IdeaWazaWiki - User contributions [en]

Archive:Fanboy

2008-03-28T12:43:00Z

130.88.91.47: /* Background */

{{Otheruses4}}
{{Refimprove|date=October 2007}}

'''Fanboy''' (sometimes spelled '''fanboi''') is a term used to describe an individual who is devoted to a single fannish subject, or to a single point of view within that subject, often to the point where it is considered an obsession. Fanboys remain loyal to their particular obsession.

== Background ==
Stereotypical fanboys are attributed with a devotion to the creators and principles behind a work with which they are currently enthralled. Fanboys are noted for a very emotional attachment to their chosen subject. They will readily engage in debates about their chosen subject.

As electronic entertainment gained popularity, the term became increasingly applied to [[video games]] with people often developing an obsessive loyalty towards one console platform. This may be due in part to the price of the consoles limiting many to a choice of one console, with the obsession possibly stemming from defence of that decision. The term is also applied increasingly to enthusiasts of computer platforms such as [[OS X]], [[Windows]] and [[Linux]], although the term is also applied to fans of certain [[television]] programmes. As a result, a subculture emerged which readily labeled itself as "fanboys." Within this group, more effort is taken to fit in with a perceived standard, resulting in a more outgoing attitude, even among those with insecurities. This outgoing stance is often felt to be abrasive by those not involved in the culture as deeply. The term originated in [[comic book]] circles, to describe someone who immersed himself in the fictional worlds of comics and the culture of comics fandom. The term is most commonly associated with adolescent and teen males but can be applicable to any age or sex.

The term fangirl, while similar, often carries slightly different connotations. The term fangirl is often applied to any enthusiastic female fan, regardless of obsessive qualities or not, and is often used with overtones of "[[teenybopper]]".

==History of fanboys and the term==
The term "fanboy" is most commonly associated with adolescent and teen males but can be applicable to any age or sex. The term originated in [[comic book]] circles to describe someone immersed in the fictional worlds of comics and the culture of comics fandom. Common subjects of reverence by fanboys are specific: [[TV show]]s; [[film|movie]]s; [[music]]; [[anime]]; [[comic book]]s; [[car]]s; [[video game console]]s, [[video games]] and [[MMORPG]]s; and [[computer]] [[operating system]]s, [[computer Hardware|hardware]] and [[software]].

Popular depictions of Fanboy stereotypes include the [[Comic Book Guy]] on ''[[The Simpsons]]'' and columnist [[Larry Groznic]] from the satirical newspaper ''[[The Onion]]''. In the songs of the fannish [[parody]] [[musician]] [[Luke Ski]], many characters proudly consider themselves ''fanboys.''

The earliest published uses of the word "fanboy" have been dated to 1982. One reference is to the cover of the "Official Underground and Newave Comix Price Guide". On this cover page are sketched overweight, overzealous comic book collectors wearing T-shirts that state "Fanboys of America," who are describing the extreme measures they would go to, including moving to San Francisco, to preserve their comics.

Also published in 1982, a comic strip appeared in Jim Engel and Chuck Fiala's "Fandom Confidential" comic. In the strip, Jim and Chuck met comic artist/writer [[John Byrne]] and collapsed into "mindless paroxysms of adoration." The John Byrne character responded that they were "a couple of fanboys in bondage" (a play on words referring to a [[List of Monty Python’s Flying Circus episodes#10. E. Henry Thripshaw.27s Disease|Monty Python sketch]] in which an Elizabethan era character reads what she claims to be a new Shakespeare work called "Gay Boys in Bondage". <ref>[http://www.byrnerobotics.com/FAQ/listing.asp?ID=7&T1=Miscellaneous+Questions#154 Byrne Robotics: FAQ]</ref> Another early use is in a smart-aleck editorial reply by "[[Ambush Bug]]" to a letter in his comic in [[1985]].

