13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- 4~5 reported for other metals [5,6]. Figure 5. Crack growth length versus fatigue cycles for 30 �m thick single-edge notch Ti foil specimen foil specimens subjected to tension-tension fatigue at RT. The data scatter is very limited for similar experimental conditions. Figure 6. Cyclic crack growth rate data for 30 �m thick Ti foil specimens subjected to tension-tension fatigue loading at room temperature. The typical crack growth path is observed after specimen failure; these images show the side view of the flat fracture surface in crack growth region II, and the corrugated facture surface in the high crack growth rate region prior to failure. The crack growth was generally perpendicular to the tensile loading direction until a final shear slip forms during failure. According to experimental measurements, the stable crack growth length was around 7~8 mm, which covers two crack growth regimes. For instance, in crack growth region II, the applied �K is lower than 30 MPa m1/2 and the crack growth rate is less than 10-6 m/cycle. In this crack growth regime, the crack growth rate vs. applied �K can be described by the Paris relationship with the exponent value m between 4~5. With the crack growth length increasing, the applied �K increases and the crack propagation fit in very high crack growth regime (crack growth region III). The angle of the “knife edge” fracture surface ranges between 44° and 48°. To evaluate the morphological characteristics of Ti foil fracture
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