Issue 50

P. Livieri et alii, Frattura ed Integrità Strutturale, 50 (2019) 613-622; DOI: 10.3221/IGF-ESIS.50.52 618 By setting 2 2 x y    , w x i y   , Q  is equivalent to:   0 1 1 Re Im r r r r r A A w B w        (23) For example, if ( ) 1 cos R A     with 1 0 2 A   , the condition Q  becomes 2 0 Ax      (24) Finally, the equation for SIF assessments can be rewritten as: ( ') ( , ') ( ') ( ) I I K Q K Q Q D O        (25) with ( ) 2 ( , ') jk ij I Q B K Q k       (26) (for more details see reference [21]). N UMERICAL EXAMPLE n order to verify the accuracy of the proposed procedure, now we analyse two reference cases: the first is a circular defect at the weld toe, the second is an irregular crack under uniform tensile loading. Fig. 4 shows a welded T-joint under tensile nominal stress. In Fig. 4, a disc is put at the weld toe of the welded T-joint and the stress intensity factor is evaluated by considering the asymptotic stress field as reported in [22–23]. The crack lies along the bisector at variable distance d from the weld corner. The T-joint is subjected to a tensile nominal stress, but along the bisector of the weld corner the hoop stress assumes the simple form: 326 .0 399 .0   rK N   (27) where K N is the Notch Stress Intensity Factors of mode I and it is equal to 2.46 MPa mm 0.326 for a nominal tensile stress σ n of 1 MPa. This value was calculated by means of a careful notch stress analysis by considering the T-joints of Fig. 5 as three- dimensional components without taking into account the effects of the width as analysed in [24]. Figure 4 : Welded T-joint under tensile loading. I