A BLUNT NOTCH EXTENDED COMPACT TENSION (BN-ECT) SPECIMEN FOR THE STUDY OF SHORT AND LONG CRACK PROPAGATION

摘要

Linear-elastic fracture mechanics methods are routinely used for fatigue life prediction of metallic components and structures. It is now accepted that fatigue cracks initiate from defects, grow as small cracks (up to 1 mm) for a substantial fraction of the total fatigue life and then propagate as long cracks up to fracture. Pearson1 was the first to point out that the linear-elastic stress intensity factor range (A/0 failed to correlate the growth rates of very small (0.006 to 0.5 mm) and large fatigue cracks in an aluminum alloy. Since the mid-1970s, numerous investigators have confirmed that small cracks grow, in some materials and under certain loading conditions, at values of &K below the large-crack threshold and also that they can grow faster than large cracks at the same A/C level above the threshold.