PSI - Issue 42

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Author name / Structural Integrity Procedia 00 (2019) 000–000

ScienceDirect 23 European Conference on Fracture - ECF23 Friction stir welds with enhanced fatigue strength and life post laser peening J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conference on Fracture - ECF23 Friction stir welds with enhanced fatigue strength and life post laser peening J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conference on Fracture - ECF23 Friction stir welds with enhanced fatigue strength and life post laser peenin J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conference on Fracture - ECF23 Friction stir welds with enhanced fatigue strength and life post laser peening J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conference on Fracture - ECF23 Friction stir welds with enhanced fatigue strength and life post laser peening J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conference on Fracture - ECF23 Friction stir welds with enhanced fatigue strength and life post laser peenin J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 2 3 Friction ith enhanced fatigue strength and life post laser ntunes , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchio 2 rictio ith enhance fatigue strength and life post laser ntunes , S. rving , D. Furfari , D. Busse , M. Pacchio Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Confer nce on Fracture - ECF23 Friction stir welds with e hanced fati ue strength and life post laser peenin J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irvin 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conf rence on Fracture - ECF23 Frictio tir welds with enhanced fati ue strength and life post laser pe ning J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conf rence on Fracture - ECF23 Friction stir welds ith enhanced fatigue strength and life post laser pe ning J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Author name / Structural Integrity Procedia 00 (2019) 000–000 23 European Conf r ce on Fracture - ECF23 Friction stir welds with enhanc d fatigue strength and life post laser peening J.R. Antunes 1* , S. Ganguly 1, , Y. Xu, 1, , P.E. Irving 1 , D. Furfari 2 , D. Busse 2 , M. Pacchione 2 Available online at www.sciencedirect.com Procedia Structural Integrity 42 (2022) 588–593 © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the 23 European Conference on Fracture – ECF23 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. 1. Introduction and background Friction Stir Welding (FSW) is being studied as a viable solid-state joining process for aircraft fuselage structures. As with any other high-temperature joining process, FSW will form an integrated structure with variably distributed residual stress fields and a microstructural gradation. This will adversely affect the structural performance of a joint. The FSW process may also introduce defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) has been demonstrated as an effective tool to improve overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of both fatigue crack initiation and propagation behaviour in aerospace aluminium alloys due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover the fatigue life of a joint. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual stress field produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Material and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specimen designs were provided by the project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. Abstract This study aims to quanti y he influence of laser pe ning on the struct ra integri y of FSWelded aluminium fuselage jo nt . Fa igue tests with different stress amplitudes were performed for sample in as-machined and friction stir welded conditions to char cterise th loss of fatigu strength and th effect of tress amplitude o th degradation of fat gu life. Optimisatio of laser param ters was carri d out to achieve n appropri e through-th kness stress profile. The optimised parameters were used to peen tensile c upon specimens and analyse the fatigue l fe recovery. The residual stress fields were quantified using the central incremental hole drilling method on peened and unpeened samples. It was found that both the micr structure and superposition of residual stresses from the welding proc ss and pe ning treatment play a rucial role in the fatigue behavi ur of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase the fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. © 2020 The Autho s. Published by Elsevier B.V. This is an open access arti le under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. 1. Introduction and background Friction Stir Welding (FSW) is being studied as a viable solid-state joining process for aircraft fuselage structures. As with any other high-temperature joining process, FSW will form an integrated structure with variably distributed residual stress fields and a microstructural gradation. This will adversely affect the structural performance of a joint. The FSW process may also introduce defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) has been demonstrated as an effective tool to improve overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of both fatigue crack initiation and propagation behaviour in aerospace aluminium alloys due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover the fatigue life of a joint. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual stress field produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Material and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specimen designs were provided by the project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. Abstract This study aims to quantify the influence of laser peening on the structural integrity of a FSWelded aluminium fuselage joint . Fatigue tests with different stress amplitudes were performed for samples in as-machined and friction stir welded conditions to characterise the loss of fatigue strength and the effect of stress amplitude on the degradation of fatigue life. Optimisation of laser parameters was carried out to achieve an appropriate through-thickness stress profile. The optimised parameters were used to peen tensile coupon specimens and analyse the fatigue life recovery. The residual stress fields were quantified using the central incremental hole drilling method on peened and unpeened samples. It was found that both the microstructure and superposition of residual stresses from the welding process and peening treatment play a crucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase the fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. 1. Introduction and background Friction Stir Welding (FSW) is being studied as a viable solid-state joining process for aircraft fuselage structures. As with any other high-temperature joining process, FSW will form an integrated structure with variably distributed residual stress fields and a microstructural gradation. This will adversely affect the structural performance of a joint. The FSW process may also introduce defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) has been demonstrated as an effective tool to improve overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of both fatigue crack initiation and propagation behaviour in aerospace aluminium alloys due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover the fatigue life of a joint. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual stress field produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Material and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specimen designs were provided by the project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded speci ens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. Abstract This study aims to quantify the influence of laser peening on the structural integrity of a FSWelded aluminium fuselage joint . Fatigue tests with different stress amplitudes were performed for samples in as-machined and friction stir welded conditions to characterise the loss of fatigue strength and the effect of stress amplitude on the degradation of fatigue life. Optimisation of laser parameters was carried out to achieve an appropriate through-thickness stress profile. The optimised parameters were used t peen tensile coupon specimens and analyse the fatigue life recovery. The residual stress fields were quantified using the central incremental hole drilling method on peened and unpeened samples. It was found that both the microstructure and superposition of residual stresses from the wel ing process and peening treatment play a crucial role in the fatigue behaviour of the FSWelded joint. Using the param ters and layout described in this article, laser peening was able to increase t e fatigue life of as-welded s mples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) P er-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. 1. Introduction and background Friction Stir Welding (FSW) is being studied as a viable solid-state joining process for aircraft fuselage struc ures. As with y other high-temperature j ining process, FSW will form an integrated struc ure with variably distributed residual stress fields nd a micr structural gradation. This will adv sely affect the structural p rformance of a joint. The FSW proce s may als int oduce defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) has been de onstrated as an effectiv tool to improve overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of both fatigue crack initiation and propagation behaviour in aerospace aluminium lloy due to the introduction of a through-thickness compressiv residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover he fatigue life of a joint. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual tr field produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Mate ial and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specimen designs were provided by the project sponsor. The supplied sheets were machined into dogbon -shaped fatigue samples while ke ping the FSW weld line oinciding with the c ntre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. Abstract This s udy aims to quanti y the influence of laser pe ning on the struct a integri y of FSWelded aluminium fuselage joint . Fa igue tests with different stress amplitudes were p rformed for samples in a -machined and friction stir welded conditions to char cterise th loss of fatigu str ngth and h effect of stress amplitude on th degradation of fat gu life. Optimisatio of laser parameters was car i d out to achieve an appropri e through-th kness stress profile. The optimised parameters w re us d to peen tensile coupon specimens and analyse the fatigue l fe recovery. The residual stress fields were quantified using the central incr ment l hole drilling method on peened and unpeened samples. It was found that both the microstructure and su erposition of esidual st esses from the welding process and pe ning treatment play a rucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase the fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. 1. Introduction and background Friction Stir Welding (FSW) is being studied as a viable solid-state joining process for aircraft fuselage structures. As with any other high-temperature joining process, FSW will form an integrated structure with variably distributed residual stress fields and a microstructural gradation. This will adversely affect the structural performance of a joint. The FSW process may also introduce defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) has been de onstrated as an effective tool to improve overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of both fatigue crack initiation and propagation behaviour in aerospace aluminium alloys due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover the fatigue life of a joint. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual stress field produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Material and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specimen designs were provided by the project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. Abstract This study aims to quantify the influence of laser peening on the structural integrity of FSWelded aluminium fuselage joint . Fatigue tests with different stress amplitudes were performed for samples in as-machined and friction stir welded conditions to char cterise th loss of fatigu strength and the effect of stress amplitude on the degradation of fatigue life. Optimisation of laser parameters was carri d out to achieve an appropri te through-thickness stress profile. The optimised parameters were used to peen tensile c upon specimens and analyse the fatigue life recovery. The residual stress fields were quantified using the central incr ment l hole drilling method on peened and unpeened samples. It was found that both the microstructure and superposition of residual stresses from the welding process and pe ning treatment play a rucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase the fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. © 2020 Th Autho s. Publish d by Elsevier B.V. This is an open access arti le und r the CC BY-NC-ND license (http://creativecommons.o g/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. 1. Introduction and background Friction Sti Welding (FSW) is being studied s a vi bl solid-state joining process for aircraft fuselage structures. As with y oth r high-temperature j ining pr cess, FSW will form an integrated structu e with variably distributed residual stress fields and a microstructural gradation. This will adversely a fect the structural p rformanc of a joint. The FSW process may also introduc defects that would ct as sites for fatigue crack initi tion during service. Laser Peening (LP) has been d onstrated as an effecti tool to improve overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvem nt of both fatigu crack initiation and propagation behaviour in aerospace aluminium all ys due to the introduction of a through-thickness compressiv residual tress. This w uld also act as a deterr nt for crack initiation f om a pre-existing def ct and potentially recover the fatigue life of a joint. In this paper, friction stir welded aerospace fu elage aluminium structural alloys were treater with laser peening. The residual str ss field produced by laser ee ing will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Material and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickn was used in this study and all th materials and specimen designs were provided by th project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. Ab ac influ d e r s a re drilling method on peened and un i i o m © p y of 23 European o ferenc o Fra K 1. Introduction and b kground F ra re joining process, FSW ill r t defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) has been demonstrat tool to im v ra l ti life (Sm 9 r 1 . t th s r p me initiation and propagati f rough-thickness compressive t ld l o ct ex n stress field produced by laser peening will be superimposed e i s c rs and speci ca e o d T s s p r i c y P el a it g g e m b co a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus O rations Gmbh, K eetslag 10, Hamburg 21129, Germany Abstract This study aims to quantify the inf u ce of laser peening on the struct ral integrity of a FSWel ed aluminium fuselage joint . Fatigue tests w th differ nt stress a litu es were perfo med for samples in as-machined and fricti n stir welded c nditions to characte ise the loss of fatigue strength and the effect of stress amplitude on the degradation of fatigue life. Optimisation f la er par meters was car ied out o chieve an appropriate thro gh-thickness stres profi e. The optimised parameters w r used to peen ten ile c upon specimens and analyse the f tigue life re overy. The residual stress fields were quantified using the central incr mental hole drilling method on peened and unpeen d samples. It was found that both the micr structure and superposition of residual stresses from the welding process and peening treatment play a crucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase t e fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference sam les. © 2020 The Autho s. Publ shed by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; frictio -stir-welding; laser peening; residual stress s. 1. Introduction and back round Friction Stir Welding (FSW) is being studied as a vi ble solid-state joining process for air raft fuselage struc ures. As with any oth r high-temperature joining process, FSW will form an integrated structure with variably distributed residual stress fields and a microstructural gradation. This will adv sely affect the structural performance of a join . The FSW process may als introduce defects th t would ct as sites for fatigue crack initiation during service. Laser Peening (LP) has been d monstra ed as an ffect tool to mprove overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors r port the improvement of bo h fatigue c ack initiation and propagation behaviour in aerospace aluminium alloy due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation f om a pre-exi ting def c and potentially recover h fatigue lif of a joint. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The re idual stress field produced by laser peening will be superimpos over the weld residual stresses. The extent and irection of the surface stress field hange will depend on the size and distribution of the laser peening stresses nd their int raction with the FSW stress field. 