Editing Fracture (section)

==Strength==
{{Redirect|Breaking strain|the short story by Arthur C. Clarke|Breaking Strain|the novel by Paul Preuss|Venus Prime}}

[[File:Stress v strain Aluminum 2.png|thumb|Stress vs. strain curve typical of aluminum {{ordered list
  |[[Ultimate tensile strength]]
  |[[Yield strength]]
  |Proportional limit stress
  |Fracture
  |Offset strain (typically 0.2%)
}}]]

Fracture strength, also known as breaking strength, is the stress at which a specimen [[structural integrity and failure|fails]] via fracture.<ref name="degarmo">{{citation |last1=Degarmo |first1=E. Paul |last2=Black |first2=J T. |last3=Kohser |first3=Ronald A. |title=Materials and Processes in Manufacturing |publisher=Wiley |page=32 |year=2003 |edition=9th |isbn=0-471-65653-4 |postscript=.}}</ref> This is usually determined for a given specimen by a [[tensile test]], which charts the [[stress–strain curve]] (see image). The final recorded point is the fracture strength.

Ductile materials have a fracture strength lower than the [[ultimate tensile strength]] (UTS), whereas in brittle materials the fracture strength is equivalent to the UTS.<ref name="degarmo"/> If a ductile material reaches its ultimate tensile strength in a load-controlled situation,{{#tag:ref|A simple load-controlled tensile situation would be to support a specimen from above, and hang a weight from the bottom end. The load on the specimen is then independent of its deformation.|group="Note"}} it will continue to deform, with no additional load application, until it ruptures. However, if the loading is displacement-controlled,{{#tag:ref|A simple displacement-controlled tensile situation would be to attach a very stiff [[jack (device)|jack]] to the ends of a specimen. As the jack extends, it controls the displacement of the specimen; the load on the specimen is dependent on the deformation.|group="Note"}} the deformation of the material may relieve the load, preventing rupture.

The statistics of fracture in random materials have very intriguing behavior, and was noted by the architects and engineers quite early. Indeed, fracture or breakdown studies might be the oldest physical science studies, which still remain intriguing and very much alive. [[Leonardo da Vinci]], more than 500 years ago, observed that the tensile strengths of nominally identical specimens of iron wire decrease with increasing length of the wires (see e.g.,<ref>{{citation |last1=Lund |first1=J. R. |last2=Bryne |first2=J. P. |title=Civil. Eng. and Env. Syst. 18 (2000) 243}}</ref> for a recent discussion). Similar observations were made by [[Galileo Galilei]] more than 400 years ago. This is the manifestation of the extreme statistics of failure (bigger sample volume can have larger defects due to cumulative fluctuations where failures nucleate and induce lower strength of the sample).<ref name="Chakrabarti 2017">{{cite journal |last1=Chakrabarti |first1=Bikas K. |title=Story of the Developments in Statistical Physics of Fracture, Breakdown and Earthquake: A Personal Account |journal=Reports in Advances of Physical Sciences |date=December 2017 |volume=01 |issue=4 |pages=1750013|issn=2424-9424 |doi=10.1142/S242494241750013X |doi-access=free}}

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