Issue 41

E. Tolmacheva (Lyapunova) et alii, Frattura ed Integrità Strutturale, 41 (2017) 552-561; DOI: 10.3221/IGF-ESIS.41.65 558 The investigation of CT images of deeper slices revealed the presence of comminuted area in the vicinity of the indenter, which can be distinguished by the local absence of pores and higher brightness corresponding to higher local density of the material. Fig. 8 presents 3D image of the inner porous structure obtained for sample no. 4 of Fig. 6 using the ImageJ visualization software package. For easy reading of the graph the forepart of the sample is veiled and the sample is rotated in such a way that the indentation direction coincides with the blue arrow (Fig. 8). We determined the depth of this comminuted area H for different values of the applied load, which was also found to be a linear dependence (Fig. 9). However, the width of the comminuted area W , calculated in plane perpendicular to the indenter penetration direction, changes non-monotonically from the surface to the deeper layers (Fig. 10). The initial interval of linearly increasing W corresponds to the indenter conical shape, whereas the following points correspond to the comminuted area in the vicinity of the indenter tip. Decay of width of comminuted area is associated with vanishing of the comminuted zone deep within the material. Figure 8 : 3D image of inner structure of the sample no. 4 of Fig. 6. Blue arrow indicates the direction of indentation and the bottom of the cavity. 1- comminuted area, 2 – cracked area, 3 - undisturbed area. Inset: xy projection of the slice. The forepart of the sample as well as surrounding non-deformed material is veiled for easy reading of the graph. Figure 9 : Depth of compressed area as a function of the maximum applied load.