failure opinions 3

[JPMBC66]

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?

 

[metengr]

This looks like the crack handle was subjected to an impact load under torsion. The multi-fracture planes would seem to imply a heavily banded structure, similar to long fiber orientation in wood planks. This is all I could tell from what you have provided. More information would require a more detailed metallurgical lab analysis.

 

[redpicker]

Wow!
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

 

[Guest102023]

Interesting suggestions both. I would start with chemical analysis and then metallography of a complete cross section of the bar, near to where the shredding begins, and maybe another just beyond the start of it. Even if the material was crap, this is a remarkable failure.

You didn't mention the material, but it looks like steel of some kind.

 

[jtseng123]

something attack or residual stress through the grain bounday flow, which is due to cold or hot drawn or forging process or sudden impact torsion load periodically that overloaded it time after time. The material should have been stress relieved or normalized prior to using, and use larger diameter.

 

[EdStainless]

Great photo.
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.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[tbuelna]

JPMBC66,

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

 

[mrfailure]

Not that this makes ANY sense, but the handle looks more like it was made of extruded rods or wires which then were given a thick plating to provide the illusion of a single solid part. I cannot wait to find out what this really was. I did notice that all of the strands in the picture were oxidized, indicating these these surfaces existed prior to failure.

 

[JPMBC66]

I believe the oxidation occurred while waiting for repair. I don't believe it was fractured prior to total failure. But I did get more information. It is a driveshaft to the slide motor. This would mean it is subject to far more than human generated torque and actually exposed to the output of the gear reduction. But still the most interesting I have seen. Given the interest I will conclude that is unusual and try and get it into our labs at work for some more in depth analysis. Thanks for all the feedback.

 

[arunmrao]

JPMBC66,

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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