Ductile extension of 3-D external circumferential cracks in pipe structures

2011, Volume 5, Issue 3

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Frontiers of Structural and Civil Engineering >> 2011, Volume 5, Issue 3 doi: 10.1007/s11709-011-0115-9

Ductile extension of 3-D external circumferential cracks in pipe structures

Department of Civil and Environmental Engineering, National University of Singapore, Singapore 119077

Available online: 2011-09-05

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Abstract

This study investigates the ductile fracture resistance of 3-D external circumferential cracks in the wall of a steel pipe under remote tension, using a damage-mechanism model originally proposed by Gurson and Tvergaard. The ductile crack extension utilizes an element extinction technique implemented in the computational cell framework. The key parameter for the computational cell method, i.e., the initial porosity ratio , is calibrated using both the fracture resistance and the load-deformation responses obtained from fracture tests of multiple single-edge bend [SE(B)] specimens made of high-strength steel, HY80, which has a yield strength of 630 MPa. The fracture resistance along the 3-D semi-elliptical crack front is computed from the calibrated cell model. Based on the similarity concept in the near-tip stress-strain fields, this study demonstrates that an equivalent 2-D axi-symmetric model provides conservative estimations of the fracture resistance for 3-D circumferential cracks in pipes.

Keywords

ductile fracture ; computational cell method ; G-T model ; J-R curve

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