Monitoring Fatigue Failure of a High Strength Titanium Alloy by Acoustic Emission Techniques.

摘要

This effort describes the application of acoustic emission techniques to cyclically loaded specimens in an attempt to detect crack initiation. Both notched and unnotched fatigue specimens were cycled at 30 cps in the low cycle fatigue region, i.e., the stress level in each test was above the endurance limit of the material. Fifteen specimens, both notched (K sub T = 4.0) and unnotched, were tested. Results of the tests on the unnotched specimens indicate acoustic emission signals being recorded 30 to 150 cycles prior to fracture; and the crack initiation and propagation phases appear to be quasi-simultaneous as expected in a high strength material. The tests on the notched specimens indicate acoustic emission signals corresponding to crack initiation being recorded as long as 2500 cycles prior to fracture. As a result of this study, it appears that acoustic emission can be a useful technique for detecting material flaws prior to catastrophic failure. (Author)