PSI - Issue 77

J.A. Alves et al. / Procedia Structural Integrity 77 (2026) 440–446

443

σ a 1 − σ m σ y

b f

= aN

(4)

σ Soderberg =

σ a 1 − σ m

b f

= aN

(5)

σ ASME =

σ y

2

3. Results

3.1. S-N curves

The S–N curve obtained from fatigue tests for the DIN 34CrNiMo6 steel is presented in Figure 2.

Fig. 2. S-N curve

Eleven specimens reached the run-out condition at stress levels between 35% and 48% of the σ uts (350 to 440 MPa), which is close to the endurance limit of 50% reported in the literature Budynas et al. (2015). The thirteen specimens that failed between 1 . 06 E 5 and 5 . 58 E 8 cycles were fitted using the Basquin equation. The parameters a and b were found to be 732.03 and –0.0256, respectively.

3.2. Partially reversible tests and equivalent stress

Table 4 presents the results obtained from the partially reversible tests, followed by the corresponding equivalent stresses calculated using Equations 2, 3, 4 and 5.