@inproceedings{64129, abstract = {{Selecting scan angles such that surface segments are aligned with straight X-ray paths (i.e., rays are tangential to the surface and therefore perpendicular to the local surface normal) is known to produce sharper transitions of those surface segments in the reconstructed volume. This enhances dimensional accuracy in sparse-view computed tomography (CT). However, existing approaches offer no direct means to exploit this criterion for automatic scan-angle optimization. We propose a method that uses a virtual representation of the CT setup, including an STL surface model of the inspected part, to automatically identify taskspecific scan angles. Using elementary vector calculus, the algorithm determines projection directions that generate tangential X-rays for targeted surface segments. To support different levels of geometric complexity, we introduce two variants of the angle-selection procedure. The methods were experimentally validated on two objects with distinct absorption and geometric characteristics. For a steel gauge block, employing the minimum number of task-specific projections required for surface-data completeness substantially outperformed a conventional high-projection scan. For a geometrically more complex test object, surface-related errors were still reduced within the region of interest. The proposed approach – particularly suited for flat surface structures and not accounting for image-degrading factors other than cone-beam artifacts – shows promise for high-throughput dimensional metrology of mono-material parts.}}, author = {{Butzhammer, Lorenz and Braun, Matthias Robert Oskar and Herath, Colin and Hausotte, Tino}}, booktitle = {{e-Journal of Nondestructive Testing}}, issn = {{1435-4934}}, location = {{Linz}}, number = {{3}}, publisher = {{NDT.net GmbH & Co. KG}}, title = {{{Higher accuracy with fewer projections? Automated scan angle selection for dimensional Computed Tomography based on a simple data completeness measure for the part surface}}}, doi = {{10.58286/32560}}, volume = {{31}}, year = {{2026}}, } @article{64678, abstract = {{One of the major topics in the modern automotive industry is reducing emissions and increasing the mileage range. To tackle this challenge, on the one hand, modifying the powertrain system is a possibility, and on the other hand, lightweight design offers various possibilities. Multi-Material Design (MMD) involves designing car bodies that combine different materials that require joining. Given the variety of materials, mechanical joining processes are preferred. Especially the current development of the Giga/Mega-casting process concerning aluminium casting and the subsequent mechanical joining illustrates the challenges of this material group. In car production, aluminium castings are mainly made from aluminium-silicon (AlSi) alloys. Ultimately, the alloy system's insufficient ductility leads to crack initiation during mechanical joining. Cast parts are therefore often used in areas of the car body that are exposed to high-pressure loads. For example, self-piercing riveting (SPR) is used due to its high load-bearing capacity. In this study, improved joinability is demonstrated by influencing the microstructure through tailored solidification rates and a developed heat-treatment chain strategy adapted for hypoeutectic AlSi systems. Data on microstructure, mechanical, and joining properties are used to develop a solidification-joining correlation for the SPR process across a range of Si contents and solidification rates. The purpose is to develop the ability to produce suitable aluminium castings with sufficient joinability, thereby improving versatility.}}, author = {{Neuser, Moritz and Kaimann, Pia Katharina and Stratmann, Ina and Bobbert, Mathias and Klöckner, Johann Moritz Benedikt and Mann, Moritz and Hoyer, Kay-Peter and Meschut, Gerson and Schaper, Mirko}}, journal = {{Journal of Manufacturing Processes}}, keywords = {{Mechanical joining, Aluminium, Self-piercing riveting, Casting, Microstructure, Joinability AlSi-alloys}}, publisher = {{Elsevier}}, title = {{{Solidification-joinability correlation of hypoeutectic aluminium casting alloys for self-piercing riveting (SPR)}}}, doi = {{https://doi.org/10.1016/j.jmapro.2026.02.040}}, volume = {{164}}, year = {{2026}}, } @article{65153, author = {{Butzhammer, Lorenz}}, issn = {{0141-6359}}, journal = {{Precision Engineering}}, pages = {{377--400}}, publisher = {{Elsevier BV}}, title = {{{Conversion between detector- and rotary-table-related misalignment parameterisations for unified projection-matrix-based geometry calibration in dimensional X-ray computed tomography}}}, doi = {{10.1016/j.precisioneng.2026.03.015}}, volume = {{100}}, year = {{2026}}, } @article{58495, abstract = {{ To reduce CO2 emissions, the industry, particularly in the mobility sector, focuses on lightweight vehicles with multi-material structures. As thermal joining processes are reaching their limits, mechanical techniques such as self-piercing riveting are being used. One innovative solution is the versatile self-piercing riveting process (V-SPR), which combines different material combinations with a multi-range rivet. 