{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T04:01:00Z","timestamp":1788321660245,"version":"build-2803163510"},"reference-count":40,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2022,10,3]],"date-time":"2022-10-03T00:00:00Z","timestamp":1664755200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>In order to obtain a widespread application of Additive Manufactured (AM) technology in the aircraft industry for fatigue critical parts, a detailed characterization of the Fatigue and Damage Tolerance (F&amp;DT) behavior of structural components is required. Metal AM techniques in particular are prone to internal defects inherently present due to the nature of the process, which have a detrimental effect on fatigue properties. In the present work, Ti6Al4V and Inconel 718 coupons with artificially induced defects of different dimensions were produced by the Laser Powder Bed Fusion (LPBF) technique. Fatigue tests were performed, and a different defect sensitiveness was observed between the two materials with Inconel being more defect tolerant compared to Titanium. The environmental role at the crack tip of internal defects was discussed, and based on a purely fracture mechanics approach, a simplified stress\u2013life\u2013defect size model was finally devised. The experimental test results together with the information obtained from the fracture surface analysis of tested samples are used to validate the model predictions. The proposed approach could be adopted to define a critical defect size map to be used for tailored Non-Destructive Testing (NDT) evaluation.<\/jats:p>","DOI":"10.3390\/ma15196882","type":"journal-article","created":{"date-parts":[[2022,10,9]],"date-time":"2022-10-09T01:43:11Z","timestamp":1665279791000},"page":"6882","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between Ti6Al4V and Inconel 718"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3310-6325","authenticated-orcid":false,"given":"Nicola","family":"Cersullo","sequence":"first","affiliation":[{"name":"Airbus Operations GmbH, 20355 Hamburg, Germany"},{"name":"Institute of Mechanics and Adaptronics, Technische Universit\u00e4t Braunschweig, 38092 Braunschweig, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jon","family":"Mardaras","sequence":"additional","affiliation":[{"name":"Airbus Operations SAS, 31060 Toulouse, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philippe","family":"Emile","sequence":"additional","affiliation":[{"name":"Airbus Operations SAS, 31060 Toulouse, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katja","family":"Nickel","sequence":"additional","affiliation":[{"name":"Airbus Operations GmbH, 20355 Hamburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vitus","family":"Holzinger","sequence":"additional","affiliation":[{"name":"Airbus Operations GmbH, 20355 Hamburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2218-1223","authenticated-orcid":false,"given":"Christian","family":"H\u00fchne","sequence":"additional","affiliation":[{"name":"Institute of Mechanics and Adaptronics, Technische Universit\u00e4t Braunschweig, 38092 Braunschweig, Germany"},{"name":"Institute of Composite Structures and Adaptive Systems, German Aerospace Center (DLR), 38108 Braunschweig, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1016\/j.ijfatigue.2016.05.001","article-title":"Fatigue performance of additive manufactured TiAl6V4 using electron and laser beam melting","volume":"94","author":"Greitemeier","year":"2017","journal-title":"Int. J. Fatigue"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"178","DOI":"10.1016\/j.ijfatigue.2016.06.020","article-title":"A comparison of fatigue strength sensitivity to defects for materials manufactured by AM or traditional processes","volume":"94","author":"Beretta","year":"2017","journal-title":"Int. J. Fatigue"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.phpro.2014.08.120","article-title":"Effects of Defects in Laser Additive Manufactured Ti-6Al-4V on Fatigue Properties","volume":"56","author":"Wycisk","year":"2014","journal-title":"Phys. Procedia"},{"key":"ref_4","first-page":"20-00362","article-title":"Relationship between internal defect size and fatigue limit in selective laser melted Inconel 718","volume":"8","author":"Ogawahara","year":"2020","journal-title":"Mech. Eng. J."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"463","DOI":"10.1016\/j.msea.2018.08.072","article-title":"Influence of defects and as-built surface roughness on fatigue properties of additively manufactured Alloy 718","volume":"735","author":"Balachandramurthi","year":"2018","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"485","DOI":"10.1016\/j.ijfatigue.2018.08.002","article-title":"Defect analysis and fatigue design basis for Ni-based superalloy 718 manufactured by selective laser melting","volume":"117","author":"Yamashita","year":"2018","journal-title":"Int. J. Fatigue"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/j.prostr.2017.11.063","article-title":"Influence of defect size on the fatigue resistance of AlSi10Mg alloy elaborated by selective laser melting (SLM)","volume":"7","author":"Nadot","year":"2017","journal-title":"Procedia Struct. Integr."