PSI - Issue 66

Venanzio Giannella et al. / Procedia Structural Integrity 66 (2024) 71–81 Venanzio Giannella et al./ Structural Integrity Procedia 00 (2025) 000 – 000 7 reference to a S355 steel tested under pure mode I loading with R = 0.1 (see Table 2) and they have been given as input to FRANC3D® in order to compute the related crack growth rate ⁄ and in turn the fatigue life of specimens. ( ) m I da C K dN =   (4) Table 2: Parameters of the Paris curve, taken from (Pedrosa et al. 2022); units are [MPa] and [m] for stresses and lengths respectively. Material S355 structural steel Nominal load ratio, R 0.1 Crack-growth rate da/dN m/cycle Paris’ coefficient C 7.27∙10 -13 Paris’ exponent m 3.54

77

ΔF

DOFs coupled to simulate the grips

~120k C3D10 elements

c i = 0.1 mm

Semi-circular pre-crack with a i = 0.1 mm introduced in the experimental crack initiation location

a i = 0.1 mm

Fig. 5. FE mesh pattern adopted in the crack propagation simulations. The figure reports as an example the longitudinal joint geometry with idealized weld ends. The figure highlights also the constraint and loading conditions.

Once defined the initial crack size, shape and location, this is inserted in the uncracked FEM model (see Figure 5) involving a localised remeshing to accommodate such a user-defined crack. Afterwards, the crack propagation simulation is performed by repeating the following steps: 1. the FE model is solved in the Abaqus® environment; 2. the mode I, II and III Stress Intensity Factors (SIFs) are calculated by FRANC3D® along the crack front by taking advantage of M -integral method; 3. the crack propagation direction is predicted by FRANC3D® by means of the Maximum Tangential Stress (MTS) criterion (Erdogan and Sih 1963);