Equation 20 · Part 2 · Why Materials Fail: Fracture, Flaws and the Inspection Interval
Symbol N
What this part means
N occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.
Its job in the formula
N occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.
Full expression→Symbol N→Article meaning
The passage around this formula
The governing correlation is empirical. Paris and Erdogan proposed that crack growth per cycle depends on the range of the stress intensity factor over the cycle: . The parameters C and m are fitted, not derived, and depend on environment, frequency, temperature and stress ratio. A mechanics review that proposes a generalised form of the law opens by conceding that “fatigue life prediction is still very much an empirical art rather than a science”, and notes that the power law holds only in an intermediate regime, deviating near the threshold below which cracks do not propagate and again in the fast-growth stage approaching final fracture [ 6 ] . The same review sets out…
Learn the underlying idea
A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.
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Sources cited in the surrounding passage
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