PSI - Issue 13

Daniel Vavřík et al. / Procedia Structural Integrity 13 (2018) 1967 – 1970 Author name / Structural Integrity Procedia 00 (2018) 000–000

1969

3

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(1)

where σ y is the nominal yielding stress, E is Young’s modulus and m=2 for plane strain condition, see Anderson (2005).

Fig. 1. Visualization of the vertical slice of the reconstructed micro-CT measurement (resolution 15 �m) showing the crack growing from the notch (left). Crack path is hard to identify due to stone microstructure. However, the crack/FPZ shape is well recognizable in the differential CT (right). 3. Results Local COD progress in vicinity of the identified crack path is plotted in Fig. 2. COD values have approximately linear dependence on the distance from the crack tip. Change in this behavior is assumed at the crack tip – leading to estimated CTOD = 3.4  m. Similarly, it is assumed that drop-down of the “COD” is related with end of the local FPZ. The length of the FPZ was therefore estimated to be equal to 2.7mm. By inspection of the CT slices, the local increse of the “COD” behind crack tip is connected with a larger particle in the crack path direction. Note that in contrary to the crack path, the FPZ is visible only partially in the CT slice. On the basis of the estimated CTOD, local fracture toughness was calculated yielding K Ic = 0.6 MPa/m 0.5 with  c = 5 MPa and E =10 GPa. Similar K Ic value can be found in Spagnoli at all. (2015).