Issue 49

S.A.G. Pereira et alii, Frattura ed Integrità Strutturale, 49(2019) 412-428; DOI: 10.3221/IGF-ESIS.49.40 423 In his presentation of the Strain Energy Density (SED) criterion, [18], Sih found that this was closer to the experimental points obtained in the earlier experiments of Erdogan and Sih, [2]. In the present work the same situation was verified, Fig. 12, although the circle seems to be an even better approximation of the presented experimental points. T HREE POINT BENDING RESULTS or the 3-point bending tests, K Ic =1.4 MPa m was obtained for the non-standard specimen (two tests), and K Ic =1.5 MPa m for the specimens with standard geometry (two tests). The average K Ic =1.45 MPa m was considered. The results obtained for the 3-point bending mixed mode experiments are presented in Tab. 1. SPECIMEN I K     MPa m     MPa m II K 0 φ [º] 0 expected φ [º] 9 1.451 0.565 58 69 10 0.889 0.960 52 43 Table 1 : Values of K I and K II , as the angles expected according to the MTS criterion, and the ones obtained. T - STRESS RESULTS ig. 13 a) shows the values of T -stress obtained in Abaqus software for the specimens tested in 4-point bending. Fig. 13 b) shows the values obtained in three point bending tests for a range of / a W values. In Fig. 13 a) the value of the T stress made non-dimensional using Eqn. (7) is presented as a function of the mixed mode parameter M e . The correlation value between the experimental points and a linear regression is also presented. Fig. 13 b) shows the increase of T values with the increase of the / a W ratio. Eqn. (15) was used to evaluate the T -stress. The simulations were performed with linear quadratic elements (reference CPS4 in Abaqus) with 1 mm element length. Figure 13 : a) 4-point bending test specimens, b) 3-point bending simulation 0.2< / <0.5. F F