PSI - Issue 77

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ScienceDirect

Procedia Structural Integrity 77 (2026) 575–583 Structural Integrity Procedia 00 (2026) 000–000 Structural Integrity Procedia 00 (2026) 000–000

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© 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSI organizers Abstract Prior to deployment, industrial transformers undergo vacuum drying and structural integrity tests to ensure that they are struc turally sound and safe to operate. Optical methods o ff er a promising, non-contact solution for three-dimensional measurements of structural deformation across di ff erent sections of a transformer in a factory environment. Preliminary tests were conducted using a stereo optical system and a phase-shifting (PS) terrestrial laser scanner (TLS) to measure surface displacements on EFACEC industrial transformers during a near-vacuum pressure test. The stereo system captured image pairs of speckle patterns a ffi xed to one transformer wall, which were processed using digital image correlation (DIC), while the TLS acquired point clouds of the same surfaces. The measurements were then compared against simulation data. Since painting the transformer’s surface was not possible, alternative speckle patterns were evaluated, such as using magnets and printing on adhesive paper. Both the DIC and TLS produced adequate measurements in a factory setting, with some variation found in the measurements between methods and simulated data. These discrepancies could be attributable to ambient vibrations, necessary personnel access through the area where the optical systems were installed, the alternative speckle implementation, which may yield lower quality results when compared to painted patterns, non optimal speckle sizes due to uncertainty in available space prior to testing, and errors in the simulated data. Despite these challenges, the results show small absolute di ff erences, the highest with an order of magnitude of 10 − 3 m, the lowest with10 − 5 m, and the remaining di ff erences with an order of magnitude of 10 − 4 m, motivating further research. This work is a result of Agenda “ATE – Alianc¸a para a Transic¸a˜o Energe´tica”, no. C644914747-00000023, investment project no. 56, financed by the Recovery and Resilience Plan (PRR) and by European Union – NextGeneration EU. © 2026 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ICSI organizers. Keywords: Digital Image Correlation; Terrestrial Laser Scanner; Structural Analysis Francisco Afonso a, ∗ , Hugo Mesquita Vasconcelos a , Joa˜o Nunes a , Susana Dias a , Pedro J. S. C. P. Sousa a,b , Paulo J. Tavares a , Pedro M. G. J. Moreira a , Cassiano Linhares c , Andre´ Branquinho c a INEGI, Institute of Science and Innovation in Mechanical Engineering and Industrial Engineering, Rua Dr. Roberto Frias 400, Porto 4200-465, Portugal b Departamento de Engenharia Mecaˆnica, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s / n, Porto 4200-465, Portugal c EFACEC, Parque Empresarial Arroteia Poente, Porto 4466-952, Portugal Abstract Prior to deployment, industrial transformers undergo vacuum drying and structural integrity tests to ensure that they are struc turally sound and safe to operate. Optical methods o ff er a promising, non-contact solution for three-dimensional measurements of structural deformation across di ff erent sections of a transformer in a factory environment. Preliminary tests were conducted using a stereo optical system and a phase-shifting (PS) terrestrial laser scanner (TLS) to measure surface displacements on EFACEC industrial transformers during a near-vacuum pressure test. The stereo system captured image pairs of speckle patterns a ffi xed to one transformer wall, which were processed using digital image correlation (DIC), while the TLS acquired point clouds of the same surfaces. The measurements were then compared against simulation data. Since painting the transformer’s surface was not possible, alternative speckle patterns were evaluated, such as using magnets and printing on adhesive paper. Both the DIC and TLS produced adequate measurements in a factory setting, with some variation found in the measurements between methods and simulated data. These discrepancies could be attributable to ambient vibrations, necessary personnel access through the area where the optical systems were installed, the alternative speckle implementation, which may yield lower quality results when compared to painted patterns, non optimal speckle sizes due to uncertainty in available space prior to testing, and errors in the simulated data. Despite these challenges, the results show small absolute di ff erences, the highest with an order of magnitude of 10 − 3 m, the lowest with10 − 5 m, and the remaining di ff erences with an order of magnitude of 10 − 4 m, motivating further research. This work is a result of Agenda “ATE – Alianc¸a para a Transic¸a˜o Energe´tica”, no. C644914747-00000023, investment project no. 56, financed by the Recovery and Resilience Plan (PRR) and by European Union – NextGeneration EU. © 2026 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ICSI organizers. Keywords: Digital Image Correlation; Terrestrial Laser Scanner; Structural Analysis International Conference on Structural Integrity Non-contact structural analysis of transformer housings under dynamic loading conditions using vision-based 3D measurement techniques Francisco Afonso a, ∗ , Hugo Mesquita Vasconcelos a , Joa˜o Nunes a , Susana Dias a , Pedro J. S. C. P. Sousa a,b , Paulo J. Tavares a , Pedro M. G. J. Moreira a , Cassiano Linhares c , Andre´ Branquinho c a INEGI, Institute of Science and Innovation in Mechanical Engineering and Industrial Engineering, Rua Dr. Roberto Frias 400, Porto 4200-465, Portugal b Departamento de Engenharia Mecaˆnica, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s / n, Porto 4200-465, Portugal c EFACEC, Parque Empresarial Arroteia Poente, Porto 4466-952, Portugal International Conference on Structural Integrity Non-contact structural analysis of transformer housings under dynamic loading conditions using vision-based 3D measurement techniques

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSI organizers 10.1016/j.prostr.2026.01.073 ∗ Corresponding author E-mail address: fafonso@inegi.up.pt 2210-7843 © 2026 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ICSI organizers. ∗ Corresponding author E-mail address: fafonso@inegi.up.pt 2210-7843 © 2026 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ICSI organizers.