@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{64251, abstract = {{ABSTRACT Clinching is a widely adopted joining technique in the automotive industry, enabling the fabrication of lightweight structures from dissimilar sheet materials. Accurate prediction of the fatigue life of clinched joints is essential for ensuring structural safety and minimizing development costs. However, full 3D fatigue simulations over millions of cycles are computationally intensive due to the complexity of contact mechanics. This study introduces a 2D numerical model that circumvents direct contact modeling by applying a slip condition at the sheet interface, significantly reducing computational demands. A micro‐slip friction model is used to represent the mechanical interface behavior, while a two‐scale damage model captures the fatigue damage evolution. The model is validated against experimental data and used to investigate the influence of friction coefficient and tangential contact stiffness on fatigue life, highlighting its efficiency and predictive capability.}}, author = {{Chen, Chin and Hofmann, Martin and Wallmersperger, Thomas}}, issn = {{1617-7061}}, journal = {{PAMM}}, number = {{1}}, publisher = {{Wiley}}, title = {{{A 2D Approach to Predict the High‐Cycle Fatigue Life of Clinched Joints}}}, doi = {{10.1002/pamm.70035}}, volume = {{26}}, year = {{2026}}, } @article{64250, abstract = {{Abstract Salt-spray testing is widely used in the automotive and materials industries to assess the corrosion resistance of protective coatings, where uniform corrosion is a key indicator of material performance. This work presents a numerical uniform corrosion model that predicts the corrosion rate of hot-dip zinc in salt-spray environments by incorporating electrochemical reactions, mass transport via the Nernst–Planck equation, and ionic-strength effects through the Brønsted–Bjerrum relation. The model is calibrated using immersion-test data and extended to account for electrolyte layer growth, droplet deposition, and periodic run-off in salt-spray environments. The calibration establishes a relationship between the porosity of the zinc oxide layer and the rate constant of zinc oxide precipitation. The validated model reproduces the transition from activation- to diffusion-controlled corrosion and captures the experimentally observed corrosion kinetics with an error margin of 20% when electrolyte renewal is included. The results highlight the decisive role of electrolyte dynamics in salt-spray environments and provide a foundation for extending the framework to more complex cyclic corrosion tests.}}, author = {{Chen, Chin and Hofmann, Martin and Wallmersperger, Thomas}}, issn = {{2397-2106}}, journal = {{npj Materials Degradation}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Modeling the uniform corrosion behavior of zinc in salt spray testing}}}, doi = {{10.1038/s41529-026-00749-0}}, 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{64985, abstract = {{Modern industrial development has necessitated a wide range of joining technologies. Self-pierce riveting has become a prevalent technique for sheet metal assembly, especially in automotive applications. Achieving proper joint geometry and adequate load-bearing capacity depends on appropriate tool selection and precise process control. Material properties and condition also play a significant role in process performance. To accommodate the inevitable variations in component characteristics during production, a robust and stable joining process is essential. The study focuses on investigating the influence of preformed joining partners on the joining process and the joint's load capacity. An EN AW-6014 in T4 condition, as well as an HCT590X, are used as materials for this study. For this purpose, an exemplary process chain consisting of the steps of performing, joining, and shear load testing is studied. Each process step is implemented using an FE model to predict the outcome of subsequent steps. For analysis of the influence of pre-strain, an optimisation software is used to plan and execute variations of the process. These variations are used to create a meta-model that can describe the relationships between pre-forming and characteristic parameters of subsequent process steps. The resulting model is validated by comparing simulation and experimental data. Finally, in a novel approach, the robustness of the presented process chain is analyzed in terms of a tolerable performance level for the joining partners.