焊缝强度对薄壁焊管绕弯起皱及壁厚的影响

Influence of weld relative strength on wrinkling and wall thickness distribution of thin-walled seamed tube in rotary draw bending process

在薄壁焊管绕弯成形中,焊管起皱及壁厚分布受焊缝相对基体材料强度的影响.提出了焊缝相对强度因子Sf的概念,以反映焊缝相对于基体材料的强弱性,并推导了其解析表达式,给出了适用于焊管的起皱趋势判断公式.同时,基于有限元模拟,分析了焊缝相对强度因子对焊管绕弯成形过程中起皱及壁厚变化的影响规律.研究表明:1)当焊缝相对强度因子Sf的变化由焊缝强度系数改变引起时,起皱趋势随Sf的增大而略有增大;Sf的变化由焊缝硬化指数或厚向异性指数改变引起时,起皱趋势随Sf的增大而减小.2)随着焊缝相对强度因子Sf的增大,壁厚减薄率逐渐减小.当Sf的改变由焊缝厚向异性指数引起时,Sf对壁厚减薄率的影响最大,当Sf增大0.89%时(由1.2788增加到1.2902),壁厚减薄率的变化率为37.61%(由10.9%降至6.8%).

In thin-walled seamed tube rotary draw bending,the relative strength of weld to base meal has an influence on the wrinkling and wall thickness distribution.In this study,a concept of weld relative strength factor S f is proposed and its expression is deduced.A criterion is put forward to evaluate the wrinkling tendency of seamed tube.By employing FE simulation,the influence of weld relative strength factor on the wrinkling and wall thickness distribution of the seamed tube is studied.The results show that： 1） The wrinkling tendency increases marginally with the increasing of S f,when the change of S f is induced by weld strength coefficient;decreases with the increasing of S f,when the change of S f is caused by the weld strain hardening exponent or anisotropy exponent.2） The wall thinning degree decreases with an increase in S f.The S f has the most significant influence on the wall thinning degree when the change of S f is caused by the weld anisotropy exponent.The changing ratio of wall thinning degree is 37.61%（from 10.9% to 6.8%）,when the S f increases 0.89%（from 1.2788 to 1.2902）.