ABSTRACT
The ultrasonic fatigue test method differs from the conventional fatigue test method that has frequency limited to 100 Hz of cyclic stressing of material. The frequency of ultrasonic fatigue testing ranges from 15 kHz to 30 kHz, with a typical frequency being 20 kHz. With this high frequency, the time and cost to obtain a fatigue limit (if one does exist) or crack growth rate threshold data can be dramatically reduced. For instance, the test time for 107 cycles is within 9 minutes by ultrasonic method, while conventional fatigue testing at 100 Hz will take about 12 days. For even higher cycles-for instance, 109-the ultrasonic method requires only 14 hours, whereas it would take more than 3 years at 100 Hz for a single specimen. The ultrasonic method also provides a reliable way of testing at the extremely small rates of crack growth in the threshold regime, for example in the range of 109 mm=s to 1011 mm=s.