}}, author = {{Ludwig, Jean-Patrick and Tolke, Emil and Schlichter, Malte Christian and Bobbert, Mathias and Meschut, Gerson}}, issn = {{2666-3309}}, journal = {{Journal of Advanced Joining Processes}}, keywords = {{Self-pierce riveting, FE modelling, Plastic pre-deformation, Meta modelling}}, publisher = {{Elsevier BV}}, title = {{{Numerical analysis of the robustness of self-pierce riveting with pre-formed joining partners}}}, doi = {{10.1016/j.jajp.2026.100391}}, volume = {{13}}, year = {{2026}}, } @article{65373, abstract = {{To reduce CO₂ emissions, the automotive industry is adopting multi-material structures. Fusion-based joining reaches its limits for aluminium–steel due to brittle intermetallic phases and mismatched thermophysical properties; therefore, mechanical joining (e.g., SPR) is used. Though conventional SPR requires tool changes for different stack-ups. Versatile self-piercing riveting (V-SPR) addresses this with an extended punch actuator and a multi-range-capable rivet (Kappe in PERD16:363–378, 2022), enabling joints up to 600 MPa across varying thicknesses without retooling. With the use of ultra-high-strength steels up to 1000 MPa, optimisation is required. This study quantifies how rivet shank geometry affects joint formation using a design of experiments and validated 2D axisymmetric FE simulations. The optimum depends strongly on the material system. For CP1000–EN AW-6014, maximum interlock f is predicted for a medium shank thickness of about 0.73 mm, a small internal foot radius of 0.620 mm, and a deeper drill depth of 3.136 mm, yielding f fc =0.4503 mm with a desirability of 0.954. For EN AW-6014–EN AW-6014, the optimum shifts to a thinner shank of 0.670 mm, a larger internal foot radius of 0.820 mm and a shallow drill depth of 2.30 mm, giving ffc = 0.3023 mm with a desirability of 1.0. A compromise geometry of 0.713 mm shank thickness, 0.776 mm internal foot radius and 2.755 mm drill depth achieves ffc = 0.3641 mm for CP1000–aluminium and ffc = 0.1851 mm for aluminium–aluminium with an overall desirability D = 0.6378, expanding V-SPR to ultra-high-strength steel–aluminium joints while maintaining aluminium joinability.}}, author = {{Kaimann, Pia Katharina and Ritter, Nico and Bobbert, Mathias and Meschut, Gerson}}, issn = {{2731-6564}}, journal = {{Discover Mechanical Engineering}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Influence of the shank geometry on the joint formation of the versatile self-piercing riveting of ultra-high-strength steel-aluminium and aluminium-aluminium assemblies}}}, doi = {{10.1007/s44245-026-00221-y}}, volume = {{5}}, year = {{2026}}, } @article{65435, author = {{Devulapally, Deekshith Reddy and Tröster, Thomas}}, journal = {{Discover Mechanical Engineering}}, publisher = {{Springer Nature}}, title = {{{Improving the load-bearing capacity of clinched joints through cavity filling with structural epoxy adhesive.}}}, doi = {{https://doi.org/10.1007/s44245-026-00223-w}}, volume = {{5}}, year = {{2026}}, } @article{65488, author = {{Mergheim, Julia and Wallmersperger, Thomas and Wolf, Eugen and Schlichter, Malte and Ludwig, Jean-Patrick and Friedlein, Johannes and Gerritzen, Johannes and Devulapally, Deekshith Reddy and Chen, Chin and Weiss, Deborah and Krome, Sven and Reschke, Gregor and Gude, Maik}}, issn = {{2666-3309}}, journal = {{Journal of Advanced Joining Processes}}, publisher = {{Elsevier BV}}, title = {{{Simulation-based process chain for aluminum clinched joints: Predicting geometry, strength, and failure behavior}}}, doi = {{10.1016/j.jajp.2026.100402}}, year = {{2026}}, } @article{65582, abstract = {{The mechanical joining of continuous fiber-reinforced thermoplastics (cFRTP) and metal sheets represents a promising approach for manufacturing hybrid lightweight structures. To reduce the time and cost associated with extensive experimental investigations, numerical modeling strategies are increasingly applied. In this numerical study, a further step in the modelling strategy for the direct pin-pressing (DPP) process of cFRTP and metal sheets is presented. The study focuses on modeling and simulating the occurring deformation mechanisms of decomposition, compaction, and separation of individual rovings on the mesoscale to analyze the resulting material structure. For this purpose, two simplified models were derived. The textile architecture is represented based on micrographs of cross-sections and discretized using the finite element method. The deformation of individual rovings during joining leads to a deformation of their initial elliptical cross section. To capture this level of resolution, both a cohesive zone and a pure contact approach are applied within the rovings. The highly viscous thermoplastic melt is modeled as a fluid employing the Arbitrary Lagrange–Eulerian (ALE) method. Matrix and roving meshes are coupled to account for fluid–structure interaction (FSI) during process. The study shows that coupling of matrix and rovings is necessary to obtain more accurate predictions of the deformation behaviour. Furthermore, the cohesive zone approach is better suited to simulate the emerging deformation mechanisms.