1 The joining process is divided into the piercing process and the forming process of the rivet head to the respective sheet thickness. The rivet shaft requires sufficient strength to punch through the punch-sided sheet, and sufficient ductility of the rivet head is required to form onto the punch-sided sheet. To achieve a combination of these requirements, local inductive heat treatment strategies are used for the rivet. To ensure reproducible rivet hardening, a specialised device has been developed for precise rivet positioning in the induction coil and the subsequent quenching process. The heat treatment differs in terms of hardening times and temperatures. In addition, the heat treatment is combined with a subsequent tempering process. The study aims to determine the resulting hardness distributions and microstructures of the rivet and to investigate the influence of different heat treatment strategies on joint formation and load-bearing capacities. The results show that a graded hardening profile has a positive effect on the spreading behaviour of the rivet foot and the forming behaviour of the rivet head. Furthermore, the load-bearing behaviour of the joints is increased. }}, author = {{Holtkamp, Pia Katharina and Kappe, Fabian and Probst, Paula and Bobbert, Mathias and Meschut, Gerson}}, issn = {{1464-4207}}, journal = {{Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications}}, publisher = {{SAGE Publications}}, title = {{{Investigation of local heat treatment strategies for a multi-range capable rivet and the influence on joint formation and load-bearing capacity}}}, doi = {{10.1177/14644207241307508}}, year = {{2025}}, } @inproceedings{59483, abstract = {{Abstract. The assessment of mechanically joined connections, such as clinched connections, is usually conducted destructively. Applicable non-destructive testing methods like computed tomography are time-consuming and costly, or, like electrical resistance measurement, provide only a limited amount of information. A fast, non-destructive evaluation of the joints condition shall be made possible by using transient dynamic analysis (TDA). It is based on the introduction of sound waves and the evaluation of the response behavior after passing through the structure. This study focuses the application of TDA to clinched shear connections to evaluate the performance of the tactile measuring setup. Twenty-one series were investigated, covering variations in joining task, manufacturing and defect. The evaluation was carried out using machine learning to determine for which series characteristic signals may be detected. It was shown that a classification of the investigated specimens is possible, whereby the classification accuracy depends on the examined variation. Furthermore, the accuracy was evaluated as a function of frequency and results were concluded to identify the limits of the used measuring setup.}}, author = {{Reschke, Gregor and Brosius, Alexander}}, booktitle = {{Materials Research Proceedings}}, issn = {{2474-395X}}, keywords = {{Joining, Machine Learning, Transient Dynamic Analysis}}, location = {{Paderborn}}, pages = {{293--300}}, publisher = {{Materials Research Forum LLC}}, title = {{{Transient dynamic analysis: Performance evaluation of tactile measurement}}}, doi = {{10.21741/9781644903551-36}}, volume = {{52}}, year = {{2025}}, } @inproceedings{60108, abstract = {{Abstract. In the field of mechanical engineering, destructive tests such as shear tests of mechanical joints are usually followed by imaging methods such as microsectioning or computed tomography (CT). They can help to interpret the measured load-displacement curves, analyze the failure behavior and validate numerical models. However, due to unloading, springback effects and crack closures can occur, which influence the state of the investigated specimen. In this context, in situ CT is able to explore the testing process with a specimen under load avoiding these influences. For in situ CT investigations, the displacement increase