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"112","DOI":"10.1016\/j.engfracmech.2005.06.005","article-title":"Multiaxial fatigue limit criterion for defective materials","volume":"73","author":"Nadot","year":"2006","journal-title":"Eng. Fract. Mech."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"324","DOI":"10.1016\/j.ijfatigue.2019.04.008","article-title":"A new FE post-processor for probabilistic fatigue assessment in the presence of defects and its application to AM parts","volume":"125","author":"Romano","year":"2019","journal-title":"Int. J. Fatigue"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1602","DOI":"10.1111\/ffe.12799","article-title":"Fatigue life prediction of additively manufactured material: Effects of surface roughness, defect size, and shape","volume":"41","author":"Yadollahi","year":"2018","journal-title":"Fatigue Fract. Eng. Mater. Struct."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1745","DOI":"10.1007\/s00161-020-00878-0","article-title":"Simulation of fatigue small crack growth in additive manufactured Ti\u20136Al\u20134V material","volume":"32","author":"Gupta","year":"2020","journal-title":"Contin. Mech. Thermodyn."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1826","DOI":"10.1016\/j.ijfatigue.2005.12.001","article-title":"On the possible generalizations of the Kitagawa\u2013Takahashi diagram and of the El Haddad equation to finite life","volume":"28","author":"Ciavarella","year":"2006","journal-title":"Int. J. Fatigue"},{"key":"ref_13","unstructured":"Muhammad, M., Carrion, P., and Shamsaei, N. (2020, January 12\u201314). Fatigue Life Prediction of Additive Manufactured Materials Using a Defect Sensitive Model. Proceedings of the 2019 International Solid Freeform Fabrication Symposium, Austin, TX, USA."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"105584","DOI":"10.1016\/j.ijfatigue.2020.105584","article-title":"A new approach to correlate the defect population with the fatigue life of selective laser melted Ti-6Al-4V alloy","volume":"136","author":"Hu","year":"2020","journal-title":"Int. J. Fatigue"},{"key":"ref_15","first-page":"167","article-title":"Effects of Small Defects and Nonmetallic Inclusions on the Fatigue Strength of Metals","volume":"32","author":"Murakami","year":"1989","journal-title":"JSME Int. J. Ser. Solid Mech. Strength Mater."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1016\/j.ijfatigue.2018.06.012","article-title":"Probabilistic fatigue-life assessment model for laser-welded Ti-6Al-4V butt joints in the high-cycle fatigue regime","volume":"116","author":"Fomin","year":"2018","journal-title":"Int. J. Fatigue"},{"key":"ref_17","unstructured":"Gong, H., Rafi, H., Starr, T., and Stucker, B. (2012, January 6\u20138). Effect of defects on fatigue tests of as-built TI-6AL-4V parts fabricated by selective laser melting. Proceedings of the 2012 International Solid Freeform Fabrication Symposium, Austin, TX, USA."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1016\/j.ijfatigue.2011.12.001","article-title":"Material defects as the basis of fatigue design","volume":"41","author":"Murakami","year":"2012","journal-title":"Int. J. Fatigue"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1319","DOI":"10.1016\/S0142-1123(03)00065-3","article-title":"Fatigue propagation threshold of short cracks under constant amplitude loading","volume":"25","author":"Chapetti","year":"2003","journal-title":"Int. J. Fatigue"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"573","DOI":"10.1016\/0013-7944(79)90081-X","article-title":"Prediction of Non-Propagating Cracks","volume":"11","author":"Haddad","year":"1979","journal-title":"Eng. Fract. Mech."},{"key":"ref_21","unstructured":"Kitagawa, H. (1976, January 16\u201320). Applicability of fracture mechanics to very small cracks or the cracks in the early stage. Proceedings of the 2nd International Conference on the Mechanical Behavior of Materials, Cleveland, OH, USA."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.scriptamat.2019.05.018","article-title":"Fabrication of artificial defects to study internal fatigue crack propagation in metals","volume":"171","author":"Junet","year":"2019","journal-title":"Scr. Mater."