Equation 10 · Part 1 · Why Materials Fail: Fracture, Flaws and the Inspection Interval
Symbol gamma_s
What this part means
the modulus e and surface energy.
Its job in the formula
gamm is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol gamma_s→Article meaning
Where the article explains it
For a through-thickness crack of half-length a in a linear-elastic plate with modulus E and surface energy , the critical remote stress is = .
The passage around this formula
Applied directly to metals, the criterion underpredicts fracture stress badly, because accounts only for the two new surfaces. In a metal, the overwhelming majority of the energy consumed goes into plastic work in a zone ahead of the tip — dislocation motion, void nucleation, blunting. The repair is to replace the surface energy with an effective work-of-fracture term that absorbs plastic dissipation. That substitution is conceptually cheap and physically enormous: it can raise the energy cost of crack extension by three or four orders of magnitude, and it is the reason a ductile alloy tolerates flaws that would destroy a glass of the same nominal strength.
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
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