Ultrasonic Fatigue Testing of Aluminum and Magnesium Alloys

鋁及鎂合金的超音波疲勞試驗

陳永增(Yeong-Jern Chen) ； 魏百盛(Bai-Sen Wei) ； 許文濃(Wen-Nong Hsu)

《中國機械工程學刊》 29卷4期 (2008/08) Pp. 299-308

https://doi.org/10.29979/JCSME.200808.0004

摘要

超音波疲勞試驗主要在頻率20 kHz的高頻振動下使材料發生疲勞破壞，不但可大幅縮減疲勞試驗的時間，同時可克服傳統疲勞試驗無法預估材料在高頻使用時發生高應變率疲勞破壞的狀況，因此超音波疲勞試驗的發展在材料性質測試上值得重視。
超音波疲勞試片必需與試驗系統形成共振才會發生疲勞試驗，因此共振試片設計是超音波疲勞試驗是否成功的主要關鍵。近年來汽車、航空及3C產業的蓬勃發展使得鋁及鎂合金的使用日益普遍，因此本研究針對2024鋁合金、AZ91D及AZ80鎂合金共振試片的幾何外形及尺寸加以設計，以提供超音波疲勞試驗實務測試之用。本研究對於超音波疲勞共振試片的設計，捨棄傳統經驗法則的設計模式，而以有限元素法分析來輔助設計，最後透過實際的超音波疲勞試驗加以驗證，並測定鋁及鎂合金之超音波疲勞性質，以及進行疲勞斷面的觀察與分析。

並列摘要

An ultrasonic fatigue testing device, capable of fracturing the tested materials at an ultrasonic frequency of 20 kHz is demonstrated. Such a testing device, operating at high frequencies, not only reduces the testing time to far less than that of conventional testing machines, but may also better simulate extremely high-frequency loading and the strong influence of strain rate on the fatigue behavior of the tested materials. This makes the development of an ultrasonic fatigue testing device for testing materials is an important endeavor.
To induce fracturing during the ultrasonic fatigue testing process the testing device needs to be set to the resonant state of the specimen. Therefore design of the most effective resonant specimen is the key point for ultrasonic fatigue testing. In this study we designed 2024 aluminum alloy and AZ91 and AZ80 magnesium alloy specimens with the most suitable geometry and dimensions for application to practical engineering. We did not base the design of the ultrasonic resonant specimens only on the engineer's experience and judgment; rather we used a finite element method to assist the design process. The practicality of the specimens was verified by ultrasonic fatigue testing. The ultrasonic fatigue properties and fractography analysis of the specimens are also investigated and discussed.

並列關鍵字

ultrasonic fatigue ； resonant specimen ； finite element method ； aluminum alloy ； magnesium alloys