Issue 49

S.A.G. Pereira et alii, Frattura ed Integrità Strutturale, 49(2019) 412-428; DOI: 10.3221/IGF-ESIS.49.40 419 Figure 7 : left, 4-point bending; right, 3-point-bending (mixed-mode). Figure 8 : left, 3-point bending (ASTM E399); right, 3-point bending (non standard). F OUR - POINT BENDING ig. 9 shows the experimental results obtained in laboratory for different ratios of / I II K K . These tests were also performed using an MTS servo-hydraulic machine, under the same displacement speed and control mode as mentioned above. A simple representation of K I / K II versus  0 , according to the Maximum Tangential Stress (MTS) criterion was obtained from Eqns. (17) and (18), presented in Fig. 10 a). In Fig. 10 b) the points obtained from the substitution of the maximum load recorded per specimen in Eqns. (1) and (2), are compared with the analytical curves. 1 3cos  sin I II K K     (17)   1 0.92729  53.13 I II K rad K         (18) The experimental values can still be plotted against a theoretical curve that represents the kink angle as a function of the pre-crack angle and the mixity parameter e M , once again according to the MTS criterion, Fig. 11. This curve is obtained from Eqns. (19) and (20). e M is a trigonometrical function I K and II K presented by [3]. F