is interrupted at certain stop points. While the displacement is kept constant, the CT scan is performed. However, it was observed that the reaction force reduces during CT scanning, e. g. due to settling effects in the test setup. Although in situ CT is established now in research, little attention is paid to the uncertainties which arise from the discontinuous testing procedure. This study systematically explores the impact of these interruptions on the load-displacement behavior and the geometry of clinch points during tensile shear testing. To quantify the influence of the interruptions, loads at defined displacement levels and the final geometry are evaluated statistically. We found, that the load-displacement behavior of both test groups is similar. Despite some small but significant statistical deviations of the loads and the final geometry, our results show that, discontinuous testing has a high level of significance for the phenomena overserved in shear tests with clinch points.}}, author = {{Köhler, D. and Troschitz, J and Kupfer, R. and Gude, M.}}, booktitle = {{Materials Research Proceedings}}, issn = {{2474-395X}}, publisher = {{Materials Research Forum LLC}}, title = {{{In situ computed tomography – Analysis of settling effects during single-lap shear tests with clinch points}}}, doi = {{10.21741/9781644903551-15}}, volume = {{52}}, year = {{2025}}, } @article{61825, abstract = {{Abstract Industrial x-ray computed tomography (CT) systems with high geometric flexibility are increasingly utilized for large-scale measurement objects or challenging measurement tasks. To maintain high accuracy when deviating from the established circular scan trajectory, trajectory calibration methods using multi-sphere reference objects with known marker positions are commonly employed. These multi-sphere objects can either be scanned together with the measurement object (online trajectory calibration) or in a separate scan (offline trajectory calibration). While offline calibration increases machine time, it generally results in higher scan quality. However, a sufficient pose repeatability is necessary to ensure comparable or even superior accuracy to online calibration. In this contribution, we present a straightforward procedure to compare both types of trajectory calibration in a way that the differences of the results can directly be traced back to the influence of the pose repeatability. The multi-sphere reference object is not only used for trajectory calibration, but simultaneously as a measurement object for repeated measurements. The methodology is tested on both a twin robotic CT system and a conventional CT system that is additionally equipped with a hexapod manipulator for adaptive object tilting. Results showed, independent from the type of trajectory calibration, systematic measurement errors in the order of 10−5–10−4 of measured sphere distances and sphericity values below 50 μ m . For sphere distances, random errors were increased by a factor of 5 due to the offline trajectory calibration, but were still low ( < 1 μ m ) in comparison to systematic errors and the spread of different measurement features. Overall, both investigated systems demonstrated sufficient positioning repeatability for offline trajectory calibration. The method is in general also applicable to any other types of manipulator systems used for CT devices. It provides a workflow for the decision which type of trajectory calibration is preferable for a given CT system.}}, author = {{Butzhammer, Lorenz and Handke, Niklas and Wittl, Simon and Herl, Gabriel and Hausotte, Tino}}, issn = {{0957-0233}}, journal = {{Measurement Science and Technology}}, number = {{2}}, publisher = {{IOP Publishing}}, title = {{{Direct assessment of the influence of pose repeatability on the accuracy of dimensional measurements for computed tomography systems with high degrees of freedom}}}, doi = {{10.1088/1361-6501/ada05a}}, volume = {{36}}, year = {{2025}}, } @inproceedings{60440, abstract = {{The versatile self-pierce riveting (V-SPR) is a further development of semi-tubular self-pierce riveting. V-SPR enables adaptation to changing boundary conditions, such as a change in the material thickness combination, without varying the rivet die combination due to increased punch actuation and the use of multi-range capable rivets [1]. The inner punch first sets the rivet. The outer punch then forms the rivet head to the respective sheet thickness. For this, the rivet requires a hard shank and a ductile rivet head, which is achieved by an inductive local hardening process [2]. Until now, the joint