On fatigue crack growth and stable tearing

An experimental and analytical investigation has been performed to examine the effect of concurrent fatigue cycling and stable tearing on the crack growth fracture resistance of EN3A steel at 3600C. The steel was tested in the as-received and hardened conditions, hardening being achieved by pre-cracking at a load comparable to the elastic limit of the test specimens. For each condition of the steel, resistance curves are obtained both with and without concurrent fatigue cycling. A significant increase in the crack growth rates occurred as a result of concurrent fatigue cycling. The rates are in reasonably close agreement with the values predicted from the sum of the fatigue crack growth and stable tearing components. The J-estimation formula of Ainsworth is used to demonstrate that there is no interaction between stable tearing and fatigue in the tests for the steel in the as-received condition. (author)