Experimental analysis of stress-strain field with stress concentrator using digital image correlation

0455947 - ÚTAM 2016 RIV CZ eng B - Monography
Jandejsek, Ivan
Experimental analysis of stress-strain field with stress concentrator using digital image correlation.
Praha: ČVUT v Praze, Fakulta stavební, 2016. 104 s. ISBN 978-80-01-05890-9
R&D Projects: GA ČR(CZ) GA15-07210S
Institutional support: RVO:68378297
Keywords : fracture mechanics * digital image correlation * J-integral * CTOD * experimental measurement
Subject RIV: JL - Materials Fatigue, Friction Mechanics

The aim of this work is to develop an experimental methodology based on the Digital Image Correlation (DIC) method for precise full-field in-plane stress-strain analysis in regions containing a stress concentrator. Several techniques and corrections were proposed and developed improving the conventional DIC and data post-processing to achieve a high degree of accuracy of full-field strain/stress results. It is shown that fracture parameters such as the J-integral can be extracted directly from measured fields without the need for external FEM simulations. The optical nature of the DIC method also allows simultaneous measurements of CTOD and crack growth. The developed methodology is employed in the field of elastic plastic fracture mechanics to study the fracture behaviour of ductile metals. Two particular experimental studies are carried out in this work. The first fracture test with a non-standard thin-sheet specimen made of aluminium alloy addresses the known problem of the different fracture behaviour of thin-sheets, while the second study deals with a fracture test with a low-strength steel commonly used in the pipeline industry. The second test satisfied the ASTM standard for J integral testing; therefore, the results of the proposed methodology are compared with the standard engineering approach. It was shown that the ASTM standard gives non-conservative results. The fracture toughness of the tested materials in terms of the critical J integral is determined in both cases.
Permanent Link: http://hdl.handle.net/11104/0256563