==Media==
===Comic Book===
*[[Sergio Aragonés]]' ''Fanboy''
*[[Galactic Storm]]'s ''Fanboy''

===Television===
*''[[The Simpsons]]''' [[Comic Book Guy]] refers to himself as a fanboy.
*''[[Freakazoid!|Freakazoid]]'''s [[freakazoid!#Other characters|Fan Boy]]

===Radio/Podcasts===
*[[Fanboy Radio]] - [http://fanboyradio.com]

===Webcomics===
*[[Fanboys]] - [http://ngeb.net/fanboys]
*[[F@NBOY$]] - [http://fanboys-online.com]

==See also==
* [[Addiction]]
* [[Cyberstalking]]
* [[Editor war]]
* [[Anorak (slang)|Anorak]]
* [[Astroturfing]]
* [[Otaku]]
* [[Obsession]]

==References==
{{reflist}}

==External links==
* [http://www.urbandictionary.com/define.php?term=fanboy Urban dictionary: fanboy]
* [http://www.netjak.com/review.php/1013 Dissecting the Fanboy Mind] - A discussion of the fanboy behavior in regard to video games.
* [http://palgn.com.au/article.php?id=6463 The trial of the Fanboy] - A criticism of the fanboy concept and overusage of the term.

[[Category:Fandom]]
[[Category:Anime and manga terminology]]

[[de:Fan#Konsum]]
[[fr:Fanboy]]

Archive:Fanboy

2008-03-28T12:42:36Z

130.88.91.47: /* Background */

{{Otheruses4}}
{{Refimprove|date=October 2007}}

'''Fanboy''' (sometimes spelled '''fanboi''') is a term used to describe an individual who is devoted to a single fannish subject, or to a single point of view within that subject, often to the point where it is considered an obsession. Fanboys remain loyal to their particular obsession.

== Background ==
Stereotypical fanboys are attributed with a devotion to the creators and principles behind a work with which they are currently enthralled. Fanboys are noted for a very emotional attachment to their chosen subject. They will readily engage in debates about their chosen subject.

As electronic entertainment gained popularity, the term became increasingly applied to [[video games]] with people often developing an obsessive loyalty towards one console platform. This may be due in part to the price of the consoles limiting many to a choice of one console, with the obsession possibly stemming from defence of that decision. The term is also applied increasingly to enthusiasts of computer platforms such as [[OS X]], [[Windows]] and [[Linux]], although the term is also applied to fans of certain [[television]] programmes also. As a result, a subculture emerged which readily labeled itself as "fanboys." Within this group, more effort is taken to fit in with a perceived standard, resulting in a more outgoing attitude, even among those with insecurities. This outgoing stance is often felt to be abrasive by those not involved in the culture as deeply. The term originated in [[comic book]] circles, to describe someone who immersed himself in the fictional worlds of comics and the culture of comics fandom. The term is most commonly associated with adolescent and teen males but can be applicable to any age or sex.

The term fangirl, while similar, often carries slightly different connotations. The term fangirl is often applied to any enthusiastic female fan, regardless of obsessive qualities or not, and is often used with overtones of "[[teenybopper]]".

==History of fanboys and the term==
The term "fanboy" is most commonly associated with adolescent and teen males but can be applicable to any age or sex. The term originated in [[comic book]] circles to describe someone immersed in the fictional worlds of comics and the culture of comics fandom. Common subjects of reverence by fanboys are specific: [[TV show]]s; [[film|movie]]s; [[music]]; [[anime]]; [[comic book]]s; [[car]]s; [[video game console]]s, [[video games]] and [[MMORPG]]s; and [[computer]] [[operating system]]s, [[computer Hardware|hardware]] and [[software]].

Popular depictions of Fanboy stereotypes include the [[Comic Book Guy]] on ''[[The Simpsons]]'' and columnist [[Larry Groznic]] from the satirical newspaper ''[[The Onion]]''. In the songs of the fannish [[parody]] [[musician]] [[Luke Ski]], many characters proudly consider themselves ''fanboys.''

The earliest published uses of the word "fanboy" have been dated to 1982. One reference is to the cover of the "Official Underground and Newave Comix Price Guide". On this cover page are sketched overweight, overzealous comic book collectors wearing T-shirts that state "Fanboys of America," who are describing the extreme measures they would go to, including moving to San Francisco, to preserve their comics.