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.ijfatigue.2016.05.024","article-title":"Effects of vacuum environment on small fatigue crack propagation in Ti-6Al-4V","volume":"91","author":"Yoshinaka","year":"2016","journal-title":"Int. J. Fatigue"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"45239","DOI":"10.1038\/srep45239","article-title":"Location, location & size: Defects close to surfaces dominate fatigue crack initiation","volume":"7","author":"Buffiere","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"978","DOI":"10.1016\/j.prostr.2019.07.079","article-title":"Effects of vacuum-like environment on small internal crack growth processes in very high cycle fatigue","volume":"14","author":"Nakamura","year":"2019","journal-title":"Procedia Struct. Integr."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/j.prostr.2017.11.056","article-title":"Fatigue Crack Initiation And Propagation From Defects In Metals: Is 3D Characterization Important?","volume":"7","author":"Buffiere","year":"2017","journal-title":"Procedia Struct. Integr."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"601","DOI":"10.1046\/j.1460-2695.1999.00206.x","article-title":"Stepwise S-N curve and fish-eye failure in gigacycle fatigue","volume":"22","author":"Nishijima","year":"2001","journal-title":"Fatigue Fract. Eng. Mater. Struct."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"391","DOI":"10.1007\/BF02644106","article-title":"The effect of air and vacuum environments on fatigue crack growth rates in Ti-6Al-4V","volume":"5","author":"Irving","year":"1974","journal-title":"Metall. Trans."},{"key":"ref_29","first-page":"211","article-title":"Fatigue crack growth of titanium rotor alloys in vacuum and air","volume":"1","author":"Mcclung","year":"1999","journal-title":"Fatigue Behav. Titan. Alloy."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/j.ijfatigue.2012.02.012","article-title":"Fatigue crack propagation properties of Ti\u20136Al\u20134V in vacuum environments","volume":"50","author":"Oguma","year":"2013","journal-title":"Int. J. Fatigue"},{"key":"ref_31","unstructured":"Abikchi, M., Billot, T., Cr\u00e9pin, J., Longuet, A., Mary, C., Morgeneyer, T., and Pineau, A. (2013, January 16\u201321). Fatigue life and initiation mechanisms in wrought Inconel 718 DA for different microstructures. Proceedings of the 13th International Conference on Multiaxial Fatigue and Fracture (ICMFF13), Beijing, China."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/0025-5416(82)90167-7","article-title":"The effect of microstructure and environment on the crack growth behaviour of Inconel 718 alloy at 650 \u00b0C under fatigue, creep and combined loading","volume":"56","author":"Pineau","year":"1982","journal-title":"Mater. Sci. Eng."},{"key":"ref_33","unstructured":"Oguma, H. (2006). Very High Cycle Fatigue Properties of Ti6Al4V Alloy. [Ph.D. Thesis, Hokkaido University]."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"209","DOI":"10.1007\/BF00703882","article-title":"Crack opening displacement and the rate of fatigue crack growth","volume":"8","author":"Donahue","year":"1972","journal-title":"Int. J. Fract. Mech."},{"key":"ref_35","unstructured":"SWRI (2004). Fatigue Crack Growth Computer Program \u2018NASGRO\u2019, Southwest Research Institute. Version 4.2."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"476","DOI":"10.1016\/j.ijfatigue.2008.06.005","article-title":"Probabilistic fatigue life prediction using an equivalent initial flaw size distribution","volume":"31","author":"Liu","year":"2009","journal-title":"Int. J. Fatigue"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1016\/j.ijfatigue.2018.07.020","article-title":"Influence of Defects, Surface Roughness and HIP on the Fatigue Strength of Ti-6Al-4V Manufactured by Additive Manufacturing","volume":"117","author":"Masuo","year":"2018","journal-title":"Int. J. Fatigue"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1002\/mawe.19860171105","article-title":"Assessment of concepts for Fatigue Crack Initiation and propagation life prediction","volume":"17","author":"Heuler","year":"1986","journal-title":"Mater. Werkst."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Gassner, E., and Schuetz, W. (1969). Assessment Of The Allowable Design Stresses And The Corresponding Fatigue Life. Fatigue Design Procedures, Pergamon.","DOI":"10.1016\/B978-0-08-011697-6.50016-3"},{"key":"ref_40","first-page":"1743284715Y.000","article-title":"Effect of surface roughness on fatigue performance of additive manufactured Ti-6Al-4V","volume":"32","author":"Greitemeier","year":"2015","journal-title":"Mater. Sci. Technol."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/15\/19\/6882\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:46:07Z","timestamp":1760143567000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/15\/19\/6882"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,10,3]]},"references-count":40,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2022,10]]}},"alternative-id":["ma15196882"],"URL":"https:\/\/doi.org\/10.3390\/ma15196882","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,10,3]]}}}