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





RE: reason for fluting appearance
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: reason for fluting appearance
Parallel converations here:
http://maintenanceforums.com/eve/forums/a/tpc/f/37...
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(2B)+(2B)' ?
RE: reason for fluting appearance
Also here:
http://maintenanceforums.com/eve/forums/a/tpc/f/37...
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(2B)+(2B)' ?
RE: reason for fluting appearance
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
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: reason for fluting appearance
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
RE: reason for fluting appearance
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....
.. 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.
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(2B)+(2B)' ?
RE: reason for fluting appearance
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(2B)+(2B)' ?
RE: reason for fluting appearance
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
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: reason for fluting appearance
Bill
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"Why not the best?"
Jimmy Carter
RE: reason for fluting appearance
Muthu
www.edison.co.in
RE: reason for fluting appearance
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
RE: reason for fluting appearance
I see that you are new here. Browse the site. There are lots to be learned.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.