Talk:Fatigue (material)

Cyclic overload and LCF

i also agree that bending a paperclip is not a good example for fatigue, but rather for work hardening. on the other hand, the paragraph of LCF says, that LCF is usually measured in the plastic regime. so what is now the exact difference between LCF and cyclic overload? schwobator, german wikipedia

Bending a paperclip is LCF. Work hardening or softening doesn't change that. Cyclic overload is a term used in fatigue whenever large plastic strain amplitudes are applied in an otherwise small amplitude/elastic strain history. This would be covered when discussing variable amplitude fatigue. Sigmund 21:16, 2 June 2007 (UTC)

This answer is confusing. Best surely to say that bending a paperclip is not fatigue as known normally. Low cycle fatigue is normally associated with strain within the elastic range. I have thus reverted the edit. Peterlewis 10:26, 3 June 2007 (UTC)

Low cycle fatigue is associated with cyclic plasticity. Just look up the Coffin-Manson relation further down the page. An example of cyclic overload is: 1) bend the paperclip back and forth with a certain amplitude. 2) apply one larger amplitude. 3) continue cycling as in 1). This is often done to study the effect of hardening and residual stresses on fatigue life. Sigmund 09:25, 4 June 2007 (UTC)

No. Low cycle fatigue is brittle crack growth over a few cycles, and plasticity is irrelevant. These variables are quite distinct and separate. Peterlewis 10:10, 4 June 2007 (UTC)

Please consult any textbook on the subject before you make any assertions. Fatigue of metallic materials by Klesnil and Lukas is an excellent read. Sigmund 10:13, 4 June 2007 (UTC)

I would recommend Dowling as well.—Preceding unsigned comment added by 129.22.154.194 (talk • contribs)

Textbooks are always out of date unfortunately! I don't recall any sign of plasticity in the low cycle fatigue cracks which brought the Comets down. You should not try to confuse the issue of what is and what is not fatigue. I have published several papers on low cycle fatigue (4 to be exact) in the failure of a large storage tank, with no trace of plasticity whatsoever. Peterlewis 18:04, 4 June 2007 (UTC)

I really hope you had nothing to do with de Havilland. Here's the most recent article I could find on the topic: http://dx.doi.org/10.1016/j.ijfatigue.2007.04.014 This one may also be of interest: http://dx.doi.org/10.1016/j.ijfatigue.2006.09.004 Note that subscript p denotes plastic. If you've found something wrong or outdated in the book of Klesnil and Lukas, I'd be very interested. So would the fatigue community, so please, go ahead and publish that as well.

Welcome Peterlewis, to wikipedia, where experts are told off by their armchair-bound betters. —Preceding unsigned comment added by 131.215.115.31 (talk) 23:17, 13 October 2009 (UTC)

IIRC, in the Comet the designers and stress calculators were misled by the fuselage test sections that were pressure tested, in that the fuselage material underwent work hardening due to previous progressive testing, so the material fared better in the repeated pressure tests than was subsequently the case on production aircraft. — Preceding unsigned comment added by 80.7.147.13 (talk) 14:47, 17 December 2013 (UTC)

LCF (Low Cycle Fatigue) is a shortcut for a fatigue process in which the piece break after a relative low number of cycles, different to HCF (High Cycle Fatigue). In LCF we are speaking of ten of thousand or less of cycles to fracture, while in HCF we expect million of cycles. In both cases there are plastic deformation involved, but in LCF is much greater than the elastic deformation. Dpilo (talk) 18:35, 9 June 2015 (UTC)

Low Cycle Fatigue is a not a "shortcut" since it is more complicated than HCF with S-N curves. -Fnlayson (talk) 20:59, 9 June 2015 (UTC)

Difference of fatigue strength in vacuum and air

Completed merge of the above article. Placed the contents including references into the "Factors that affect fatigue-life" section. Seems to have worked out fairly well. scope_creep (talk) 00:20, 8 July 2013 (UTC)

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Requested move 19 June 2018

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: no consensus to move the page to any particular title at this time, per the discussion below. Dekimasuよ! 16:25, 26 June 2018 (UTC)

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Fatigue (material) → Fatigue of materials – (...or Material fatigue). WP:NATURAL disambiguation is preferred over the parenthetical one, and the current title looks really stilted to me. I propose the somewhat more verbose "Fatigue of materials" as the most commonly encountered in Google book search: even a search for "material fatigue" produces books universally titled as "Fatigue of [x] materials". In fact, I would say that the proposed title is the WP:COMMONNAME in the literature – "fatigue" alone only works once the context of material science is given. No such user (talk) 13:33, 19 June 2018 (UTC)

• Strong oppose Note that this is just a response to the reversion of an undiscussed rename, and the proposer isn't even consistent in their choice of this vital new name, so I fail to see that there can be strong evidence for either of these two new names being the right one if even that isn't clear.