formation of rivets with graded hardness profile has been challenging to estimate in the FEM simulation due to the inhomogeneous material conditions in the rivet. In this study, a method capable of reproducing the experimentally determined hardness levels of rivets in detail is shown. This FE model enables the realistic modelling of the mechanical properties of the rivet on the basis of the hardness profile in order to predict the correct deformation processes and stresses during the riveting process. First, the detailed experimental hardness mapping of the locally heat-treated rivets is transferred into the FE model. The FEM material model can predict the local strength of the rivet based on hardness by scaling the flow curves. To estimate the predictive capability of the FEM model, the joint formation of rivets with different graded hardness profiles is compared experimentally and simulative. Based on the validated model, the influence of different rivet hardness profiles on the joint formation is analysed numerically. By adapting the material model, a high level of correlation between the experiment's joint formation and the simulation can be achieved.}}, author = {{Holtkamp, Pia Katharina and Bielak, Christian Roman and Bobbert, Mathias and Meschut, Gerson}}, booktitle = {{Materials Research Proceedings}}, issn = {{2474-395X}}, publisher = {{Materials Research Forum LLC}}, title = {{{Simulation of the joining process of graded hardened multi-range capable rivets}}}, doi = {{10.21741/9781644903599-153}}, volume = {{54}}, year = {{2025}}, } @article{61767, abstract = {{Abstract A clinch point’s quality is usually assessed using ex situ destructive testing methods. These, however, are unable to detect phenomena immediately during the joining process. For instance, elastic deformations reverse and cracks close after unloading. In situ methods such as the force-displacement evaluation are used to investigate a clinching process, though deviations in the clinch point geometry cannot be derived with this method. To overcome these limitations, the clinching process can be investigated using in situ computed tomography (in situ CT). When investigating the clinching of aluminum parts in in situ CT, the sheet-sheet interface is hardly visible. Earlier investigations showed that radiopaque materials can be applied between the joining parts to enhance the detectability of the sheet-sheet interface. However, the layers cause strong artefacts, break during the clinching process or change the clinch joint’s properties significantly. In this paper, a minimally invasive method to enhance the interface detectability is presented. First, the aluminum oxide layer is removed by etching. Second, the specimen is electroplated with copper or gold, respectively. In some cases, a mask is applied to create a cross-shaped plating pattern. Then, the plated specimen is clinched with a non-plated counterpart and the interface detectability of the clinch points is assessed in CT scans. It is shown that a copper plating of 2.6–4 μm can visualize some parts of the interface, while 7–9 μm is suitable to enhance the detectability of the sheet-sheet interface almost continuously.}}, author = {{Köhler, Daniel and Dargel, Alrik and Troschitz, Juliane and Gude, Maik and Kupfer, Robert}}, issn = {{0195-9298}}, journal = {{Journal of Nondestructive Evaluation}}, number = {{4}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{In Situ CT of Clinch Points – Enhancing Interface Detectability Using Electroplated Patterns of Radiopaque Materials}}}, doi = {{10.1007/s10921-025-01270-1}}, volume = {{44}}, year = {{2025}}, } @inproceedings{61149, abstract = {{The use of continuous fiber-reinforced thermoplastics (FRTP) in automotive industry increases due to their excellent material properties and possibility of rapid processing. The scale spanning heterogeneity of their material structure and its influence on the material behavior, however, presents significant challenges for most joining technologies, such as self-piercing riveting (SPR). During mechanical joining, the material structure is significantly altered within and around the joining zone, heavily influencing the material behavior. A comprehensive understanding of the underlying phenomena of material alteration during the SPR process is essential as basis for validating numerical simulations. This study examines the material structure at ten stages of a step-setting test of SPR with two FRTP sheets with glass-fiber reinforcement. Utilizing X-ray computed tomography (CT), the damage phenomena within different areas of the setting test are analyzed three-dimensionally and key parameters are quantified. Dominating phenomena during the penetration of the rivet into the laminate are fiber failure (FF), interfiber failure (IFF) and fiber bending, while delamination, fiber kinking and roving splitting are also observed. At the final stages, the bottom layers of the second sheet collapse and form a bulge into the cavity of the die.