Also published in 1982, a comic strip appeared in Jim Engel and Chuck Fiala's "Fandom Confidential" comic. In the strip, Jim and Chuck met comic artist/writer [[John Byrne]] and collapsed into "mindless paroxysms of adoration." The John Byrne character responded that they were "a couple of fanboys in bondage" (a play on words referring to a [[List of Monty Python’s Flying Circus episodes#10. E. Henry Thripshaw.27s Disease|Monty Python sketch]] in which an Elizabethan era character reads what she claims to be a new Shakespeare work called "Gay Boys in Bondage". <ref>[http://www.byrnerobotics.com/FAQ/listing.asp?ID=7&T1=Miscellaneous+Questions#154 Byrne Robotics: FAQ]</ref> Another early use is in a smart-aleck editorial reply by "[[Ambush Bug]]" to a letter in his comic in [[1985]].

==Media==
===Comic Book===
*[[Sergio Aragonés]]' ''Fanboy''
*[[Galactic Storm]]'s ''Fanboy''

===Television===
*''[[The Simpsons]]''' [[Comic Book Guy]] refers to himself as a fanboy.
*''[[Freakazoid!|Freakazoid]]'''s [[freakazoid!#Other characters|Fan Boy]]

===Radio/Podcasts===
*[[Fanboy Radio]] - [http://fanboyradio.com]

===Webcomics===
*[[Fanboys]] - [http://ngeb.net/fanboys]
*[[F@NBOY$]] - [http://fanboys-online.com]

==See also==
* [[Addiction]]
* [[Cyberstalking]]
* [[Editor war]]
* [[Anorak (slang)|Anorak]]
* [[Astroturfing]]
* [[Otaku]]
* [[Obsession]]

==References==
{{reflist}}

==External links==
* [http://www.urbandictionary.com/define.php?term=fanboy Urban dictionary: fanboy]
* [http://www.netjak.com/review.php/1013 Dissecting the Fanboy Mind] - A discussion of the fanboy behavior in regard to video games.
* [http://palgn.com.au/article.php?id=6463 The trial of the Fanboy] - A criticism of the fanboy concept and overusage of the term.

[[Category:Fandom]]
[[Category:Anime and manga terminology]]

[[de:Fan#Konsum]]
[[fr:Fanboy]]

Archive:Fanboy

2008-03-28T12:38:30Z

130.88.91.47: /* Background */

{{Otheruses4}}
{{Refimprove|date=October 2007}}

'''Fanboy''' (sometimes spelled '''fanboi''') is a term used to describe an individual who is devoted to a single fannish subject, or to a single point of view within that subject, often to the point where it is considered an obsession. Fanboys remain loyal to their particular obsession.

== Background ==
Stereotypical fanboys are attributed with a devotion to the creators and principles behind a work with which they are currently enthralled. Fanboys are noted for a very emotional attachment to their chosen subject. They will readily engage in debates about their chosen subject.

As electronic entertainment gained popularity, the term became increasingly applied to [[video games]] with people often developing an obsessive loyalty towards one console platform. This may be due in part to the price of the consoles limiting many to a choice of one console, with the obsession possibly stemming from defence of that decision. The term is also applied increasingly to enthusiasts of computer hardware vendors such as [[Apple Inc.]] and [[television]] programmes. As a result, a subculture emerged which readily labeled itself as "fanboys." Within this group, more effort is taken to fit in with a perceived standard, resulting in a more outgoing attitude, even among those with insecurities. This outgoing stance is often felt to be abrasive by those not involved in the culture as deeply. The term originated in [[comic book]] circles, to describe someone who immersed himself in the fictional worlds of comics and the culture of comics fandom. The term is most commonly associated with adolescent and teen males but can be applicable to any age or sex.

The term fangirl, while similar, often carries slightly different connotations. The term fangirl is often applied to any enthusiastic female fan, regardless of obsessive qualities or not, and is often used with overtones of "[[teenybopper]]".

==History of fanboys and the term==
The term "fanboy" is most commonly associated with adolescent and teen males but can be applicable to any age or sex. The term originated in [[comic book]] circles to describe someone immersed in the fictional worlds of comics and the culture of comics fandom. Common subjects of reverence by fanboys are specific: [[TV show]]s; [[film|movie]]s; [[music]]; [[anime]]; [[comic book]]s; [[car]]s; [[video game console]]s, [[video games]] and [[MMORPG]]s; and [[computer]] [[operating system]]s, [[computer Hardware|hardware]] and [[software]].

