Nut failure- What do you think?
Nut failure- What do you think?
(OP)
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
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





RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
Hydrogen embrittlement is a possibility, as is a glass-hard and brittle heat treatment, or too rapid a quench.
RE: Nut failure- What do you think?
JMW
www.ViscoAnalyser.com
RE: Nut failure- What do you think?
Don
Kansas City
RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
Is it possible for something to fracture that straight? Is it possible it was cut with a hacksaw?
JHG
RE: Nut failure- What do you think?
Can you take close up shots of the fractured faces?
RE: Nut failure- What do you think?
What was the spec on the nut?
Are there any markings on the nut?
Do you have any more of similar nuts laying around that you can check?
First off this failure has the appearance of being busted by a chisel or nut buster, with the exception that the picture where the nut is on the stud it appears that there is some bright metal in a sea of black. There is apparent markings on the flanks if drive points from an ill fitting socket.
As stated above it would be nice to see the fracture surface. I would finish breaking the nut without damaging
any fracture surface.
RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
I begged the guy for a defective nut. Vendor fedex him new hardware and he sent it all back. So, just speculation unless the manufacture admits to the problem.
If I do happen to get a nut- I'll take a close up pic at work with inspection equipment and get a Rc number of the material.
It didn't fail on intial preload.
Thanks for the speculation!
Michael
RE: Nut failure- What do you think?
With geometry like that, even Unobtainium would crack...
Mike Halloran
Pembroke Pines, FL, USA
RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
Ouch!
Initial gut feel is that the sizes were incompatible (and possibly exacerbated by conditions noted above). It'd be interesting to know whether the degree of resistance felt when turning the nut down was greater than expected.
"Made in China?" Maybe the heat was contaminated by melamine
Ciao,
HevïGuy
www.heviitech.com
RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
Embrittlement can be caused by the solution used to blacken the parts. Having said that,
I agree with unclesyd a cracked nut failure especially one that is likely CrMo nut, is a bit unusual.
By the way the photo appears to be edited, two cracked nut images are shown and the washer is missing in both
RE: Nut failure- What do you think?
I'm talking about a radial deformed barrel.
The type nut in the failure doesn't normally use a washer as the flange area on the nut acts as a washer and also carries the majority of the preload.
I have to go along with jmw as it looks like the nut ran out of threads and started to climb the thread runout.
RE: Nut failure- What do you think?
Maybe the nut was already hoop-stressed before being installed.
Ted
RE: Nut failure- What do you think?
RE: Nut failure- What do you think?
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.
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RE: Nut failure- What do you think?