APPLICATION OF THE CYCLIC J-INTEGRAL TO FATIGUE CRACK-PROPAGATION OF A1 2024-T351

In this investigation, an experimental/numerical study of the cyclic J-integral, DELTA-J, is carried out in order to more clearly explain the meaning of this parameter for fatigue crack growth studies. Constant amplitude fatigue tests with two R-ratios (R congruent-to 0.05 and R congruent-to 0.5) are performed on compact tension specimens fabricated from Al 2024-T351. A simulation of tests is carried out numerically by means of the finite element method with the material modeled to be elasto-plastic. From the numerical results, values of DELTA-J are calculated from both a path independent integral and load vs load-line displacment data. Comparisons between these values, as well as to those determined from experimental data, are seen to be reasonable. The parameter DELTA-J, is seen to properly correlate the crack growth rate under elastic and small scale yielding conditions.