PSI - Issue 25

Pietro Foti et al. / Procedia Structural Integrity 25 (2020) 201–208 Pietro Foti, Filippo Berto / Structural Integrity Procedia 00 (2019) 000–000

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Dealing with blunt notches, as with the geometries analysed in the present work, the application of the SED method to this kind of geometry has been evaluated Lazzarin et al. (2004; 2005a and 2005b) amd Yosibash et al. (2004). It is important to do some considerations about the control volume that, under mode I loading, assumes a crescent shape, with 0 R being its maximum width along the notch bisector line, differently from sharp V notches. In this case, the control volume is given by the intersection between the component and a circle of radius 0  r R centred on the notch bisector, between the notch edge and the notch-fitting radius centre, at a distance r from the notch edge as shown in Fig 3 a) for rounded V-notches and in Fig. 3 c) for U-notches. The use of the SED method under mixed-mode loading has been studied by Gómez et al. (2007; 2008 and 2009), Lazzarin et al. (2003 and 2013) and Berto et al. (2007 and 2012) the maximum elastic stress is out of the notch bisector line and its position along the notch edge is a function of mode I and mode II stress distributions. In this case, the control volume is no longer centred with respect to the notch bisector, but rigidly rotated with respect to it and centred on the point where the SED reaches its maximum value, following, essentially, the mode I dominance concept as shown in Fig 3 a) for rounded V-notches and in Fig. 3 c) for U-notches.

    2 / 2 2 r          ); b) blunt V-notch under mixed mode r   ); d) U-notch under mixed mode loading ( / 2 r   ) / 2

Figure 3:Control volume for: a) blunt V-notch under mode I loading (

    2 / 2 2 r          ); c) U-notch under mode I loading (

loading (

3. FE Analysis In order to summarize the fatigue tests considered in this work in terms of averaged SED, the geometry of the specimens was modelled through the software Ansys APDL. To obtain more efficient analyses and minimize the computational time, the symmetries of the details considered were exploited modelling only half of it with a 2D model as shown in fig. 4. The appropriate symmetry condition where used to carry out the simulation. However, it is important to underline that, in order to apply the SED method to the detail analysed in the present work, two different numerical simulations are required. In the first simulation the point of maximum of the first principal stress has been evaluated. The position of this point is used as an input for the second simulation to build the control volume. In Fig. 4, it is possible to see that the coordinate of the point of maximum of the first principal stress acquired