Talk:Creep (deformation)

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Contents 1 Rate of deform : function of time?? 2 Creep and flow 3 Creep (failure mode)->Creep (deformation mode) 4 Vandalism? 5 Ashby? 6 Temperature 7 Are 'tired' clock springs an example of creep?

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)