13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- Figure 6: Magnified 3D tomographic images showing the range of sizes and shapes of voids quantified below the fracture surface. 3.2 Quantification results The variation of the void volume fraction as a function of distance below the fracture surface in the CT specimens is illustrated in Figure 7. The data were calculated by quantifying the average VVF for cylindrical cells of 100µm in height and starting from the fracture surface. The VVF for each specimen location (0mm, 0.5mm…) was averaged over all three specimens (B, C and G) to obtain an average VVF for the first 100µm below the fracture surface and every 100µm down to 3.6mm. The presence of voids ahead of the final crack tip was also taking into consideration. Samples B and G had crack extensions of approximately 2mm, the extractions beyond the crack front were averaged separately and labeled as “beyond crack tip” on the plot. Figure 7: VVF as a function of distance below the fracture surface The following observations can be made: • The void volume fraction is highest close to the fracture surface and reduces to zero as a function of distance below the crack. A maximum VVF of 9.75 × 10-3 is measured
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