Issue 33

V. Veselý et alii, Frattura ed Integrità Strutturale, 33 (2015) 120-133; DOI: 10.3221/IGF-ESIS.33.16 124 Several examples of the nodal selection are shown in Fig. 3 – the selected FE nodes are displayed as dots within the modelled specimen body. nodal distance length interval constant distribution nodal distance length interval x 2 distribution nodal distance length interval e x distribution a) Angle selection with 90° wedge, initial angle 10°,  = 0.45 b) Angle selection with 90° wedge, initial angle 45°,  = 0.3 c) Angle selection with 90° wedge, initial angle 80°,  = 0.55 d) Angle selection with 180° wedge, initial angle 0°,  = 0.7 Distance selection with: e) constant, f) quadratic, and g) exponential distribution Figure 2 : Variants of selection of nodes within an angle range and distance from the crack tip. a) constant distance distribution, 90° wedge, initial angle 10°,  = 0.3 b) exponential distance distribution, 90° wedge, initial angle 45°,  = 0.5 c) quadratic distance distribution, 90° wedge, initial angle 80°,  = 0.3 d) constant distance distribution, 180° wedge, initial angle 0°,  = 0.5 Figure 3 : Examples of performed nodal selection within the FE model. R ESULTS AND DISCUSSION Geometry functions ig. 4 shows the results from the ODeMApp procedure, the dimensionless values of Williams terms coefficients g n (for 1;12 n  ) as functions of the relative crack length  determined for all considered variants of nodal selection. It can be seen that trends of the g -functions for individual nodal selection variants are not uniform, especially in the cases of short and long cracks (the short cracks are represented by  < 0.2 and the long ones by  > 0.8). In the case of short cracks the 90°(10°) variants significantly differ from the rest. On the other hand, the 90°(80°) variants exhibit different trends in the long cracks region, especially for n > 6 (see Fig. 4g to l). The nodal distance distribution function also plays a role; there can be seen a substantial difference between the exponential distribution in comparison F 90° 10° 45° 90° 90° 180° 80° 0° a) b) c) d) e) f) g) a) b) c) d) qua , 90° (80°) exp , 90° (45°) con , 90° (10°) con , 180° (0°)