Abstract: The fatigue crack growth behaviour of engineering small cracks under elasto-plastic condition is studied. The J-integral expression as a main control parameter of fatigue crack growth under elasto-plastic condition is presented.It is suggested that the modified ΔJeft-integral can he used as a main control parameter for engineering cracks in cyclic and plastic area of a notch. The method was verified by the experimental results.

Key words: engineering small crack, elasto-plastic condition, cyclic plastic area of a notch