A UNIFIED APPROACH OF FRACTURE AND DAMAGE MECHANICS TO FATIGUE DAMAGE PROBLEMS

The paper demonstrates how combined fracture and damage mechanics may be used to establish a fatigue damage model for polycrystalline materials in a stress-controlled test. Damage is defined as the product of the longest or "equivalent" surface crack length and the accumulated strain range, both taken with certain exponents which are found from loading conditions and failure criterion. The short to long crack transition is described through El Haddad's redefined stress intensity factor at threshold, while the failure is determined by the behaviour of the major crack. The quality of the results is encouraging. Even though some partial comparisons with already published results are presented, the model is yet to be subjected to more extensive experimental verification.