}}, author = {{Dargel, Alrik and Gröger, Benjamin and Schlichter, Malte Christian and Gerritzen, Johannes and Köhler, Daniel and Meschut, Gerson and Gude, Maik and Kupfer, Robert}}, booktitle = {{Proceedings of the 8th International Conference on Integrity-Reliability-Failure (IRF2025)}}, editor = {{Gomes, J.F. Silva and Meguid, Shaker A.}}, isbn = {{9789727523238}}, keywords = {{self-piercing riveting, computed tomography, thermoplastic composites, process-structure-interaction}}, location = {{Porto}}, publisher = {{FEUP}}, title = {{{LOCAL DEFORMATION AND FAILURE OF COMPOSITES DURING SELF-PIERCING RIVETING: A CT BASED MICROSTRUCTURE INVESTIGATION}}}, doi = {{10.24840/978-972-752-323-8}}, year = {{2025}}, } @article{63828, author = {{Gerritzen, Johannes and Chopra, Kunal and Reschke, Gregor and Hornig, Andreas and Brosius, Alexander and Gude, Maik}}, issn = {{2666-3309}}, journal = {{Journal of Advanced Joining Processes}}, publisher = {{Elsevier BV}}, title = {{{Quality assurance of clinched joints using explainable machine learning}}}, doi = {{10.1016/j.jajp.2025.100368}}, volume = {{13}}, year = {{2025}}, } @article{58807, abstract = {{One of the most important strategies for reducing CO2 emissions in the mobility sector is lightweight construction. In particular, the car body offers several opportunities for weight reduction. Multi-material designs are increasingly being applied to select the most suitable material for the respective load and ultimately achieve synergy effects. For example, aluminium castings are used at the nodes of a spaceframe body. Subsequently, these are joined with profiles to form the bodyshell. To join different materials mechanical joining techniques, such as semi-tubular self-piercing riveting, are deployed. According to the current state of the art, cracks occur in the aluminium castings during the mechanical joining process as a result of the high degree of deformation. Although the aluminium casting alloys of the AlSi-system exhibit low ductility, these alloys reveal excellent castability. In particular, the ability to cast thin structural parts is enabled by the low liquidus point of the near eutectic aluminium casting alloys. This study addresses the mechanical joining properties of the near eutectic aluminium casting alloy AlSi12, depending on different microstructures. These are achieved by annealing processes and modifying agents. Through an adapted heat treatment, the previously lamellar morphology can be transformed into a globular morphology, which leads to increased ductility and prevents the formation of cracks during the self-piercing riveting (SPR). The joinability is investigated using different die geometries, whereas the joint formation is analysed regarding crack initiation. To evaluate the increased ductility, microstructural and mechanical tests are performed and finally, a microstructure-joinability correlation is established.}}, author = {{Neuser, Moritz and Holtkamp, Pia Katharina and Hoyer, Kay-Peter and Kappe, Fabian and Yildiz, Safak and Bobbert, Mathias and Meschut, Gerson and Schaper, Mirko}}, journal = {{The Journal of Materials: Design and Applications, Part L}}, keywords = {{aluminium, casting, microstructure, joinability, self-piercing riveting}}, location = {{Porto, Portugal}}, publisher = {{Sage Publications}}, title = {{{Mechanical properties and joinability of the near-eutectic aluminium casting alloy AlSi12}}}, doi = {{10.1177/14644207251319922}}, year = {{2025}}, } @inproceedings{60290, abstract = {{The constantly increasing demand for climate protection and resource conservation requires innovative and versatile joining processes that improve adaptability to the joining task and robustness to enable flexible manufacturing on a production line. Therefore, the versatile SPR (V-SPR) and tumbling SPR (T-SPR) were developed. Using the example of a mixed material combination HCT590X+Z (t0 = 1.0 mm) / EN AW-6014 T4 (t0 = 2.0 mm), these processes were examined and compared with regard to the binding mechanisms form closure and force closure using micrographs, non-destructive resistance measurements and destructive torsion tests. For this purpose, a new sample geometry was defined, and the methods were adapted to the SPR process variants.