Stress life

The stress life criterion is typically used for high cycle fatigue. The maximum stress level is generally very low and the number of cycles to failure is generally very high. Durability uses maximum principal stress amplitudes and corresponding mean stresses for stress life equations.

Stress life without mean stress effects

If you choose not to include the mean stress effects in the damage calculation, the stress life equation of the S-N curve is written as:

where:

• is the maximum principal stress amplitude.

• 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.

The software uses Newton's method to solve for the reversals to failure by a given stress amplitude.

Stress life with mean stress effects

If you choose to include the mean stress effect in the damage calculation, the software uses one of the following methods to update the S-N curves by including the mean stress in the stress life equation:

• Goodman method

• Soderberg method

• Gerber method

• Morrow method

where, in addition to the variables defined for the stress life equation for the S-N curve:

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

• Su is the ultimate tensile strength material property.

• Sy is the yield strength material property.

See Updating stress-based life equations for more information on the stress life equations modified for the biaxial damage propagation.

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Strain life

BWI fatigue life criterion

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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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Stress life, Simcenter 3D 2021.1 Series

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