Smith-Watson-Topper

The Smith-Watson-Topper life equation always accounts for mean stress, and is typically used for low cycle fatigue.

The Smith-Watson-Topper life equation of the S-N curve is as follows NOTE:

where:

• is the maximum principal stress amplitude.

• is the maximum principal strain amplitude.

• σm is the mean stress of the cycle along the principal axis.

• 2Nf is the number of reversals to failure.

• σ'f is the fatigue strength coefficient material property.

• b is the fatigue strength exponent material property.

• ε'f is the fatigue ductility coefficient material property.

• c is the fatigue ductility exponent material property.

The software uses Newton's method to solve for the number of reversals from the given strain amplitude, stress amplitude, and mean stress.

See Updating Smith-Watson-Topper equations for more information on the Smith-Watson-Topper life equation modified for the biaxial damage propagation.

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Fatigue life criteria

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User-defined S-N curve

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Orthotropic material fatigue analysis

Plate thickness correction

Von Mises effective amplitude approach

Material properties for durability analysis

Understanding cyclic stress-strain behavior

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Smith-Watson-Topper, Simcenter 3D 2021.1 Series

© 2020 Siemens

Dowling, N. E., “Mechanical Behavior of Materials”, Prentice-Hall, 1993, p. 670.

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