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Steel Endurance Limit

Reference data and engineering information about steel endurance limit for material properties applications.

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Overview

The endurance limit (fatigue limit) is the maximum stress amplitude a material can withstand for an infinite number of cycles without failure.

Formula

Se′≈0.5SutS_e' \approx 0.5 S_{ut}

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Notes

  • Results are approximate and should be verified for critical applications
  • Input values should be within reasonable engineering ranges

Key Concepts

Fatigue

Failure of a material due to repeated cycles of stress or strain, occurring at stress levels below the material's yield strength. This is a common failure mode in cyclically loaded components like connecting rods, crankshafts, and turbine blades.

Creep

Time-dependent deformation of a material under a sustained load over a long period. Creep strength generally decreases with increasing temperature. For steel bolts and piping, a typical allowable creep strain specification is ~0.1%/year.

Important Material Properties

  • Yield Strength (σ_y): The stress at which a material transitions from elastic to plastic deformation.
  • Tensile Strength (σ_u or UTS): The maximum stress a material can withstand while being stretched before necking and breaking.
  • Endurance Limit (σ_e): The maximum cyclic stress amplitude a material can endure for an "infinite" number of cycles without fatigue failure. Also called the fatigue limit.

Formula: General Relationship

For many steels, a useful rule of thumb for the endurance limit is:

σe≈σu2\sigma_e \approx \frac{\sigma_u}{2}

This relationship is approximate and varies based on steel composition, treatment, and surface finish, as shown in the table above (where the ratio σe/σu\sigma_e / \sigma_u ranges from 0.41 to 0.53).

Interactive Charts

References