Talk:Fatigue (material)/Archive 1

Archive 1

Good Job

This article is very well done. Its is much better than most materials science articles on Wikipedia. Good Job! Perhaps this will be up to featured article caliber soon. Iepeulas 13:12, 12 June 2006 (UTC)

I disagree. The article deals almost exclusively with metal fatigue... Other materials exhibit fatigue properties dependent upon different mechanisms. Fatigue in plastics is an especially interesting topic. Also note that the references cited omit Sines and Waisman! —Preceding unsigned comment added by 131.215.115.31 (talk) 23:13, 13 October 2009 (UTC)

I agree with Iepulas. It's a short article, readable in just a few minutes without getting bogged down or losing interest, and this is a big merit. Within this scope, it's excellent in its perspective, coverage of key points, and blend of technical concepts with historical perspectives and examples of contemporary importance. To be sure, there are many more specialized aspects of fatigue that could be addressed in Wikipedia. I'd like to see that done in separate articles, rather than compromise the excellent overview values of this one. Adrian Pollock (talk) 15:23, 31 August 2010 (UTC)

May be it also would be interesting to know about theories on fatigue. —Preceding unsigned comment added by 195.243.148.26 (talk) 13:59, 21 May 2010 (UTC)

I came to the discussion just to comment on the lack of a specific article on thermal fatigue. I appreciate the article on metal fatigue. But thermal fatigue is an important engineering topic in itself. This is a forest vs trees discussion. Thermal fatigue studies generally are a bigger picture than metal fatigue discussions. Metal fatigue looks at it from a metallurgist point of view. I am a mechanical development engineer, not a metallurgist. I don't care about microstructures, grains or microscopic cracks. I want to know about balancing thermal stresses, unbalanced structures, stress concentrations, localized Biot Numbers, and how this all helps design a part right in the first place. Or how to fix a design that already exists but fails. A well-sourced and well written article on the topic of thermal fatigue would be a great addition to Wikipedia, and NO, it is NOT the same topic as metal fatigue in general. Any takers? I have never created a new wiki entry. If someone creates one, I will help flesh it out. — Preceding unsigned comment added by 192.158.61.139 (talk) 14:54, 5 August 2011 (UTC)

Are you talking about fatigue due to strain due to expansion and contraction due to thermal cycling, or something else? —Ben FrantzDale (talk) 17:50, 5 August 2011 (UTC)

I don't know how specialised your research needs are but for information on repeated thermal stresses (and its fatigue effects) on structures you can't go far wrong by starting with the research carried out in the 1960s for the Concorde supersonic airliner. This is likely to be useful as for this aeroplane the problem was one of repeated aerodynamic heating and cooling over a long lifetime, something that wasn't so applicable to rockets and missiles, and high-speed military aircraft. — Preceding unsigned comment added by 80.4.57.101 (talk) 20:20, 10 September 2011 (UTC)

Bending but not breaking

Hey does anyone know how you can bend metal without breaking it? —68.17.132.200

If you heat the metal up sufficiently while forming, it will become more ductile and so shouldn't break. If you want to bend it while it is cold, you may be able to anneal it to remove any work hardening effects. —BenFrantzDale 14:47, 18 January 2006 (UTC)

Metal is routinely bent without breaking it. That is part of the usefulness of metals. It is repeated or excessive bending that causes problems. —Preceding unsigned comment added by 82.36.90.96 (talk • contribs)

Additionally one can change the stress state that the material undergoes. For example rolling and extrusion are both used to form metal through the modification of the stress state.—Preceding unsigned comment added by 129.22.154.194 (talk • contribs)

Stress frequency influence in fatigue

The "S-N" curve for a material represents its life, in terms of cycles, for a determined applied stress. My question is: How does the fatigue life vary to the applied load frequency? Is this life unchanged for different frequencies? Pedro.makiyama 12:33, 30 January 2007 (UTC)

Frequency appears not to have much effect on fatigue life, unless time is also important through environmental effects or static fracture processes are also involved.—Preceding unsigned comment added by 82.36.90.96 (talk • contribs)

Frequency dependence depends on the material and environment. In many metals, frequency may become important at high temperatures and/or when combined with corrosive environments. The theory is that lower frequency (such as when you apply the load and hold it awhile before releasing it) allows more time for detrimental chemical reactions to attack the material. For those scenarios, the fatigue life for a given stress generally decreases at lower frequencies. Jagad5 22:13, 27 April 2007 (UTC)

Fatigue life in polymers can be very much affected by loading frequency; this phenomenon is thought to be a function of localized heating. 208.65.48.45 (talk) 13:06, 24 November 2010 (UTC)(246Dino)

Phenomenology

Shouldn't this article contain some reference to the phenomenology of fatigue, like Persistant Slip Bands (PSB), dislocation cell structures etc? There don't seem to be any references to these phenomena in any other article. Mike 09:37, 14 May 2007 (UTC)

Yes. —Ben FrantzDale 10:50, 14 May 2007 (UTC)

Ultrasonic Impact Treatment - biased promotional material?

