Three dimensional model for heat transfer and plastic flow of friction stir welding

In order to study the temperature field,velocity field and viscosity field of friction stir welding under the interaction of thermal and fluid,the material was regarded as laminar, viscosity,non-Newtonian fluid.Based on the theory of fluid mechanics, three dimensional thermal and fluid model of the friction stir welding was founded.A mathematical relationship between the welding heat input and rotating speed,workpiece motion velocity, size of stirring tool and the shear stress of material was adopted, which is used as the thermal boundary conditions in modeling.Analysis results indicate that the temperature of the head of stirring tool is lower than that of the tail,but the temperature gradient is larger.Affected by material flow around the stirring tool,the temperature in retreating side is higher than that of the advancing side.Velocity and viscosity of upper material is affected mainly by shoulder,while the lower material is affected mainly by stirring pin.The calculated thermal mechanical affected zone (TMAZ) has a good corresponding relationship with the experimental result.