13th International Conference on Fracture June 16–21, 2013, Beijing, China Observation was performed on the laminography instrument installed at ID19 at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). The axis inclination angle used was around 30° and a white beam was set up, centered around a 60 keV X-ray energy. The scanned region of interest (ROI) was about 1 mm3. (a) (b) Figure 3: (a) the sample used in in-situ laminography observation and loading direction. (b) Schematic demonstration of stepwise loading applied during the in-situ observation. 3. 2D in-situ visualization of damage evolution from a cut-edge The figure 4a-f shows the reconstructed 2D laminography sections at different loading stages. Ferrite and martensite phases have the same grayscale due to the fact that the phases have similar attenuation coefficients. They are shown in gray and the initial internal voids can be seen in black in the matrix (ferrite+martensite). Figure 4a shows the material at delivery state after punching in the L-T plane. The 2D sections (figures 4a-f) were taken from the burnish zone. The circular punched hole can be seen at the bottom of the sample. Some artifacts can be observed (cf [12]) that do not influence the segmentation of the voids (figure 5). The 2D sections (figure 4a-f) were taken from the burnish zone. A geometrical defect can be seen in the cut-edge. Figure 4c, taken from at loading step corresponding to a CMOD equal to 2 mm, shows that a microcrack initiates on the cut-edge close to the geometrical defect. These observations of ductile crack propagation from a cut-edge and coalescence with internal porosities have never been seen before using SRCL with such a high level of details. The coalescence sheets are inclined by 45° compared to the L-direction. Other microcracks initiate from cut-edge but the crack located close to the geometrical defect grows faster. This is consistent with the increased level of stress triaxiality caused by the geometrical defect. -4-
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