Paris Law


Definition - What does Paris Law mean?

The Paris Law is a widely accepted rule of facts in the field of physics and material science that states that the range of stress intensity of a material is characterized by the sub-critical crack growth present under fatigue.

The Paris Law is used to empirically describe the occurrence of cracking, which is a type of coating or material defect that is characterized by the chipping away of the applied paint film in small sections or entirely. This results in the exposure of the substrate metal to corrosion causing agents and eventual degradation.

Corrosionpedia explains Paris Law

When observed in pure metals, cracking is the weakening of granular or microscopic matter under a given external force application.

The basic formula of the Paris Law is:

 \frac{{\rm d}a}{{\rm d}N} = C \Delta K^m


a is the crack length

{\displaystyle {\rm {d}}a/{\rm {d}}N} is the crack growth rate

C and m are constants that depend on the material, environment and stress ratio

\Delta K is the range of the stress intensity factor during the fatigue cycle, i.e.,

{\displaystyle \Delta K=K_{max}-K_{min}}

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