"The most recent development in the field of surface treatments utilizes ultrasonic energy to create residual compressive stresses that surpass those achieved by shot peening, laser peening, and other legacy methods."

Sounds to me like a non-neutral advertisement that somebody is trying to slip in for their technique. If you can show a peer-reviewed citation for these highly unlikely statements, feel free to put them back in. Tarchon 21:11, 17 May 2007 (UTC)

It's just peening using ultrasonic frequencies. "Ultrasonic energy" and "surpass" is BS IMO. Sigmund 21:22, 2 June 2007 (UTC)

Simple Illustration of da/dN vs dK plot needed

It would be helpful to include a simple plot of da/dN vs dK when making reference of the Paris slope.—Preceding unsigned comment added by 129.22.154.194 (talk • contribs)

Separation and clarification of stress and strain controlled fatigue crack growth

Equations for both stress and strain controlled fatigue crack growth are presented but no discussion of their differences is included.—Preceding unsigned comment added by 129.22.154.194 (talk • contribs)

Paris Slope Clarification

Under the Paris Slope paragraph of the article it states, "and m is typically in the range 3 to 5.". This is correct for metals, but not other materials such as ceramics which have a much higher Paris slope(m). Additionally the value needs to be cited. —Preceding unsigned comment added by 129.22.154.194 (talk • contribs)

Fair use rationale for Image:Ewing and Humfrey fatigue cracks.JPG

Image:Ewing and Humfrey fatigue cracks.JPG is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to ensure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.

If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images lacking such an explanation can be deleted one week after being tagged, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you. BetacommandBot (talk) 14:00, 25 February 2008 (UTC)

Intrinsic and Extrinsic Toughening mechanisms

A section on the intrinsic and extrinsic fatigue toughening mechanisms might be helpful as well. R.O. RITCHIE's paper Mechanisms of fatigue-crack propagation in ductile and brittle solids does a nice job of covering the various fatigue toughening mechanisms and could be used as a guide for inclusion in the article. —Preceding unsigned comment added by 129.22.154.234 (talk) 19:12, 15 April 2008 (UTC)

Fatigue limit vs endurance limit

I've copied this here from the Fatigue limit discussion page in case that's a backwater that no one watches.

The article currently defines fatigue limit as the constant amplitude (or range) of cyclic stress that can be applied to a material without causing fatigue failure, and endurance limit as the stress amplitude for a chosen number of cycles (usually 10⁷) for structural metals such as aluminium, that do not have a distinct fatigue limit and will eventually fail even from small stress amplitudes.

However:

• Beer and Johnston, in Mechanics of Materials (ISBN: 0-07-837340-9), state "The endurance limit is the stress for which failure does not occur, even for an indefinitely large number of loading cycles." "For nonferrous metals, such as aluminum and copper...one defines the fatigue limit as the stress corresponding to failure after a specified number of loading cycles, such as 500 million." This sounds like the exact opposite of Roger Tyler MSc's comments above and the current article.
• R.C. Hibbeler, in Mechanics of Materials (ISBN: 0-13-008181-7), states "this limiting stress is called the endurance or fatigue limit." Although he points out the difference between the "well definined" limit for steel and the "not well defined" limit for aluminum, he makes no further distinction between the two expressions.
• N.E.Dowling, in Mechanical Behavior of Materials (ISBN: 0-13-905720-X), states "such lower limiting stress amplitudes are called fatigue limits or endurance limits.
• Bannantine, Comer, and Handrock, in Fundamentals of Metal Fatigue Analysis (ISBN: 0-13-340191-X), state "certain materials, primarily body-centered cubic (BCC) steels, have an endurance or fatigue limit, S_e, which is a stress level below which the material has an "infinite" life." "Most nonferrous alloys have no endurance limit..." "A pseudo-endurance limit or fatigue strength for these materials is taken as the stress value corresponding to a life of 5 x 10⁸ cycles."
• The currectly cited reference says "The Fatigue limit is the maximum completely reversed stress for which it is assumed that the material will never fail regardless of the number of cycles." It uses but does not define endurance limit. It does, however use the expression "endurance/fatigue limit" twice, suggesting that they may be interchangable.