2. Mate ial and f tigu sam le design a School of Aerospace, Transport and Manufacturi g, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany Abstract This study aims to quantify the influence of las r pee ng on the structural integri y of a FSWe ded aluminium fuselage joint . Fatigue tests with differ nt stress amplitudes were perfo med for samples in as-machined and friction stir welded conditions to characterise the loss of fatigue stre gt nd t e effect of ess amplitude on the degradation of fatigue life. Optimisation of laser par meters was carried out to achieve an appropriate through-thickness stress profile. The optimised parameters w r used t peen ten ile coupon specimens and analyse the fatigue life recovery. The residual stress fields were q antified using the central incremental hole drilling method on peen d and unpeen d samples. It was found that both the microstructure and s perposition of residual stresses from the wel ing process and peening treatm nt play a crucial role in the fatigue behaviour of the FSWelded joint. Using the param ters and layout described in this article, laser peening was able to increase th fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the p istine aluminium reference samples. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-N -ND license (http://creativecommons. rg/licenses/by-nc-nd/4.0/) Peer-review under responsib lity of 23 European Conference on Fracture - ECF23 Keywords: Fatig e; joints; friction-stir-welding; laser peening; residual stresses. 1. Introducti n and b ckground Friction Stir Welding (FSW) is being studied as viable solid-state joining process for aircraft fuselage structure . As with any other high-temperature joining pr cess, FSW will form an integrated structure with variably distributed residual stress fields and a microstruc ural gradation. This will adversely affect the structural performance of a joint. The FSW process may also introduce defects that would act as ites for fatigue crack initiation d ring service. Laser Peening (LP) h s been de onstrated as an effective tool to mprove overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of b th fa igue cr k initiation and propagation behaviour in aerospace aluminium alloys due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover the fatigue life of a joint. a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany Abstract This study aims to quantify the influe ce of laser pee ing on the structural integrity of a FSWelded aluminium fuselage joint . Fatigue tests w th different stress amplitudes were performed for samples in as-machined and friction stir welded conditions to haract ise the loss of fatigue strength and the effect of stress amplitude on the degradation of fatigue life. Optimisation of laser parameters was car ied out o chieve an appropriate through-thickness stress profile. The optimised parameters were used to peen tensil coupon specimens and analyse the fatigue life recovery. The residual stress fields were quantified using the central incremental hole drilling method on peened and unpeened samples. It was found that both the microstructure and superposition of re idual stresses fro the welding process and peening treatment play a crucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase the fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-welding; laser peening; residual stresses. a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany Abstract This s udy aims to quanti y the influence of laser pe ning on the struct r integri y of FSWel ed aluminium fuselage joint . Fa igue tests w th different stress a litu es w re performed for samples in as-machined and fricti n stir welded conditions to characterise th loss of fatigu strength and th effect of tress amplitude on th degradati n of fatigue life. Optimisation of la er parameters was car i d out o achieve an appropri e through-th ckness s res profile. The optimised parameters were used to peen tensile coupon specimens and analyse the fatigue l fe recovery. The residual stress fields were quantified using the central incr ment l hol drilling method on peen d a d unpeen d samples. It w s f und that both the micr structure and superposition of esidual st esses from the wel ing process and pe ning treatm t play a rucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to inc eas the fatigue life of as-welded samples by a factor of 2.4 for the lower e d of the oad spectrum tested. This represents a recovery of 65% w en compared to the pristin aluminium reference samples. © 2020 The Autho s. Published by Elsevier B.V. This is an open access art le under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under respons bility of 23 European Conference on Fracture - ECF23 Keywords: Fatigue; joints; friction-stir-weldin ; la er peening; residual stresses. a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany a School of Aerospace, Transport and Manufacturing, Cranfield University, MK43 0A, UK. b Airbus Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany rsity, MK43 us Operations Gmbh, Kreetslag 10, Hamburg 21129, Germany Abstract This study aims to quantify the influence of laser peening on the structural integrity of a FSWelded aluminium fuselage joint . Fatigue tests with different stress amplitudes were performed for samples in as-machined and friction stir welded conditions to characterise the loss of fatigue strength and the effect of stress amplitude on the degradation of fatigue life. Optimisation of laser parameters was carried out to achieve an appropriate through-thickness stress profile. The optimised parameters were used to peen tensile coupon specimens and analyse the fatigue life recovery. The residual stress fields were quantified using the central incremental