}}, author = {{Gröger, Benjamin and Gerritzen, Johannes and Hornig, Andreas and Gude, Maik}}, issn = {{1662-9795}}, journal = {{Key Engineering Materials}}, pages = {{227--234}}, publisher = {{Trans Tech Publications, Ltd.}}, title = {{{Modelling Deformation Mechanisms Decomposition, Separation and Compaction in Mechanical Joining Processes of Fiber Reinforced Thermoplastics on Meso Scale}}}, doi = {{10.4028/p-e8wywr}}, volume = {{1050}}, 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}}, } @inproceedings{65483, abstract = {{Clinched joints with non-rotationally symmetric geometries exhibit orientation-dependent mechanical behavior that is commonly neglected in structural-scale simulations. Reuleaux triangle shaped clinched joints, in particular, show pronounced in-plane anisotropy depending on their orientation. While such effects have been studied at joint and specimen scale, their relevance at the structural level remains largely unexplored. In this work, the influence of joint orientation on the bending response of a joined structure is investigated using numerical simulations. A simplified joint replacement model based on the *CONSTRAINED_SPR2 point-connector formulation in LS-DYNA is employed, with parameters calibrated from previously obtained experimental force displacement data. A hat shaped profile structure subjected to three-point bending is analyzed in a parametric study considering variations in joint orientation, joint spacing, and profile geometry. The results show that joint orientation has little influence during the initial deformation phase but becomes increasingly significant at larger displacements, where joint behavior governs load transfer. Orientation dependent effects are found to influence the global force displacement response and local load redistribution among joints, with magnitudes comparable to those induced by changes in joint spacing and structural geometry. The findings confirm that joint orientation effects remain relevant at the structural level and should be considered in the design of structures assembled using non-rotationally symmetric clinched joints.}}, author = {{Devulapally, Deekshith Reddy and Tröster, Thomas}}, booktitle = {{Materials Science Forum}}, issn = {{1662-9752}}, pages = {{161--169}}, publisher = {{Trans Tech Publications, Ltd.}}, title = {{{A Numerical Study on the Mutual Influence of Joint Orientation and Component Geometry in Non-Rotationally Symmetric Clinched Joints}}}, doi = {{10.4028/p-0tiihi}}, volume = {{1185}}, year = {{2026}}, } @article{65620, abstract = {{Abstract The design of clinch joints is a cost- and time-intensive iterative process due to the complex relationships between tool and process parameters and the resulting joint properties. To address this, this contribution proposes a novel hybrid workflow that combines knowledge- and data-based approaches. Relationships are categorized based on their knowledge quality and the need for a quantitative prediction. Well-established, generalizable relationships are formalized in an ontology as design guidelines (no quantification required) or SWRL rules (quantification required) to model expert knowledge. In contrast, hard-to-formalize or not-fully-understood relationships are treated with regression models for continuous or classification models for binary criteria. These approaches are combined in a generic user interface (GUI), where the ontology can be accessed using predefined SPARQL queries to select and adapt parameters using expert knowledge. These parameters are then used as input for the metamodels. The developed workflow is evaluated on two exemplary joining tasks to illustrate, how designers can retrieve similar prior joints, adapt parameters using the encoded design rules and predict resulting joint properties under varying process conditions. In summary, the combination of ontology and metamodels facilitates the transition of trial and error into an efficient, documentable design process.}}, author = {{Einwag, Jonathan-Markus and Wiemer, Maximilian and Wartzack, Sandro and Goetz, Stefan}}, issn = {{2731-6564}}, journal = {{Discover Mechanical Engineering}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{A hybrid knowledge based and data based approach for efficient clinch joint design}}}, doi = {{10.1007/s44245-026-00230-x}}, volume = {{5}}, year = {{2026}}, } @article{65615, abstract = {{Self-piercing riveting (SPR) is a well-established joining technique in lightweight construction, as it enables the joining of different materials without requiring pre-drilling. However, the necessary adaptation of the rivet-die combination to the respective material and thickness combinations requires a large number of specific tool sets, which significantly limits the process's flexibility. To overcome