TY - CONF AB - Abstract. The application of the mechanical joining process clinching allows the assembly of different sheet metal materials with a wide range of material thickness configurations, which is of interest for lightweight multi-material structures. In order to be able to predict the clinched joint properties as a function of the individual manufacturing steps, current studies focus on numerical modeling of the entire clinching process chain. It is essential to be able to take into account the influence of the joining process-induced damage on the load-bearing capacity of the joint during the loading phase. This study presents a numerical damage accumulation in the clinching process based on an implemented Hosford-Coulomb failure model using a 3D clinching process model applied on the aluminum alloy EN AW-6014 in temper T4. A correspondence of the experimentally determined failure location with the element of the highest numerically determined damage accumulation is shown. Moreover, the experimentally determined failure behavior is predicted to be in agreement in the numerical loading simulation with transferred pre-damage from the process simulation. AU - Bielak, Christian Roman AU - Böhnke, Max AU - Friedlein, Johannes AU - Bobbert, Mathias AU - Mergheim, Julia AU - Steinmann, Paul AU - Meschut, Gerson ID - 43090 SN - 2474-395X T2 - Materials Research Proceedings TI - Numerical analysis of failure modeling in clinching process chain simulation ER - TY - CONF AB - Abstract. In the numerical simulation of mechanical joining technologies such as clinching, the material modeling of the joining parts is of major importance. This includes modeling the damage and failure behavior of the materials in accordance with varying occurring stress states. This paper presents a calibration method of three different fracture models. The calibration of the models is done by use of experimental data from a modified punch test, tensile test and bulge test in order to map the occurring stress states from clinching processes and to precisely model the resulting failure behavior. Experimental investigations were carried out for an aluminum alloy EN AW-6014 in temper T4 and compared with the simulative results generated in LS-DYNA. The comparison of force-displacement curves and failure initiation shows that the Hosford–Coulomb model predicts the failure behavior for the material used and the tests applied with the best accuracy. AU - Böhnke, Max AU - Bielak, Christian Roman AU - Friedlein, Johannes AU - Bobbert, Mathias AU - Mergheim, Julia AU - Steinmann, Paul AU - Meschut, Gerson ID - 43462 SN - 2474-395X T2 - Materials Research Proceedings TI - A calibration method for failure modeling in clinching process simulations ER - TY - CHAP AU - Böhnke, Max AU - Bielak, Christian Roman AU - Bobbert, Mathias AU - Meschut, Gerson ID - 52454 SN - 2195-4356 T2 - Lecture Notes in Mechanical Engineering TI - Experimental and Numerical Investigation of Clinched Joints Under Shear Tensile Loading at High Strain Rates ER - TY - CONF AU - Friedlein, Johannes AU - Bielak, Christian Roman AU - Böhnke, Max AU - Bobbert, Mathias AU - Mergheim, Julia AU - Steinmann, Paul AU - Meschut, Gerson ID - 43463 T2 - Materials Research Proceedings TI - Influence of plastic orthotropy on clinching of sheet metal ER - TY - CHAP AU - Bielak, Christian Roman AU - Böhnke, Max AU - Bobbert, Mathias AU - Meschut, Gerson ID - 52614 SN - 2195-4356 T2 - Lecture Notes in Mechanical Engineering TI - Numerical Investigation of the Coupled Friction Behavior in the Clinching Process Chain ER - TY - JOUR AB - 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. AU - Ewenz, L. AU - Bielak, Christian Roman AU - Otroshi, Mortaza AU - Bobbert, Mathias AU - Meschut, Gerson AU - Zimmermann, M. ID - 34213 IS - 2-3 JF - Production Engineering KW - Industrial and Manufacturing Engineering KW - Mechanical Engineering SN - 0944-6524 TI - Numerical and experimental identification of fatigue crack initiation sites in clinched joints VL - 16 ER - TY - JOUR AB - Background. Clinching is a conventional cold forming process in which two or more sheets can be joined without auxiliary parts. A pre-forming of the parts to be joined, which is introduced by previous manufacturing steps, has an influence on the joining result. When considering the suitability for joining with regard to the formability of the materials, the influence of the preforming steps must be taken into account. The influences of strain hardening and sheet thickness on the joining properties must be investigated. In this context, a Finite Element Method (FEM) based metamodel analysis of the clinching process was carried out in [1] to investigate the robustness of the clinching process with respect to the different material pre-strains. In [2], the method was extended to the load bearing simulation.Procedure. The metamodel from preliminary work based on various FE models, which predicts the load-bearing capacity of a clinched joint influenced by pre-straining, is compared here with experimental data and the accuracy of the metamodel prediction is discussed. For this purpose an experimental procedure was further develop which allows the preforming of metal sheets from which joining