二维搅拌摩擦焊接过程的数值模拟

Numerical simulation of 2D 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,建立了二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: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,直接影响到材料的流动;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,而不是在探针两侧绕流;绕过探针以后,焊缝金属材料又以恒定的速度,继续向前移动;变形区域内流变材料的流动速度大于探针直径范围外流变材料的流动速度。采用“标记嵌入技术”对焊缝金属流动进行了可视化研究,并对实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。

The material transport in the welding process was regarded as a laminar, viscous and non-Newtonian liquid flows past a rotating cylinder pin. Based on fluid mechanics a two-dimensional friction stir welding (FSW) process model was developed. The results of the simulation show that just a little material close to the pin is affected during the welding process, and the material has experienced extreme deformation. Material within the pin diameter passes the pin only on the retreating side in the rotation direction and not on both sides of the pin. The speed of the material in the region affected by the pin is faster than the material outside of the deformed region. Material flow visualization experiments of “marker insert technology” are used to validate the simulated results. The experimental images agree well with the simulated results and the two-dimensional model predicts many of the trends observed in the experiments.