PSI - Issue 19

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

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ScienceDirect

Procedia Structural Integrity 19 (2019) 259–266

Fatigue Design 2019 Low cycle fatigue of welded very and ultra-high strength steels Jennifer Hrabowski a *, Thomas Ummenhofer b a KoRoH GmbH – CCTH Center of Competence for Tubes and Hollow Sections, Schoenfeldstrasse 8, 76131 Karlsruhe, Germany b KIT Steel & Lightweight Structures, Research Center for Steel, Timber and Masonry, Otto-Ammann-Platz 1, 76131 Karlsruhe, Germany Fatigue Design 2019 Low cycle fatigue of welded very and ultra-high strength steels Jennifer Hrabowski a *, Thomas Ummenhofer b a KoRoH GmbH – CCTH Cent r of Competence for Tubes and Hollow Sections, Schoenfeldstrasse 8, 76131 Karlsruhe, G rmany b KIT Steel & Lightweight Structures, Research Center for Steel, Timber and Masonry, Otto-Ammann-Platz 1, 76131 Karlsruhe, Germany

Abstract Abstract

Low-cycle fatigue behavior of modern very high strength and ultra-high strength steels with nominal strengths up to 1100 N/mm² in welded condition is described and the application limit of elastic design rules is defined. Design recommendations are given based on the nominal stress approach as well as the notch stress approach. Thus, welded details made of high-strength steels can be designed for low-cycle fatigue applications. Furthermore, a more accurate assessment can be done, allowing for an economical application of high-strength fine-grain structural steels. Lo -cycle fatigue behavior of modern very high strength and ultra-high strength steels with nominal strengths up to 1100 N/mm² in welded condition is described and the application limit of elastic design rules is defined. Design recommendations are given based on the nominal stress approach as well as the notch stress approach. Thus, welded details made of high-strength steels can be designed for low-cycle fatigue applications. Furthermore, a more accurate assessment can be done, allowing for an economical application of high-strength fine-grain structural steels.

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

Keywords: Low cycle fatigue, very high strength steel, butt weld, transverse attachment, nominal stress approach, structural stress approach Keywords: Low cycle fatigue, very high strength steel, butt weld, transverse attachment, nominal stress approach, structural stress approach

Nomenclature K t Nomenclature K t

Stress intensity factor Stress intensity factor Number of load cycles to failure Load cycle limit to low cycle fatigue Number of load cycles to failure Load cycle limit to low cycle fatigue

k m k m m m      

Magnification factor Magnification factor Inverse slope of the S-N-curve Inverse slope of the S-N-curve  ngular misalignment  ngular misalignment

N f

N LCF f N LCF

R R R e R e

Stress range ratio Deformation limit 0.2 % Yield strength Standard deviation Stress range ratio Deformation limit 0.2 % Yield strength Standard deviation

Stress range Stress range

Reference value of fatigue strength at N f = 2·10 6 Reference value of fatigue strength at N f = 2·10 6

* *

C C

R p0,2 R p0,2

Maximum nominal stress Minimum nominal stress aximum nominal stress Minimum nominal stress

 max  min  max  min

S S

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. * Corresponding author. Tel.: +49-721-8244890-30; Fax: +49-721-8244890-99. E-mail address: jennifer.hrabowski@koroh.de * Corresponding author. Tel.: +49-721-8244890-30; Fax: +49-721-8244890-99. E-mail address: jennifer.hrabowski@koroh.de

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 10.1016/j.prostr.2019.12.028