleation time, explaining the correlation of predicted propagation life to fatigue life.

Type of Work:Ph.D. thesis.
Supervisor(s):Campbell, John
School/Faculty:Schools (1998 to 2008) > School of Engineering
Department:School of Metallurgy and Materials
Subjects:TL Motor vehicles. Aeronautics. Astronautics
TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:7030
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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