In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.
ASTM defines fatigue life, Nf, as the number of stress cycles of a specified character that a specimen sustains before failure of a specified nature occurs.
Historically, most a...
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In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.
ASTM defines fatigue life, Nf, as the number of stress cycles of a specified character that a specimen sustains before failure of a specified nature occurs.
Historically, most attention has focused on situations that require more than 10 cycles to failure where stress is low and deformation primarily elastic.
In high-cycle fatigue situations, materials performance is commonly characterised by an S-N curve, also known as a Wöhler curve . This is a graph of the magnitude of a cyclical stress (S) against the logarithmic scale of cycles to failure (N).
S-N curves are derived from tests on samples of the material to be characterised (often called coupons) where a regular sinusoidal stress is applied by a testing machine...
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