Issue 43

M. Davydova et alii, Frattura ed Integrità Strutturale, 43 (2018) 106-112; DOI: 10.3221/IGF-ESIS.43.08 110 study of porous structure of the non-deformed samples using X-ray Computed Tomography (CT) indicates that the key role in fracture and fragmentation process for studying ceramic is belong to the interparticle pores system. X- RAY C OMPUTED T OMOGRAPHY (CT) STUDY he investigation of porous structure (inter-particle porosity) of ceramic samples with initial powder porosity of 20% and 60% was done using X-ray Computed Tomography (Nikon Metrology XT H 225+180 LC, Perm State University). The CT data obtained for the sample with initial porosity of 60% (diameter is 13 mm and height is 12 mm) were represented by a stack of 1039 cross-section images of the sample, (Fig.2(a)), and for the sample with initial porosity of 20% (diameter is 8 mm and height is 7 mm) – by a stack of 1350 images, (Fig.3(a)). Dark areas in Fig.2(a) and Fig.3(a) correspond to pores. Processing of the CT data was done using the ImageJ (IJ1.46r) open source software, which allowed us to calculate the number and volume of the pores, porosity, area and perimeter of the pores in all slices and to perform 3D visualization. The results of stack processing showed that the real porosity of the sample produced from the powder with initial porosity of about 60% was 30% and the real porosity of the sample with initial powder porosity of about 30% was 2%. The cumulative pore size distribution function for the pore size greater than a prescribed value is presented in Fig.4. In the calculation we used the stack of 1350 slices in the case of 2% porosity sample and the stack of 900 slices in the case of 30% porosity sample. Gray dots indicate the pore size distribution for the low porosity (2%) sample. The pore size distribution for the sample with porosity of 30% is described by a curve consisting of orange dots and separately located big red dot. The construction of 3D images, (Fig.5 and Fig.6), of the sample pore structure allowed us to establish that volume of 374 mm 3 (red dot) is the pore cluster, and the orange curve describes the size distribution of pores that stand alone (outside the cluster). Moreover, cluster covers 98% of porosity and this is the main reason of its considerable influence on the fracture process. Note that it will be impossible to obtain the above cluster if we try to construct 3D image of the pore ensemble using a small number of slices, (10 or 20, Fig.6(a)): the formation of 3D cluster is feasible only with a sufficiently large number of slices, (more than 100, Fig. 6(b)). Figure 4: Cumulative pore size distribution functions for samples with porosity 2 % and 30% C ONCLUSION he experiments on dynamical fragmentation of ZrO 2 ceramics showed, that the initial porosity of the samples has effect on the shape of the stress-strain curves, (Fig. 1(b)), the scatter of the power law exponent of the fragment size distribution, (Fig. 2(b) and Fig.3(b)), and the type of the time interval distribution function, (Fig. 2(c), Fig. 3(c)). T T