PSI - Issue 47

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ScienceDirect

Procedia Structural Integrity 47 (2023) 227–237 Structural Integrity Procedia 00 (2023) 000–000 Structural Integrity Procedia 00 (2023) 000–000

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© 2023 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 IGF27 chairpersons Abstract Warm prestressing (WPS) is a phenomenon where cracked ferritic–martensitic steels get a higher fracture resistance in the lower shelf region after first being deformed in the upper-shelf region. In the current study, a predictive model for the WPS e ff ect was developed based on a fracture mechanics based strip-yield approach. The strip yield-model was modified to account for strain hardening during plastic deformation. It was found that a suitable fracture criterion was to assume failure at the point where the lower-shelf crack tip plastic zone reached the same size as the plastic zone introduced during deformation in the upper-shelf. The model predicted the WPS e ff ect with acceptable accuracy for several temperature–load cycles. © 2023 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 the IGF27 chairpersons. Keywords: warm prestressing; fracture mechanics; strip-yield model; prediction; turbine steel; fracture toughness 27th International Conference on Fracture and Structural Integrity (IGF27) A modified strip yield model to predict warm prestressing e ff ects in turbine steel Robert Eriksson a, ∗ , Ahmed Azeez a a Department of Management and Engineering, Linko¨ping University, Linko¨pings universitet, Linko¨ping 58183, Sweden Abstract Warm prestressing (WPS) is a phenomenon where cracked ferritic–martensitic steels get a higher fracture resistance in the lower shelf region after first being deformed in the upper-shelf region. In the current study, a predictive model for the WPS e ff ect was developed based on a fracture mechanics based strip-yield approach. The strip yield-model was modified to account for strain hardening during plastic deformation. It was found that a suitable fracture criterion was to assume failure at the point where the lower-shelf crack tip plastic zone reached the same size as the plastic zone introduced during deformation in the upper-shelf. The model predicted the WPS e ff ect with acceptable accuracy for several temperature–load cycles. © 2023 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 the IGF27 chairpersons. Keywords: warm prestressing; fracture mechanics; strip-yield model; prediction; turbine steel; fracture toughness 27th International Conference on Fracture and Structural Integrity (IGF27) A modified strip yield model to predict warm prestressing e ff ects in turbine steel Robert Eriksson a, ∗ , Ahmed Azeez a a Department of Management and Engineering, Linko¨ping University, Linko¨pings universitet, Linko¨ping 58183, Sweden

1. Introduction 1. Introduction

Warm prestressing (WPS) is the phenomenon where a (typically ferritic or ferritic–martensitic) steel experiences an increase in fracture resistance, K f , (above the fracture toughness, K Ic ) below its ductile to brittle transition temperature (DBTT) after going through a temperature–load history above its DBTT. The WPS e ff ect may give an additional margin of safety and has mainly been utilized in the nuclear sector Blumenauer and Krempe (2001); Kordisch et al. (2000); Hure et al. (2015). The WPS e ff ect is mainly attributed to three mechanisms Blumenauer and Krempe (2001); Kordisch et al. (2000): Warm prestressing (WPS) is the phenomenon where a (typically ferritic or ferritic–martensitic) steel experiences an increase in fracture resistance, K f , (above the fracture toughness, K Ic ) below its ductile to brittle transition temperature (DBTT) after going through a temperature–load history above its DBTT. The WPS e ff ect may give an additional margin of safety and has mainly been utilized in the nuclear sector Blumenauer and Krempe (2001); Kordisch et al. (2000); Hure et al. (2015). The WPS e ff ect is mainly attributed to three mechanisms Blumenauer and Krempe (2001); Kordisch et al. (2000):

• The introduction of a residual stress field at the crack tip. • Crack tip blunting. • Increased yield strength at the crack tip due to strain hardening. • The introduction of a residual stress field at the crack tip. • Crack tip blunting. • Increased yield strength at the crack tip due to strain hardening.

∗ Corresponding author. Tel.: + 46-13-281139 E-mail address: robert.eriksson@liu.se ∗ Corresponding author. Tel.: + 46-13-281139 E-mail address: robert.eriksson@liu.se

2452-3216 © 2023 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 IGF27 chairpersons 10.1016/j.prostr.2023.07.016 2210-7843 © 2023 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 the IGF27 chairpersons. 2210-7843 © 2023 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 the IGF27 chairpersons.