PSI - Issue 34

Rhys Jones et al. / Procedia Structural Integrity 34 (2021) 39–44 Rhys Jones/ Structural Integrity Procedia 00 (2021) 000 – 000

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Table 1. Values of the Hartman-Schijve constants used in Figure 2 for Scalmalloy. D (m/cycle) n A (MPa √m)

Δ K thr (MPa √m)

R = 0.1 R = 0.7

2.64 x 10 -9 2.64 x 10 -9

1.83 1.83

75 75

1.38 0.83

4. Conclusions As noted in US Army Directive 2019-29 advanced manufacturing has the potential to address the readiness challenges posed by parts obsolescence, diminishing sources of supply, and sustained operations in austere environments. In this context it has previously been suggested that additively manufactured Scalmalloy has the potential to be used to replace aluminium alloys. However, certification often requires a DADT analysis. To this end we have compared the da/dN curves associated with SLM Scalmalloy with the commonly used aluminium alloys AA7075-T7351 and AA7050-T7451 and shown that its curve is similar to that of AA7075-T7351. We have also shown that crack growth in these SLM Scalmalloy specimens can be reasonably accurately represented by the Hartman-Schijve crack growth equation and that the R ratio effect on crack growth can be captured by allowing for changes in the threshold term Δ K thr . Acknowledgments John Michopoulos and Athanasios Iliopoulos acknowledge support for this work by the Office of Naval Research (ONR) through the Naval Resear ch Laboratory’s core funding. References ASTM, 2014. Measurement of FCG Rates . ASTM E647-13. West Conshocken, USA. Brunner AJ., Pinter G., Murphy N., 2009. Development of a Standardized Procedure for the Characterization of Interlaminar Crack Growth in Advanced Composites under Fatigue Mode I Loading Conditions. Engineering Fracture Mechanics 76, 2678-2689. Forman, RG., Shivakumar V., Cardinal JW., Williams LC., and McKeighan PC. (2005) Fatigue crack growth database for damage tolerance analysis, DOT/FAA/AR-05/15. Gorelik M., Regulatory considerations for AM qualification and status of FAA Roadmap, Proceedings Additive Manufacture for Reactor Materials & Components: Public Meeting, November 28-29th, 2017, North Bethesda. Available online: https://www.nrc.gov/docs/ML1733/ML17338A886.pdf, (accessed on 02/02/2021). Hartman, A., Schijve J., 1970. The Effects of Environment and Load Frequency on the Crack Propagation Law for Macro FCG in Aluminium Alloys. Engineering Fracture Mechanics 1, 615-631. Jones, R., 2014. Fatigue crack growth and damage tolerance, Fatigue & Fracture of Engineering Materials & Structures, 37, 463-483. Jones, R., Michopoulos, JG., Illiopoulos, AP., Raman, RS., Phan, N., and T. Nguyen, 2018. Representing crack growth in additively manufactured Ti-6Al-4V, International Journal of Fatigue, 116, 610-622. Jones R., Peng D., Singh Raman RK., and Huang P., Computing the growth of small cracks in the assist round robin helicopter challenge, Metals 2020, 10, 944; doi:10.3390/met10070944 Jones R., Rans C., Iliopoulos AP., Michopoulos JG., Phan N., Peng D., Modelling the Variability and the Anisotropic Behaviour of Crack Growth in SLM Ti-6Al-4V, Materials 2021, 14, 1400. https://doi.org/10.3390/ma14061400. Iliopoulos, A.P.,Jones, R., Michopoulos, JG., Phan, N., and Raman, RS., 2018. Crack growth in a range of additively manufactured aerospace structural materials, Aerospace, 5, 118-136. Iliopoulos AP., Jones R., Michopoulos JG., Phan N., and Rans C., Further Studies into Crack Growth in Additively Manufactured Materials, Materials 2020, 13, 2223; doi:10.3390/ma13102223 McMichael, E., Frazer, E. NAVAIR Additive Manufacturing, 2015. Proceedings Summary Report: Joint Federal Aviation Administration-Air Force Workshop on Qualification/Certification of Additively Manufactured Parts, DOT/FAA/TC-16/15, 2015 (Available online: http://www.tc.faa.gov/its/worldpac/techrpt/tc16-15.pdf (accessed on 04/20/2020).