@inproceedings{21598, abstract = {{Static analysis is used to automatically detect bugs and security breaches, and aids compileroptimization. Whole-program analysis (WPA) can yield high precision, however causes long analysistimes and thus does not match common software-development workflows, making it often impracticalto use for large, real-world applications.This paper thus presents the design and implementation ofModAlyzer, a novel static-analysisapproach that aims at accelerating whole-program analysis by making the analysis modular andcompositional. It shows how to computelossless, persisted summaries for callgraph, points-to anddata-flow information, and it reports under which circumstances this function-level compositionalanalysis outperforms WPA.We implementedModAlyzeras an extension to LLVM and PhASAR, and applied it to 12 real-world C and C++ applications. At analysis time,ModAlyzermodularly and losslessly summarizesthe analysis effect of the library code those applications share, hence avoiding its repeated re-analysis.The experimental results show that the reuse of these summaries can save, on average, 72% ofanalysis time over WPA. Moreover, because it is lossless, the module-wise analysis fully retainsprecision and recall. Surprisingly, as our results show, it sometimes even yields precision superior toWPA. The initial summary generation, on average, takes about 3.67 times as long as WPA.}}, author = {{Schubert, Philipp and Hermann, Ben and Bodden, Eric}}, booktitle = {{European Conference on Object-Oriented Programming (ECOOP)}}, title = {{{Lossless, Persisted Summarization of Static Callgraph, Points-To and Data-Flow Analysis}}}, year = {{2021}}, } @article{30208, abstract = {{

In this work the solubility of 15 amino acids and 18 peptides in aqueous 2-propanol solutions was successfully modelled using PC-SAFT that used recently determined experimental melting properties as input data.

}}, author = {{Do, Hoang Tam and Franke, Patrick and Volpert, Sophia and Klinksiek, Marcel and Thome, Max and Held, Christoph}}, issn = {{1463-9076}}, journal = {{Physical Chemistry Chemical Physics}}, keywords = {{Physical and Theoretical Chemistry, General Physics and Astronomy}}, number = {{18}}, pages = {{10852--10863}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Measurement and modelling solubility of amino acids and peptides in aqueous 2-propanol solutions}}}, doi = {{10.1039/d1cp00005e}}, volume = {{23}}, year = {{2021}}, } @inproceedings{26829, author = {{Bothe, Mike and Fedorov, Alexander and Frei, Herrmann and Kenig, Eugeny}}, location = {{Shanghai, China (online)}}, title = {{{Modeling and investigations of chemical absorption process for prevention of emergencies }}}, year = {{2021}}, } @article{30647, abstract = {{The increasing economic and ecological demands on the mobility sector require efforts to reduce resource consumption in both the production and utilization phases. The use of lightweight construction technologies can save material and increase energy efficiency during operation. Multi-material systems consisting of different materials and geometries are used to achieve weight reduction. Since conventional joining processes reach their limits in the connection of these components, new methods and technologies are necessary in order to be able to react versatilely to varying process and disturbance variables. For fundamental investigations of new possibilities in joining technology, numerical investigations are helpful to identify process parameters. To generate valid results, robust and efficient material models are developed which are adapted to the requirements of versatile joining technologies, for instance to the high plastic strains associated with self-piercing riveting. To describe the inherent strain-induced plastic orthotropy of sheet metal an anisotropic Hill-plasticity model is formulated. Tensile tests for different sheet orientations are conducted both experimentally and numerically to adjust the anisotropic material parameters by inverse parameter identification for aluminium EN AW-6014 and steel HCT590X. Then, the layer compression test is used to validate the model and the previously identified parameters.}}, author = {{Friedlein, J. and Wituschek, S. and Lechner, M. and Mergheim, J. and Steinmann, P.