Issue 41

F. Berto, Frattura ed Integrità Strutturale, 41 (2017) 464-474; DOI: 10.3221/IGF-ESIS.41.58 470 In this contribution,  = 0.001 mm has been introduced in order to model quasi-pointed V-notches. The values of s have been evaluated by solving Eq. (14) numerically for different values of the mode ratio M and keeping constant  *=0.1 mm together with  =0.001 mm. The data are plotted in Fig. 2. The support factor s rises with the mode ratio M varying from M = 0 (pure mode 1) to M = 1 (pure mode 2). Whereas the rise is rather weak for the keyhole (2  = 0), it is rather strong for larger notch opening angles (2  = 60°). It has to be noted that large values of s mean large fictitious notch radii  f , i.e. uncritical strength conditions. Figure 2 : Support factor s as a function of the mode ratio M for different values of the notch opening angle 2  V ALIDATION OF THE PROPOSED FNR APPROACH FOR MIXED MODE LOADING CONDITIONS he FNR approach applied to in-plane mixed mode loading is validated by comparisons based on the FE method considering inclined V-notches with end holes (notch radius  f = s  *) characterized by different notch opening angles 2  . Geometry and dimensions of the double-V-notched plate are shown in Fig. 3 together with the applied remote boundary conditions. The values of the notch stress intensity factors K 1 and K 2 found by FE analysis for the corresponding pointed V-notches (  =0) are presented in Tab. 1 for different notch opening angles 2  and notch inclination angles  . Tab. 2 also summarises the mode ratio M , the crack propagation angle  0 and the support factor s determined by solving Eq. (14) for the specific parameters. The following parameters are considered in the numerical investigation by FE analysis: – the notch opening angle 2  = 0, 30, 45 and 60°, – the notch inclination angle  = 15, 30, 45 and 60° corresponding to a value of M varying between 0.16 and 0.73, – the microstructural support length  * varying between 0.05 and 0.3 mm, – the notch depth 2 a = 10 2 mm combined with the plate width w = 100 mm. The averaged stress has been obtained by numerical integration over the length  * of the hoop stress component (  th =   ) along the direction  0 evaluated by using Eq. (8).   * 0 0 1 σ σ , dr ρ * th r     (19) The stress concentration factor characterising the averaged notch stress over  * in pointed V-notches is defined in Eq. (20) with reference to the nominal stress  n . * 0 1 K σ dr ρ* t th n n        (20) 0 5 10 15 20 25 30 35 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Mode ratio, M Support factor, s 2 α = 60° 2 α = 45° 2 α = 30° 2 α = 0° T