PSI - Issue 18

Available online at www.sciencedirect.com Structural Integrity 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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Procedia Structural Integrity 18 (2019) 457–471

25th International Conference on Fracture and Structural Integrity Some observations on failure of austenitic stainless steel: effects of in- and out of plane constraint Mehdi Mokhtarishirazabad*, Mahmoud Mostafavi Department of Mechanical Engineering, University of Bristol, Bristol, UK Abstract Modern engineering design for safety-critical structures demands meticulous failure assessments. While conventional fracture toughness parameters (e.g. J IC or K IC ) are perceived as a reliable tool for characterizing the fracture behaviour of many engineering components, excessive plasticity in low-strength materials with high strain hardening capability, such as austenitic stainless steels, can change the predominant failure mode to plastic collapse. In this case, assessing the component integrity assuming fracture can introduce significant conservatism in its estimated load bearing capacity. Low constraint structures such as thin sections or sections with short cracks can suffer from plastic collapse rather than fracture but there is not a measure that can predict the change of failure mechanism. In this study, the effect of crack tip constraint in terms of the thickness and initial crack size on failure behaviour of AISI Type 316L austenitic stainless steel is studied. To this end, several single edge notched bending (SENB) specimen were manufactured with different initial crack lengths and thicknesses to account for in- (i.e. crack length) and out of (i.e. thickness) plane constraint effect. Fracture tests performed according to ASTM E1820-18 except for the sample thickness and crack lengths. The challenges for measuring the crack extension for resistance curve method as a result of deviating from the standard is discussed. The failure of the samples was also assessed by Failure Assessment Diagram (FAD). The results showed that unloading compliance extremely underestimate the crack extension in the presence of significant plastic deformation of the samples. The results also showed that the plastic collapse occurs in all samples before crack starts to grow, in the blunting regime. 25th International Conference on Fracture and Structural Integrity Some observations on failure of austenitic stainless steel: effects of in- and out of plane constraint Mehdi Mokhtarishirazabad*, Mahmoud Mostafavi Department of Mechanical Engineering, University of Bristol, Bristol, UK Abstract Modern engineering d sign for safety-critical structures demands meticulous failure assessments. While c nventional fracture toughness param ters (e.g. J IC or K IC ) are p rceived as a reliable tool for char ct rizing the fracture behaviour of many engineering omponents, excessive plasticity in low-strength materi ls with high strain harde ing capability, such as austenitic stainless steels, can change the predominant failure mod to plastic collapse. In this case, assessi g the component integrity assuming fracture can introduce significant conservatism in its estimat d load bearing capacity. Low constraint structures such as thin s ctio s or sections with short cracks can suffer from plastic collapse rather than fracture but there is not a measure that can predict the change of failure mechanism. In this study, the effect of crack tip constraint in terms of the thickness and initial crack size on failure behaviour of AISI Type 316L austenitic stainless steel is studied. To this end, several single edge notched bending (SENB) specimen were m ufactured with different initial crack lengths and thicknesses to account for in- (i.e. crack length) and out of (i.e. thickness) plane constraint effect. Fracture tests performed according to ASTM E1820-18 except for the sample thickness and crack lengths. challenges for easuring the cr ck extension for resistance curve method as a result of deviating from the standard is discussed. The failure of the sa ples was also assessed by Failure Assessment Diagram (FAD). The results sh wed that unloading compliance extremely und restimate the crack exte sion in th pr sence of significant plastic deformation of the samples. The results also showed that the plastic collapse occurs in all samples before crack starts to grow, in the blunting regime.

© 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.

Keywords: Austenitic stainless steel; fracture toughness; in-plane constraint; out of plane constraint; plastic collapse Keywords: Austenitic stainless steel; fracture toughness; in-plane constraint; out of plane constraint; plastic collapse

* Corresponding author. Tel.: +44 7746872877. E-mail address: m.mokhtari@bristol.ac.uk * Correspon ing author. Tel.: +44 7746872877. E-mail address: m.mokhtari@bristol.ac.uk

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.

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.2019.08.188