Characterization of mechanical properties in weld metal using inverse modelling

Abstract

Nowadays, more oil and gas transportation pipelines are constructed in areas with permafrost and/or higherseismic activity. These pipelines can be subjected to longitudinal plastic deformations necessitating a strainbased design. Since girth- and seam welds are critical in terms of structural integrity, it is desirable to knowtheir mechanical properties. In a strain based design context, the accurate determination of yield strengthand hardening are necessary. A longitudinally extracted (is parallel to the pipe axis) specimen notched atthe weld region and loaded in tension, in combination with inverse modelling is assumed to be a valuabletool to determine these properties. This notched cross weld test ensures that the largest deformations willoccur at the weld, thereby allowing to fully determine the stress-strain behaviour of the weld metal. Inversemodelling combines experimental full-field strain data with numerical simulations to determine theconstitutive parameters. Strains will be measured experimentally and compared with simulated data. Byminimizing their difference, i.e. a certain cost function, a correspondence is found and the desiredparameters are determined. This paper focuses on one aspect of the inverse modelling framework, thedevelopment of the parametric finite element model.