Towards an adaptable quality monitoring process for self-piercing riveting

Algorithms and the Foundations of Software technolog

Simulationsbasierte Lebensdauerabschätzung einer stanzgenieteten Fügeverbindung unter zyklischer Belastung

Die Auslegung von Bauteilen mit stanzgenietetem Fügepunkt ist im Hinblick auf die Betriebsfestigkeit mit einem erheblichen Versuchsaufwand verbunden. Um dieses zeit- und kostintensive Verfahren zu vereinfachen, wird in diesem Beitrag eine Möglichkeit zur rechnerischen Lebensdauerabschätzung für einen Fügepunkt mit dem Örtlichen Konzept auf Basis von Ergebnissen einer Finite-Elemente-Analyse dargestellt

Characterisation of load-bearing capacity and failure behaviour of different mechanical joints under crash load of steel intensive structures

The aim of this work is to find a general correlation to describe the reduction in strength of spot welded sheet metals made out of hot-stamped 22MnB5 in relation to the geometrical dimensions of the softened heat affected zone. Tensile tests with spot welded microstructure in the measurement length of the specimen were conducted and used for validation purposes. The resulting analytical model was derived in [1], [2] from a model by Satoh [3] for seam welded plates with a soft interlayer under tensile loading. The derived model was experimentally and numerically validated for different values of the relative thickness of the softened heat affected zone

Numerical analysis of the robustness of clinching process considering the pre-forming of the parts

Clinching is a conventional cold forming process in which two or more sheets of materials can be joined without any auxiliary parts. To achieve the required geometrical characteristics of the joint, it is essential to use the desired joining tools. The motivation of this study is to investigate the influence of forming steps prior to the joining process on the joint quality. The influences of strain hardening and the variation of sheet thickness on the joint characteristics are to be studied. In this regard, a metamodel-based analysis of the clinching process is performed to investigate the robustness of the clinching process with respect to the different material pre-stains. Three different material combinations made of steel and aluminium sheets (HCT590x; t = 1.5 mm, EN AW-6014, T4; t = 2.0 mm) are examined to illustrate the influence of different material properties on the joint characteristics. The numerical FEM-Simulation is used to predict the geometrical properties of the joint during the simulation of clinching process. For this purpose, an optimization software is used to conduct varieties of simulations and to create a meta-model, which is able to describe the relationship between the pre-straining and the quality relevant parameters of the clinched joint. To validate the model, the results of simulation and experiment are compared. It is shown that there is a good agreement between the simulation and the experiment concerning the geometrical parameters and force-displacement diagram. Finally the joinability of the investigated material-geometry combinations with regard to a tolerable pre-forming is described

Numerical and experimental identification of fatigue crack initiation sites in clinched joints

In this paper, a study based on experimental and numerical simulations is performed to analyze fatigue cracks in clinched joints. An experimental investigation is conducted to determine the failure modes of clinched joints under cyclic loading at different load amplitudes with single-lap shear tests. In addition, numerical FEM simulations of clinching process and subsequent shear loading are performed to support the experimental investigations by analyzing the state of stresses at the location of failure. An attempt is made to explain the location of crack initiation in the experiments using evaluation variables such as contact shear stress and maximum principal stress

Einfluss fertigungsbedingter Toleranzen auf das Versagens- und Verformungsverhalten mechanisch gefügter Verbindungen unter Crashbelastung

Als experimentell ermittelte Versagens- und Verformungsverhalten der Verbindungen bildet zusammen mit den Detailsimulationen die Grundlage für die Klassifizierung der Fertigungseinflüsse hinsichtlich ihrer Auswirkungen auf die Festigkeit, das Bruchverhalten und Energieabsorption in Abhängigkeit der Belastung. Das Ziel der Klassifizierung ist es, einen Zusammenhang zwischen Ausprägung eines Fertigungseinflusses und dem Einfluss auf das Verformungs- und Versagensverhalten der Verbindung herzustellen und diesen zu bewerten. Die hierbei erarbeiteten funktionalen Zusammenhänge werden anschließend durch Modifikation der Modellparameter in die Ersatzmodellierung implementiert. So kann untersucht werden in welchem Maß Änderungen deterministischer Variablen aus dem Prozess Auswirkungen auf die Berechnungsgenauigkeit haben. Die an Kleinproben gewonnen Erkenntnisse und die entwickelten Ersatzmodelle werden anhand von Musterbauteilproben, z.B. T-Stoßproben, validiert. So kann die Anwendbarkeit der Modellierungsmethode bei komplexen Belastungszuständen der Fügestelle untersucht werden. Hierdurch können Empfehlungen für die Anwendung in Gesamtfahrzeugsimulationen gegeben werden

Crash simulation of mechanical joints with automatically determined model parameters based on test results and prediction algorithms

The increasing usage of innovative light weight concepts in automobile production leads to the application of different mechanical joining techniques like self-pierce riveting- semi tubular (SPR-ST) and -solid (SPR-S), flow drilling screwing (FDS) and high speed bolt joining (HSB) for multi-material constructions. These mechanical joints are used at positions of car bodies which show high stresses under impact loading. For the prediction of the load-bearing capacity, the failure behavior and the energy absorption in crash simulations complete and reliable models are needed. Therefore experimental results on single joint specimens and simulation of these specimen tests are necessary to determine the model parameters. If this had to be done for all existing sheet metal combinations of all mechanical joints in a body-in-white it would result in a very time and cost intensive process. The aim of the research project CraSiFue[1] was to reduce these efforts by developing a forecast algorithm and implementing it in a software. The developed software JoiningLab predicts the joint properties and model parameters of the *CONSTRAINED INTERPOLATION SPOTWELD (Model 2, SPR4) [2], [3] in LS-DYNA® for untested i.e. unknown mechanical joints. This results in saving real tests and accelerates the crash safety investigations especially in the concept phase of construction, where materials, sheet thicknesses and joints are not definitely specified yet

Daten- und prognosebasierte Generierung von Modellparametern für die Crashsimulation mechanisch gefügter Verbindungen

Durch die immer stärker fokussierte Umsetzung von innovativen Leichtbaukonzepten findet ein vermehrter Einsatz von mechanischen Fügeverfahren (Halbhohlstanznieten, Vollstanznieten, fließlochformendes Schrauben, Schließringbolzen- und Hochgeschwindigkeitsbolzensetzen) in Multi-Material-Konstruktionen statt. Diese Materialkombinationen und mechanischen Fügeverfahren werden an hoch belasteten Stellen für den Crash-Lastfall eingesetzt