Nut failure- What do you think? 1

[strWennie1]

I grabbed this off an hot-rod website.

It was holding a cylinder head on .. running high boost. Failure mode looks strange to me for a nut. I expect shearout of either nut or stud threads.
Reading around my only viable scenerious are ..

1) just wasn't heattreated and residual forming stresses give a hoop stress failure
2) Heat-treated and then acid bath for cleanup. The part experienced hydrogen embrittlement.
3)Manufacture used too high a heat-treatment for the material and failure is fatigue related- still would have expected thread shear.



Michael

 

[IRstuff]

How It's Made shows a billet that's center punched and forged to the external round shape, which should result in no seam lines.

Perhaps this one's starting billet is somehow elongated and wrapped around the center die and forged, leaving a single seam that would be randomly oriented to the peaks and valleys. Such a process could result in a failure at a seam.

TTFN

FAQ731-376

 

[foglights]

cheap aluminum alloy run down too tight then subject to serious vibrations. (my fun guess.)