×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

reason for fluting appearance
6

reason for fluting appearance

reason for fluting appearance

(OP)
What is the mechanism that creates the particular appearance of fluting (when bearings are exposed to electrical damage) ?

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

RE: reason for fluting appearance

Same as dirt road wash board pattern. Mechanical resonance. No relation (almost) to frequency or speed.

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

RE: reason for fluting appearance

(OP)
Thanks. Surely there are other mechanical defects that cause similar mresonance vibration behavior. Is it the interaction of the resonant vibration with the current flow?

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

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

RE: reason for fluting appearance

6
I can see that the standard crap about frequency and speed is alive and kicking in the maintenance forum.

I was invited to GE HQ in Schenetady in february to talk about these things. The presentation I made is available here:
http://www.gke.org/presentationer/files/GE%20Beari... and it was also recorded and is available live on the GE intranet for those that have access to it.

There is a reason why the text about "conventional wisdom" has the colour it has (brown).

The discharges create little craters in the raceways and these craters, when there are enough of them, reduce the surface hardness so that the balls (or rolls) start to bounce and gradually create the fluting pattern.

The whole thing starts as a "misty" pattern aka "frosting" and that pattern does not have any periodicity in the beginning. It is only when the balls start to bounce that a periodic pattern develops and gets stronger and stronger until you gave to replace the bearing - or until it fails catastrophically.

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

RE: reason for fluting appearance

gave = have

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

RE: reason for fluting appearance

Thanks Gunnar - that is a useful reference.

RE: reason for fluting appearance

(OP)
Thanks Gunnar.
I will file this with two other previous presentations of yours
“All” about EDM in bearings on one page
EDM – Physics and Reality

The part I still want to clarify....

Quote:

The discharges create little craters in the raceways and these craters, when there are enough of them, reduce the surface hardness so that the balls (or rolls) start to bounce and gradually create the fluting pattern.

The whole thing starts as a "misty" pattern aka "frosting" and that pattern does not have any periodicity in the beginning. It is only when the balls start to bounce that a periodic pattern develops and gets stronger and stronger until you gave to replace the bearing - or until it fails catastrophically.
.. Surely there are other mechanical defects that create a variety of defects (poor lubrication, contamination of various sizes, skidding... etc), yet none of those gives the fluting. So maybe the story should include something to do with current flowing as the rolling elements bounce on the races? (that would make more sense to me).

Attached is excerpt from section 6.4 of "Solving Tribology Problems in Rotating Machines" that was attached in the other thread and also attached here. Yet another spin on the story ... a little tough to follow.

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

RE: reason for fluting appearance

(OP)

Quote (elecrtricpete)

Attached is excerpt from section 6.4 of "Solving Tribology Problems in Rotating Machines" that was attached in the other thread and also attached here. Yet another spin on the story ... a little tough to follow.
Forgot that... here it is

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

RE: reason for fluting appearance

Comment to Pete:

Other failure types than EDM do not form an even hardness reduction. It is only the repeated discharge through the oil film that creates millions and billions of small craters and the corresponding hardness reduction (low temperature tempering in SKF parlance). And it is only when you have a reduced hardness that the ball/roller bouncing occurs. Other failure types create other defects in the raceway surfaces. It is only the smooth and "wide area" reduction in hardness that creates bouncing. Just like a dirt road and not a paved road shows a wash-board pattern. The dirt road corresponds, of course, to the surface-tempered raceway.

The paper that Pete refers to says:
"The passage of current causes local surface heating, which leads to lowtemperature
tempering, and accelerates formation of corrugations with time.

The pitch of corrugations on the roller tracks depends on the bearing
kinematics, the frequency of rotation, the position of plane of action of radial
loading, the bearing quality and the lubricant characteristics"

I agree (almost) totally. The "frequency of rotation" (speed in my world) does not seem to be very important - fluting can also be seen in bearings running at variable speed. Winders in paper industry is a good example. Fast winders spend most of their time accelerating and decelerating and they still show very characteristic fluting.

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

RE: reason for fluting appearance

Great thread. Thank you Gunnar. lps

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: reason for fluting appearance

Thanks Gunnar. I learnt a few 'facts'. Now to beat my clients with them.

Muthu
www.edison.co.in

RE: reason for fluting appearance

Great information, thankyou.

Does anyone have comments or experiences with oil lubricated sleeve bearings issues that have not been insulated when powered by VFD's? Does the electrical discharges damage the babbit materials?

TIA

RE: reason for fluting appearance

If you make up a small brush from conductive material like a copper brade and attach one side to an occiloscope and the other to earth, and look for high frequency distortion by placing your "brush" on the shaft, that may tellyou it exists. If it does there are several products on the market that can assist. These range from rings containing carbon fibre bristles to spring loaded gold brushes . Which country are you in?

RE: reason for fluting appearance

Welcome to the world of real problem solving, squeeky.
I see that you are new here. Browse the site. There are lots to be learned.

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources