FATIGUE CRACK GROWTH DATA FOR VARIOUS MATERIALS DEDUCED FROM THE FATIGUE LIVES OF PRECRACKED PLATES.

Data previously obtained for a wide range of metallic materials, using thin plates containing edge cracks between 0. 3 and 7. 5 mm (0. 01 and 0. 3 in. ) long, have shown for both zero mean load and the general tensile stress cycle sigma //m plus or minus sigma //a where delta //m greater than delta //a that whether a crack grows or remains dormant can be predicted from the value of DELTA K, the range of stress intensity factor during the fatigue cycle: a critical value DELTA K//c is necessary for crack growth. Fatigue crack growth data for many materials can conveniently be represented by an equation. If this equation is integrated the initial rate of crack growth can be calculated from the total fatigue life of a cracked specimen. Data for low crack growth rates, obtained in this way from the broken plate specimens, are in good agreement with data obtained from conventional crack growth tests.