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首页> 外文期刊>Materials Science and Engineering >Fatigue crack closure in submicron-thick freestanding copper films
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Fatigue crack closure in submicron-thick freestanding copper films

机译：亚微米厚的独立铜膜的疲劳裂纹闭合

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The fatigue crack closure in approximately 500-nm-thick freestanding copper films were investigated by in situ field emission scanning electron microscope (FESEM) observations of the fatigue crack opening/ closing behavior at three stress ratios of R=0.1, 0.5, and 0.8 in the low-K_(max) (maximum stress intensity factor) region of K_(max) ＜ 4.5 MPam~(1/2). The direct observation of fatigue cracks clarified that crack closure occurred at R=0.1 and 0.5, while the fatigue crack was always open at R=0.8. Changes in the gage distance across the fatigue crack during a fatigue cycle were measured from the FESEM images, and the crack opening stress intensity factor K_(op) was evaluated on the basis of the stress intensity factor K vs. the gage distance relationship. The effective stress intensity factor range ΔK_(eff)=K_(max)-K_(op) was then evaluated. The R-dependence of the da/dN vs. ΔK_(eff) relationship was smaller than that of the da/dN vs. ΔK relationship. This suggests that ΔK_(eff) is a dominating parameter rather than ΔK in the fatigue crack propagation in the films. This paper is the first report on the presence of the fatigue crack closure in submicron-thick freestanding metallic films.
机译：用原位场发射扫描电子显微镜（FESEM）观察了三种应力比R = 0.1、0.5和0.8时疲劳裂纹的开/闭行为，研究了大约500 nm厚的独立铜膜中的疲劳裂纹闭合。 K_（max）的低K_（max）（最大应力强度因子）区域<4.5 MPam〜（1/2）。对疲劳裂纹的直接观察表明，裂纹闭合在R = 0.1和0.5时发生，而疲劳裂纹总是在R = 0.8时打开。从FESEM图像中测量出疲劳循环过程中跨疲劳裂纹的标距距离的变化，并基于应力强度因子K与标距的关系来评估开裂应力强度因子K_（op）。然后评估有效应力强度因子范围ΔK_（eff）= K_（max）-K_（op）。 da / dN与ΔK_（eff）关系的R相关性小于da / dN与ΔK关系的R相关性。这表明在膜的疲劳裂纹扩展中，ΔK_（eff）是主要参数，而不是ΔK。本文是有关亚微米厚的独立式金属膜中存在疲劳裂纹闭合的第一份报告。

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