Investigations on combined in situ CT and acoustic analysis during clinching

Research output: Contribution to journalConference articleContributedpeer-review


Clinching is a cost efficient method for joining components in series production. To assure the clinch point’s quality, the force displacement curve during clinching or the bottom thickness are monitored. The most significant geometrical characteristics of the clinch point, neck thickness and undercut, are usually tested destructively by microsectioning. However, micrograph preparation goes ahead with a resetting of elastic deformations and crack-closing after unloading. To generate a comprehensive knowledge of the clinch point’s inner geometry under load, in-situ computed tomography (CT) and acoustic testing (TDA) can be combined. While the TDA is highly sensitive to the inner state of the clinch point, it could detect critical events like crack development during loading. If such events are indicated, the loading process is stopped and a stepped in-situ CT of the following crack and deformation development is performed. In this paper, the concept is applied to the process of clinching itself, providing a detailed three-dimensional insight in the development of the joining zone. A test set-up is used which allows a stepwise clinching of two aluminium sheets EN AW 6014. Furthermore, this set-up is positioned within a CT system. In order to minimize X-ray absorption, a beryllium cylinder is used within the set-up frame and clinching tools are made from Si3N4. The actuator and sensor necessary for the TDA are integrated in the set-up. In regular process steps, the clinching process is interrupted in order to perform a TDA and a CT scan. In order to enhance the visibility of the interface, a thin tin layer is positioned between the sheets prior clinching. It is shown, that the test-set up allows a monitoring of the dynamic behaviour of the specimen during clinching while the CT scans visualize the inner geometry and material flow non-destructively.


Original languageEnglish
Pages (from-to)1489-1497
Number of pages9
JournalKey Engineering Materials
Publication statusPublished - 22 Jul 2022


Title25th International ESAFORM Conference on Material Forming
Abbreviated titleESAFORM 2022
Conference number25
Duration27 - 29 April 2022
Degree of recognitionInternational event
LocationAltice Forum Braga

External IDs

unpaywall 10.4028/p-32330d
Mendeley 7c4f0e65-bab8-31ed-9c64-025e459bc72b
Scopus 85140481270
ORCID /0000-0003-0014-3039/work/142233846
ORCID /0000-0003-1370-064X/work/142243773
ORCID /0000-0001-6422-2196/work/142250489



  • X-ray, Clinching, Process monitoring, Active acoustic testing