Talk:Creep (deformation)

"no grain size dependance"?

"Therefore, dislocation creep has a strong dependence on the applied stress and no grain size dependence" - does this not disagree with say the Hall-Petch effect? —Preceding unsigned comment added by 143.167.219.26 (talk) 01:41, 18 December 2009 (UTC)

Rate of deform : function of time??

The article says "The rate of this damage is a function of the material properties and the exposure time, exposure temperature and...". What catches my eye is that the rate of deformation is supposed to be dependent upon exposure time. That sounds strange to me. Obviously, the amount of deformation increases with time, but is the rate affected? If anybody could shed some light on this, that'd be great. Or, if someone with enough education to know agrees with me, just edit it. 85.224.198.251 10:43, 7 April 2007 (UTC)

Perhaps the wording could be improved, but creep rate is not constant with time. as the article explains, the classical picture is that strainrate first decreases with time (primary), then plateaus to a constant minimum (secondary), and then increases with time (tertiary). --Karnesky 16:37, 7 April 2007 (UTC)

Creep and flow

I am confused after reading this article. If creep occurs below the yield point, then the deformation should not be permanet? What am I missing?

Also, what is the difference between creep and flow? Is it that you need to enter a nonlinear regime to achieve creep?

Good questions. They should get answered by the article, but they aren't at the moment. Creep is plastic flow that occurs below the yield point over a long period of exposure to high stress. It only happens to some materials and usually only happens when they are above half their absolute melting temperature. —BenFrantzDale 04:26, 10 October 2005 (UTC)

you must take in your mind the definition of creep,we define creep az

time dependent plastic deformation which occur mostly at hich temperature but unfortunatly i do not know mechanism of creep to explain why creep is occure at high temperature. you must know that creep can occure at plastic region too not only below the yield point

Creep is thermally activated (occurs at higher temperatures) because it is dictated by processes with thermally dependent rates. Dislocations and atoms can move faster at higher temperatures. --75.0.148.22 13:59, 4 April 2006 (UTC)

Creep (failure mode)->Creep (deformation mode)

The text of the article is correct--creep isn't really a failure mode, but a deformation or damage mode. Any objections to moving the article? -- Karnesky 00:18, 1 November 2005 (UTC)

Vandalism?

I removed the recently-added statement "One of the founders of creep is sir matthew ferns and prof ashley combes who conducted a series of breakthrough creep tests on gas turbine engine blades that revolutionised the gas turbine engine industry". In addition to being borderline nonsense, a Google search for both "matthew ferns creep" and "ashley combes creep" revealed nothing. I do not know if there is any validity to this sentence or not, but if so, let's please have somebody with a better grasp of English edit it back in. Egomaniac 20:21, 20 March 2007 (UTC)

Ashby?

The overview section of the article seems to follow lines very close to the creep and creep fracture chapter (20) by Ashby and Jones. Its not a word-for-word job, but the article's examples and layout is eerily similar. Perhaps some more examples and other texts may be used? Unfortunately I am no expert on this topic User A1 08:40, 24 July 2007 (UTC)

Temperature

"Generally 30-40% of the melting point for metals and 40-50% of melting point for ceramics is required before creep can occur." I would assume this is in K (or absolute temperature, anyway) - perhaps the sentence should be edited? Muad 09:51, 29 August 2007 (UTC)

it'll be 30-40% regardless of the temperature unit used in that case so that's not super important... what is important is the "thousand" degrees mentioned early in the article in reference to when Tungsten begins to creep, as 1000F is very different than 1000C or 1000K... and while I doubt he means rankine, he could, as we don't know. —Preceding unsigned comment added by 70.137.174.111 (talk) 07:11, 4 May 2009 (UTC)

Sorry, but Muad is right; 30% of the melting Temperature of e.g. Gallium will be two very different temperatures when taken in °C or in K. Either about 10°C or about 100 K. Really saying "30%" of a temperature doesn't make sense unless an absolute scale (such as Kelvin) is used. So the sentence should IMHO be edited. -- 92.229.164.108 (talk) 22:55, 28 October 2009 (UTC)

I agree that the fact that the temperature must be on a thermodynamic scale should be mentioned. I feel that it's an important distinction that might not be obvious to the general wikipedia readership or someone new to science or engineering. Maybe I'll just go ahead and add the comment. --LikeFunYouAre (talk) 19:05, 26 March 2011 (UTC)

Are 'tired' clock springs an example of creep?

