shaft failure 1

[mech_john]

From the pics, can we tell which end failure started. Thoughts are appreciated. Motor shaft break mounted to clamp collar inside gearbox.

Thanks...John

 

[kingnero]

Don't have any (significant) first hand experience, so I can't comment anything useful but here's something to read in the meanwhile...

 

[mfgenggear]

recommend to submit to a metallurgical lab for failure analysis.
who made the part? material? what were the requirements? material, heat treat treating and NDT requirements?

 

[mrfailure]

You can see cracks initiated under torsion loading, with complimentary cracks intersecting with each other. The crack that became the fracture has a thumbnail, indicating fatigue is the most likely mode. Other features of fracture are not really visible, perhaps because of lighting/quality, but more likely because fracture features were flattened from contact between mating sides of the fracture as the crack propagated. None of this is unusual in a shaft failure, and none of it really tells you why the shaft fractured. You really need a metallurgical failure evaluation to get at the cause(s).

 

[Tmoose]

Is this a mature product, or FOAK?

Who designed it? What do they have to say?

Please post an arrangement drawing showing the motor, clamp, and gearbox.
And any details about operating conditions for the last 6 months.

There appears to be fretting, and fretting can be a POWERFUL instigator of fatigue failure attacking from two different avenues.

 

[Dhurjati Sen]

It is a torsional failure.
The fracture surface has a predominantly ductile (dimpled) appearance.



DHURJATI SEN