Could the distinction between these two terms be just a cultural thing, or is the distinction between these terms just not that well defined? -AndrewDressel (talk) 14:08, 18 April 2008 (UTC)

They are basically the same thing. For ferrous metals they are. For non-ferrous metals and materials without a infinite life strength (or a very low one), a stress level at a set number of cycles is often used and called fatigue limit. The fatigue limit article seems to have it backwards. -Fnlayson (talk) 14:47, 18 April 2008 (UTC)

Cool. Is there an absolute authority that I should cite, or are Beer and Johnston good enough? -AndrewDressel (talk) 15:08, 18 April 2008 (UTC)

• That should be fine. Some of my books say endurance limit is the stress for an infinite life and say fatigue limit is synonymous or state it is the fatigue strength for ~10⁸ cycles. In any event the defination for endurance limit seems clear. -Fnlayson (talk) 15:31, 18 April 2008 (UTC)

Are 'tired' clock mainsprings caused by fatigue?

Was wondering if the well known phenomonon of clock and watch mainsprings losing some of their torque and becoming 'tired' or 'set' after decades of use is caused by metal fatigue? Talk:Creep (deformation) says it's not creep. I'm editing Mainspring and can't find any information on this failure mode. Thanks --Chetvorno^TALK 21:33, 15 May 2008 (UTC)

• More related to fatigue. The spring is yielding under repeated loading. Has to be a low cycle fatigue problem. The yield strength can change under cyclic loading. In any event it is deformating under the repeated loads. -Fnlayson (talk) 21:59, 15 May 2008 (UTC)

Basquin's Law

A good job. Nice explanation.

I miss some elaboration on the Basquin's Law and especially its relation to material properties. Basquin’s law of fatigue states that the lifetime of the system has a power-law dependence on the external load amplitude :

$N*s^{k}=C$

where: N is fatigue life, s is remote stress (maximum stress?), k is metarial dependent factor. Camille T (talk) 17:26, 22 May 2008 (UTC)

Timeline

In the section "Timeline of early fatigue history", there is this item:

1968: Tatsuo Endo and M. Matsuiski devise the rainflow-counting algorithm and enable the reliable application of Miner's rule to random loadings.

I am very suspicious of the name "Matsuiski", and think it may be a misspelling of Matsuishi. Matsuiski with "ski" is not a possibility in a Japanese name. Also, it gets 7 pages in a Google search, while the name Matsuishi gets over 45.

In more refined searches, like "Matsuiski rainflow Endo" and its rival with an "shi" both get results, but at a glance, those with "ski" are more likely to be encyclopedia articles (some copied from Wikipedia), while those with "shi" are more likely to be scientific articles.

Which is all rather unimportant, because as I said, Matsuiski just can't be a Japanese name. It looks like a ridiculous mutation into part of a Polish suffix.

All guesswork . . . all based on the assumption that M. "Matsuiski" is Japanese . . . but I'm suspicious. Misha Vargas (talk) 04:20, 22 January 2009 (UTC)

The original paper is (almost) universally referenced as: "Matsuishi, M., Endo, T., 1968, Fatigue of Metals Subjected to Varying Stress, Japan Society of Mechanical Engineers, Jukvoka, Japan." I cannot trace a web version of this to link in, but will add this detail and correct the name in the article. (I'm old enough to remember that mis-spellings spread virally long before the electronic age!) John M Brear (talk) 13:07, 9 March 2011 (UTC)

Fatigue crack growth

I know of no evidence for faster crack growth rates in low moduli material, so have deleted the sentence. Growth rates depend on the load and cycles applied. Peterlewis (talk) 16:06, 27 March 2009 (UTC)

Speidel published some research estimating that da/dN = 1.7 x 10^6 *(delta K / E)^3.5 m/cycle. It's been a long time since I read the paper but there was a graph that showed a clear trend so when there's no data available, I've used that with a healthy safety factor. Jagad5 (talk) 13:03, 22 March 2012 (UTC)

Rip-stop doubler?

I've created an article stub for the Rip-stop doubler, which is briefly mentioned in the article for the De Havilland Comet..

