3D modeling for effect of tool eccentricity on coupled thermal and material flow characteristics during friction stir welding

搅拌头摆动对搅拌摩擦焊接耦合热流行为影响的三维数值模拟

A novel three-dimensional numerical model is proposed to investigate the effect of tool eccentricity on the coupled thermal and material flow characteristics in friction stir welding(FSW) process.An asymmetrical boundary condition at the tool-workpiece interface,and the dynamic mesh technique are both employed for the consideration of the tool eccentricity during tool rotating.It is found that tool eccentricity induces the periodical variation of the heat densities both at the tool-workpiece interface and inside the shear layer,but the fluctuation amplitudes of the heat density variations are limited.However,it is demonstrated that tool eccentricity results in significant variation of the material flow behavior in one tool rotating period.Moreover,the material velocity variation at the retreating side is particularly important for the formation of the periodic characteristics in FSW.The modeling result is found to be in good agreement with the experimental one.

提出一种新的三维数值模型,研究搅拌头摆动对搅拌摩擦焊接过程中热流耦合特征的影响。模型中考虑搅拌头在旋转过程中的偏心现象,采用搅拌头-工件界面的非对称边界条件,并使用动态网格技术。研究发现,搅拌头偏心会引起搅拌头-工件界面和剪切层内部热流密度的周期性变化,但是,热流密度变化的波动幅度有限。模拟结果证明搅拌头偏心会使得搅拌头旋转周期内的材料流动行为发生显著变化。此外,材料在后退侧的速度变化对搅拌摩擦焊接周期性特征的形成尤为重要。模拟结果与实验结果吻合良好。