failure opinions
failure opinions
(OP)
I have been a marine engineer technician with the Navy for 25 years, and I have never seen this kind of failure. It is a emergency crank handle for anretracting an RV slide. The 1/2" dia handle which appears to have failed under torsion split like string cheese. i have seen many sheared bolts and shafts but nothing like this. What I wanted to ask was about the quality of the metal which is obviously low. What went wrong in the manufacturing or was it actually overloaded in its last use?





RE: failure opinions
RE: failure opinions
That is an unusual looking failure. Any addiitonal information you could give as to what the material is and the environment it was exposed to?
As to is whether or not this is an example of low material quality, that really depends on what the original material was specified to be.
My gut reaction (past the Wow!) is that, as an emergency handle, it saw infrequent service. Perhaps a heavily cold-worked austentitc stainless (cold-worked to increase yield strength) and was stored in a high-chloride environment, or perhaps, a high acid environment. Environmentally-assisted cracking from the environment and residual stresses from the fabricaition resulted in the longitudinal cracks during storage. When used under torsion, the longitudinal cracks combined to form the twisted mess you see. Of course, this is merely a blind guess and could be completely wrong.
But, it is an impressive piece.
rp
RE: failure opinions
You didn't mention the material, but it looks like steel of some kind.
RE: failure opinions
RE: failure opinions
I hope that you didn't get hurt when it let go.
No, it wasn't the last use, this failure was set up when they made the steel.
Either an extreme amount of inclusions, or internal cracks, or both.
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Plymouth Tube
RE: failure opinions
I've never seen a failure like that and I have no idea what caused the problem. But as I follow this thread I'm sure I'll learn something new. This is the exact sort of topic that makes these forums so useful. If you get any feedback from your Navy resources regarding a failure analysis I'd appreciate it if you could post the information.
Thanks for your contribution!
Terry
RE: failure opinions
RE: failure opinions
RE: failure opinions
Thanks for sharing your unique experience. Will appreciate,if you revert back with the analysis from lab.To a lay person like me,it appears as wire strands,which have separated,but as you mention it to be a drive shaft,it cannot be what I imagine.
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"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year