Equation 19 · Part 1 · Why Materials Fail: Fracture, Flaws and the Inspection Interval
Symbol K_Ic
What this part means
the plane-strain fracture toughness.
Its job in the formula
c 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 K_Ic→Article meaning
Where the article explains it
Fracture then occurs when K reaches a material-specific critical value, the plane-strain fracture toughness .
The passage around this formula
Two caveats belong here rather than in a footnote. The linear-elastic parameter K is only meaningful under small-scale yielding, where the plastic zone at the tip is small relative to the crack and the remaining ligament. When it is not — thin sections, tough alloys, high temperatures — elastic-plastic parameters such as the J-integral or crack-tip opening displacement are required instead. And is measured under a standardised constraint condition; a thin plate of the same alloy will exhibit a higher apparent toughness because plane-stress conditions permit more plastic work. Toughness quoted without its measurement conditions is close to meaningless.
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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