Talk:Rolling-element bearing

Lubrication

The article on lubricants states that some roller bearings aren't lubricated at all. Maybe that kind of information could be incorporated here? Rvollmert 11:15, 2004 Jul 31 (UTC)

Adding images to the article?

I added a number of images to the article, but these have been repeatedly removed for, I believe, no good reason.

The reasons were:

rm images that are already covered in sub-articles. +commons link so all images are accessible

Yeah, along with about 50 other images... you can't be serious.WolfKeeper 20:31, 18 August 2006 (UTC)

This is an unusually high number of images,

No, not really. Actually most articles don't have enough images.WolfKeeper 20:31, 18 August 2006 (UTC)

and the two images on the left stack up and break up text..

A little, but less so than if we put them on the right. If that's a problem for you, reformat the article, don't remove information. Make them a bit smaller or move them around.WolfKeeper 20:31, 18 August 2006 (UTC)

Hmm there seems to be a bug or something in the layout software if the width of the browser is over a particular range the image jumps in and leaves a hole. I've reformatted it and it no longer does that.WolfKeeper 20:31, 18 August 2006 (UTC)

While potentially useful, overview articles don't show all pictures used in sub-articles.

There's no such policy. Show me such a policy. In any case we don't show all the pictures, we show one example of each bearing, in thumbnail form, and most of the specific articles have several different examples of the bearing, or they really should have.

Or perhaps you think this is duplication, but it really isn't, the images aren't really in the article they're still in the commons, and are being referred to, so it's not as if we're using more space, the images aren't copied anywhere. And if the image was modified it would change everywhere. There's no problem at all with using images in several places where appropriate.WolfKeeper 20:31, 18 August 2006 (UTC)

It's not a policy or technical issue, it's an aesthetics issue. As such, it's pointless to revert multiple times over it. Anyway, the smaller images do look better. The images on the left still jump away from the left side at ~1280px wide. And MSIE renders a lot of gaps between the paragraphs at 1920px wide. But maybe it's impossible to get perfect. --Interiot 00:02, 19 August 2006 (UTC)

I like the images the way they are now. It looks really good and helped me understand the article MUCH better. -Rebent 14:03, 15 May 2007 (UTC)

Cause of fatigue

Fatigue is not caused by bending it is caused by stress. Particularly in tension. (See fatigue article) (This unsigned comment was added by 69.213.70.93 at 20:54, 30 March 2007)

I think the article is fine. The opening of the Fatigue article says fatigue is caused by "cyclic or fluctuating strains", and in this case the strain arises from the sharp bending at the contact points. As the fatigue article also points out, the stresses involved in fatigue "have maximum values less than (often much less than) the static yield strength of the material". In this sense, it would be very misleading to say fatigue is "caused by" stress. 132.244.246.25 11:00, 15 June 2007 (UTC)

Manufacture of balls for ball bearings

The section under "Types" says "Clever use of surface tension allows balls of high accuracy to be made much more cheaply than comparable cylinders", but the external link "How ball bearings, races, and cages are manufactured" describes a manufacturing method that doesn't seem to involve surface tension at all. Please could someone knowledgeable clarify this? Thanks. 132.244.246.25 11:00, 15 June 2007 (UTC)

I have done several searches on the internet, and have found no information indicating that bearing balls are made using surface tension, nor how they would be made using surface tension (aside from a quick mention of making bearing balls in space, which is certainly not "much more cheaply" than anything). I think the statement is appealing, but inaccurate. If no one can clarify this statement, perhaps it ought to be removed. 67.41.251.212 (talk) 05:01, 27 August 2008 (UTC)

Tapered Bearing Image

The image for the tapered bearings appears to show cylindrical bearings, which are not covered by the article. At any rate, the bearings are most certainly not tapered in any way, so I have removed the image. Apologies if I am missing something important. BeeJones (talk) 15:56, 16 June 2009 (UTC)

Unfortunately, they very definitely are tapered, and they are tapered roller bearings. If you look carefully you will notice that the angle of the race way is not parallel with the rotation axis, but a section of a cone.- (User) Wolfkeeper (Talk) 16:29, 16 June 2009 (UTC)

Thrust roller element bearings

I completely disagree with moving the thrust bearing section to the applications section. Roller and ball thrust bearings have a unique design; see [1] and [2]. Yes, tapered roller bearings can be used in thrust applications, but that doesn't make it a thrust bearing. Moreover, Conrad style bearings cannot be properly used in thrust applications, because they are not designed to handle that type of load. Therefore the previous layout should be restored. Wizard191 (talk) 17:47, 12 October 2010 (UTC)

