PSI - Issue 18

Available online at www.sciencedirect.com Available o line at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Structural Integrity Procedia 00 (2019) 000–000

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Procedia Structural Integrity 18 (2019) 556–569 25th International Conference on Fracture and Structural Integrity Fatigue Strength of Laser Beam Welded Steel-Aluminium Joints Considering Variable Amplitude Loading and Corrosive Environment Benjamin Möller*, Simon Albrecht, Rainer Wagener, Tobias Melz Fraunhofer Institute for Structural Durability and System Reliability LBF, Bartningstr. 47, 64289 Darmstadt, Germany Abstract Hybrid material combinations of steel and aluminium are currently being joined by explosive welding in ship design, in order to reduce fuel consumption and increase transport weight. As an alternative to the elaborate and expensive explosive welding, a replacement for steel-aluminium adapters by means of laser beam welding in a lap joint configuration is being aimed at. Therefore, a laser beam welding process has been developed and optimised with regard to the different melting points and coefficients of thermal expansion of the materials as well as the formation of intermetallic phases due to the limited solubility of the elements. The characteristic of the weld seam, which is the result of a melt pool through the steel into the aluminium material, has a major impact on the quasi-static and cyclic strength of the joint. Especially the weld width and penetration depth have been identified as main influencing parameters. In the end, the developed laser beam welding process under spectroscopic control of the penetration depth is validated by fatigue investigations of lap joints and compact designed adapters. In addition to the fatigue strength under constant amplitude loading (CAL), the fatigue performance under variable amplitude loading (VAL) is particularly promising, even though the scatter increases from CAL to VAL and a linear damage accumulation is not applicable. A change in the fracture behaviour is explained by the intensity of the loading. Finally, the corrosion fatigue behaviour is shown by constant amplitude loading in a corrosive environment with a sodium chloride solution of 5 %, which causes a strength reduction from high cycle to long life fatigue. 25th International Conference on Fracture and Structural Integrity Fatigue Strength of Laser Beam Welded Steel-Aluminium Joints Consid ring Variable Amplitude Loading and Corrosive Environment Benjamin Möller*, Simon Albrecht, Rainer Wagener, Tobias Melz Fraunhofer Institute for Structural Durability and System Reliability LBF, Bartningstr. 47, 64289 Darmstadt, Germany Abstract Hybrid material combinations of steel and aluminium are currently being joined by explosive welding in ship design, in order to reduce fuel consumption and increase transport weight. As an alternative to the elaborate and expensive explosive welding, a replacement for steel-aluminium adapters by means of laser beam welding in a lap joint configuration is being aimed at. Therefore, a laser beam welding process has been developed and optimised with regard to the different melting points and coefficients of thermal expansion of the materials as well as the formation of intermetallic phases due to the limited solubility of the elements. The characteristic of the weld seam, which is the result of a melt pool through the steel into the aluminium material, has a major impact on the quasi-static and cyclic strength of the joint. Especially the weld width and penetration depth have been identified as main influencing parameters. In the end, the developed laser beam welding process under spectroscopic control of the penetration depth is validated by fatigue investigations of lap joints and compact designed adapters. In addition to the fatigue strength under constant amplitude loading (CAL), the fatigue performance under variable amplitude loading (VAL) is particularly promising, even though the scatter increases from CAL to VAL and a linear damage accumulation is not applicable. A change in the fracture behaviour is explained by the intensity of the loading. Finally, the corrosion fatigue behaviour is shown by constant amplitude loading in a corrosive environment with a sodium chloride solution of 5 %, which causes a strength reduction from high cycle to long life fatigue. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo.

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo.

* Corresponding author. Tel.: +49-6151-705-8443; fax: +49-6151-705-214. E-mail address: benjamin.moeller@lbf.fraunhofer.de

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. * Corresponding author. Tel.: +49-6151-705-8443; fax: +49-6151-705-214. E-mail address: benjamin.moeller@lbf.fraunhofer.de

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo.

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 10.1016/j.prostr.2019.08.200