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Bearing testing

Bearing testing

(OP)
Hey All,

I have 2 bearings of the same part number supplied from a company.The manufacturing process of both the bearings are same except that one bearing raceway is manufactured from 'cold forging' and the other raceway is manufactured from 'turning process'. The bearing manufactured from cold forging is giving better life than the one which is manufactured from turning process.There is a premature flaking occuring early in the turned raceway bearing.The supplier says that the manufacturing process does not alter the life of the bearing.I want to test the bearing and find out and prove that forged raceways are better.
Can you suggest me how i go about the process and what tests should be done to approach and compare the results.

Regards,
Manjunath

RE: Bearing testing

Hello Manjunath21,

What happens is that for most of the tests done in the industry you should have more than one bearing of the same type to perform endurance tests (about five bearing manufactured from cold forging and another five from turning process). Of course, you can test these 2 bearings and see what happens but the final result may not be as expected as it should. Check for "sudden death tests" on the web. This is far the most commom method used in the industry.
Now, what kind of process? Well, let's say that the fatigue/endurance of a bearing is tested when you apply a specific load to the bearings under the same (e.g. ambient/grease/humidity) conditions. Note that bearing endurance testing is a time-consuming and costly process, however, to reduce testing time and cost, bearings are usually tested under accelerated conditions (e.g. increasing applied bearing load, which is perhaps the most commonly adopted mean). Yet one must care to ensure that the load increase does not alter the bearings’ failure mode. Let's say that the maximum applicable load shouldn't cause any plastic deformation.
By the way, what kind of bearing is that? Deep-Groove ball bearings, tapered roller bearings, angular-contact ball bearings...?

Yours,
Luis Felipe

RE: Bearing testing

Forged rings are, as far as I know, the rule if you want endurance. Forging creates "fibers" that follow the ring while milling does not.
Roll forging is akin to forging and is also used with good results.

I think that the difference is known and accepted and the supplier's "the manufacturing process does not alter the life of the bearing" s not true.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Bearing testing

(OP)
Hi Luis Felipe,

Firstly I thank you for the reply.The bearings which I am using is a Single Row Deep Groove Ball bearing.The bearings are used in an alternator.Since the bearings are mounted in the alternator,do i have to consider the vibrations too.So instead of doing endurance test,will a vibration test help me getting the result?

RE: Bearing testing

(OP)
One more thing i wanted to know about the manufacturing process is that in what way cold forging is enhancing the life.what is that factor which is differentiating the two raceways.i have done the macroscopic analysis on the fresh bearings and the forged raceway is showing continuous flow lines following the contour of the component.The bearing raceway manufactured from turning process show fine grain structure with no flow lines.what do i conclude with these 2 results?

RE: Bearing testing

The flow lines that you have observed are the same thing as the "fibers" I mentioned. I am not in mtallurgy, but to me, a forged part has always been strongaer and more durable in every respect than a machined part.

There are other guys around that can explain it better.

You mention an alternator. Did you see any traces of EDM? What kind of an alternator is it? Do you happen to excite the rotor with a variable frequency? Or is it plain ol' DC?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Bearing testing

(OP)
does anyone have the video or picture which shows how Cold Forging and Trepanning is done on ball bearing? If yes, Kindly attach the link .

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