超声加速疲劳实验研究

通过20kHz压电超声加速疲劳试验机对多种金属材料进行测试，实验地证明了超高周疲劳裂纹往往从试件内部萌生的机制，试件在超过10^7周应力循环后继续发生破坏，研究还发现，材料超高周疲劳的S－N曲线可以表现出另两种有别于传统规范的10^7 极限型，即持续下降型和阶梯下降型。还总结了近年来超声疲劳的研究进展，结合作者多年国外的研究工作，着重从加速超声试验设备的发展，多种材料及条件下的实验研究结果及其重要结论作了概述与讨论。

Accelerated Fatigue Testing by Ultrasonic loading

To clarify the subsurface crack initiation mechanism in gigacycle fatigue, several alloy steels were tested at very high numbers of cycles through ultrasonic accelerated fatigue test at 20 kHz. The specimens continued to fail over 10 7, even 10 7 stress cycles. A continuously decreasing stress life response and a stepwise shape in S-N curve was observed. In this study, investigations in the area of gigacycle fatigue are reviewed with special emphasis on the development of ultrasonic accelerated testing equipments, the large amounts of test results and the main conclusions in gigacycle fatigue. Standardization of gigacycle fatigue design and test concept is required to make accelerated fatigue testing by ultrasonic frequency more universally accepted.