铝合金搅拌摩擦焊接头残余应力分布

Residual stresses for friction stir welded Al sheets

采用小孔法对3 mm厚2024-T4铝合金板搅拌摩擦焊对接接头的残余应力分布规律进行研究。为了衡量钻孔引入应变对结果的影响,测量了退火2024铝合金板钻孔产生的应变,将其作为附加应变对焊接试件上测得的应变结果进行修正。结果表明,在试验条件下得到的焊接接头的残余应力以纵向应力为主,横向应力相对很小;纵向高应力区集中在轴肩作用区域,呈不对称分布,前进侧应力高于返回侧,在轴肩作用区域之外应力值迅速降低,在距焊缝中心较远的区域转变为压应力;纵向残余应力峰值为164.5 MPa。分析认为,机械搅拌和焊接温度场的叠加作用造成焊缝两侧纵向残余应力的不对称分布。

The residual stresses for friction stir welded 3 mm-thick 2024-T4 aluminum alloy sheets had been investigated by using Mathar method.To reduce the influence of drilling process induced strains on the experimental results,stress-free 2024 aluminum alloy sheets were drilled and the relieved strains were measured.The results showed that the longitudinal residual stresses are much greater than the transverse residual stresses in the friction stir welded joint;the longitudinal tensile residual stresses are concentrated near the tool shoulder direct affected zone and asymmetrically distributed at the different sides of the weld center and it is high at the advancing side and relatively low at the retreating side;the longitudinal residual stresses at outside the tool shoulder direct affected zone are decreasing remarkably and become compressive residual stresses away from the weld center;the peak value of the longitudinal residual stresses is 164.5 MPa.The mechanism of the residual stresses distribution of the welded joint was discussed preliminarily.