Popular depictions of Fanboy stereotypes include the [[Comic Book Guy]] on ''[[The Simpsons]]'' and columnist [[Larry Groznic]] from the satirical newspaper ''[[The Onion]]''. In the songs of the fannish [[parody]] [[musician]] [[Luke Ski]], many characters proudly consider themselves ''fanboys.''

The earliest published uses of the word "fanboy" have been dated to 1982. One reference is to the cover of the "Official Underground and Newave Comix Price Guide". On this cover page are sketched overweight, overzealous comic book collectors wearing T-shirts that state "Fanboys of America," who are describing the extreme measures they would go to, including moving to San Francisco, to preserve their comics.

Also published in 1982, a comic strip appeared in Jim Engel and Chuck Fiala's "Fandom Confidential" comic. In the strip, Jim and Chuck met comic artist/writer [[John Byrne]] and collapsed into "mindless paroxysms of adoration." The John Byrne character responded that they were "a couple of fanboys in bondage" (a play on words referring to a [[List of Monty Python’s Flying Circus episodes#10. E. Henry Thripshaw.27s Disease|Monty Python sketch]] in which an Elizabethan era character reads what she claims to be a new Shakespeare work called "Gay Boys in Bondage". <ref>[http://www.byrnerobotics.com/FAQ/listing.asp?ID=7&T1=Miscellaneous+Questions#154 Byrne Robotics: FAQ]</ref> Another early use is in a smart-aleck editorial reply by "[[Ambush Bug]]" to a letter in his comic in [[1985]].

==Media==
===Comic Book===
*[[Sergio Aragonés]]' ''Fanboy''
*[[Galactic Storm]]'s ''Fanboy''

===Television===
*''[[The Simpsons]]''' [[Comic Book Guy]] refers to himself as a fanboy.
*''[[Freakazoid!|Freakazoid]]'''s [[freakazoid!#Other characters|Fan Boy]]

===Radio/Podcasts===
*[[Fanboy Radio]] - [http://fanboyradio.com]

===Webcomics===
*[[Fanboys]] - [http://ngeb.net/fanboys]
*[[F@NBOY$]] - [http://fanboys-online.com]

==See also==
* [[Addiction]]
* [[Cyberstalking]]
* [[Editor war]]
* [[Anorak (slang)|Anorak]]
* [[Astroturfing]]
* [[Otaku]]
* [[Obsession]]

==References==
{{reflist}}

==External links==
* [http://www.urbandictionary.com/define.php?term=fanboy Urban dictionary: fanboy]
* [http://www.netjak.com/review.php/1013 Dissecting the Fanboy Mind] - A discussion of the fanboy behavior in regard to video games.
* [http://palgn.com.au/article.php?id=6463 The trial of the Fanboy] - A criticism of the fanboy concept and overusage of the term.

[[Category:Fandom]]
[[Category:Anime and manga terminology]]

[[de:Fan#Konsum]]
[[fr:Fanboy]]

Archive:Nagina Group

2007-05-20T07:49:13Z

130.88.168.16: /* History */

{{Infobox_Company |
| company_name =Nagina Group
| company_logo =[[Image:Nagina group.JPG]]
| company_type =[[Public corporation]]
| foundation = [[1972]]
| location_city = Gilburg-III, Lahore
| location_country = Pakistan
| key_people = Shaikh Inam Ellahi, co-founder Shaukat Ellahi Shaikh, Shafqat Ellahi Shaikh, Shahzada Ellahi Shaikh, co-founder 
| industry = [[textiles, energy, trading,]]
| revenue = {{profit}} [[Pakistani rupee|Rs.]] 832 million, $100 million [[United States dollar|USD]] ([[fiscal year|FY]] 2006)
| homepage = http://www.nagina.com/
}}

'''Nagina Group''' is a [[public corporation]] based in [[Pakistan]]i that manufactures a wide variety of [[textile]] products. Founded in [[1972]] by Inam Ellahi Shaikh and Ashan Ellahi Shaikh, it was listed by [[Forbes Magazine]] as the best-performaning company with less than US$1 billion in revenue in [[2003]].

