École Nationale Supérieure de
Techniques Avancées

Abstract

The purpose of this work is to establish a reliable computational method for the simulation of friction stir welding. The numerical simulation consists of two successive steps. First, a thermohydrodynamic model based on a viscous incompressible non-Newtonian constitutive law is used to establish the temperature field and the material flow around the tool. To this end, two coefficients related to the contact description have been determined by an optimisation procedure using experimental data obtained by IR thermography. The second part is devoted to the determination of the residual state of a friction stir welded assembly. To this end, an elastoviscoplastic constitutive law for aluminium alloys at temperatures between $20^oC$ and $500^oC$ has been developed. Furthermore, the whole thermal, metallurgical and mechanical history of each particle is taken into account by using the path lines previously computed. A metallurgical model is used to calculate the fraction of dissolved precipitates which is related to the yield stress of the alloy. Finally, the steady state assumption leads to a substantial reduction of computational time. A good agreement between experimental and simulated data has been observed. Moreover, a parametric study about the influence of welding and rotation speeds on residual stresses has been carried out.