The remaining Comet 1s and 1As were either scrapped or modified with oval window rip-stop doublers (a thick, structurally strong ring of material prevents a crack from spreading further)..

Is this the correct name for whatever this really is? Googling for the term turns up extremely limited results which makes me think this was actually more technically called something else. (I am asking here since materials science experts probably read this talk page.) DMahalko (talk) 10:48, 1 June 2010 (UTC)

I believe in general features such as that are referred to a crack arrestors. Ribs and other stiffeners can serve the same purpose. -Fnlayson (talk) 13:07, 1 June 2010 (UTC)

A 'Rip-stop doubler' is a patch of the same thickness as the base material affixed over a site of high load. It's called a 'doubler' because it 'doubles' the thickness and strength of the patched area, so is a form of localised strengthening. The 'Rip-stop' part just means that it is intended to provide a stronger than normal area that will stop any tears in the material from spreading any further. i.e., it 'stops rips'.

The principle is neatly simulated with a pair of old denim jeans - try tearing a piece of the material - it will tear quite readily until it comes to one of the re-inforced seams. Then it stops and requires much greater force to continue ripping.

The Comet's problem was that once a rip in the pressure cabin had started there was nothing to stop it continuing to tear until the point where the whole cabin burst. The rip-stop is intended to confine a tear to a small area, allowing more gradual decompression without bursting. BTW, there's a pdf of the official RAE report on the tests carried out on the water tank Comet 1 G-ALYR here: [1] which some of you might find interesting. —Preceding unsigned comment added by 86.112.91.65 (talk) 18:09, 18 October 2010 (UTC)

Fatigue Testing

Do we need a separate heading for fatigue testing? Sub-heading should include:

• Load-Controlled Smooth Specimen Tests
• Strain-Controlled Smooth Specimen Tests
• Fatigue Crack Growth Testing

--Amgreen (talk) 11:46, 22 September 2010 (UTC)

For sure! Wizard191 (talk) 14:20, 22 September 2010 (UTC)

S-N Graph

High cycle life is mentioned in the text; however, the associated graph includes low cycle data. Given the presumption of plasticity at low cycle life, perhaps a stain-life graph should be employed? Alternately, the low cycle data could be excluded from the graph.208.65.48.45 (talk) 13:26, 24 November 2010 (UTC)(246Dino)

Seems like corrosion should be more prominent in this article

Corrosion gets only a passing mention in this article, but it seems like it should get much more attention in the sections discussing micro-cracking. Though I am not a material scientist and don't know the references needed for such an addition.

Oxygen is corrosive to pure aluminum and iron, and micro-cracking essentially exposes pure metal to atmospheric air, resulting nearly immediate corrosion in the micro-crack. Iron oxide is lighter density than pure iron, so the oxidation helps to expand and wedge the micro-crack open, so that similar future forces are able to pry the micro-crack ever further and further open, resulting in continuing corrosion deep within the micro-cracking until structural failure occurs. Aluminum likely fatigues much more easily than iron, since it so aggressively and quickly corrodes when exposed to oxygen. DMahalko (talk) 20:05, 19 October 2011 (UTC)

The concept deserves encyclopedic coverage, but I'd suggest that it's best covered in a separate article. Corrosion is not necessarily part of fatigue (their combination is something specific and separate - fatigue takes place without it too). The risk of confusion in a combined article is serious and would be avoidable through separation of the articles. Andy Dingley (talk) 20:37, 19 October 2011 (UTC)

• And there is a related article at Corrosion fatigue. -Fnlayson (talk) 20:40, 19 October 2011 (UTC)

History of Fatigue

Is there a picture of Louis F. Coffin anywhere in the www to find? A litte bit more of historical information would increase the quality of this article! — Preceding unsigned comment added by 95.115.63.82 (talk) 17:43, 13 April 2012 (UTC)

multiaxial fatigue

article is missing any mention of multiaxial loading and how it is addressed. there needs to be a section on critical plane analysis. — Preceding unsigned comment added by 2001:5B0:22FF:1CF0:0:0:0:39 (talk) 22:14, 13 April 2013 (UTC)

Liberty Ships

Didn't these suffer from metal fatigue in WW II ? Look at the talk page for Henry J Kaiser. Someone called Tipper showed that the Liberty ships suffered from something that falls under the umbrella of metal fatigue. So the list that has the Comet jet and the French train should also have the Liberty ships.