Digital visual testing on welds under water by high-resolution optical 3D surface reconstruction

The goal of the project is to supplement the classic visual inspection (VT) of welded joints under water with an optical 3D measurement system. Based on high-resolution 2D (image) data, metric 3D (surface) data will be generated by photogrammetric methods. The data ba-sis is to be used to derive inspection characteristics and to realise a partially automated pre-classification of a welded joint. By developing an optical 3D measuring system, the basis is created to carry out the data collection digitally and spatiotemporally detached from the testing process. A stereo camera system records the weld seam and generates high-resolution image data from which 3D surface data can be calculated. Due to the harsh environment under water as well as phy-sical limits of the optics, the development is particularly challenging. The influence of the particles in the water as well as the calibration in situ are scientifically investigated. The findings will lead to optimisations with regard to the accuracy and completeness of the op-tical measurement technology under water for the special application case of the shiny me-tallic weld seam. The calculated 3D data will be processed in such a way that test characteristics of ISO 5817 can be automatically derived and classified according to the deposited standard. In addition to the high-resolution image data, the inspector receives the measurement and inspection results via a digital interface and decides on the classification of a welded joint. Since the system also works under water at very low visibility levels, SMEs can generate immediate benefits through more flexible diving operations. The loadable data basis, the semi-automated classification and the automatic archiving result in a high benefit for SMEs in terms of documentation and proof for the customer. In the long term, additional data will lead to new business fields, such as 3D monitoring.
people

Prof. Dr.-Ing. habil. Dr. h.c. Thomas Luhmann (head)

Oliver Kahmen, M.Sc.

Funding source

Federal Ministry for Economic Affairs and Climate Action


Books and Papers

Kahmen, O.; Rofallski, R.; Luhmann, T. (2023): Digital visual testing of welds under water using optical 3D measurement technology with image-variant illumination. Unterwassertechnik 2023 - DVS Media, DVS Berichte, Band: 374, S. 93-101, ISBN: 978-3-96144-159-4 , Weblink
Kahmen, O.; Luhmann, T. (2022): Monocular Photogrammetric System for 3D Reconstruction of Welds in Turbid Water. PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science, Vol. 90, Issue 1, pp. 19-35 , doi: 10.1007/s41064-022-00191-2

Presentations

Kahmen, O. : Digitale Sichtprüfung von Schweißverbindungen unter Wasser durch photogrammetrische Verfahren. 9. BIM-Tag / 20. Oldenburger 3D-Tage, September 2022