Investigation of fracture in small-scale SENT tests of a welded X80 pipeline steel using Digital Image Correlation with node splitting

Abstract Single Edge Notch Tension (SENT) tests have been carried out on girth welded X80 pipeline steel using two different weld materials to investigate the effect of weld metal mismatch on ductile crack growth. In addition to the traditional clip gauge CMOD/CTOD measurements, information has been obtained by applying Digital Image Correlation (DIC). The DIC mesh has been modified to allow for node splitting in order to capture the discontinuous displacement field of the propagating crack. Parameters such as crack path, crack length and crack opening have been successfully measured using this modification to the standard DIC analysis. The paper contains a description of the material and the experimental setup, as well as results from the experimental tests, where the SENT specimens have been subjected to monotonic tension loading. Emphasis is laid on the DIC analysis and the additional information gained from this approach. Parallelization of the DIC algorithm and a discussion on the accuracies of 2D versus 3D DIC analyses are also included in this paper.

[1]  Tore Børvik,et al.  Experimental and numerical investigation of fracture in a cast aluminium alloy , 2010 .

[2]  Stéphane Roux,et al.  Extended digital image correlation with crack shape optimization , 2008 .

[3]  T. Børvik,et al.  Continuous out-of-plane deformation measurements of AA5083-H116 plates subjected to low-velocity impact loading , 2010 .

[4]  Egil Fagerholt.  Field Measurements in Mechanical Testing Using Close-Range Photogrammetry and Digital Image Analysis , 2012 .

[5]  Bård Nyhus,et al.  SENT Specimens an Alternative to SENB Specimens for Fracture Mechanics Testing of Pipelines , 2003 .

[6]  M. Langseth,et al.  The behaviour of an offshore steel pipeline material subjected to bending and stretching , 2012 .

[7]  Erling Østby,et al.  Fracture response of pipelines subjected to large plastic deformation under tension , 2004 .

[8]  Claudio Ruggieri,et al.  Correlation of fracture behavior in high pressure pipelines with axial flaws using constraint designed test specimens––Part I: Plane-strain analyses , 2005 .

[9]  J. Kajberg,et al.  Characterisation of materials subjected to large strains by inverse modelling based on in-plane displacement fields , 2004 .

[10]  Michael A. Sutton,et al.  The effect of out-of-plane motion on 2D and 3D digital image correlation measurements , 2008 .

[11]  Nikzad Nourpanah,et al.  Development of a reference strain approach for assessment of fracture response of reeled pipelines , 2010 .

[12]  Christian Thaulow,et al.  A notched cross weld tensile testing method for determining true stress–strain curves for weldments , 2002 .

[13]  Jun Zhang,et al.  On the use of the digital image correlation method for heterogeneous deformation measurement of porous solids , 2011 .

[14]  S. Roux,et al.  “Finite-Element” Displacement Fields Analysis from Digital Images: Application to Portevin–Le Châtelier Bands , 2006 .

[15]  P. J. Budden.  Failure assessment diagram methods for strain-based fracture , 2006 .