Issue 42

M. Davydova et alii, Frattura ed Integrità Strutturale, 42 (2017) 170-180; DOI: 10.3221/IGF-ESIS.42.18 177 Figure 9: Circularity for five samples: blue indicates circularity for fragments in sieve with cell size 0.63 mm; red for cell size 1 mm. Figure 10: Fragment number per unit mass vs specific strain energy. Dependence of power law exponent, D , from number of fragments per unit mass, m N , has been analyzed for five materials (quartz, 2 ZrO and SiC ceramics, syminal and granite), which exhibits power law as fragment size distribution, Fig.11. Alumina fragment size distribution is the combination of power and exponential laws. The quantity D depends on the load intensity (specific strain energy E ), material structure (the porosity of 2 ZrO ceramics samples varied from 2% to 30%), and specimen pre-treatment (end polishing, strict parallel alignment, flatness of contact with the bars). As is seen from Fig.11, preliminary treatment of ceramic specimens (data within an oval) significantly reduces the spread of the distribution exponent, D . Data analysis suggests that D increases with the rising number of fragments per unit mass (with the rising load intensity). To compare fragmentation process of granite, quartz and ceramic, we construct on the same plot fragment size distribution for three samples (Fig.12) with similar values of fractal dimension D (which characterizes fragmentation process): for granite  1.95 D ; for quartz  2.09 D ; for 2 ZrO  2.03 D (with porosity 30%). The samples are indicated by arrows on Fig. 11. The value, r, on the plot shown in Fig.12 is expressed as:  3 T m r M (4) 0.65 0.7 0.75 0.8 0.85 1 2 3 4 5 Circularity, C 0.63 mm 1 mm 12                         5                        7                         10                        15 Sample number