==History==
What is now known as The Nagina Group began as a single company, Nagina Mills Limited, established by Shaikh Inam Ellahi and Ashan Ellahi Shaikh in [[1967]]. Focusing on the production of [[cotton]] [[yarn]], it grew with the acquisition of [[tannery|tanneries]], [[factory|factories]] that produced shoes and ice, and Pakistan's largest [[jute|jute mill]]. These assets were lost, however, when [[East Pakistan]] separated from the Pakistani Federation to become [[Bangladesh]] in [[1971]].

The company reformed in [[1971]] as the Nagina Group, consolidating its assets under a single [[umbrella corporation]]. The group currently manages Nagina Cotton Mills Limited, Ellcot Spinning Mills Limited, and Prosperity Weaving Mills Limited. Together, the facilities hold approximately 100,000 modern [[spindle]]s, and produce forty-eight million pounds of carded and combed yarn annually.

Nagina Group also operates three private [[power plants]] to provide electricity for its mills. The installed capacity of its generators is 30.57 [[Megawatt]]s. Excess energy is sold to other industrial facilities in the area.

Nagina Group has an ambitious 5 year strategic objective. This objective includes expanding into logistics, consolidating position in energy production, and opening a 6 star beach resort in Karachi.

Nagina Cotton Mills Limited (Winner of Forbes Global Award "Best under a Billion-200") is the mother company of the Group, established in 1967. The company operates state of art spinning machinery comprising 47,040 Spindles with related process machines. Latest equipment from Japan, Europe and China allow production of high quality Spun Yarns in Carded and Combed versions for use in high speed looms and knitting machines. MUNDRI and ANGOTHI are popular brands of the company.

directors are pleased to report that prestigious International Business Magazine FORBES Global included the company in their list of "Best under a billion 200".

According to the magazine "Our list of 200 successful companies outside U.S. is drawn up from among 19,000 publicly traded concerns with annual below $ 1 billion. We screened out most corporation that didn't have operating margin of atleast 5% over the past five aiming for the businesses that were profitable and that rewarded shareholders. A handful of companies that failed these tests were considered if they had outstanding results otherwise. The remaining 4000-odd concerns were graded against one another using various dollar based performance measures, and the top 500 reviewed for inclusion on this list".

==External links==
{{Primarysources|date=February 2007}}
* http://www.nagina.com/

[[Category:Companies of Pakistan]]

Archive:Nagina Group

2007-05-20T07:48:49Z

130.88.168.16:

{{Infobox_Company |
| company_name =Nagina Group
| company_logo =[[Image:Nagina group.JPG]]
| company_type =[[Public corporation]]
| foundation = [[1972]]
| location_city = Gilburg-III, Lahore
| location_country = Pakistan
| key_people = Shaikh Inam Ellahi, co-founder Shaukat Ellahi Shaikh, Shafqat Ellahi Shaikh, Shahzada Ellahi Shaikh, co-founder 
| industry = [[textiles, energy, trading,]]
| revenue = {{profit}} [[Pakistani rupee|Rs.]] 832 million, $100 million [[United States dollar|USD]] ([[fiscal year|FY]] 2006)
| homepage = http://www.nagina.com/
}}

'''Nagina Group''' is a [[public corporation]] based in [[Pakistan]]i that manufactures a wide variety of [[textile]] products. Founded in [[1972]] by Inam Ellahi Shaikh and Ashan Ellahi Shaikh, it was listed by [[Forbes Magazine]] as the best-performaning company with less than US$1 billion in revenue in [[2003]].

==History==
What is now known as The Nagina Group began as a single company, Nagina Mills Limited, established by Shaikh Inam Ellahi and Ashan Ellahi Shaikh in [[1967]]. Focusing on the production of [[cotton]] [[yarn]], it grew with the acquisition of [[tannery|tanneries]], [[factory|factories]] that produced shoes and ice, and Pakistan's largest [[jute|jute mill]]. These assets were lost, however, when [[East Pakistan]] separated from the Pakistani Federation to become [[Bangladesh]] in [[1971]].

The company reformed in [[1971]] as the Nagina Group, consolidating its assets under a single [[umbrella corporation]]. The group currently manages Nagina Cotton Mills Limited, Ellcot Spinning Mills Limited, and Prosperity Weaving Mills Limited. Together, the facilities hold approximately 100,000 modern [[spindle]]s, and produce forty-eight million pounds of carded and combed yarn annually.