these limitations, the versatile self-piercing riveting (V-SPR) was developed, which features enhanced punch actuation in combination with a multi-range-capable rivet . In this context, the concept of a movable die was introduced, which enables an extended process window and adaptable joint formation. Kappe et al. presented initial studies demonstrating the potential of this approach . However, a detailed numerical understanding of the underlying mechanisms remains lacking. This paper presents a numerical analysis of V-SPR with a movable die using a finite element (FE) model. The model includes deformable rivets, sheet metal materials and a kinematically controlled die with adjustable movement. A parameter study was conducted to analyse the influence of die movement on the material flow of the rivet and sheets, as well as joint formation. The simulations were validated using selected experimental data. The goal is to compare the joint geometries achieved with fixed and moving dies and expand the process windows of VSPR. The results demonstrate that the movable-die concept significantly enhances the material flow of both the sheets and the rivet, resulting in a noticeably larger and more reliable interlock than what is achievable with V-SPR using a fixed die. The numerical analyses support the observations reported by Kappe et al. and extend them by providing a quantitative description of how die displacement influences the resulting interlock size. Moreover, the ability to precisely control the die movement makes it possible to join challenging sheet-metal combinations that are difficult to process with conventional setups, particularly in cases involving thicker sheet materials.}}, author = {{Kaimann, Pia Katharina and Bobbert, Mathias and Meschut, Gerson}}, issn = {{1662-9752}}, journal = {{Materials Science Forum}}, pages = {{149--160}}, publisher = {{Trans Tech Publications, Ltd.}}, title = {{{Numerical Analysis of the Influence of a Movable Die on Joint Formation in Versatile Self-Piercing Riveting}}}, doi = {{10.4028/p-8jkha8}}, volume = {{1185}}, year = {{2026}}, } @article{66067, abstract = {{Abstract Mechanical joining processes have played an increasingly important role in the manufacturing of modern lightweight structures due to a greater variety of materials. The growing number of joining tasks requires a large number of joining elements. Friction spun joint connectors (FSJC) offer an innovative approach that meets the growing demand for flexibility. This process combines rotational movement and axial force to create targeted friction heating, enabling the production of FSJCs and the joining of various sheet metal materials. The shape of the FSJC can be optimally adapted to the joining situation in question, providing a significant advantage in terms of process chain versatility. This paper investigates FSJCs made of the steel grades C45E+C (1.1191) and 115CrV3 (1.2210), the effect of in situ quenching during the joining process. The influences of the essential parameters of rotational speed, feed rate, and FSJC length on the mechanical properties after quenching are being focused on and compared to similar conditions during joining without quenching. At the same time, the material change is analyzed to determine the effect of different alloy approaches on hardness profiles and strength characteristics in cross-tensile testing. For this purpose, systematic test series with varying process parameters are conducted and evaluated using hardness measurements and cross-tensile tests.}}, author = {{Nordieker, Ansgar Bernhard and Homberg, Werner}}, issn = {{0972-2815}}, journal = {{Transactions of the Indian Institute of Metals}}, number = {{6}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Quenching During Thermomechanical Joining Using Friction Spun Joint Connectors}}}, doi = {{10.1007/s12666-026-03846-5}}, volume = {{79}}, year = {{2026}}, } @article{66457, abstract = {{Abstract The service life of fatigue-loaded components that already contain manufacturing‑induced microcracks is primarily governed by the direction and the rate of fatigue-crack growth. When multiple loading components (e.g., tension, compression, shear) act simultaneously but not in temporal synchrony, out‑of‑phase mixed‑mode conditions occur. Such loadings are typical for automotive chassis parts and mechanically joined sheet‑metal assemblies. For optimized design of structural components, the crack kinking angle that occurs under mixed‑mode loading must be predicted as accurately as possible. At present, however, this is still challenging for out‑of‑phase loading conditions. To investigate the associated crack kinking behavior, a novel Compact‑Tension‑Shear‑Mini (CTSM) specimen was developed, enabling controlled generation of plane out-of-phase mixed-mode loading states. Experiments were performed under various combinations of cyclic and static mode I and mode II load components and compared with the analytical predictions of the Out-of-Phase Mixed-Mode (OMM) concept. The measured crack kinking angles showed very good agreement with the predicted values, with mean deviations of only a few degrees, demonstrating the validity and reproducibility of the approach. These findings confirm the applicability of the OMM concept for describing fatigue‑crack propagation under non‑proportional mixed‑mode loading and provide a basis for fatigue‑life assessment of clinched joints and other cyclic multi-axially loaded components.