specimens can be separated with a certain degree of unidirectional deformation. In the study, the procedure for preparing the joint specimens and the results of the loading tests are presented. Different possible relevant pre-strain combinations are investigated and compared with the simulation results, to validate the FE models and choose suitable metamodel. AU - Bielak, Christian Roman AU - Böhnke, Max AU - Bobbert, Mathias AU - Meschut, Gerson ID - 32413 JF - Key Engineering Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 1662-9795 TI - Experimental and Numerical Investigation on Manufacturing-Induced Pre-Strain on the Load-Bearing Capacity of Clinched Joints VL - 926 ER - TY - JOUR AB - Many mechanical material properties show a dependence on the strain rate, e.g. yield stress or elongation at fracture. The quantitative description of the material behavior under dynamic loading is of major importance for the evaluation of crash safety. This is carried out using numerical methods and requires characteristic values for the materials used. For the standardized determination of dynamic characteristic values in sheet metal materials, tensile tests performed according to the guideline from [1]. A particular challenge in dynamic tensile tests is the force measurement during the test. For this purpose, strain gauges are attached on each specimen, wired to the measuring equipment and calibrated. This is a common way to determine a force signal that is as low in vibration and as free of bending moments as possible. The preparation effort for the used strain gauges are enormous. For these reasons, an optical method to determine the force by strain measurement using DIC is presented. The experiments are carried out on a high speed tensile testing system. In combioantion with a 3D DIC high speed system for optical strain measurement. The elastic deformation of the specimen in the dynamometric section is measured using strain gauges and the optical method. The measured signals are then compared to validate the presented method. The investigations are conducted using the dual phase steel material HCT590X and the aluminum material EN AW-6014 T4. Strain rates of up to 240 s-1 are investigated. AU - Böhnke, Max AU - Unruh, Eduard AU - Sell, Stanislaw AU - Bobbert, Mathias AU - Hein, David AU - Meschut, Gerson ID - 33002 JF - Key Engineering Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 1662-9795 TI - Functionality Study of an Optical Measurement Concept for Local Force Signal Determination in High Strain Rate Tensile Tests VL - 926 ER - TY - CHAP AU - Böhnke, Max AU - Bielak, Christian Roman AU - Bobbert, Mathias AU - Meschut, Gerson ID - 33003 SN - 2367-1181 T2 - The Minerals, Metals & Materials Series TI - Development of a Modified Punch Test for Investigating the Failure Behavior in Sheet Metal Materials ER - TY - JOUR AU - Böhnke, Max AU - Bielak, Christian Roman AU - Bobbert, Mathias AU - Meschut, Gerson ID - 34572 JF - Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications TI - Experimental and numerical investigation of the influence of multiaxial loading conditions on the failure behavior of clinched joints ER - TY - JOUR AB - Mechanical joining technologies are increasingly used in multi-material lightweight constructions and offer opportunities to create versatile joining processes due to their low heat input, robustness to metallurgical incompatibilities and various process variants. They can be categorised into technologies which require an auxiliary joining element, or do not require an auxiliary joining element. A typical example for a mechanical joining process with auxiliary joining element is self-piercing riveting. A wide range of processes exist which are not requiring an auxiliary joining element. This allows both point-shaped (e.g., by clinching) and line-shaped (e.g., friction stir welding) joints to be produced. In order to achieve versatile processes, challenges exist in particular in the creation of intervention possibilities in the process and the understanding and handling of materials that are difficult to join, such as fiber reinforced plastics (FRP) or high-strength metals. In addition, predictive capability is required, which in particular requires accurate process simulation. Finally, the processes must be measured non-destructively in order to generate control variables in the process or to investigate the cause-effect relationship. This paper covers the state of the art in scientific research concerning mechanical joining and discusses future challenges on the way to versatile mechanical joining processes. AU - Meschut, Gerson AU - Merklein, M. AU - Brosius, A. AU - Drummer, D. AU - Fratini, L. AU - Füssel, U. AU - Gude, M. AU - Homberg, Werner AU - Martins, P.A.F. AU - Bobbert, Mathias AU - Lechner, M. AU - Kupfer, R. AU - Gröger, B. AU - Han, Daxin AU - Kalich, J. AU - Kappe, Fabian AU - Kleffel, T. AU - Köhler, D. AU - Kuball, C.