PSI - Issue 79

Déborah de Oliveira et al. / Procedia Structural Integrity 79 (2026) 248–258

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This anomaly may be attributed to a defect or irregularity in the specimen, which might not reflect the true fatigue resistance of the material.

Fig. 3. S-N curve for vertical specimens.

Fig. 4. S-N curve for horizontal specimens.

Another noteworthy observation is the considerable variation in the number of cycles to failure at the same stress level, as seen with specimens V6 and V1. Both were tested at 302.4 MPa; however, V6 survived approximately 3.12 times more cycles than V1. Such variability is likely due to deviations from geometric tolerances and surface roughness standards, potentially causing premature material failure. Ermakova et al. (2023) also conducted uniaxial fatigue tests on ER70S-6 wire samples deposited via CMT, using a frequency of 20 Hz, a load ratio of R = 0.01, and specimens with a circular cross-section. From these tests on samples extracted in both vertical and horizontal orientations, the S N curve shown in Fig. 5 was obtained. Ermakova et al. (2023) reported achieving "infinite life" values (2 × 10^6