PSI - Issue 28

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

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 28 (2020) 2078–2085

© 2020 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 European Structural Integrity Society (ESIS) ExCo Abstract When characterising the failure behaviour of materials, it is often necessary to construct a ductile failure locus which relates the strain at failure to the level of stress triaxiality exhibited. The data required for a locus can be determined through multiaxial tensile testing of notched bars, using a range of notch radii to produce different levels of triaxiality. The triaxiality and strain values may be calculated using expressions derived by Bridgman, which only require knowledge of the cross-sectional radius and edge profile radius of curvature. However, the validity of such expressions may not extend to sharp notches. Experimental testing of notch bars was performed, and specimen profiles measured through image capture for the duration of the tests. These data were processed and triaxiality and strain values were calculated using the Bridgman expressions. Finite element analyses were performed to simulate the test specimen geometries, and results for the triaxiality and strain were compared to Bridgman’s estimates. Very poor agreement was found between the two methods of determining the triaxiality values, and Bridgman’s assumption that the strain is uniform across the radius of the specimen was found invalid under these conditions. It is thought this is likely due to the fact Bridgman’s analysis was for specimens that were initially smooth and formed a neck at high strains, as opposed to specimens that are initially notched. These findings suggest that it is not accurate to use the Bridgman expressions to formulate a failure locus for tensile notch bar tests, and it is instead recommended that the finite element analysis is employed for these purposes. © 2020 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 European Structural Integrity Society (ESIS) ExCo Keywords: Ductile failure; Bridgman; notch bar; triaxiality m 1st Virtual European Conference on Fracture A comparison of stress triaxiality and strain distributions in notched bar geometries as determined by Bridgman expressions and finite element analysis Michael Jones a *, Matthew Hole a , Catrin Mair Davies a a Department of Mechanical Engineering, Imperial College London, South Kensington, SW7 2AZ, United Kingdom

* E-mail address: michael.jones12@imperial.ac.uk

2452-3216 © 2020 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 European Structural Integrity Society (ESIS) ExCo

2452-3216 © 2020 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 European Structural Integrity Society (ESIS) ExCo 10.1016/j.prostr.2020.11.032