Nagina Group also operates three private [[power plants]] to provide electricity for its mills. The installed capacity of its generators is 30.57 [[Megawatt]]s. Excess energy is sold to other industrial facilities in the area.

Nagina Group has an ambitious 5 year strategic objective. This objective includes expanding into logistics, consolidating position in energy production, and opening a 6 star beach resort in Karachi.

Recent News

Nagina Cotton Mills Limited (Winner of Forbes Global Award "Best under a Billion-200") is the mother company of the Group, established in 1967. The company operates state of art spinning machinery comprising 47,040 Spindles with related process machines. Latest equipment from Japan, Europe and China allow production of high quality Spun Yarns in Carded and Combed versions for use in high speed looms and knitting machines. MUNDRI and ANGOTHI are popular brands of the company.

directors are pleased to report that prestigious International Business Magazine FORBES Global included the company in their list of "Best under a billion 200".

According to the magazine "Our list of 200 successful companies outside U.S. is drawn up from among 19,000 publicly traded concerns with annual below $ 1 billion. We screened out most corporation that didn't have operating margin of atleast 5% over the past five aiming for the businesses that were profitable and that rewarded shareholders. A handful of companies that failed these tests were considered if they had outstanding results otherwise. The remaining 4000-odd concerns were graded against one another using various dollar based performance measures, and the top 500 reviewed for inclusion on this list".

==External links==
{{Primarysources|date=February 2007}}
* http://www.nagina.com/

[[Category:Companies of Pakistan]]

Archive:Nagina Group

2007-05-20T07:46:39Z

130.88.168.16:

Archive:Nagina Group

2007-05-20T07:44:12Z

130.88.168.16:

About fracture mechanics

2006-07-05T23:13:25Z

130.88.164.47: /* Elastic-Plastic Fracture Mechanics */

{{cleanupdate|April 2006}}
{{references}}
{{wikify-date|April 2006}}

'''Fracture mechanics''' is a method for predicting failure of a structure containing a crack. It uses methods of analytical [[Solid Mechanics]] to calculate the driving force on a crack and those of experimental [[Solid Mechanics]] to characterize the material's resistance to fracture.

In modern [[Materials Science]], fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the [[physics]] of [[stress (physics)|stress]] and [[strain]], in particular the theories of [[elasticity]] and [[plasticity (physics)|plasticity]], to the microscopic [[crystallographic defect]]s found in real materials in order to predict the macroscopic mechanical failure of bodies.

== The Need for Fracture Mechanics ==
[[Image:Tay1.jpg|left|thumb|Tay Bridge Disaster (1879)]]In many cases, failure of engineering structures through fracture can be fatal; one example is that of the [http://www.mcgonagall-online.org.uk/poems/pgdisaster.htm Tay Bridge Disaster] (left). Often disasters occur because engineering structures contain cracks - arising either during production or during service (e.g. from [[Fatigue (material)|fatigue]]). For instance, growth of cracks in pressure vessels due to crack propagation could cause a fatal explosion. If failure were ever to happen, we would rather it were by [[yield (engineering)|yield]] or by leak before break.

Since cracks can lower the strength of the structure beyond that due to loss of load-bearing area a material property, above and beyond conventional strength, is needed to describe the fracture resistance of engineering materials. This is the reason for the need for fracture mechanics - the evaluation of the strength of cracked structures.

== The History of Fracture Mechanics ==
=== Griffith's Energy Relation ===
Fracture Mechanics was invented during World War I by English aeronautical engineer, [[Alan Arnold Griffith|A.A.Griffith]], to explain the failure of brittle materials. Griffith was faced with the problem that theoretical calculations showed that the stress at the tip of a sharp crack approaches infinity. Accordingly, any structure containing a crack should fail, no matter how small the crack or how light the load. To solve this dilemma, Griffith developed a thermodynamic approach. He assumed that growth of a crack requires creation of surface energy, which is supplied by the loss of strain energy accompanying the relaxation of local stresses as the crack advances. Failure occurs when the loss of strain energy is sufficient to provide the increase in surface energy, as shown in the Appendix to this article.

