PSI - Issue 13

A. Vedernikova et al. / Procedia Structural Integrity 13 (2018) 1165–1170 Author name / Structural Integrity Procedia 00 (2018) 000–000

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(ultimate tensile strength) at some distance l from the stress concentrator and the value of this distance should be bigger than critical spatial scale which coincides with the half of the critical distance.

a)

b)

c)

11  over the specimen; (c) Evolution of the spatial distribution of 11 p over

Fig. 2. (a) Finite-element mesh of the specimen; (b) Distribution of

the cut plane along the loading direction.

a)

b)

c)

Fig. 3. (a) Values of p 11 versus distance from the notch ( / 2 c L L  ). Evolution of the spatial distribution of 11 p component in the cross-sectional area perpendicular to the loading direction: (b) uniform distribution; (c) localization. 5. Results of material structure investigation To propose a possible explanation of the link between the critical distance value and the characteristic length of fracture surface structure we examined carried out an optical microscope investigation of fracture surface of titanium Grade 2. Figure 4 shows the fracture surfaces of a specimens with U-shaped and V-shaped stress concentrators at fourfold magnification, respectively. The analysis of data presented in figure 4 shows the existence of two areas with a different macro-relief on the fracture surface. A red line in figure 4 separates the areas. In the annular region located near specimen surface has relatively smooth macro-relief. While the relief of the central specimen area is strongly pronounced. A rough structure with ridges and macro-cracks was observed. The characteristic size (along the radius direction) of the transition zone coincides with the value of the critical distance. c    11 on the spatial scale

a

b

Fig. 4. Photos of the fracture surface of a specimens with U-shaped (4a) and V-shaped (4b) stress concentrators at fourfold magnification.