All bearings can take differing amounts of axial and radial thrust. If a bearing is designed to take mainly an axial thrust, then it's a thrust bearing. Otherwise it's a radial bearing.Planetscared (talk) 22:35, 12 October 2010 (UTC)

But thrust bearings are not a distinct type of bearing in the same sense as ball bearing, roller bearing, tapered rolling bearing etc. are, because (for example) by changing the geometry of the bearing you can change the percentages of axial and radial thrust it can take. There's no distinctly different type of bearing there. And the other types are mutually exclusive, it's either a roller bearing or it isn't. It's either a tapered roller bearing or it isn't. But it can be a roller bearing and thrust bearing or a roller bearing and a radial bearing or you can angle the rollers and be a bit of each.Planetscared (talk) 22:35, 12 October 2010 (UTC)

In terms of the text, by putting it in with the others, you're implying that it's distinct from the others, but really it's orthogonal to the others.Planetscared (talk) 22:35, 12 October 2010 (UTC)

I mean, tapered roller thrust bearings absolutely do exist, and are a common type.For example And I'm sure that Planetscared (talk) 22:36, 12 October 2010 (UTC)

The term "roller thrust bearing" refers to one and only one type of bearing (again see [3]). It is not a "radial roller bearing", more commonly called a "roller bearing", nor is it a "tapered roller bearing"; therefore it is mutually exclusive of the other types and a unique type of roller bearing. The exact same argument can be made for the ball type bearings (except there's no such thing as a tapered ball bearing, but this is replaced with an "angular contact ball bearing"). As such, it is distinct from the other and not orthogonal, therefore please revert your edits. Wizard191 (talk) 13:56, 13 October 2010 (UTC)

It seems to me that this article is/was not trying to define any of those terms, it's talking about rolling element bearings and trying to explain their principles to the reader.Planetscared (talk) 14:50, 13 October 2010 (UTC)

Well after you recent changes, I like the new layout, where it independently discusses the elements and the motions/loadings. I've made some more improvements. I'm glad to see that this discussion has brought about an even better article. Cheers! Wizard191 (talk) 18:19, 13 October 2010 (UTC)

Excellent, it does seem better, and your changes improved it even more.Planetscared (talk) 21:58, 13 October 2010 (UTC)

'Rolling-element bearing', 'Rolling contact bearing', or 'Rolling bearing'?

This is a question referring to the article title. There is some debate or uncertainty in the academic community and industry as to what these types of bearings are properly referred to as. I believe the title of the article 'Rolling-element bearings' best refers to the bearing type, but am otherwise indifferent to the 'official label', but it seems that some discussion should be had to settle the argument. I have searched quite a bit and found reference to all three labels in both patent listings and academic papers with no seemingly clear bias to nationality or location.Gregzore (talk) 16:34, 19 August 2011 (UTC)

Life calculation models - adding information to existing text

Life calculation models

The life of a rolling bearing is expressed as the number of revolutions or the number of operating hours at a given speed that the bearing is capable of enduring before the first sign of metal fatigue (also known as spalling) occurs on the raceway of the inner or outer ring, or on a rolling element. Calculating the endurance life of bearings is possible with the help of so-called life models. More specifically, life models are used to determine the bearing size – since this must be sufficient to ensure that the bearing is strong enough to deliver the required life under certain defined operating conditions.

Under controlled laboratory conditions, however, seemingly identical bearings operating under identical conditions can have different individual endurance lives. Thus, bearing life cannot be calculated based on specific bearings, but is instead related to in statistical terms, referring to populations of bearings. All information with regard to load ratings is then based on the life that 90% of a sufficiently large group of apparently identical bearings can be expected to attain or exceed. This gives a clearer definition of the concept of bearing life, which is essential to calculate the correct bearing size. Life models can thus help to predict the performance of a bearing more realistically.

The prediction of bearing life is described in ISO 281 and the ANSI/American Bearing Manufacturers Association Standards 9 and 11.

The traditional method to estimate the life of the rolling-element bearings uses the basic life equation:

$L_{10}=(C/P)^{p}$

Where:

$L_{10}$ is the 'basic life' (usually quoted in millions of revolutions) for a reliability of 90%, i.e. no more than 10% of bearings are expected to have failed

$C$ is the dynamic load rating of the bearing, quoted by the manufacturer

$P$ is the equivalent dynamic load applied to the bearing

$p$ is a constant: 3 for ball bearings, 4 for pure line contact and 3.33 for roller bearings

Basic life or $L_{10}$ is the life that 90% of bearings can be expected to reach or exceed. The median or average life, sometimes called Mean Time Between Failure (MTBF), is about five times the calculated basic rating life. Several factors, the 'ASME five factor model', can be used to further adjust the $L_{10}$ life depending upon the desired reliability, lubrication, contamination, etc.

