Equation 9 · Part 1 · Why Materials Fail: Fracture, Flaws and the Inspection Interval
Symbol sigma_f
What this part means
the critical remote stress.
Its job in the formula
sigm is part of the quantity the equation computes from the expression on the right.
Full expression→Symbol sigma_f→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
Griffith’s criterion is an accounting statement. Extending a crack by a small increment releases stored elastic strain energy from the material that unloads around the new crack faces, and consumes energy in creating those faces. If the release exceeds the cost, extension is spontaneous and the crack runs. 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 structure of this expression matters more than its coefficients. Strength scales as the inverse square root of flaw size, so halving the largest flaw raises strength by roughly forty per cent, and doubling it costs…
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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