Cracking of Railroad Wheels
by
Brian G. Thomas
Abstract
This project was undertaken to summarize known work on the sudden fracture of eutectoid steel railroad wheels, with the objective of finding new areas for future research into this serious problem. Cracking occurs due to a combination of high thermal stresses, primarily generated during braking, and extreme metallurgical embrittlement. This report focuses on the metallurgical embrittlement aspects of the problem, as stress generation has been studied previously. Since the mechanism of wheel fracture is still not fully understood, this report discusses related cracking problems in steel that seem to occur via a similar mechanism. The remainder of the report explores a wide range of embrittlement mechanisms, ranging from intergranular to transgranular brittle fracture and, finally a summary of fracture toughness studies on the affected eutectoid steel grades. Although numerous possibilities deserving future attention are exposed, the most promising avenues for future research appear to lie in: 1) the development of new alloys that achieve improved fracture toughness through lower carbon content and 2) renewed attention on stress generation.
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