13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- behavior of 99.6% purity Ti foil can be found in Refs [13, 14]. Single-edge-notched specimens were cut from the foil sheets using a single-blade paper cutter. To determine if differences in specimen geometry with the same notch to width ratio would affect test results, specimens with widths of 12 mm and 10 mm were tested. The first type of specimen (Group A) had a nominal thickness of 30 �m, a width of 12 mm and an overall length of 120 mm. Group A specimens had a notch length of 1.6 mm along one edge of the specimen. A second group of specimens (Group B), with the same thickness and length, but a smaller 10 mm width and shorter 1.35 mm long edge-notch were also tested. Note that both specimen groups had the same notch-to-width ratio of 0.13. Figure 2. Close-up of the experimental setup 3.2 Experimental Procedure All fatigue experiments were performed at room temperature at a nominal stress ratio of 0.1 and loading frequency of 2 Hz. At the start of each experiment, and with a specimen installed, the distance between the rotor and magnet was adjusted to achieve the desired maximum stress level in the specimen; in parallel, the tensile mean stress (and therefore the minimum load level) was adjusted by use of a weight applied through the cable attached to the moving grip/magnet assembly. Table 1. Overview of the test conditions used to investigate the Mode I fatigue crack growth rate of thin titanium foils Type A Type B Loading mode Tension-Tension Tension-Tension Stress ratio, R 0.1 0.1 Frequency, f 2 Hz 2Hz Max stress, �max, MPa 111~124 122~ 124 Table 1 summarizes the specimens and test conditions that were used in the investigation. Two types of specimens having different width. For specimen in fatigue tests, crack length was measured with a 20X optical microscope attached to a video camera and digital micrometer. During the fatigue tests, crack length was measured at the end of each fatigue loading block. The optical microscope had a resolution of 0.002 mm and a repeatability of 0.005 mm. At the completion of testing, fracture surface characteristics were examined by optical and scanning electron microscopy. 4. Data analysis
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