}}, author = {{Lüder, Stephan and Holtkamp, Pia Katharina and Wituschek, Simon and Bobbert, Mathias and Meschut, Gerson and Lechner, Michael and Schmale, Hans Christian}}, booktitle = {{Materials Research Proceedings}}, editor = {{Meschut, Gerson and Bobbert, Mathias and Duflou, Joost and Fratini, Livan and Hagenah, Hinnerk and Martins, Paulo A. F. and Merklein, Marion and Micari, Fabrizio}}, issn = {{2474-395X}}, keywords = {{Joining, Self-Piercing Riveting, Sheet Metal}}, location = {{Paderborn}}, pages = {{101 -- 108}}, publisher = {{Materials Research Forum LLC}}, title = {{{Analysis of the binding mechanisms depending on versatile process variants of self-piercing riveting}}}, doi = {{10.21741/9781644903551-13}}, volume = {{52}}, year = {{2025}}, } @article{60441, abstract = {{Conventional mechanical joining processes are typically rigid in their tool systems and can only react to changing process and disturbance variables to a limited extent. At the same time, various industries are increasingly trending towards multi-material systems consisting of parts with varying geometric and mechanical properties. Due to the varying properties, rigid mechanical joining processes require sampling procedures and periodic changes of tool components or auxiliary joining parts. Consequently, research is focusing on versatile mechanical joining processes that allow increased control by modifying the process parameters. Two processes based on self-piercing riveting can achieve a significant increase in process influence possibilities through a multi-linear actuator as versatile self-piercing riveting (V-SPR) and a tumbling superimposed actuator as tumbling self-piercing riveting (T-SPR). Initial research into V-SPR has shown that this process can be used to achieve a higher variation in overall package thickness by adapting the rivet geometry and using multiple linear actuators. The T-SPR process also enables increased material flow control by means of targeted compression of the rivet using the tumbling actuator, thereby extending the range of joints that can be manufactured. Based on these two processes, a combination of the two mechanisms of action is to be developed.}}, author = {{Holtkamp, Pia Katharina and Wituschek, Simon and Lechner, Michael and Meschut, Gerson}}, issn = {{2261-236X}}, journal = {{MATEC Web of Conferences}}, publisher = {{EDP Sciences}}, title = {{{Integration of multiple-linear and tumbling kinematics into self-piercing riveting}}}, doi = {{10.1051/matecconf/202540801069}}, volume = {{408}}, year = {{2025}}, } @inproceedings{60439, abstract = {{Abstract. Mechanical joints are traditionally analyzed through destructive micrograph analysis, which may compromise internal geometry and morphology, as evidenced by radial cracks in semi-tubular self-pierce riveting. In contrast, industrial X-ray computed tomography (XCT) offers a non-destructive method for component diagnosis, providing volumetric insights without damaging the sample and enabling dimensional measurement. The DFG-funded Collaborative Research Center TRR 285 is exploring XCT's application in assessing mechanical joinability across various joining processes and materials, particularly in multi-material systems like steel-aluminum joints. XCT faces challenges in accurately capturing multi-material compositions, leading to artifacts that complicate interface detection. This research aims to validate XCT for joint investigations, yielding quantitative characteristics that surpass those from traditional micrograph analysis.}}, author = {{Lechner, M. and Borgert, Thomas and Busch, Matthias and Harms, A. and Holtkamp, Pia Katharina and Römisch, D. and Wituschek, Simon and Kappe, Fabian}}, booktitle = {{Materials Research Proceedings}}, issn = {{2474-395X}}, publisher = {{Materials Research Forum LLC}}, title = {{{Non-destructive testing in versatile joining processes}}}, doi = {{10.21741/9781644903551-12}}, volume = {{52}}, year = {{2025}}, } @article{58348, abstract = {{ Clinching is a mechanical joining technology, in which a mainly form-fit joint is created by means of local cold forming. To characterize the load-bearing behavior of such joints, they are typically analyzed destructively, for example by tensile-shear tests in combination with metallographic sections. However, both the initiation and progress of failure can only be described to a limited extent by this method. Furthermore, these tests allow only limited conclusions about clinch points under in-service loading. More purposefully, clinch points can be analyzed nondestructively by