搅拌摩擦焊接材料流动模型及在缺陷预测中的应用

为了研究搅拌头倾角对搅拌摩擦焊接过程的影响机理，基于DEFORM-3D软件建立了带倾角的FSW三维热-力耦合模型，模拟了搅拌摩擦焊接过程中焊缝区材料的三维运动轨迹，对比分析了有无倾角时FSW过程中材料流动行为的差异. 结果表明，前进侧材料绕搅拌针旋转后大部分沉积于搅拌头后方前进侧区域，返回侧的材料大部分被搅拌头旋推至后方而沉积；采用倾角可以增强搅拌头后方材料从返回侧运动至前进侧区间的流动性，同时还有利于增强材料在厚度方向的运动能力. 根据模拟的材料流动行为对接头缺陷进行了趋势预测，预测结果与试验结果吻合良好.

Modeling of material flow during friction stir welding and the application for defect prediction

In order to research the mechanism influenced by the tilt angle of tool pin during friction stir welding, the thermal-mechanical coupled model considering the tilt angle was established based on DEFORM-3D software. The three-dimensional material flow in the welding seam region was simulated, and the difference of the material flow behavior influenced by tool tilt angle of 0° and 2° was compared and analyzed. The results showed that most of the materials in the front advancing side deposited in the region of rear advancing side after rotating around the tool pin, while most of the materials in the front retreating side were pushed by the tool pin and deposited in the rear region. It was observed that the tilt of tool pin increased the fluidity of the material between the rear retreating side and the rear advancing side, meanwhile, the flowing behavior in the thickness was increased accordingly. The simulation results of the joint morphology agreed well with the corresponding experimental results, which illustrated that the numerical model of the material flow considering the tool tilt angle can be used for predicting the tendency of welding joint defect.