搅拌摩擦焊接头残余应力的试验

搅拌摩擦焊是 90年代出现的一种新型焊接技术 ,特别适用于熔化焊接性差的铝合金等材料。搅拌摩擦焊接头的纵向残余应力分布具有高应力梯度的特点 ,传统的应变片钻孔法不能满足测量要求。提出了云纹干涉钻孔法测量非均匀分布残余应力的计算公式和试验方法。该方法由云纹干涉法测量钻孔释放的位移条纹 ,通过确定孔边待测区域内三个测量点的条纹值 ,可直接得到该区域内的残余应力。利用该方法测量了铝合金薄板搅拌摩擦焊接头纵向残余应力沿深度和横向的分布 ,其分布规律表现为在搅拌带内为拉应力 ,搅拌带外残余应力的值迅速下降 ,并变为压应力以保持平衡。

Study on Residual Stress of Friction Stir Welding by Moiré Interferometry and Hole-Drilling Method

Friction stir welding(FSW) is a new welding technique since 90''s,which is especially suitable for materials of poor fusion weldability,such as aluminium alloy.Residual stress distribution of FSW has high gradient,which makes the conventional strain gauge hole drilling method unsuitable.A combined method of moiré interferometry and incremental hole drilling was conducted to study non uniform residual stresses,calculation formula and the experimental technique were presented.This method makes use of moiré fringe patterns of three measurement points to calculate the local residual stresses of the interested region around the hole.This paper studied the non uniform residual stresses of a friction stir welded aluminium alloy plate in plane and in depth using the presented method.Experimental results show that the dominant longitudinal residual stress field is tensile within the friction band,just outside the band where the field drops steeply.Further out there are regions of balancing compression residual stress falling to near zero.