Nowadays automated welding processes produce high-quality welds with smooth and regular global weld geometry. However, the local geometry of the weld exhibits a certain amount of variance in its topography due to dynamic effects of the welding process itself. The subsequent change in local stress concentrations affects the fatigue behaviour of welded structures. In literature, numerous equations for the estimation of a weld’s stress concentration based on characteristic parameters of the weld geometry are available.

Three-dimensional scans of ultra high-strength steel butt welds exhibiting local undercuts are processed with digital image acquisition to derive weld geometry parameters, which facilitate a subsequent statistical analysis. Hereby, a novel approach to estimate the local weld toe radius is presented. Furthermore, the derived values are utilized to calculate the respective stress concentration at various locations of the weld using state-of-the-art notch-factor approximation equations. For undercut-free samples, a comparison of the investigated notch stress concentration equations and the results of numerical simulations of the actual weld geometry show good accordance for all models. However, at locations with a distinct undercut, the stress concentration is consequentially underestimated. Therefore, an improved approach extending the existing notch-factor equations is presented. It enables the consideration of the stress concentrating effect of a local undercut at the weld toe.

如今，自动化焊接工艺可生产出具有平滑且规则的整体焊缝几何形状的高质量焊缝。然而，由于焊接过程本身的动态影响，焊缝的局部几何形状在其形貌上表现出一定量的变化。随后局部应力集中的变化会影响焊接结构的疲劳性能。在文献中，有许多基于焊缝几何特征参数来估算焊缝应力集中的方程式。

超高强度钢对接焊缝的三维扫描显示局部底切，并通过数字图像处理进行处理，以导出焊缝几何参数，这有助于后续的统计分析。因此，提出了一种估计局部焊趾半径的新颖方法。此外，利用最新的缺口因子近似方程式，可将得出的值用于计算焊缝各个位置的相应应力集中。对于无咬边的样品，所研究的缺口应力集中方程式的比较和实际焊缝几何形状的数值模拟结果表明，所有模型均具有良好的一致性。但是，在有明显咬边的位置，应力集中会因此被低估。所以，提出了一种扩展现有陷波因子方程的改进方法。它可以考虑在焊趾处局部咬边的应力集中效应。