三维搅拌摩擦焊接传热与塑性流动分析模型

为研究搅拌摩擦焊接过程热流相互作用下的温度场、速度场和粘度场,将材料看成是层流、粘性、非牛顿流体,基于流体力学理论,建立了搅拌摩擦焊接过程的三维热流分析模型.给出了焊接过程热输入与搅拌头的旋转频率、工件运动速度、搅拌头尺寸及材料发生屈服时的剪应力的数学关系式,并将其作为热边界条件加入到了模型中.结果表明,搅拌头前部温度低于后部,温度梯度前部大于后部；受搅拌头周围材料流动的影响,接近搅拌针的区域,后退侧温度高于前进侧；材料上部速度、粘度受轴肩影响较大,下部主要受搅拌针影响；计算得到的热力影响区与试验结果有较好的对应关系.

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.