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

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.

► SENT tests of X80 base material with over- and under-matched weld material.
► Combining traditional clip gauge measurements with optical measurements.
► A node-splitting approach in DIC has been implemented.
► Extraction of fracture parameters such as crack path, crack length, CMOD and CTOD.
► Measurements of discontinuous displacement and strain fields close to a crack.