Issue 45

L.M. Viespoli et alii, Frattura ed Integrità Strutturale, 45 (2018) 121-134; DOI: 10.3221/IGF-ESIS.45.10 123 To provide a comparison between the results provided by the different techniques, a certain geometry has been assumed as reference. That is a non-load carrying T-shaped joint, constituted by a plate and a welded longitudinal attachment. The weld fillet originates a V-notch of opening angle 135º, constituting the critical point for this class of joint. The joint has been produced in six specimens and fatigue tested to longitudinal traction with load ratio R=0. The nominal dimensions of the specimens are reported in Fig. 1. N OTCH S TRESS I NTENSITY F ACTORS AND S TRAIN E NERGY D ENSITY t is necessary, in the opinion of the authors, to present a brief overview on the analytical basis of the NSIFs and SED [4,5,9]. The weld toe of a joint constitutes practically a lateral open notch, which may be, according to the radius at the notch tip, sharp or blunt. The stress field is singular at the tip, with singularity exponent function of the notch opening angle. The exponents for the symmetric and the skew-symmetric stress field are, respectively, the William’s eigenvalues [6] defined by:           q q 1 1 sin sin 0           q q 2 2 sin sin 0 Being q related to 2α by 2α = π (2 – q). The linearity of the problem allows to write the stress field as the sum of two components, each one defined but for two constant values a1 and a2. The stress components for the opening mode (Mode I fracture) are:                                                                                                   r r r a 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 cos 1 cos 1 3 cos 1 1 cos 1 1 sin 1 sin 1 And those for the sliding mode (Mode II fracture) are:                                                                                                   r r r a 2 2 2 12 2 2 2 2 2 2 2 2 2 2 1 sin 1 sin 1 3 sin 1 1 sin 1 1 cos 1 cos 1 being:                      i i q q 1 sin 1 / 2 sin 1 / 2 where i is 1 or 2 depending on the mode considered. The symmetric and skew-symmetric components are uncoupled along the notch bisector direction θ = 0, with the shear component τrθ depending only on the sliding mode while the σr and σθ components depend only on the opening mode. Along this particular direction it is possible to extend the idea of Stress Intensity Factor to open notches, originating the sequent definition for Notch-Stress Intensity Factor:            r K r 1 1 1 0 0 2 lim            r r K r 1 2 2 0 0 2 lim I