The through-thickness distribution of residual stress at weld toes and weld center lines was conducted and studied, which was the basic input parameter for engineering critical assessment (ECA) in BS 7910 Annex Q. A thermal-mechanical coupled welding residual stress simulation with/without repair welding of thick wall pipeline was carried out first. To further investigate the r/t ratio effect and heat input effect on welding stress profile, welding pass size merging strategy was built based on mechanical basis, whereas a minimum number of 10 weld layers were utilized in FEA to improve efficiency, without affecting the through-thickness residual stress distribution. The effect of r/t ratio on through-thickness residual stress distribution was obtained and was described as membrane stress and bending stress. The hoop and axial bending stress at weld toe decreased gradually as r/t ratio increased, while hoop membrane stress at weld toe gradually increased as r/t ratio increased. Moreover, a similar trend was also observed at weld centerline. Analytical equations for through-thickness residual stress predictions were established both for origin welding as well as repair welding in depth. The more ideal residual stress distribution after repair welding can be obtained by repairing a smaller depth, which is the shallower the better. Residual stress was expressed as logarithmic functions for original weld and repaired weld, in terms of axial bending, hoop bending, and hoop membrane.

对焊趾和焊接中心线处残余应力的全厚度分布进行了研究，这是 BS 7910 Annex Q 中工程临界评估 (ECA) 的基本输入参数。厚壁管道先不补焊。为了进一步研究 r/t 比和热输入对焊接应力分布的影响，基于机械原理构建了焊道尺寸合并策略，而 FEA 中使用最少 10 个焊层来提高效率，同时不影响通过- 厚度残余应力分布。获得了 r/t 比对厚度方向残余应力分布的影响，并将其描述为膜应力和弯曲应力。焊趾环向和轴向弯曲应力随着r/t比的增大而逐渐减小，而焊趾处的环向膜应力随着r/t比的增大而逐渐增大。此外，在焊缝中心线处也观察到类似的趋势。建立了原点焊和深部补焊的全厚度残余应力预测分析方程。补焊后的残余应力分布越小越好，越浅越好。残余应力表示为原始焊缝和修复焊缝的对数函数，在轴向弯曲、环向弯曲和环向膜方面。在焊接中心线处也观察到类似的趋势。建立了原点焊和深部补焊的全厚度残余应力预测分析方程。补焊后的残余应力分布越小越好，越浅越好。残余应力表示为原始焊缝和修复焊缝的对数函数，在轴向弯曲、环向弯曲和环向膜方面。在焊接中心线处也观察到类似的趋势。建立了原点焊和深部补焊的全厚度残余应力预测分析方程。补焊后的残余应力分布越小越好，越浅越好。残余应力表示为原始焊缝和修复焊缝的对数函数，在轴向弯曲、环向弯曲和环向膜方面。