PSI - Issue 57

Cheng Huang et al. / Procedia Structural Integrity 57 (2024) 42–52

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Cheng Huang et al./ Structural Integrity Procedia 00 (2023) 000 – 000

built WAAM material, relative to the machined material. Note that the findings from the fatigue analysis based on nominal stresses depend largely on the printed geometries of the WAAM elements.

10 3

Fitted S - N curve for machined material

m = 3

10 2 Nominal stress range ∆ σ nom (MPa)

Fitted S - N curve for as-built material

This study, as-built Ref. [43], as-built This study, machined Ref. [44], machined Run-out As-built, Bartsch et al. (2021) As-built, this study Machined, this study Machined, Dirisu et al. (2020)

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10 4

10 5

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Number of cycle to failure N

Fig. 8. Comparison of fatigue test results of as-built and machined WAAM coupons.

5. Conclusions A comprehensive experimental study into the fatigue behaviour of WAAM plates made of ER70S-6 steel wire has been presented. A total of 75 high-cycle fatigue tests on both as-built and machined coupons, covering various stress ranges and stress ratios, have been conducted. The obtained fatigue test results were assessed using constant life diagrams (CLDs) and S - N diagrams. The CLDs revealed that the fatigue strength of the as-built WAAM steel (for two million cycles) was relatively insensitive to the mean stress levels, generally remaining at a nominal stress range of 170 MPa under different stress ratios. The S - N diagrams showed that, owing to the surface undulations, the as-built WAAM material exhibited a reduction of about 35% in the fatigue endurance limit relative to the machined material, and a reduction of about 60% in the fatigue life if subjected to the same cyclic load level. Nominal stress-based fatigue classes, FAT 80 and FAT 130, with an inverse slope of m = 3, were proposed for WAAM ER70S-6 steel in as-built and machined conditions, respectively, although additional test data are considered necessary for further confirmation and reliability assessment. Acknowledgements The authors also would like to acknowledge MX3D for the fabrication of the test specimens and Mr Robert Widmann and Mr Davide Ferrari for their assistance in the research. References ASTM International, 2017. Additive manufacturing—general principles—terminology. ISO/ASTM 52900, West Conshohocken, PA. ASTM International, 2021. Standard practice for conducting force controlled constant amplitude axial fatigue tests of metallic materials. ASTM E466-21, West Conshohocken, PA. Bartsch, H., Kühne, R., Citarelli, S., Schaffrath, S., Feldmann, M., 2021. Fatigue analysis of wire arc additive manufactured (3D printed) components with unmilled surface. Structures 31:576–89. Bathias C, Paris PC. Gigacycle fatigue in mechanical practice. New York: Marcel Dekker Publishing; 2006, ISBN 0-8247-2313-9. BSI (British Standards Institution), 2010. Aerospace series—metallic materials—test methods—constant amplitude fatigue testing. BS EN 6072:2010, Brussels. CEN (European Committee for Standardization), 2005. Eurocode 3—Design of Steel Structures—Part 1-9: Fatigue. EN 1993-1-9:2005, Brussels. CEN (European Committee for Standardization), 2016. Metallic materials—tensile testing—Part 1: method of test at room temperature. EN ISO 6892-1:2016, Brussels.