Talk:Toughness

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"...when suddenly stressed." : is the suddenly important/essential? Looks quite hard to pin down, and not very relevant surely? Out of my field, so I'll leave this one to someone more knowledgeable. 194.106.59.2 15:34, 25 Mar 2005 (UTC)

It says square inches, but then the math is inches cubed.

For some reason this confuses a lot of people. The correct units are energy/volume (J/m^3 or in-lbf/in^3). This is dimensionally equivalent to force/area (N/m^2 or lbf/in^2). Toiyabe 15:18, 9 April 2007 (UTC)

[edit] Toughness

It seems to me that the area under the stress/ strain curve is an indication of toughness but not the measure of toughness. Conventionally, the Izod or Charpy impact tests are used although the previous comment about the inexactness of defining "sudden" is valid. The Charpy and Izod tests give a value in Joules per square meter which then relates directly with the gamma term used by Griffith and the "G" used by Irwin in Fracture Mechanics equations. In this way, so-called Impact Toughness can be related to Fracture Toughness and the dimensional analysis balances.

Roger Tyler MSc

The area under the stress strain curve is twice the fracture energy per unit volume of a tensile sample; i.e. 'G'. This only hold when the stress-strain curve occurred through stable crack growth. Under stable crack growth the crack grows at equilibrium. Under unstable crack growth there is elastic energy which is transformed to kinetic energy of the two fractured half's. Toughness is not measured as Joules per square meter but as a pascal times squareroot(meter).