Issue 53

E. M. Strungar et alii, Frattura ed Integrità Strutturale, 53 (2020) 406-416; DOI: 10.3221/IGF-ESIS.53.31 410 Figure 5: The diagram of samples deformation at uniaxial tensile test. The work deals with structurally non-homogeneous solids, and a change in the size of the sample and the hole affects the bearing capacity, it can be assumed that it is attributed to the material structure. In this regard, a diagram of dependence of the limiting value of the average stress on non-homogeneity parameter was obtained for samples with different hole diameters (Fig. 6). Figure 6: The diagram of dependence of the limiting value of the average stress on non-homogeneity parameter and the image of destroyed sample with fiber breakage and matrix delamination areas. Non-homogeneity parameter was introduced for quantitative analysis, it depends on the hole diameter and the size of the structural element and is calculated by the formula ξ =d/ δ . The size of the structural element for this material was δ = 4 mm (weave width). The dependence of the specific strength characteristics on the specified parameter is shown in Fig. 6. It is seen, that a critical value of non-homogeneity parameter can be introduced ξ critical = 1,5. Conditionally, the diagram in Fig. 6 can be divided into two sections: section I ( ξ ≤ ξ critical ) and section II ( ξ < ξ critical ). When the values of the structural non- homogeneity parameter are less than the critical value, the limiting values of the average stress decreased (Section I); the obtained data indicate the presence of a scale effect. When the structural non-homogeneity parameter is greater than the critical value for the specific material, there is practically no change in the limiting values of the average voltage (section II), while there is no scale effect. The use of the video-system makes it possible to use the deformation fields in the vicinity of the concentrator. The analysis of longitudinal strain ( ε yy ) distribution on the surface, along the line L drawn from the hole to the edge of the plate