One Ball fatigue failure at Deep Groove Ball bearing

[Ranganath Nagaraju]

I am working on finding a solution for a gear box field failure.

Failure description:
In the deep groove ball bearing only one rolling element has a pre-mature fatigue failure (Image-6.jpg) and rest of the all ball is in good condition (image-05.jpg).

Do anyone has seen the same kind of failure mode in the gear box.

 

[anorlunda]

How much research did you do before posting?
The picture of the ball you showed very clearly shows spalling.

It took my only 10 seconds with Google to find this.

Fatigue failure-usually referred to as spalling-is the fracture of the running surfaces and subsequent removal of small. discrete particles of material. Spalling can occur on the inner ring, outer ring, or balls

Why only one ball rather than all is more difficult, and I'm not sure relevant. Failures of the balls must always start with one ball first.

 

[Ranganath Nagaraju]

How much research did you do before posting?
The picture of the ball you showed very clearly shows spalling.

It took my only 10 seconds with Google to find this.
Why only one ball rather than all is more difficult, and I'm not sure relevant. Failures of the balls must always start with one ball first.

I know that's spalling. You need not to google it, if you know about bearing.
Spalling do happen due do many criteria and each way or kind of spalling will have a different cause.

<< Mentor Note -- post edited to fix text speak and to remove mild insult >>[/color]

 

[JBA]

Within any set of "identical" items there are going to be variations that result from tolerance variations along the manufacturing of those items (material, dimensional, heat treating, plating, etc) that will result in one of those items being more susceptible damage than all of the rest but still within the manufacturer's design specifications; or, one item could actually just be defective. Alternatively, in the case of a bearing set, the passage of a contaminating particle can also result in initiating the failure of one of balls.
In your case, if this is an isolated case of this type of failure, then either of these factors can explain what you have seen. On the other hand, if this is a new design, it might be considered that this could be evidence that the bearing is being subjected to a loading in excess of it design parameters that has caused it weakest ball element to fail.

 

[Ranganath Nagaraju]

Within any set of "identical" items there are going to be variations that result from tolerance variations along the manufacturing of those items (material, dimensional, heat treating, plating, etc) that will result in one of those items being more susceptible damage than all of the rest but still within the manufacturer's design specifications; or, one item could actually just be defective. Alternatively, in the case of a bearing set, the passage of a contaminating particle can also result in initiating the failure of one of balls.
In your case, if this is an isolated case of this type of failure, then either of these factors can explain what you have seen. On the other hand, if this is a new design, it might be considered that this could be evidence that the bearing is being subjected to a loading in excess of it design parameters that has caused it weakest ball element to fail.

Hello JBA

Thanks for the advice. I have taken the sample to the metallurgy lab to check the hardness, chemical composition and the micro structure.
I checked the dimension in a passometer and the variation between the rolling elements are OK. I need to wait for the metallurgy lab report

 

[HowlerMonkey]

That doesn't look like spalling to me but more like corrosion.

A single drop of water sitting at the lowest part of the outer race will cause erosion of the ball and possibly a corresponding spot in the race...but not always.

 

[Ranganath Nagaraju]

That doesn't look like spalling to me but more like corrosion.

A single drop of water sitting at the lowest part of the outer race will cause erosion of the ball and possibly a corresponding spot in the race...but not always.

There is hardly any damage on the raceways. Just some smearing pits, formed due to over rolling on the contaminants.

 

[Ranganath Nagaraju]

Thanks for the your reply. There is hardly any damage on the raceways. Just some smearing pits, formed due to over rolling on the contaminants.

 

[HowlerMonkey]

The corroded metal bits don't evaporate into nothing so they take a few trips around the race.

What is the application, lubrication type, and conditions of installation?

 

[Ranganath Nagaraju]

The corroded metal bits don't evaporate into nothing so they take a few trips around the race.

What is the application, lubrication type, and conditions of installation?

Thanks for the suggestions, its an automotive gear box and which has 5 liters of oil. There is no signs of lubrication failure.
Its the oil specialized for the CVT gear box.
The deep groove ball bearing is installed as per the recommendation , pushing inner ring on shaft and pushing outer on the housing,

 

[Mech_Engineer]

Spalling is a relatively specific bearing failure and usually caused by over-loading the bearing at or near its fatigue strength. It sounds like you might be over-loading the bearing, in which case you should consider increasing the specification of the bearing used in this application.

See here:
http://www.reliableplant.com/Read/30255/reasons-bearings-fail

8. Fatigue (Spalling)
Spalling is often the result of overloading, an excessive preload, tight inner-ring fits and using the bearing beyond its calculated fatigue life.

What to Look for
Fatigue can be indicated by the fracture of running surfaces and subsequent removal of small, discrete particles of material from the inner ring, outer ring or rolling elements. Spalling is progressive and will spread with continued operation. It is always accompanied by a noticeable increase in vibration and noise.

How to Fix it
Replace the bearing and/or consider a redesign that uses a bearing with greater calculated fatigue life, internal clearances, and proper shaft and housing recommendations.

 

[Meky]

Isn't the outer ring clamped by a bearing plate (fixed position)?

Your comment: "The deep groove ball bearing is installed as per the recommendation , pushing inner ring on shaft and pushing outer on the housing," sounds like you have a press-fit on inner and outer ring, which is not usual due to the assembly.