hole drilling method on peened and unpeened samples. It was found that both the microstructure and superposition of residual stresses from the welding process and peening treatment play a crucial role in the fatigue behaviour of the FSWelded joint. Using the parameters and layout described in this article, laser peening was able to increase the fatigue life of as-welded samples by a factor of 2.4 for the lower end of the load spectrum tested. This represents a recovery of 65% when compared to the pristine aluminium reference samples. * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk 1 1 1 1 1 1 1 1 1 2452-3216 © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the 23 European Conference on Fracture – ECF23 10.1016/j.prostr.2022.12.074 * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Corresp nding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk onding author. Tel.:+351 961-667-032; E-mai dress: joana.antunes@cranfield.a uk d Aluminium 2024-T351 with 2.3 mm thickne was used in this study and all th materials and specimen designs were provided by th project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded speci ens. FSW parameters and specimen design can be foun in Figure 1. Two different sample c nditions are ana ysed in this study: reference (pristine aluminium material) and as-welded. In this paper, friction stir welded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual stress field produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surface stress field change will depend on the size and distribution of the laser peening stresses and their interaction with the FSW stress field. 2. Material and fatigue sample design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specimen designs were provided by the project sponsor. The supplied sheets were machined into dogbone-shaped fatigue samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample con itions are analysed in this study reference (pristine aluminium material) and as-welded. 1. Introducti n and b ckground Friction Stir Welding (FSW) is b ing studied as viable solid-state joining process for aircraft fuselage struc ure . As with y other high-temperature j ining process, FSW will form n integrated structure with variably distributed residual stress fields nd a mi r structural gradation. This will adv sely affect the structural p rformance of a joint. The FSW proce s may also introdu d fects that would act as ites for fatigue cra k initiation d ring service. Laser Peening (LP) h s been d monstrated as an f ective tool to mprove overall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both authors report the improvement of b th fa igue cr k initiation and propagation behaviour in aerospace aluminium lloy due to the introduction of a through-thickness compressive residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover h fatigu lif of a joint. In this paper, friction stir w lded aerospace fuselage aluminium structural alloys were tre ter with laser p ening. The residual stress fiel produced by laser peening will be superimposed over the weld residual stresses. The extent and direction of the surfac stress field change will depend on the size and distribution of the laser p ening stresses and their interaction with the FSW stress field. 2. Material and fatigue sam le design Aluminium 2024-T351 with 2.3 mm thickness was used in this study and all the materials and specim n designs were provided by the project sponsor. The supplied sheets were mac ined into dogbon -shaped fatigu samples while keeping the FSW weld line coinciding with the c ntre of the minimum cross-sectional area of the welded specimens. FSW parameters and specimen design can be found in Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded. 1. Introduction and back round Friction Stir Welding (FSW) is being studied as vi ble solid-state joining process for aircraft fusela e structures. As with ny other high-temperature j i ing process, FSW will form an integrated structure with variably distributed residual stress fields and a mi rostructura gradation. This will adversely affect the struct ral p rformance of a join . The FSW proce s may lso introduce defects that would act as sites for fatigue crack initiation during service. Laser Peening (LP) as been demonstra ed as n ffectiv tool to mprove ov rall fatigue life (Smyth (2019); Furfari et al. (2017) ) . Both author report the improvement of b th fatigue crack initiation and propagation behaviour in aerospace aluminium lloys due to the introduction of a through-thickness compressiv residual stress. This would also act as a deterrent for crack initiation from a pre-existing defect and potentially recover the fatigue life of a joint. In this paper, friction stir w lded aerospace fuselage aluminium structural alloys were treater with laser peening. The residual ss fi produced by laser peening will be superimpos d over the weld residual stresses. The extent nd direc ion of the surface stress field change will depend on the size and distribution of the laser peening stresses nd their int ractio with the FSW stress field. 2. Material and fatigu sample design Aluminium 2024-T351 with 2.3 mm thickness was us d in this study and all the materials and specimen designs were provided by the project sponsor. The s pplied sheets were ma hined into dogbone-shaped fatigu samples while keeping the FSW weld line coinciding with the centre of the minimum cross-sectional area of the welded speci ens. FSW parameters and specimen design can be found i Figure 1. Two different sample conditions are analysed in this study: reference (pristine aluminium material) and as-welded.

* Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Corresponding author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk * Correspon ing author. Tel.:+351 961-667-032; E-mail address: joana.antunes@cranfield.ac.uk