Was wondering if the well-known phenomonon (1) of clock and watch mainsprings losing some of their torque and becoming 'tired' or 'set' after decades of use was an example of creep? I'm rewriting the Mainspring article, and I can't find any info on this failure mode. Thanks --Chetvorno^TALK 14:34, 3 December 2007 (UTC)

I think that is more likely due to metal fatigue or to repetetive "overloading" of the spring, causing plastic deformation. The deformed spring will be deformed in such a way as to minimize stress, hence reducing torque. Creep really occurs at really elevated temperatures, a couple of hundred degrees (C) for most metals Veddan (talk) 17:20, 30 March 2008 (UTC)

Thanks a lot for the info. I had actually mentioned creep in the mainspring article; I'll take it out. I'd appreciate any further info or references anyone has on the cause of 'tired' mainsprings, you can leave a note on my talk page. --Chetvorno^TALK 01:35, 20 April 2008 (UTC)

While it's likely not creep, the creep rate is non-zero at low temperatures... for instance if you leave those plastic bands on the boxes for years, they'll loosen some. We're talking about decades of time here AND small components, so even a little bit of creep could result in a large effect over the time scale's we're talking about. Much more likely explanation *is* slight overwinding, with time, increase the length of the spring, reducing it's "spring constant" which results in a lower applied force (which in this case is a torque). The basic equation for creep (from "materials science and engineering an introduction" by william callister) is strain rate = K2 * (stress)^n * e^(-Qc/RT) , where Qc is the "activation energy" for creep, n and K2 are constant fitting parameters for the material in question, R is our favorite gas constant and T is temperature. so even if we're talking about T = 300K vs T = 1300K there is still a non-zero strain rate (slow, but still there). If the springs are set so that at max wind they do not experience any plastic deformation (not just below yield stress, but such that no dislocation motion actually occurs) only then would I suspect creep might be playing a significant role.

Introduction- Too detailed!

The introduction of any wikipedia article should be no longer than 10 lines in my opinion. Including examples of creep in the introduction is certainly bad practice: suggest restructuring of the entire article. Its all good stuff, but don't throw it out right at the start 131.111.243.37 (talk) 00:42, 19 May 2010 (UTC)

Re-organisation of this page needed? and a possible split??

There is a lot of good material on this page, but it needs sorting out (IMHO) and some gaps filling. Also, there are many valid questions on this talk page that have not been answered.

I am happy to have a go at this (but it will take a while and I will definitiely make my suggestions in a sandbox first).

Before starting, I would like everyone's views on the scope we should address here. Creep is important in:

• metals (my main field)
• polymers (I know something about this)
• ceramics and concrete (not my area)
• rocks and ice (not my area)

Should we have an introductory article with four subsidiary ones, or try and cover everything in one? John M Brear (talk) 21:19, 14 October 2011 (UTC)

Definition of Creep

The definition of creep in the opening sentence is not entirely accurate, in that it does not distinguish creep from Hookean behavior or other deformation modes. A better and simpler definition of creep is, time-dependent quantifiable strain at constant stress. The inverse of creep, time-dependent stress at constant strain, is stress relaxation. Creep is usually associated with a homologous temperature T_h ≥ 0.5, but varies with alloy family. For titanium alloys, elevated-temperature behavior begins at T_h ≈ 0.3, for creep-resistant superalloys, T_h ≈ 0.56. Failure by creep can occur at or below room temperature in some solids. Creep is an important form of anelastic behavior. His Manliness (talk) 21:23, 8 January 2013 (UTC)

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Style or Content: Sections 4.1 - 4.7

I'm particularly interested in the kinds of creep: 4.1 - 4.7. But I enjoyed the article till I got there, then it turned into gibberish. Each is more of a list/jumble of (presumably) truisms and facts than any whole explanations or definitions. IOW; a "D-".   …also seems needlessly stilted, student-like. I doubt if it can be repaired, I think it needs a rewrite (or deletion) by somebody with a gut feeling for this. Cheers!
--2602:306:CFCE:1EE0:78A4:7E16:C27D:29EB (talk) 03:21, 23 July 2018 (UTC)Doug Bashford

Ratcheting

It is my understanding that ratcheting is an important aspect of creep, and that article links here... but this article doesn't mention ratcheting. Am I missing something?

Yaris678 (talk) 16:31, 23 January 2020 (UTC)

Solder

What type and at what rate for each? I'm seriously doubting that electronics solder or even plumbers solder will creep at room temp. For if it did, old electronics would be failing constantly and there would be leaking water or gas problems in piping 'everywhere' in old buildings. I think the source (number two which does not mention solder) is over extremely over-estimating creep flow in soft alloys. — Preceding unsigned comment added by 193.119.100.37 (talk) 13:55, 3 July 2023 (UTC)

In university our professor for metallic materials would take standard grade Pb-containing solder, attach a weight of a few kg (carefully calculated) and then let us track the deformation. There definitely was creep happening in the course of 2-3h. I doubt tho, that a comparable stress level occurs in everyday electronics/piping. An engineer should, however, when designing circuits that are stressed, keep in mind that solder can creep. SirBedevere (talk) 09:44, 3 September 2024 (UTC)