"Fatigue" is the name that is used in the literature of the topic, and the name that will be needed in all the inbound links. "Material fatigue" is a WIKINEOLOGISM (and is admitted as such above). "Fatigue of materials" is little better - it might be used as a book title, but it's not used within that literature, or in the contexts where we'd need to link it. Disambiguation is our usual response here, and that's been working just fine for years. Andy Dingley (talk) 13:53, 19 June 2018 (UTC)

Well, there's really no need for strong reactions; per WP:BRD, I made a bold move, which you reverted, and now we're discussing (hopefully, with a broader input). While I perhaps selected the initial title material fatigue hastily (I was cleaning up the mess at fatigue and Fatigue (disambiguation) (edit | talk | history | protect | delete | links | watch | logs | views), which included abominations such as fatigue (safety)), I used the most commonly used redirect metal fatigue as the model; the book search afterwards yielded the suggested title.
Since the term "fatigue" is ambigous, we actually do look after books and other reference works as the model for our titles, and a book title is probably a better reference for our article title than the terms used within it. Per WP:NATURAL, the preferred title is an alternative name that the subject is also commonly called in English reliable sources, albeit not as commonly as the preferred-but-ambiguous title – thus the proposed move.
Finally, let me stress that (per WP:NOTBROKEN) the incoming links do not have to be changed, and pipe trick for fatigue (material) will continue to work just fine for editors who prefer it; but our titles are primarily tailored for our readers, not for editors. No such user (talk) 14:46, 19 June 2018 (UTC)

• Oppose The name is more general and acceptable. Also, metal fatigue is the more common term after just "fatigue". Book titles tend to be longer to differentiate from other similar books; book titles are probably not a good criteria for general terminology, imo. -Fnlayson (talk) 14:41, 19 June 2018 (UTC)
• Would Fatigue (materials science) be a better disambiguation? Peter James (talk) 15:37, 19 June 2018 (UTC)

Possibly. I'd have no objection if anyone thinks that's clearer. It still works for linking and piping. Andy Dingley (talk) 15:43, 19 June 2018 (UTC)

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The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Thermal Fatigue? Redirect to here, but not described.

Thermal fatigue redirects to this article - but it seems that it is not described at all here (or too well hidden to find with the search term "thermal"). --Andi47 (talk) 11:03, 12 June 2019 (UTC)

Merge Low-cycle fatigue into Fatigue (material)

Much of the topic of low-cycle fatigue is covered here in Fatigue (material). There is a strong overlap in content with low cycle fatigue, with the formula section already re-produced in the Fatigue page. Given that there is not a lot of unique content in Low-cycle fatigue, I propose to merge Low-cycle fatigue into the Fatigue (material) page and put a forwarding link. NeedsGlasses (talk) 11:52, 25 June 2019 (UTC)

Oppose - This article is the main one of fatigue. This article is long enough; it'd be better to move details from this article to Low-cycle fatigue instead, imo. -Fnlayson (talk) 12:39, 30 June 2019 (UTC)

I suspect the Fatigue page only seems long. By comparison with other pages such as fracture toughness its not really. The uneven area seems to be in predicting fatigue life which could be a page on its own. I was hoping to fix up the redundancy with a merge. Moving it (or whatever is not already there) into low-cycle fatigue is an option. Similarly the paris equation is already covered in the Paris page which is now a sub category of crack growth equations. The para "Fatigue failures, both for high and low cycle, all follow the same basic steps process of crack initiation, stage I crack growth, stage II crack growth, and finally ultimate failure." suggested there was more in common with low cycle fatigue, but the low cycle fatigue page makes no mention of any of this. NeedsGlasses (talk) 07:21, 1 July 2019 (UTC)

• OK, but you're still supposed to get a consensus here before making such a change (see WP:MERGE. -Fnlayson (talk) 14:23, 2 July 2019 (UTC)

no concensus was reached. Merge will not happen NeedsGlasses (talk) 01:09, 15 July 2019 (UTC)