combining in-situ computed tomography (CT) and transient dynamic analysis (TDA). The TDA continuously measures the dynamic behavior of the specimen and indicates failure events like crack initiation, which then can be evaluated thoroughly by stopping the test and performing a CT scan. To qualify the TDA for this task, it is necessary to link the observed damage behavior with specific dynamic characteristics. In this work, the complementation of in-situ CT and TDA is investigated by testing a clinched single-lap tensile-shear specimen made of aluminum. The testing procedure is stepwise: at certain displacement levels, the specimen is investigated by in-situ CT and TDA. While the in-situ CT provides the location, extent, and development of the failure phenomena, the TDA uses this information to evaluate the dynamic signal and detect relevant frequency ranges, which indicate damage events. The results demonstrate, that failure initiation and progression can be analyzed efficiently by combining both measuring systems. The TDA reliably detects relevant signal changes in the monitored frequency band. By means of in-situ computed tomography, the corresponding failure phenomena can be described in detail, enhancing the understanding of the load-bearing and deformation behavior of clinch points. The concatenation of characteristic signal changes and observed failure phenomena can henceforth be transferred to analyze complex structures during operation nondestructively by TDA. }}, author = {{Reschke, Gregor and Köhler, Daniel and Kupfer, Robert and Troschitz, Juliane and Gude, Maik and Brosius, Alexander}}, issn = {{0954-4089}}, journal = {{Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering}}, keywords = {{Clinching, Non-destructive testing, Transient Dynamic Analysis}}, publisher = {{SAGE Publications}}, title = {{{In-situ computed tomography and transient dynamic analysis – failure analysis of a single-lap tensile-shear test with clinch points}}}, doi = {{10.1177/09544089241251646}}, year = {{2024}}, } @article{60106, abstract = {{ Clinching is a mechanical joining technology, in which a mainly form-fit joint is created by means of local cold forming. To characterize the load-bearing behavior of such joints, they are typically analyzed destructively, for example by tensile-shear tests in combination with metallographic sections. However, both the initiation and progress of failure can only be described to a limited extent by this method. Furthermore, these tests allow only limited conclusions about clinch points under in-service loading. More purposefully, clinch points can be analyzed nondestructively by combining in-situ computed tomography (CT) and transient dynamic analysis (TDA). The TDA continuously measures the dynamic behavior of the specimen and indicates failure events like crack initiation, which then can be evaluated thoroughly by stopping the test and performing a CT scan. To qualify the TDA for this task, it is necessary to link the observed damage behavior with specific dynamic characteristics. In this work, the complementation of in-situ CT and TDA is investigated by testing a clinched single-lap tensile-shear specimen made of aluminum. The testing procedure is stepwise: at certain displacement levels, the specimen is investigated by in-situ CT and TDA. While the in-situ CT provides the location, extent, and development of the failure phenomena, the TDA uses this information to evaluate the dynamic signal and detect relevant frequency ranges, which indicate damage events. The results demonstrate, that failure initiation and progression can be analyzed efficiently by combining both measuring systems. The TDA reliably detects relevant signal changes in the monitored frequency band. By means of in-situ computed tomography, the corresponding failure phenomena can be described in detail, enhancing the understanding of the load-bearing and deformation behavior of clinch points. The concatenation of characteristic signal changes and observed failure phenomena can henceforth be transferred to analyze complex structures during operation nondestructively by TDA. }}, author = {{Reschke, G and Köhler, D and Kupfer, R and Troschitz, J and Gude, M and Brosius, A}}, issn = {{0954-4089}}, journal = {{Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering}}, publisher = {{SAGE Publications}}, title = {{{In-situ computed tomography and transient dynamic analysis – failure analysis of a single-lap tensile-shear test with clinch points}}}, doi = {{10.1177/09544089241251646}}, year = {{2024}}, } @article{60105, abstract = {{ Lightweight design by