-M. AU - Popp, J. AU - Römisch, D. AU - Troschitz, J. AU - Wischer, Christian AU - Wituschek, S. AU - Wolf, M. ID - 34216 JF - Journal of Advanced Joining Processes KW - Mechanical Engineering KW - Mechanics of Materials KW - Engineering (miscellaneous) KW - Chemical Engineering (miscellaneous) SN - 2666-3309 TI - Review on mechanical joining by plastic deformation VL - 5 ER - TY - JOUR AB - Due to the increasing use of multi-material constructions and the resulting material incompatibilities, mechanical joining technologies are gaining in importance. The reasons for this are the variety of joining possibilities as well as high load-bearing capacities. However, the currently rigid tooling systems cannot react to changing boundary conditions, such as changed sheet thicknesses or strength. For this reason, a large number of specialised joining processes have been developed to expand the range of applications. Using a versatile self-piercing riveting process, multi-material structures are joined in this paper. In this process, a modified tool actuator technology is combined with multi-range capable auxiliary joining parts. The multi-range capability of the rivets is achieved by forming the rivet head onto the respective thickness of the joining part combination without creating a tooling set-up effort. The joints are investigated both experimentally on the basis of joint formation and load-bearing capacity tests as well as by means of numerical simulation. It turned out that all the joints examined could be manufactured according to the defined standards. The load-bearing capacities of the joints are comparable to those of conventionally joined joints. In some cases the joint fails prematurely, which is why lower energy absorptions are obtained. However, the maximum forces achieved are higher than those of conventional joints. Especially in the case of high-strength materials arranged on the die side, the interlock formation is low. In addition, the use of die-sided sheets requires a large deformation of the rivet head protrusion, which leads to an increase in stress and, as a result, to damage if the rivet head. However, a negative influence on the joint load-bearing capacity could be excluded. AU - Kappe, Fabian AU - Wituschek, Simon AU - Bobbert, Mathias AU - Lechner, Michael AU - Meschut, Gerson ID - 34241 JF - Production Engineering KW - Industrial and Manufacturing Engineering KW - Mechanical Engineering SN - 0944-6524 TI - Joining of multi-material structures using a versatile self-piercing riveting process ER - TY - JOUR AB - Since the application of mechanical joining methods, such as clinching or riveting, offers a robust solution for the generation of advanced multi-material connections, the use in the field of lightweight designs (e.g. automotive industry) is steadily increasing. Therefore, not only the design of an individual joint is required but also the dimensioning of the entire joining connection is crucial. However, in comparison to thermal joining techniques, such as spot welding, the evaluation of the joints’ resistance against defined requirements (e.g. types of load, minimal amount of load cycles) mainly relies on the consideration of expert knowledge, a few design principles and a small amount of experimental data. Since this generally implies the involvement of several domains, such as the material characterization or the part design, a tremendous amount of data and knowledge is separately generated for a certain dimensioning process. Nevertheless, the lack of formalization and standardization in representing the gained knowledge leads to a difficult and inconsistent reuse, sharing or searching of already existing information. Thus, this contribution presents a specific ontology for the provision of cross-domain knowledge about mechanical joining processes and highlights two potential use cases of this ontology in the design of clinched and pin joints. AU - Zirngibl, Christoph AU - Kügler, Patricia AU - Popp, Julian AU - Bielak, Christian Roman AU - Bobbert, Mathias AU - Drummer, Dietmar AU - Meschut, Gerson AU - Wartzack, Sandro AU - Schleich, Benjamin ID - 30100 JF - Production Engineering KW - Industrial and Manufacturing Engineering KW - Mechanical Engineering SN - 0944-6524 TI - Provision of cross-domain knowledge in mechanical joining using ontologies ER - TY - CHAP AB - Due to economic and ecological requirements and the associated trend towards lightweight construction, mechanical joining technologies like self-piercing riveting are gaining in importance. In addition, the increase in lightweight multi-material joints has led to the development of many different mechanical joining technologies which can only be applied to join a small number of material combinations. This leads to low process efficiency, and in the case of self-piercing riveting, to a large number of required tool changes. Another approach focuses on reacting to changing boundary conditions as well as the creation of customised joints by using adaptive tools, versatile auxiliary joining parts or modified process kinematics. Therefore, this study investigates the influence of increased die-sided kinematics on joint formation in self-piercing riveting process. The aim is to achieve an improvement of the joint properties by superimposing the punch feed. Furthermore, it is intended to reduce required tool changes due to the improved joint design. The investigations were carried out by means of a 2D-axisymmetric numerical simulation model using the LS-Dyna simulation software. After the validation