TY - JOUR

T1 - Three-dimensional mapping of residual stresses and crack propagation in refill friction stir spot welded aluminium samples via synchrotron X-ray diffraction and X-ray micro-computed tomography

AU - Bernardi, Matteo

AU - Canelo-Yubero, David

AU - Chen, Ting

AU - Suhuddin, Uceu F.H.

AU - Bergmann, Luciano

AU - Klusemann, Benjamin

N1 - Publisher Copyright: © 2025 The Author(s)

PY - 2026/1

Y1 - 2026/1

N2 - Refill Friction Stir Spot Welding (refill FSSW) shows strong potential to replace riveting in the aerospace industry. However, the complex deformation and thermal effects associated with this process lead to residual stresses that may influence the fatigue life of the joint. This study reveals for the first time the non-uniform residual stresses across the thickness of a refill FSSW aluminium joint using synchrotron X-ray radiation in combination with a conical slit cell. Clear differences can be observed in the stresses between the region subjected to plasticisation and that affected solely by heat input. A fatigue testing campaign on the aluminium joints demonstrated their high reproducibility and robustness. X-ray micro-computed tomography enabled the three-dimensional visualisation of fatigue crack nucleation and propagation morphology, the latter correlated with the tensile residual stresses in the weld area. The results can contribute to the development of more accurate fatigue life prediction models and improve the overall reliability of refill FSSW aluminium joints in engineering applications.

AB - Refill Friction Stir Spot Welding (refill FSSW) shows strong potential to replace riveting in the aerospace industry. However, the complex deformation and thermal effects associated with this process lead to residual stresses that may influence the fatigue life of the joint. This study reveals for the first time the non-uniform residual stresses across the thickness of a refill FSSW aluminium joint using synchrotron X-ray radiation in combination with a conical slit cell. Clear differences can be observed in the stresses between the region subjected to plasticisation and that affected solely by heat input. A fatigue testing campaign on the aluminium joints demonstrated their high reproducibility and robustness. X-ray micro-computed tomography enabled the three-dimensional visualisation of fatigue crack nucleation and propagation morphology, the latter correlated with the tensile residual stresses in the weld area. The results can contribute to the development of more accurate fatigue life prediction models and improve the overall reliability of refill FSSW aluminium joints in engineering applications.

KW - Fatigue

KW - Fatigue crack propagation

KW - Refill friction stir spot welding

KW - Residual stress

KW - Synchrotron radiation

KW - Engineering

UR - http://www.scopus.com/inward/record.url?scp=105013502351&partnerID=8YFLogxK

U2 - 10.1016/j.ijfatigue.2025.109223

DO - 10.1016/j.ijfatigue.2025.109223

M3 - Journal articles

AN - SCOPUS:105013502351

VL - 202

JO - International Journal of Fatigue

JF - International Journal of Fatigue

SN - 0142-1123

M1 - 109223

ER -