The strength and fatigue performance of 319 aluminum alloy castings

Byczynski, Glenn Edwin (2002). The strength and fatigue performance of 319 aluminum alloy castings. University of Birmingham. Ph.D.

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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: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
College/Faculty: Schools (1998 to 2008) > School of Engineering
School or Department: School of Metallurgy and Materials
Funders: Other
Other Funders: Ford Foundation
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
T Technology > TN Mining engineering. Metallurgy


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