三维搅拌摩擦焊接过程数值模拟

Numerical simulation of 3D friction stir welding process

将搅拌摩擦焊接过程中材料的流动看作是层流、粘性、非牛顿流体绕过旋转的圆柱体,并基于流体力学理论,建立了三维搅拌摩擦焊缝金属塑性流动的数值分析模型。计算结果表明,在焊缝上部表面附近,由于搅拌头轴肩的影响,材料流动比较混乱,发生多次绕流现象;焊缝下部材料流动规律性较明显:只有很少一部分靠近搅拌头探针的材料在焊接过程中受到探针的作用而发生变形和流动,在大多数的模拟条件下,探针直径范围内的材料仅仅在回撤边一侧沿旋转方向绕过探针。焊缝中部具有底部和上部材料的流动特点,是探针和轴肩共同影响的结果。采用“标记嵌入技术”对焊缝金属流动进行可视化研究,试验结果与模拟结果进行了验证,模拟结果能很好地预测塑性金属流动趋势。

A three-dimensional friction stir welding process model was developed based on fluid mechanics. The material transport in the welding process was regarded as a laminar, viscous and non-Newtonian liquid flows past a rotating cylinder pin. Results of the simulation show that the flow in the top weld is disordered because affected by the shoulder of the friction stir tool and the material under the shoulder moved around the pin for several circles. The flow in the bottom weld is more disciplinary, and just a little material close to the pin has experienced extreme deformation during the welding process. Material within the pin diameter passes the pin only on the retreating side in the rotation direction. The flow in the middle weld is affected by the pin and the shoulder and has both characters of the flow in the top and bottom weld. Material flow visualization experiments of “ marker insert technology ”was used to validate the simulated results. The experimental images agree well with the simulated results and the three-dimensional model can predict many of the trends observed in the experiments.