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Equation 20 · Part 5 · Why Materials Fail: Fracture, Flaws and the Inspection Interval

Symbol m

dadN=C (ΔK)m.\frac{\mathrm{d}a}{\mathrm{d}N} = C\,(\Delta K)^{m}.
mm

What this part means

fitted, not derived, and depend on environment, frequency, temperature and stress ratio.

Its job in the formula

m is an input to the expression that computes the quantity on the left.

Where the article explains it

The parameters C and m are fitted, not derived, and depend on environment, frequency, temperature and stress ratio.

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: dadN=C (ΔK)m\frac{\mathrm{d}a}{\mathrm{d}N} = C\,(\Delta K)^{m}. 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…

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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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