Ball Bearing Failure 4

[replica]

Dear all,

Any idea what is the possible cause of the failure of this angular contact ball bearing? Attached is the photograph of the ball bearing 14 out of 15 balls have the similar pattern on the ball with the initiation site at the center and propagate radially like fatigue striation. The outer and inner raceway show microcrack and spalling but not as severe as the ball. They are 1 inch ball bearings.

Note: Why I could not upload the file...why doing this ...this statement came out.

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Anybody can help me...

Regards,

Happy New Year...

 

[israelkk]

Where is the attachment?

 

[replica]

israelkk

I could not post the attachment...I had tried many times to upload my file but the error message came out. I do not know the reason. I will try again.

Sorry for the inconvinience.

 

[metengr]

Replica
Did you try the attachment link on the tool bar where you post?

 

[replica]

metengr

Yes I had tried using toolbar..but still failed.

 

[mrfailure]

Bearing failures are among the most difficult because damage tends to cause more damage that makes you scratch your head and ask: which came first: the chicken or the egg or (in this case) did raceway damage cause the ball damage or vice-versa.

I strongly suggest looking in the chapter in the old (i.e. 9th or Red) edition of ASM Handbook on bearing failures. It is the best reference I have seen for such systemic analysis of bearings and will help you identify the mechanism or potential mechanisms of failure for your system. Good luck!

 

[replica]

mrfailure

Thank you ...noted. Will look for the book. Most of the failure analysis work on bearing dealing with path pattern either on the outer/inner raceway..not much on the ball. In my case the ball spalled badly but the raceway exhibited microcrack probably due to subsurface/surface initiated fatigue.....

 

[replica]

The image showing the initiation site on the other ball, The spalling then propagated radially. This image shows one initiation site. Other balls had 2 or 3 initiation side and propagated radially.

 

[mrfailure]

You'll want to evaluate both balls and the raceways. In particular, look for structure and whether it is what you would expect from specified heat treatment, and hardness (microhardness at both surfaces and cores of tested components). I agree about ball fatigue being present, but the real question is why it happened.

 

[metengr]

There is also good information that roller bearing manufacturer's (SKF, FAG, TIMKEN) publish and you can find this information for free on the internet.

 

[mfgenggear]

Test bearings that have not being in service. verify metallurgical, hardness values, test for material , how it was fabricated, correct material, was the hardness correct at the surface of the balls and the race. was there ample lubrication? did the bearings seat properly, was it install properly. was there contamination issues.

 

[mfgenggear]

for got ask what type service? high impact?

 

[tbuelna]

Since the damage on the ball surface is located in one area I think it is a "flaking" failure. Take a look here for possible causes of ball bearing flaking failures.

 

[replica]

Thank you everybody....I went through a couple of website and book suggested and found out that none of them describe in details about the defect on the ball. All the information focus on the path pattern on the raceways. There is also ISO describing failure modes etc and provide suggestion on the possible cause of of failure and their remedies. This ISO provides 6 causes of failure with 16 subdivisions. When looking at all the available information I could narrow down the cause of the failure that probably due to the material fatigue cause by the inadequate/oxidized lubrication/contaminant etc. Base on visual inspection there was no sign of misalignment and overheating on the raceways. The outer raceway exhibit microcracks across the width typical for spalling/flaking. The task now is to distinguish between surface and subsurface fatigue.....Agree with mrfailure about chicken and egg situation and that bearing failure in unique and demanding..,.I hope a couple of metallography, hardness test, chemical composition and fractography will provide me some light. ....

Happy New Year

 

[mrfailure]

I have dealt with a similar failure of balls, but I did not want to presuppose anything because insufficient information had been provided. That said, in our case the balls were made of 52100 steel and finished product had a very high (i.e above 60 HRC) specified hardness. There is an ASTM specification that will tell you if these were properly processed and heat treated assuming this was you material - ASTM A892. Older versions of the spec include micrographs showing carbide structures that are acceptable and those that are not, but if you use the current version you'll have to purchase the microstructural plates separately. In our investigation we looked at material taken from every step in the process starting with the wire used to make the balls, and characterized the material. Such characterization included as-polished metallography for microcleanliness, evaluation of etched carbide structure compared with A892, and microhardness. Such characterization can also help if your balls had experienced an arc strike that caused the damage, as you'll see structural differences at the surface. Again, good luck!

 

[Tmoose]

what is the bearing manufacturer's name?
What is the info stamped and etched on the sides of the races?
Including country of manufacture.

Pictures of the races and bearing separator/cage would be helpful.

Usually angular contact bearings exist in pairs, or even 3s and 4s.
Please Post pictures of the other bearings, and the housings and shaft as they were disassembled, and after being gently cleaned

How are the bearings >> supposed<< to be lubricated ?
In the first picture there is debris on the blue towel. If that came from the ball, I'm thinking the lubricant is charred or has turned to varnish.
And the ball looks quite dark, like things got pretty hot

What is the machine history?

Why did you decide to take it apart?

Did you build this machine?
If not, what is the manufacturer's name, make and model?

 

[replica]

Mr failure. ..Thank you ...
From where does the arc strike come from ...Is it similar to electrical leakage?

 

[chief]

It would greatly assist if the application of the bearing was known. I have seen bearing failures on Generator bearings due to electric tracking to earth via a bearing. This is difficult to detect and a proper earthing system is required.
Another failure .already mentioned is caused by welding on the application without correct grounding cable position.
All this is supposition without more information.
The most common failures of bearings are caused by lack of lubrication ,dirt and misalignment. Brinelling while stationary,from external vibrations is another.

Offshore Engineering&Design

 

[romke]

it looks like flaking that started at a random area of the ball that then further propagated. when that continues the balls may stop to roll and just slide on the already damaged surface, adding to the propagation. the discoloration of the ball may be the result of heat generated leading to local oxidation of lubricant.

it is hard to decide what came first: flaking and subsequent oxidation or oxidation, loss of heat transfer and subsequent flaking....

can you me more specific on operating conditions (speed, load, type of application, time in service) and lubricant type used?

 

[replica]