PSI - Issue 79

228 Santi Marchetta et al. / Procedia Structural Integrity 79 (2026) 224–232 When doing a fatigue assessment, the cyclic average SED ̅ for a given load level can be evaluated by finite element analysis as the ratio between the strain energy accumulated within the control volume and the volume itself: ̅ = 0 0 (3) In which 0 is the circular sector of radius 0 . Once evaluated, all the SED values and their corresponding experimental number of cycles to failure are compared with the SED fatigue design scatter band for the investigated material. The approach can be regarded as safe for fatigue design purposes if the obtained values fall within the scatter band. Fig. 3 illustrates an example of a SED fatigue scatter band, in this case derived for welded structural steel. The band was proposed by Livieri & Lazzarin, (2005) on the basis of a comprehensive dataset including more than 900 fatigue results obtained from welded steel joints, all of which failed at the weld toe.

P.S. 97.7%

Fig. 3. Fatigue life in steel welded joints as a function of the local average SED (Livieri & Lazzarin, (2005)).

2.3. Experimental setup Table 1 reports the materials’ elastic properties while Fig. 4 displays the experimental setup originally proposed by Taylor, (2002) for steel welded joints and later adopted by Corigliano & Palomba, (2025) for titanium joints. The horizontal lower plate is clamped with two bolts while the vertical plate is loaded with an additional clamp. As previously mentioned, both the steel and titanium joints exhibit a weld toe opening angle of 135°, which ensures Mode I crack propagation. Finally, Fig. 5 reports the dimensions of the investigated joints and the experimental data for steel (a) and titanium joints (b). In both cases, the load was applied with a ratio of R= 0.1. Finally,

Table 1. Materials’ properties.

Material

Young’s Modulus [GPa]

Poisson’s ratio

Steel

200 110

0.3 0.3

Ti6Al4V alloy