=== Irwin's Modification of Griffith's Energy Relation ===
[[Image:TankerSchenectady.jpg|left|thumb|The S.S.Schenectady Split Apart by Brittle Fracture while in Harbor (1944)]]Griffith’s work was ignored for over twenty years until a group under [[G.R. Irwin]] at the U.S. Naval Research Laboratory (NRL) took it up during World War II. Irwin and his colleagues developed a modified form of Griffith's approach; they reformulated it in terms of stress, rather than energy. Their work resulted in a new materials property, [[fracture toughness]], which is denoted KIc, and is now universally accepted as the defining property of fracture mechanics (see Appendix for equations).

But a problem arose for the NRL researchers because naval materials, e.g. ship-plate steel, are not perfectly elastic but undergo [[plastic deformation]] at the tip of a crack violating the underlying assumption of the theory. Linear-elastic fracture mechanics is of limited practical use for structural steels for two other reasons:

(1) Fracture toughness testing is very expensive and sufficient information for selection of steels can be obtained from the simpler and cheaper [[Charpy Impact Test]]

(2) If a part's response to load is sufficiently close to linear-elastic that KIc can be measured, there is little plastic relaxation at the crack tip and the steel will be [[brittle]]. Structural steels, in particular, can be prone to brittle fracture, which has led to a number of catastrophic failures.

== Elastic-Plastic Fracture Mechanics ==
[[Image:Aircraft_Crash.jpg|left|thumb|Vertical Stabilizer, which Separated from the Aircraft Leading to a Fatal Crash(2001)]]In the mid-1960s J.R. Rice (then at Brown University) developed a new toughness measure to describe the case where there is sufficient crack-tip deformation that the part no longer obeys the linear-elastic approximation. Rice's analysis, which assumes non-linear elastic deformation ahead of the crack tip, is designated the [[J integral]]. This analysis is limited to situations where plastic deformation at the crack tip does not extend to the furthest edge of the loaded part. It also demands that the assumed non-linear elastic behavior of the material is a reasonable approximation in shape and magnitude to the real material's load response. The elastic-plastic failure parameter is designated JIc and is conventionally converted to KIc using Equation (3.1) of the Appendix to this article. Also note that the J integral approach reduces to the Griffith theory for linear-elastic behavior.

== Fully Plastic Fracture Mechanics ==
If the alloy is so tough that the yielded region ahead of the crack extends to the far edge of the specimen before fracture, the crack is no longer an effective stress concentrator. Instead, the presence of the crack merely serves to reduce the load-bearing area. In this regime the failure stress is conventionally assumed to be the average of the yield and ultimate strengths of the alloy.

== Engineering Applications of Fracture Mechanics ==
The following information is needed for a fracture mechanics prediction of failure:
*Applied load
*Residual stress
*Size and shape of the part
*Size, shape, location, and orientation of the crack

Usually not all of this information is available and pessimistic assumptions have to be made.

Occasionally post-mortem fracture-mechanics analyses are carried out. In the absence of an extreme overload, the causes are either insufficient toughness (KIc) or an excessively large crack that was not detected during routine inspection.

== Short Summary ==
Arising from the manufacturing process, interior and surface flaws are found in all metal structures. Not all such flaws are unstable under service conditions. Fracture mechanics is the analysis of flaws to discover those that are safe (that is, do not grow) and those that are liable to propagate as cracks and so cause [[structural failure|failure]] of the flawed structure. Fracture mechanics as a subject for critical study has barely been around for a century and thus is relatively new. There is a high demand for engineers with fracture mechanics expertise - particularly in this day and age where engineering failure is considered 'shocking' amongst the general public.

== Appendix: Mathematical Relations ==
=== Griffith's Crack Theory: Strain Energy Release Rate ===
For the simple case of a thin rectangular plate with a crack perpendicular to the load Griffith’s theory becomes:

:<math>G = \frac{\pi \sigma^2 a}{E}\,</math>                 (1.1)

where G is the strain energy release rate, σ is the applied stress, a is half the crack length, and E is the [[Elastic modulus|Young’s modulus]]. The strain energy release rate can otherwise be understood as: the rate at which energy is absorbed by growth of the crack.

