Metal fatigue

[ian1944]

From "Train Wreck: The Forensics of Rail Disasters", an ebook by G.D.Bibel:

The major source of broken rail is metal fatigue. Metal fatigue occurs from contact between the wheel and rail and from rail bending. Metal fatigue can be explained as simply as bending a paperclip back and forth until it breaks, analogous to the minute rail bending that occurs with each passing wheel. Just as rail gradually deteriorates from wear, it also gradually deteriorates from metal fatigue.

The rail bending referred to here will be in the vertical plane, whereas that due to point operation will be in the horizontal plane. A busy point will have a lot of train movements and a lot of switching, so both bending modes will be frequent, the former more so but the latter of greater magnitude. Is it generally accepted which is the more important as a cause of rail fatigue?

 

[miikey]

Generaly the movement area of a point is very large, depending on the size of the switch. The forces arnt concentrated on a specific point on the rail. Ive never heard of a switch breaking due to it being swung. Usually if a switch is used that much the rail will be worn and the switch replaced before any rail fatigue is noticed.

 

[ian1944]

From which I presume that whichever mode of flexing of a point rail is the more damaging is irrelevant, as it is abrasive wear which determines life-expiry.