The major implication of this model is that bearing life is finite, and reduces by a cube power of the ratio between design load and applied load. This model was developed in 1924, 1947 and 1952 work by Arvid Palmgren and Gustaf Lundberg in their paper Dynamic Capacity of Rolling Bearings. The model dates from 1924, the values of the constant $p$ from the post-war works. Higher $p$ values may be seen as both a longer lifetime for a correctly-used bearing below its design load, or also as the increased rate by which lifetime is shortened when overloaded.

This model was recognised to have become inaccurate for modern bearings. Particularly owing to improvements in the quality of bearing steels, the mechanisms for how failures develop in the 1924 model are no longer as significant. By the 1990s, real bearings were found to give service lives up to 14 times longer than those predicted. An explanation was put forward based on fatigue life; if the bearing was loaded to never exceed the fatigue strength, then the Lundberg-Palmgren mechanism for failure by fatigue would simply never occur. This relied on homogeneous vacuum-melted steels, such as AISI 52100, that avoided the internal inclusions that had previously acted as stress risers within the rolling elements, and also on smoother finishes to bearing tracks that avoided impact loads. The $p$ constant now had values of 4 for ball and 5 for roller bearings. Provided that load limits were observed, the idea of a 'fatigue limit' entered bearing lifetime calculations: if the bearing was not loaded beyond this limit, its theoretical lifetime would be limited only by external factors, such as contamination or a failure of lubrication.

A new model of bearing life was put forward by FAG and developed by SKF as the Ioannides-Harris model. ISO 281:2000 first incorporated this model and ISO 281:2007 is based on it.

The concept of fatigue limit, and thus ISO 281:2007, remains controversial, at least in the US.

GBLM

In 2015, the SKF Generalized Bearing Life Model (GBLM) was introduced . In contrast to previous life models, GBLM explicitly separates surface and subsurface failure modes – making the model flexible to accommodate several different failure modes. Modern bearings and applications show fewer failures, but the failures that do occur are more linked to surface stresses. By separating surface from the subsurface, mitigating mechanisms can more easily be identified. GBLM makes use of advanced tribology models to introduce a surface distress failure mode function, obtained from the evaluation of surface fatigue. For the subsurface fatigue, GBLM uses the classical Hertzian rolling contact model. With all this, GBLM includes the effects of lubrication, contamination, and raceway surface properties, which together influence the stress distribution in the rolling contact.

In 2019, the Generalized Bearing Life Model was relaunched. The updated model offers life calculations also for hybrid bearings, i.e. bearings with steel rings and ceramic (silicon nitride) rolling elements . Even if the 2019 GBLM release was primarily developed to realistically determine the working life of hybrid bearings, the concept can also be used for other products and failure modes.

• I work at SKF (Communications) and have submitted this suggestion to update the Life Calculation section with more relevant information. Have tried to avoid any bias coming through and I am using the Talk page as suggested from the Conflict of Interest page to suggest this edit to the current life models section. RobinFSKF (talk) 13:50, 22 November 2019 (UTC)

• Hi Robin, thanks for that.

Looking at this diff, it seems that you've added two paras of intro, and two new paras on GBLM. No changes to the existing text. All looks fine, so I'm happy to copy that across. Andy Dingley (talk) 14:18, 22 November 2019 (UTC)

• Great! Thank you Andy, go ahead and copy it over when you are able to. RobinFSKF (talk) 14:26, 22 November 2019 (UTC)

References

• What I think should be changed:

In the GBLM Section, from: Modern bearings and applications show fewer failures, but the failures that do occur are more linked to surface stresses.

to: Nowadays, surface distress is the most common cause of bearing failure.

From: Even if the 2019 GBLM release was primarily developed to realistically determine the working life of hybrid bearings, the concept can also be used for other products and failure modes.

to Even if the 2019 GBLM release was primarily developed to realistically determine the working life of hybrid bearings, the concept is also used for certain other products, features and failure modes.

• Why it should be changed:

I have gotten updated input from our scientists working on these life models that these changes would be more reflective of where GBLM is today

• References supporting the possible change (format using the "cite" button):

RobinFSKF (talk) 10:40, 2 March 2022 (UTC)

References

 Not done A source was not provided to verify this information. If a source is available, please post it and reopen this request. Z1720 (talk) 01:38, 3 April 2022 (UTC)