Crack Tip Opening Angle as a Fracture Resistance Parameter to Describe Ductile Crack Extension and Arrest in Steel Pipes under Service Pressure

Autor: M. Ben Amara, Julien Capelle, Zitouni Azari, Guy Pluvinage
Přispěvatelé: Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)
Rok vydání: 2015
Předmět:
Zdroj: Physical Mesomechanics
Physical Mesomechanics, Springer, 2015, 18 (4), pp.355-369. ⟨10.1134/S1029959915040086⟩
ISSN: 1990-5424
1029-9599
DOI: 10.1134/s1029959915040086
Popis: International audience; The angle between two element sides representing the crack tip is defined as the crack tip opening angle (CTOA). Its critical value is used as a criterion of fracture resistance for characterizing stable tearing in thin metallic materials. Various methods are used for determination of the CTOA. Optical microscopy is one of the most common methods as well as fitting of experimental loaddisplacement diagrams by the finite element method (DIC). Additionally, analytical analysis using the experimental loaddisplacement curve method (SSM) derived from the plastic hinge model of deflection in three-point bending of a ductile specimen is applied. This approach assumes a constant rotation centre distance. Values of CTOA for API 5L X65 pipe steel found by three methodsDIC, CNM, and SSMare given. Values of CTOA given by these three methods are similar and close to 20°. A discussion on the different parameters used to characterize the fracture resistance of running cracks in a pipe under service pressure is presented. The energy of fracture at impact determined by Charpy or drop-weight tear test (DWTT) tests and the critical J energy parameter are considered as well as the yield locus after damage, cohesive zone energy, and CTOA is another approach. One notes that CTOA is assumed to be constant during stable crack extension and decreases linearly with crack length during the instable and primary phase. A numerical technique to describe a ductile running crack using the node release technique and using CTOA as the fracture resistance criterion is presented. This method is compared with three different two-curve methods (TCMs): the Battelle, high strength line pipe (HLP), and HLP-Sumitomo methods. The Batelle TCM, as the oldest method, based on Charpy energy, gives a strongly conservative prediction. Predictions by the CTOA method are close to those obtained by the HLP-Sumitomo one.
Databáze: OpenAIRE
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