Friction stir welding is a solid state thermo-mechanical deformation process from which the plasticisation behaviour of the stirred material can be evaluated through the study of flow stress evolution. Flow stress data also supporting the development of a local microstructural numerical model have been generated. Hot compression testing of DH36 steel has been performed at a temperature range of 700 o C1100 o C and strain rates from 10 -3 s -1 to 10 2 s -1 to study the alloys thermo-mechanical deformation behaviour in conditions which simulate the actual friction stir welding process. It has been found that the evolution of flow stress is significantly affected by the test temperature and deformation rate. The materials constitutive equation and constants have been calculated after analysis of these data. Preliminary numerical analysis results are in good agreement with experimental observations.

This paper describes the development of a multiphysics welding simulation model based on the discontinuous Galerkin (DG) finite-element method. Our numerical model implements a classical enthalpy-porosity constitutive law accounting for hydrodynamic and thermal effects occurring during the phase transition from solid to liquid metal. The objective of the study is to present the verification of our numerical framework and explore the applicability of the DG formulation to the simulation of welding processes. Three computational examples of increasing complexity are presented.

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