Assessment of the Residual Stress Measurement Quality in Welded Joints Using Hole-Drilling Method Combined with ESPI Technique Approach

Abstract Residual stress evaluation in welded joints is of major importance, since its underestimation or lack of control can lead to deformations of welded components, to its mechanical properties’ deterioration or even to failure in service. Various destructive and non-destructive techniques exist for measuring residual stress, each differing in complexity, cost, and accuracy. This study investigates the applicability of the hole-drilling method combined with Electronic Speckle Pattern Interferometry (ESPI) for residual stress evaluation specifically in welded joints, where surface conditions and material properties differ from the base metal due to reinforcement convexity, surface irregularities, and microstructural changes. The methodology involved initial equipment calibration using known strain levels, followed by residual stress measurements on bead-on-plate samples — produced with and without filler material. The analysis focused on different weld regions (fusion zone, heat-affected zone, and base metal), considering both longitudinal and transverse stress components. Calibration results showed a mean measurement error of 5.8% and a coefficient of variation around 6%. For the welded beads, the ESPI-based hole-drilling method demonstrated coherent residual stress distributions consistent with theoretical models. Higher precision was observed for the transverse stress component and in samples welded without filler material, while the longitudinal stresses in the heat-affected zone of the welds with filler addition exhibited greater variability due to local metallurgical and geometrical effects. Overall, the study confirms that the combined hole-drilling and ESPI technique is a viable and reliable approach for residual stress measurement in welded joints, provided that factors such as measurement depth, surface condition, and local stress gradients are carefully managed.