However, we also have that:

:<math>G_c = \frac{\pi \sigma_f^2 a}{E}\,</math>                 (1.2)

where Gc the critical strain energy release rate (also [[fracture energy]]), σf is the [[brittle fracture stress]], a is half the crack length, and E is the [[Elastic modulus|Young’s modulus]]. This [[fracture energy]] can otherwise be understood as: the rate of strain energy release by growth of the crack.

If G ≥ Gc, this is the criterion for which the crack will begin to propagate.

=== Irwin's Modified Griffith Crack Theory: Fracture Toughness ===
Eventually a modification of Griffith’s theory emerged from this work; a term called [[stress intensity]] replaced strain energy release rate and a term called [[fracture toughness]] replaced surface energy. Both of these terms are simply related to the energy terms that Griffith used:

:<math>K_I = \sigma \sqrt{\pi a}\,</math>                 (2.1)

and

:<math>K_c = \sqrt{E G_c}\,</math> (for [[plane stress]])                 (2.2)

:<math>K_c = \sqrt{\frac{E G_c}{1 - \nu^2}}\,</math> (for [[plane strain]])                 (2.3)

where KI is the [[stress intensity]], Kc the [[fracture toughness]], and ν is [[Poisson ratio|Poisson’s ratio]]. It is important to recognise the fact that fracture parameter Kc has different values when measured under plane stress and plane strain

Fracture occurs when KI ≥ Kc. For the special case of plane strain deformation, Kc becomes KIc and is considered a material property. The subscript I arises because of the different ways of loading a material to enable a crack to propagate. It refers to loading via Mode I - the most common form of loading:

There are three ways of applying a force to enable a crack to propagate: 
Mode I - Opening mode (a [[tensile stress]] normal to the plane of the crack) 
Mode II - Sliding mode (a [[shear stress]] acting parallel to the plane of the crack and perpendicular to the crack front) 
Mode III - Tearing mode (a [[shear stress]] acting parallel to the plane of the crack and parallel to the crack front) 
[[Image:Fracture_modes.PNG]] 
We must note that the expression for KI in Eq (2.1) will be different for geometries other than the center cracked plate, as discussed in the article on [[stress intensity]]. Consequently, it is necessary to introduce a [[dimensionless number|dimensionless correction factor]], Y, in order to characterise the geometry. We thus have:

:<math>K_I = Y \sigma \sqrt{\pi a}\,</math>                 (2.4)

where Y is a function of the crack length and width of sheet given by:

:<math>Y \left ( \frac{a}{W} \right ) = \sqrt{\sec\left ( \frac{\pi a}{W} \right )}\,</math>                 (2.5)

for a sheet of finite width W containing a through-thickness crack of length 2a, or

:<math>Y \left ( \frac{a}{W} \right ) = 1.12 - \frac{0.41}{\sqrt \pi} \frac{a}{W} + \frac{18.7}{\sqrt \pi} \left ( \frac{a}{W} \right )^2 - ...\,</math>                 (2.6)

for a sheet of finite width W containing a through-thickness edge crack of length a

=== Elastic-Plastic Fracture Mechanics Theory ===
Since engineers became accustomed to using KIc to characterise fracture toughness, a relation has been used to reduce JIc to it:

:<math>K_{Ic} = \sqrt{\frac{E J_{Ic}}{1 - \nu^2}}\,</math>                 (3.1)

The remainder of the mathematics employed in this approach is interesting, but is probably better summarised in external pages due to its complex nature (refer to the Useful Websites section).

== Useful Websites ==
*[http://www.efunda.com/formulae/solid_mechanics/fracture_mechanics/fm_intro.cfm eFunda - Fracture Mechanics]
*[http://www2.umist.ac.uk/material/research/intmic/features/charpy/notes.htm UMIST - Charpy Impact Test]
*[http://www.engin.brown.edu/courses/EN175/Notes/Failure_Plasfrac/Failure_Plasfrac.htm Brown University Engineering - Mathematical Relations]
*[http://hdl.handle.net/1813/3075 - Lecture Notes on Fracture Mechanics]

== References ==
*C. P. Buckley, "Material Failure", Lecture Notes (2005), [[University of Oxford]]

== See also ==
*[[fatigue (material)|Fatigue fracture]]

[[Category:Engineering]]
[[Category:Materials science]]
[[Category:Continuum mechanics]]
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