Abaqus welding simulation incorporating steel phase transformations and microstructural mapping

Over the last seven years, finite element (FE) simulations of fusion welding have been performed using the ABAQUS software package at the University of Nottingham. These simulations (validated using experimental measurements) can give valuable information about welding-induced residual stresses and distortions, along with microstructural evolution. The results can be fed into heat treatment models, where the material properties can evolve and the residual stresses relax and redistribute. As a final step, input may then be provided for life assessment analyses.

This paper reports a 2D axisymmetric welding simulation for the residual stress and microstructural analysis of multipass, thick-walled martensitic steel pipes for power plant applications. The different challenges experienced and the FE techniques used and their implementation in ABAQUS are discussed.

A solid mechanics approach has been adopted, which models the global thermomechanical behaviour of welding using a heat source definition to apply heat flux. Sequentially-coupled nonlinear thermal and mechanical FE analyses are performed, both requiring temperature-dependent material property data. The element birth/quiet element technique is applied to simulate the deposition of weld metal.

Pre-heat, welding, interpass, cooling and subsequent post-weld heat treatment (PWHT) stages have been accurately reproduced. Peak temperatures are used to determine columnar and equiaxed grain weld regions. Solid state phase transformations (martensite↔austenite) and their effects on volume and yield stress have also been implemented.