}}, author = {{Krome, Sven and Kullmer, Gunter and Weiß, Deborah and Duffe, Tobias and Ostwald, Richard}}, issn = {{2731-6564}}, journal = {{Discover Mechanical Engineering}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Experimental determination of kinking angles with out-of-phase mixed-mode loading by means of a novel specimen geometry}}}, doi = {{10.1007/s44245-026-00236-5}}, volume = {{5}}, year = {{2026}}, } @article{66673, abstract = {{Investigating crack growth in sheet metal originating from clinched joints is a major part of predicting the service life of mechanically joined structures. Clinching allows different materials to be joined together. A key task in this context is to perform crack growth simulations in the vicinity of clinched joints considering different load and environmental conditions. This requires formulaic descriptions of the fatigue crack growth rate curves for the materials used. For this purpose, fatigue crack growth rate curves for different R-ratios and temperatures are determined experimentally. Generally, these fatigue crack growth rate curves can be described very well using a novel two-part exponential approach for the formulaic description of fatigue crack growth rate curves developed at Applied Mechanics of Paderborn University (FAM). In this case, three parameters are sufficient to describe the fatigue crack growth rate curves. For the material HCT590X, which is frequently used in clinched joints, it is shown as an example how the parameters vary with the R-ratio and the temperature. In addition, at high crack growth rates, a significant rise in the fatigue crack growth rate curve sometimes occurs at both low and high temperatures. To account for this feature, the two-part exponential approach can be expanded to include a third part.}}, author = {{Kullmer, Gunter and Krome, Sven and Weiß, Deborah and Schramm, Britta and Ostwald, Richard}}, issn = {{2075-4701}}, journal = {{Metals}}, number = {{8}}, publisher = {{MDPI AG}}, title = {{{Influence of the R-Ratio and the Temperature on the Coefficients of a Novel Exponential Approach for the Formulaic Description of Fatigue Crack Growth Rate Curves}}}, doi = {{10.3390/met16080835}}, volume = {{16}}, 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}}, } @article{58492, abstract = {{A coupled finite plasticity ductile damage and failure model is proposed for the finite element simulation of clinch joining, which incorporates stress-state dependency and regularisation by gradient-enhancement of the damage variable. Ductile damage is determined based on a failure indicator governed by a failure surface in stress space. The latter is exemplary chosen as a combination of the Hosford–Coulomb and Cockcroft–Latham–Oh failure criteria for the high and low stress triaxiality range, respectively, to cover the wide stress range encountered in forming. Damage is coupled to elasto-plasticity to capture the damage-induced degradation of the stiffness and flow stress. This affects the material behaviour up to failure, thereby realistically altering the stress state. Consequently, especially for highly ductile materials, where substantial necking and localisation precede material fracture, the failure prediction is enhanced. The resulting stress softening is regularised by gradient-enhancement to obtain mesh-objective results. The analysis of a modified punch test experiment emphasises how the damage-induced softening effect can strongly alter the actual stress state towards failure. Moreover, the impact of successful regularisation is shown, and the applicability of the damage and failure model to clinch joining is proven.}}, author = {{Friedlein, Johannes and Mergheim, Julia and Steinmann, Paul}}, issn = {{0022-5096}}, journal = {{Journal of the Mechanics and Physics of Solids}}, keywords = {{Finite plasticity, Ductile damage, Gradient-enhancement, Stress-state dependency, Failure}}, publisher = {{Elsevier BV}}, title = {{{Modelling of stress-state-dependent ductile damage with gradient-enhancement exemplified for clinch joining}}}, doi = {{10.1016/j.jmps.2025.106026}}, volume = {{196}}, 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}}, }