基于DEFORM的搅拌摩擦焊接过程数值模拟及流动分析

Numerical simulation and analysis of the material flow of friction stir welding based on DEFORM

以塑性力学的基本理论为依据,通过Arbitrary Lagrangian-Eulerian(ALE)有限元方法,使用动态适应性网格建立焊接过程塑性金属流动有限元模型,利用金属塑性成形有限元软件Deform-3D模拟搅拌摩擦焊成形过程,得到了搅拌摩擦焊过程中的温度场分布以及焊缝区金属的流动。通过有限元模拟发现:焊接过程中由于搅拌针不断前进而在其后面形成空腔,搅拌摩擦焊的过程即为金属填充空腔的过程,FSW中常见的洋葱圆环结构就是涡旋状速度场造成的;通过模拟发现前进侧与返回侧的温度场关于焊缝分布不对称,呈倒三角形分布,且前进边温度低于返回侧,并因材料在不同温度下的剪切强度的差别而对焊缝流场产生影响,并与实际焊缝区形状相符;模拟采用点追踪技术结合嵌入性实验发现焊缝水平面内前进侧与返回侧塑性金属流动趋势不同,前进侧大量金属流向返回侧并在轴肩的下压力作用下向焊缝内部运动。

In this paper ,the numerical simulation of the flow pattern in friction stir welding was carried out base on arbitrary eulerian lagrangian finite element formulation. The adaptive meshing was utilized in order to solve large dastie - plastic deformation and material properties depending temperature. This model is calibrated by comparing with experimental results of metal flow and temperature distribution. It can be found in the simulation result： that the cavity is formed by the advancing of the pin, the process of the FSW is consisted by the falling up of the formation and disappearance of the cavity. The onion loop texture is formed by the vortex field. The temperature distribution feature can be found that the temperature of retreating side is higher than advancing side ,the geometry of the temperature field is like the upset triangular. It is uniform the simulation result and the practical form. The influence of the temperature to the material flow was gone through the difference of the shear strength. To investigate the actual material flow during friction stir welding, tracking point technology is used and the marked experiment is used as verification technique. The flow pattern of the material on the two sides of the advancing side and the retreating side is different. Material at the advancing of the weld flows to the retreating side. And backwards contributes to the extrusion of the top of the pin is the weakness of the welded joint, material on the two sides of this area flows forwards and upwards and the height which the material shifts to the upper part exceeds the thickness of the overlap - welded plate of the under layer.