Existence of fatigue limit

I suspect that a previous statement questioning the existence of a fatigue limit for any metals was removed due to another editor's opinion on the subject. While the debate over the existence of fatigue limits in the fatigue community may not be settled, there is certainly more than enough evidence to put in a clause raising doubts about its existence. In fact, leaving the existence of fatigue limits unchallenged can lead to dangerous design choices for applications that may have large numbers of cycles.Bob Clemintime (talk) 19:56, 21 March 2021 (UTC)

When was this content added and removed before? I don't remember seeing this content added or removed before, though I may have missed it. -Fnlayson (talk) 20:25, 21 March 2021 (UTC)

It took me some digging because the statement was added 28 November 2011! It turns out it you were the editor who removed the statement, claiming a single source was insufficient for such claims. Hopefully, I have provided enough sources to satisfy you from the past Bob Clemintime (talk) 01:37, 23 March 2021 (UTC)

• OK, I was expecting much more recent removal. Having only one source can appear to be a fringe theory, which is generally prohibited on Wikipedia. -Fnlayson (talk) 13:41, 24 March 2021 (UTC)

“Weakening” of material

Fatigue is not a weakening of a material, leading to growth of cracks. The strength of the material is not changed. Instead, fatigue is the nucleation and growth of cracks in a material. Thinking that a material is weakened by cyclic loading is a mistake. Hermanoere (talk) 02:32, 24 March 2021 (UTC)

Hermanoere (talk) I appreciate your point. When are cracks a part of the material and when are they part of the component? Suresh quotes a 1964 report "General principles for fatigue testing of metals" which gives the definition of fatigue as a term "which applies to changes in properties which can occur in a metallic material due to the repeated application of stresses and strains, although usually this term applies specially to those changes which lead to cracking or failure". See revised definition. NeedsGlasses (talk) 03:49, 24 March 2021 (UTC)

The cracks should be considered part of a component, rather than a material. The quote you cite says fatigue refers to "changes in properties" of materials. Which ones? Young's modulus? Yield or ultimate strength? Ductility? Except for a very small volume adjacent to the crack surface, where plastic deformation occurs (and hence work hardening), there is no change in material properties. Fatigue is properly considered a structural or component process, not a material process. Hermanoere (talk) 15:30, 24 March 2021 (UTC)

The title page says "Fatigue (material)". Suresh called his book "Fatigue of materials". While superficially failures looks like a single crack, if you look at the fracture surface of cracks generated with variable amplitude loading under an electron microscope, there is a myriad of fissures which are often broken open and reveal the same fracture surface patterns as the main crack. The main crack is just the collection of micro fractures that have been revealed. Not to mention the effect that environment plays in the mechanisms of fatigue crack growth through absorption and diffusion and the role of dislocations at the crack tip. I still think it would be generally considered to be a material phenomenon. NeedsGlasses (talk) 03:43, 25 March 2021 (UTC)

Yes, by all means, call it "Fatigue (material)". But notice that all of your examples in the previous paragraph refer to cracks, not changes in material properties. To say that fatigue makes a "material" weaker is problematic, because which material property is being altered, the yield strength or the tensile strength? The answer is that neither is being altered, but instead, cracks form and propagate.

But regardless of whether you think fatigue is a material process or a structural or component process, the intro sentence "In materials science, fatigue is the weakening of a material due to cyclic loading..." is misleading. A better intro sentence would be something like "In materials science, fatigue is the nucleation and propagation of cracks in a material due to cyclic loading...." This is more precise, and better introduces the mechanisms for fatigue failure discussed later in the article. It is less vaguely about materials somehow getting weaker. Hermanoere (talk) 19:10, 25 March 2021 (UTC)

Yes that is a better definition. NeedsGlasses (talk) 23:12, 25 March 2021 (UTC)

GA Review

This review is transcluded from Talk:Fatigue (material)/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: David Eppstein (talk · contribs) 02:22, 20 November 2022 (UTC)

Drive-by nominator appears to made only one very minor edit to the article. And with many unsourced sentences and paragraphs, and some unreliable sources (for instance the ones from Material Technologies Inc, Fatigue Technology, LAMPL, and the Cryogenic Treatment Database) this is far from meeting WP:GACR#C2. I think this can be a quick WP:GAFAIL. —David Eppstein (talk) 02:22, 20 November 2022 (UTC)

@David Eppstein thanks, I think I just need some pointers to where to start given the size of the article. Please feel to add more and hopefully by next year I will ask you to take a look before putting a GA request.

Thanks for taking a look and sorry that an article of this importance was a quick fail FuzzyMagma (talk) 18:09, 20 November 2022 (UTC)