湿潤環境におけるアルミニウム合金の超低速疲労き裂進展挙動の検討

抄録

The Ultrasonic fatigue tests were performed at 20 kHz for three types of aluminum alloys under high stress ratio in order to clarify the effect of humid environment on the characteristics of fatigue crack growth. The test results showed that cracks grew at a very slow growth rate under a low stress intensity factor range regardless of the materials and the stress ratio. Based on the observation and elemental analysis by SEM, it was found that the fracture surface, where crack grew at a very slow growth rate, covered with aluminum oxide. Observations on the specimen surface showed that some powders were developed around the crack during the testing. These results suggest that the ultra slow crack growth behavior in humid environment occur by peeling off the oxide film near the crack tip due to the cyclic loads.