A Study of Anisotropic Creep Behaviour of a 9CrMoNbV Weld Metal Using Damage Analyses with a Unit Cell Model

Abstract

The deformations and failure life ratios, obtained from creep damage analyses using a ‘unit cell’ model, are used to describe the ‘bulk’ anisotropic creep behaviour of a 9CrMoNbV weld metal. The model consists of a columnar region and a weaker equiaxed (fine-grained and coarse-grained) region, and is based on the assumption that the structure of the weld metal has a regular geometric pattern. The creep damage analyses were conducted using a single-variable Kachanov type damage law, for which the material constants are based on experimental data. The bulk material ‘uniaxial’ creep rupture lives in the three principal directions were investigated taking account of the effects of the length to width ratio of the unit cell, the material property mismatch for the two regions, and the volume fraction of the columnar region. Results from the analyses indicate that the predicted failure modes are the same as those observed in an experimental study of the weld metal.