2012 Volume 53 Issue 2 Pages 256-263
The surface acoustic wave (SAW) measurement was carried out for the bolted specimen of aluminum alloy by synchronizing the ultrasonic pulsation with a fatigue cycle in the fatigue testing. The reflection from the crack increased in the loading stage of the fatigue cycle, reached maximum and then decreased in the unloading stage of the fatigue cycle. The sigmoidal intensity change of the reflection from the fatigue crack in a fatigue cycle occurred following opening/closing behavior of the crack, and the intensity took the maximum value when the crack was fully opened. The SAW intensity distribution between the crack and the bolt hole edge was also analyzed to evaluate the depth of the crack: the SAW intensity distribution after the crack root was subjected to the band-pass filtering to recognize the creeping wave (the longitudinal wave) reflected from the crack tip, and then the crack depth was estimated from the propagation time of the creeping wave from the crack root to the crack tip, which was in good agreement with the value measured in the cross section of the specimen and evaluated through the scanning acoustic analysis.
