Effect of pre-crack in the fracture properties of steel pipes used in oil type API 5L X70

In this work, we studied the impact resistance of the weld metal of a steel API 5L X70, assessing the influence of geometry and dimensions of the specimen fracture toughness. Curves resistance to crack propagation ductile ( J – R ) following the methodology “Single Specimen” together with the variat...

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Bibliographic Details
Published in:Journal of the Brazilian Society of Mechanical Sciences and Engineering 2016-10, Vol.38 (7), p.2117-2127
Main Authors: Francisco, Julio C. S., Moreno, Joao R. S., Filho, Waldek W. B., Ruchert, Cassio O. F. T.
Format: Article
Language:English
Subjects:
Alloys
Crack initiation
Crack propagation
Ductile fracture
Elastic properties
Engineering
Fracture mechanics
Fracture toughness
High strength low alloy steels
Impact resistance
Mechanical Engineering
Notches
Plane strain
Plane stress
Surface cracks
Technical Paper
Weld metal
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Summary:In this work, we studied the impact resistance of the weld metal of a steel API 5L X70, assessing the influence of geometry and dimensions of the specimen fracture toughness. Curves resistance to crack propagation ductile ( J – R ) following the methodology “Single Specimen” together with the variation of the elastically generated by the crack initiation (CMOD) providing a load versus displacement/length graph for crack (ASTM E1820-05). Tests were conducted on samples according to the standard SE( T ) to surface cracks ( a / W  = 0.2) and deep ( a / W  = 0.5) and the ratios W / B  = 1.0 and 2.5, keeping the plane strain. The results show that regardless of initial crack dimension, no significant differences were observed in the curves J – R , confirming the similarity of the curves for W / B  = 1.0 for any a / W . However, most of the samples showed anomalous ductile crack growth, generating high plane stress along the sides of the notches. Samples tested according to the J – R curve showed no cracks of encapsulating, and the values of the crack length a i and a f are very close to those obtained by the elastic flexibility variation method. Since delamination influenced the properties of impact for increased efforts to crack propagation, mainly by microstructural conditions of the samples.
ISSN:1678-5878
1806-3691
DOI:10.1007/s40430-015-0469-3