PSI - Issue 79

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

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Fig.8. V1 fracture (a) surface characteristics and (b) topography.

4. Conclusions Fatigue behavior of ER70S-6 wire specimens produced by CMT was evaluated in horizontal and vertical build orientations under a load ratio of R = 0.1 and frequency of 20 Hz. Based on the experimental results, the following conclusions were drawn: i. Horizontal specimens exhibited consistently superior fatigue performance compared to vertical specimens. At 350 MPa, the horizontal specimen endured 2.23 times more cycles than its vertical counterpart. Moreover, horizontal specimens achieved “infinite life ” ( ≥ 2 × 10^6 cycles) at 302.4 MPa, whereas none of the vertical specimens reached this threshold. ii. Vertical specimens demonstrated significant variability in fatigue life. At 302.4 MPa, specimen V6 reached 821,180 cycles, while specimen V1 failed at 263,141 cycles—a difference of approximately 3.12 times. iii. Fractographic analysis revealed a transition from brittle fracture at the crack initiation region to ductile fracture in the final rupture zone. Specimens failing under very low cycle counts (e.g., V2 at 384 MPa, 901 cycles) exhibited homogeneous surfaces with dimple structures, whereas high-cycle specimens presented distinct brittle and ductile regions. iv. The results confirm strong anisotropy in fatigue resistance. Components built in the vertical orientation showed up to 2.2× lower endurance compared to horizontal ones, emphasizing the need for orientation control and surface finishing in CMT-fabricated parts subjected to cyclic loading. Acknowledgments The authors are grateful to their institutions, University of Brasilia and INEGI. The authors are also grateful to Brazilian funding agencies (Brazilian Federal Agency for Support and Evaluation of Graduate Education) CAPES and National Council for Scientific and Technological Development (CNPq). And the LAETA/INEGI - Associate Laboratory of Energy, Transports and Aerospace/ Institute of Science and Innovation in Mechanical Engineering and Industrial Engineering is acknowledged. Funding The authors are grateful to CNPq, grant numbers 402730/2023-2, 443148/2023-6 and 200018/2025-6 for the financial support. Declarations The authors have no competing interests to declare that are relevant to the content of this article. Data Availability Statement All data supporting the findings of this study are included within the manuscript. Additional data is available from the corresponding author upon reasonable request.