[TheForge] RE: Quesiton about a weird event

[xlch58 at swbell.net]

Jeffrey Polaski wrote:

>I can see this happening with a shaft that has lot of stress on it...
>most of the strength of the shaft is "in the surface". Putting a good
>nick in the surface of a shaft loaded almost to its limit could cause
>catastrophic failure. Especially where things are designed to run closer
>to their limit, like a helicopter. 
>
>
>Jeff Polaski
>Research and Graduate Studies Webmaster
>University of California, Irvine
>http://www.rgs.uci.edu/
>949.824.6363
>  
>
Any kind of discontinuity on the surface would be a stress riser, in 
fact the surface itself is a stress riser.  Someone mentioned old cranks 
breaking cleanly on the journals.   I have seen this many times, usually 
because the design is faulty, or more often today becaue the regrinder 
did not put the proper radius at the edges of the journal to prevent a 
serious stress riser.

Charles