A strain energy based damage model for fatigue crack initiation and growth

• Strain energy density and dislocation based fatigue damage.
• Stress-life, strain-life, and fatigue crack growth rate parameters are derived for well-known empirical relationships.
• Stress ratio effects are intrinsic to the model, and agree with the stress ratio effect proposed by Walker.
• Accurate predictions are made possible from limited test data.
• Strain-life is validated against a wide variety of materials with different processing histories and temperatures.

A strain energy based fatigue damage model is proposed which uses the strain energy from applied loads and the strain energy of dislocations to calculate stress-life, strain-life, and fatigue crack growth rates. Stress ratio effects intrinsic to the model are discussed, and parameterized in terms of the Walker equivalent stress and a fatigue crack growth driving force. The method is then validated using a variety of different metals with strain-life data and fatigue crack growth rate data available on the SAE Fatigue Design & Evaluation subcommittee database.