Issue 46

W. Song et alii, Frattura ed Integrità Strutturale, 46 (2018) 94-101; DOI: 10.3221/IGF-ESIS.46.10 96 It should be noted that the N root K  stands for the simplified form of mode I notch stress intensity factor. In order to calculate the NSIFs and SED by EFM method, Meneghetti [20] connects the peak stress with these results to obtain closed-form expression of NSIF and averaged SED values for different modes, which are written as follows: 1 1 1 , 0, 1.38 N FE peak K K d            (7) 2 2 1 , 0, 3.38 N FE r peak K K d            (8) where d is the mean finite element size. , 0, peak      and , 0, r peak      are the stress results under polar coordination from FE analysis. The N i K values can be obtained from numerical results using very refined FE mesh patterns. Finally, SED values can be deduced by the PSM equation, which is shown as follows: 1 2 2 2 1 1 2 2 1 2 , 0, , 0, , 0 0 1 2 FE peak FE r peak eq peak e e d d W K K E R E R E                                                                   (9) The equivalent peak stress can be obtained from the following equation: 2 2 2 2 , 1 , 0, 2 , 0, ( ) eq peak w w peak w r peak c f f                  (10) where 1 w f and 2 w f are induced according to element size and the corresponding control volume for SED evaluation. It should be noted that the relationship between peak   and , eq peak   for as-welded joints can be simplified by a correction parameter w f , which is shown as follows: , w peak eq peak f       (11) For the notch opening angle 2 135    and the average FE size 0.5 d mm  , the parameter w f is obtained as 1.064. If the SED values are determined from NSIF analytical solutions, the PSM values can be calculated from Eqn. 9. 2α t L h Rc Weld toe Rc Weld Root 2a Tension Bending θ Figure 1 : Geometry of cruciform welded joints and corresponding SED geometry illustration.