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Weird bearing failure mode

Weird bearing failure mode

(OP)
I've just witnessed a ball bearing failure that I've never seen before. The ball elements failed (not either race). They appeared to crumble. They were split open in two or more pieces each with a brittle looking fracture surface. It was on every ball. This happened at very low life. It is a standard size ball bearing from a "non-elite" supplier. The pieces are out to a met lab to see if it was a material issue, but I am wondering if anyone has seen anything like this. I know there will be in interest in more application info and pictures, but I have to be careful in what I post, so I'm starting with the question of if anyone has seen anything like this and what was the root cause?

RE: Weird bearing failure mode

Similar things reported on another forum (I think you have to be a forum member to view attachments or follow links there):

http://maintenanceforums.com/eve/forums/a/tpc/f/37...

http://maintenanceforums.com/eve/forums/a/tpc/f/71...


As I recall several times that symptom was also associated with craters on the balls. I had some discussion of possible connections here:
http://maintenanceforums.com/eve/forums/a/tpc/f/37...

I surmise that craters can be a brittle failure pattern, just like splitting open. Both related to ball properties. Either a result of manufacture, or some change resulting from operating conditions (chemistry, temperature, long-shot would be electric current). At least that's my broad vague swag on the situation.

=====================================
(2B)+(2B)' ?

RE: Weird bearing failure mode

"One unusual consequence of overheating is “hollow ball.” Because heat cannot be conducted away from balls as quickly as it can from rings, the center of the balls can become hot enough to melt the material there. Centrifugal forces, then, can cause heat-softened material to flow away from the center to the cooler outer surface. This produces hollow balls that can explode if the heat differential is high enough."

http://web.applied.com/site.cfm/Bearing_Failure_An...

======================

slightly different explanation from SKF here -
http://www.mromagazine.com/features/the-strange-ho...

RE: Weird bearing failure mode

As a failure analyst (though not particularly a bearing specialist), I find the 'hollow ball' phenomenon quite unbelievable. Conservation of mass, for one. I need to see pictures.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

RE: Weird bearing failure mode

we'll go with the skf explanation.

=====================================
(2B)+(2B)' ?

RE: Weird bearing failure mode

I have seen this type of failure on a low speed centrifuge (about 1000 rpm). The balls were not hollow, but many spilt like nut shell hit with a hammer. The races/rings were fault free. I suspect the bearing was/became loose and took a pounding.

Walt

RE: Weird bearing failure mode

(OP)
Thanks for the ideas. This turned out to be heat treat defect in the ball. A failure that was not able to be replicated when tested with more name brand bearings. Lesson learned: Don't let purchasing source bearings just anywhere :)

RE: Weird bearing failure mode

"Thanks for the ideas. This turned out to be heat treat defect in the ball. A failure that was not able to be replicated when tested with more name brand bearings. Lesson learned: Don't let purchasing source bearings just anywhere :) "

I think you got it right. When we've seen this failure in the past it was from poor heat treatment.

If the balls are shattered and the rings are as well, then look at impact loading. If the balls are shattered and the rings look almost new then there is most likely something wrong with the balls.

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