using low-density and load-adapted materials can reduce the weight of vehicles and the emissions generated during operation. However, the usage of different materials requires innovative joining technologies with increased versatility. In this investigation, the focus is on describing and characterising the failure behaviour of connections manufactured by an innovative thermomechanical joining process with adaptable auxiliary joining elements in single-lap tensile-shear tests. In order to analyse the failure development in detail, the specimens are investigated using in-situ computed tomography (in-situ CT). Here, the tensile-shear test is interrupted at points of interest and CT scans are conducted under load. In addition, the interrupted in-situ testing procedure is validated by comparing the loading behaviour with conventional continuous tensile-shear tests. The results of the in-situ investigations of joints with varying material combinations clearly describe the cause of failure, allowing conclusions towards an improved joint design. }}, author = {{Borgert, T and Köhler, D and Wiens, E. and Kupfer, R and Troschitz, J and Homberg, W and Gude, M}}, issn = {{1464-4207}}, journal = {{Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications}}, number = {{12}}, pages = {{2299--2306}}, publisher = {{SAGE Publications}}, title = {{{In-situ computed tomography analysis of the failure mechanisms of thermomechanically manufactured joints with auxiliary joining element}}}, doi = {{10.1177/14644207241232233}}, volume = {{238}}, year = {{2024}}, } @inproceedings{60107, abstract = {{Abstract. In lightweight constructions, clinching represents a cost-effective solution, in which joints are produced by local cold forming of the joining parts. Clinching phenomena are typically evaluated using destructive testing methods. While these methods influence the clinch point’s state, in-situ computed tomography (in-situ CT) is able to explore the clinching process with a specimen under load. Here, the path-controlled clinching process is interrupted at certain displacement levels and the specimen is scanned by CT while remaining in a stationary state. These interruptions are always accompanied by settling effects reducing the reaction force. Therefore, in this work, the influence of these interruptions on the force-displacement behavior during clinching and on the final clinch point’s geometric properties is investigated. }}, author = {{Köhler, D. and Kupfer, R. and Troschitz, J. and Gude, M.}}, booktitle = {{Materials Research Proceedings}}, issn = {{2474-395X}}, publisher = {{Materials Research Forum LLC}}, title = {{{In-situ CT of the clinching process – Influence of settling effects due to process interruptions}}}, doi = {{10.21741/9781644903131-187}}, volume = {{41}}, year = {{2024}}, } @inproceedings{54650, abstract = {{Abstract. Reducing the weight of vehicles can significantly lower the energy or fuel consumed and thus the emissions during operation. One possibility to assess this is the use of a property adapted multi-material systems containing high strength steel, light metals like aluminium or magnesium and fibre reinforced plastics. While expanding the number of materials used new challenges arise for the production and furthermore the joining technology to manufacture the vehicle made of the multi-material systems. One approach to overcome these challenges is to use innovative and adaptable joining techniques which allows the manufacturing of joints of different material combinations. Extensive research activities on the two stage thermo-mechanical joining process with adaptable joining elements was able to demonstrate the great potentials in terms of joining dissimilar materials with good strength. The previously kinematic and path-based fabrication of auxiliary joining elements is modified in this publication to a form-based approach with a perspective of establishing an efficient process chain using easily and cheaply available rods. Based on the new approach to produce the auxiliary joining elements, it can be demonstrated that a reproducible production of the geometry is possible for the investigated steel as well as aluminium material. }}, author = {{Borgert, Thomas and Nordieker, Ansgar Bernhard and Homberg, Werner}}, booktitle = {{Materials Research Proceedings}}, issn = {{2474-395X}}, location = {{Toulouse}}, publisher = {{Materials Research Forum LLC}}, title = {{{Form-based manufacturing of aluminium and steel auxiliary joining elements as the basis for an efficient joining operation}}}, doi = {{10.21741/9781644903131-180}}, year = {{2024}}, }