A continuum damage mechanics model which accounts for the coupling effect among plastic damage, fatigue damage and creep damage is proposed. The model is capable of identifying the beneficial effects of pre-hardening on fatigue life of metals. It is shown that the proposed damage model can predict the fatigue lifetime of RS50 steel subjected to single pre-hardening load and double pre-hardening load yielding satisfactory agreement with experimental results. The model can also be applied to analyze the non linear damage accumulation behavior of two-level fatigue tests.
