Fatigue analysis of austempered ductile iron suitable for automotive camshaft applications
Fatigue analysis of austempered ductile iron suitable for automotive camshaft applications
Fretting fatigue is of major concern during camshaft service, and a fundamental microstructurally based assessment of the mechanisms of single fatigue failure is required to complement the empirical studies currently being carried out by Federal Mogul Camshafts. In investigating the effects of various Austempered Ductile Iron (ADI) microstructures on fatigue initiation and early crack growth, a micro-mechanistically based understanding is being developed that can be used in defining appropriate alloy development. Three ADI microstructures have been investigated: one produced by austenitising at 800°C and austempering at 260°C, one by austenitising at 800°C and austempering at 390°C, and the other by austenitising at 900°C and austempering at 390°C. The duration for austenitisation and austempering was two hours. The present results have been compared with previous work carried out at Southampton, and the Loughborough University microstructure evolution model has been used to estimate the proportions of the various phases. Crack initiation and early growth behaviour was assessed under three point bend short fatigue crack conditions. Averaged crack propagation behaviour has been assessed by long fatigue crack tests. Under all tested stress levels the ‘900/390’ heat treatment outperformed both the ‘800/290’ and ‘800/390’ conditions. Crack initiation and propagation has been studied and two regimes of failure mechanism were identified. The softer, more damage tolerant ‘900/390’ condition exhibited a generally propagation-dominated failure, whilst the harder, less damage tolerant ‘800/260’ condition failed by varying degrees of crack linking by coalescence. The brittle ‘800/390’ condition exhibited completely coalescence dominated failure. Primary initiation events for the ‘900/390’ occurred exclusively at pores.
University of Southampton
Stokes, Ben
3a9efa7d-f87f-49f5-b8f8-0c6f4d4c812d
2003
Stokes, Ben
3a9efa7d-f87f-49f5-b8f8-0c6f4d4c812d
Stokes, Ben
(2003)
Fatigue analysis of austempered ductile iron suitable for automotive camshaft applications.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Fretting fatigue is of major concern during camshaft service, and a fundamental microstructurally based assessment of the mechanisms of single fatigue failure is required to complement the empirical studies currently being carried out by Federal Mogul Camshafts. In investigating the effects of various Austempered Ductile Iron (ADI) microstructures on fatigue initiation and early crack growth, a micro-mechanistically based understanding is being developed that can be used in defining appropriate alloy development. Three ADI microstructures have been investigated: one produced by austenitising at 800°C and austempering at 260°C, one by austenitising at 800°C and austempering at 390°C, and the other by austenitising at 900°C and austempering at 390°C. The duration for austenitisation and austempering was two hours. The present results have been compared with previous work carried out at Southampton, and the Loughborough University microstructure evolution model has been used to estimate the proportions of the various phases. Crack initiation and early growth behaviour was assessed under three point bend short fatigue crack conditions. Averaged crack propagation behaviour has been assessed by long fatigue crack tests. Under all tested stress levels the ‘900/390’ heat treatment outperformed both the ‘800/290’ and ‘800/390’ conditions. Crack initiation and propagation has been studied and two regimes of failure mechanism were identified. The softer, more damage tolerant ‘900/390’ condition exhibited a generally propagation-dominated failure, whilst the harder, less damage tolerant ‘800/260’ condition failed by varying degrees of crack linking by coalescence. The brittle ‘800/390’ condition exhibited completely coalescence dominated failure. Primary initiation events for the ‘900/390’ occurred exclusively at pores.
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Published date: 2003
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Local EPrints ID: 465029
URI: http://eprints.soton.ac.uk/id/eprint/465029
PURE UUID: 161076e4-f753-43b3-862a-42aebd40c286
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Date deposited: 05 Jul 2022 00:17
Last modified: 16 Mar 2024 19:54
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Author:
Ben Stokes
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