of the process model, the die was extended to include driven die elements. Using the model, different kinematics as well as their effects on the joint formation and the internal stress concentration could be analysed. In principle, the increased actuator technology enabled an increase of the interlock formation for both pure aluminium and multi-material joints consisting of steel and aluminium. However, the resulting process forces were higher during the process phases of punching and spreading. AU - Kappe, Fabian AU - Wituschek, Simon AU - de Pascalis, Vincenzo AU - Bobbert, Mathias AU - Lechner, Michael AU - Meschut, Gerson ID - 34275 SN - 1869-8433 T2 - Materials Design and Applications IV TI - Numerical Investigation of the Influence of a Movable Die Base on Joint Formation in Semi-tubular Self-piercing Riveting ER - TY - JOUR AU - Kappe, Fabian AU - Schadow, Luca AU - Bobbert, Mathias AU - Meschut, Gerson ID - 29858 JF - Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications TI - Increasing flexibility of self-piercing riveting by reducing tool–geometry combinations using cluster analysis in the application of multi-material design ER - TY - JOUR AU - Kappe, Fabian AU - Wituschek, Simon AU - Bobbert, Mathias AU - Meschut, Gerson ID - 29857 JF - Production Engineering TI - Determining the properties of multi‑range semi‑tubular self‑piercing riveted joints ER - TY - CHAP AB - The application of the mechanical joining process clinching enables the joining of sheet metals with a wide range of material-thickness configurations, which is of interest in lightweight construction of multi-material structures. Each material-thickness combination results in a joint with its own property profile that is affected differently by variations. Manufacturing process-related effects from preforming steps influence the geometric shape of a clinched joint as well as its load-bearing capacity. During the clinching process high degrees of plastic strain, increased temperatures and high strain rates occur. In this context, a 3D numerical model was developed which can represent the material-specific behaviour during the process chain steps sheet metal forming, joining, and loading phase in order to achieve a high predictive accuracy of the simulation. Besides to the investigation of the prediction accuracy, the extent of the influence of individual modelling aspects such as temperature and strain rate dependency is examined. AU - Bielak, Christian Roman AU - Böhnke, Max AU - Bobbert, Mathias AU - Meschut, Gerson ID - 34210 SN - 2367-1181 T2 - The Minerals, Metals & Materials Series TI - Development of a Numerical 3D Model for Analyzing Clinched Joints in Versatile Process Chains ER - TY - JOUR AB - Clinching as a mechanical joining process has become established in many areas of car body. In order to predict relevant properties of clinched joints and to ensure the reliability of the process, it is numerically simulated during the product development process. The prediction accuracy of the simulated process depends on the implemented friction model. Therefore, a new method for determining friction coefficients in sheet metal materials was developed and tested. The aim of this study is the numerical investigation of this experimental method by means of FE simulation. The experimental setup is modelled in a 3D numerical simulation taking into account the process parameters varying in the experiment, such as geometric properties, contact pressure and contact velocity. Furthermore, the contact description of the model is calibrated via the experimentally determined friction coefficients according to clinch-relevant parameter space. It is shown that the assumptions made in the determination of the experimental data in preliminary work are valid. In addition, it is investigated to what extent the standard Coulomb friction model in the FEM can reproduce the results of the experimental method. AU - Bielak, Christian Roman AU - Böhnke, Max AU - Bobbert, Mathias AU - Meschut, Gerson ID - 30962 JF - Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications KW - Mechanical Engineering KW - General Materials Science SN - 1464-4207 TI - Numerical investigation of a friction test to determine the friction coefficients for the clinching process ER - TY - JOUR AB - AbstractIn 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. AU - Ewenz, Lars AU - Bielak, Christian Roman AU - Otroshi, Mortaza AU - Bobbert, Mathias AU - Meschut, Gerson AU - Zimmermann, Martina ID - 30963 IS - 2-3 JF - Production Engineering KW - Industrial and Manufacturing Engineering KW - Mechanical Engineering SN - 0944-6524 TI - Numerical and experimental identification of fatigue crack initiation sites in clinched joints VL - 16 ER - TY - JOUR AU - Schramm, Britta AU - Friedlein, Johannes AU - Gröger, Benjamin AU - Bielak, Christian Roman AU - Bobbert, Mathias AU - Gude, Maik AU - Meschut, Gerson AU - Wallmersperger, Thomas AU - Mergheim, Julia ID - 34068 JF - Journal of Advanced Joining Processes KW - Mechanical Engineering KW - Mechanics of Materials KW - Engineering (miscellaneous) KW - Chemical Engineering (miscellaneous) SN - 2666-3309 TI - A Review on the Modeling of the Clinching Process Chain - Part II: Joining Process ER -