基于CEL方法的异种合金搅拌摩擦搭接焊数值模拟

Numerical simulation of friction stir lap welding based on CEL method

基于耦合欧拉-拉格朗日(CEL)方法,建立铝-镁异种合金搅拌摩擦搭接焊(FSLW)的数值模型,分析了等效塑性应变分布特点和焊接缺陷的形成。结果表明,焊缝表面的等效塑性应变明显高于搭接面,且焊缝两侧的等效塑性应变分布明显不对称。增大转速可提高等效塑性应变。当转速从1400 r/min增大为1600 r/min时,搭接面的等效塑性应变整体增幅不大,此时增大转速对塑性变形影响较小,但前进侧等效塑性应变明显高于后退侧。在转速1000 r/min条件下,通过数值模拟发现,搭接面前进侧出现孔洞缺陷;转速分别为800 r/min和1400 r/min条件下,通过数值模拟分析了焊缝表面飞边的特点,并通过试验验证了孔洞和飞边。在搭接量60 mm、转速1400 r/min、焊速120 mm/min的条件下,能够观察到在焊核区中心存在等轴晶粒以及2种材料结合面处的沿晶粒生长方向的柱状晶。

Based on the coupled Eulerian-Lagrange(CEL)method,the numerical model of friction stir lap welding(FSLW)of aluminum magnesium dissimilar alloy is established,and the distribution characteristics of equivalent plastic strain and the formation of welding defects are analyzed.The results show that the equivalent plastic strain on the weld surface is significantly higher than that on the lap surface,and the distribution of equivalent plastic strain on both sides of the weld is obviously asymmetric.Increasing the rotational speed can increase the equivalent plastic strain.When the rotational speed increases from 1400 r/min to 1600 r/min,the overall increase of the equivalent plastic strain on the lap surface is small.At this time,increasing the rotational speed has little effect on the plastic deformation,but the equivalent plastic strain on the advancing side is significantly higher than that on the retreating side.Under the condition of rotating speed of 1000 r/min,it is found that there are void defects on the advancing side of lap joint through numerical simulation;Under the conditions of rotating speeds of 800 r/min and 1400 r/min respectively,the characteristics of weld surface flash are analyzed through numerical simulation,and the voids and flash are verified by experiments.Under the conditions of 60 mm overlap,1400 r/min rotation speed and 120 mm/min welding speed,there are equiaxed grains in the center of the nugget zone and columnar crystals along the grain growth direction at the junction of the two materials.