}}, journal = {{IOP Conference Series: Materials Science and Engineering}}, pages = {{012004}}, title = {{{Inverse parameter identification of an anisotropic plasticity model for sheet metal}}}, doi = {{10.1088/1757-899X/1157/1/012004}}, volume = {{1157}}, year = {{2021}}, } @article{30645, abstract = {{As a new and innovative processing method for fabrication for fiber-reinforced thermoplastic composites (CFRTs), the feasibility of ultrasonic welding technology was proven in several studies. This method offers potential for the direct manufacturing of CFRT–metal structures via embedded pin structures. Despite the previous studies, a deeper understanding of the process of energy input and whether fibers work as energy directors and consequently can, in combination with chosen processing parameters, influence the consolidation quality of the CFRTs, is still unknown. Consequently, the aim of this work is to establish a deeper process understanding of the ultrasonic direct impregnation of fiber-reinforced thermoplastics with an emphasis on the fiber’s function as energy directors. Based on the generated insights, a better assessment of the feasibility of direct, hybrid part manufacturing is possible. The produced samples were primarily evaluated by optical and mechanical test methods. It is demonstrated that with higher welding time and amplitude, a better consolidation quality can be achieved and that independent of the process parameters chosen in this study, no significant fiber breakage occurs. This is interpreted as a sign of a gentle impregnation process. Furthermore, based on the examination of single roving and 5-layer set-ups, it is shown that the glass fibers function as energy directors and can influence the transformation of sonic energy into thermal energy. In comparison to industrially available CFRT material, the mechanical properties are weaker, but materials and processes offer potential for significant improvement. Based on these findings, proposals for a direct impregnation and joining process are made.}}, author = {{Popp, J. and Wolf, M. and Mattner, T. and Drummer, D.}}, journal = {{Journal of Composites Science}}, pages = {{239}}, title = {{{Energy direction in ultrasonic impregnation of continuous fiber-reinforced thermoplastics}}}, doi = {{10.3390/jcs5090239}}, volume = {{5}}, year = {{2021}}, } @article{30643, abstract = {{The multi-material design and the adaptability of a modern process chain require joining connections with specifically adjustable mechanical, thermal, chemical, or electrical properties. Previous considerations primarily focused on the mechanical properties. The multitude of possible combinations of requirements, materials, and component- and joining-geometry makes an empirical determination of these joining properties for the clinching process impossible. Based on the established and empirical procedure, there is currently no model that takes into account all questions of joinability—i.e., the materials (suitability for joining), design (security of joining), and production (joining possibility)—that allows a calculation of the properties that can be achieved. It is therefore necessary to describe the physical properties of the joint as a function of the three binding mechanisms—form closure, force closure, and material closure—in relation to the application. This approach illustrates the relationships along the causal chain “joint requirement-binding mechanism-joining parameters” and improves the adaptability of the mechanical joining technology. Geometrical properties of clinch connections of the combination of aluminum and steel are compared in a metallographic cross-section. The mechanical stress state of the rotationally symmetrical clinch points is qualified with a torsion test and by measuring the electrical resistance in the base material, in the clinch joint, and during the production cycle (after clinching, before precipitation hardening and after precipitation hardening).}}, author = {{Kalich, J. and Füssel, U.}}, journal = {{Journal of Manufacturing and Materials Processing}}, pages = {{105}}, title = {{{Influence of the production process on the binding mechanism of clinched aluminum steel mixed compounds}}}, doi = {{10.3390/jmmp5040105}}, volume = {{5}}, year = {{2021}}, } @article{30644, abstract = {{Computational homogenization is a powerful tool allowing to obtain homogenized properties of materials on the macroscale from simulations of the underlying microstructure. The response of the microstructure is, however, strongly affected by variations in the microstructure geometry. In particular, we consider heterogeneous materials with randomly distributed non-overlapping inclusions, which radii are also random. In this work we extend the earlier proposed non-deterministic computational homogenization framework to plastic materials, thereby increasing the model versatility and overall realism. We apply novel soft periodic boundary conditions and estimate their effect in case of non-periodic material microstructures. We study macroscopic plasticity signatures like the macroscopic von-Mises stress and make useful conclusions for further constitutive modeling. Simulations demonstrate the effect of the novel boundary conditions, which significantly differ from the standard periodic boundary conditions, and the large influence of parameter variations and hence the importance of the stochastic modeling.}}, author = {{Pivovarov, D. and Mergheim, J. and Willner, K. and Steinmann, P.}}, journal = {{Computational Mechanics}}, title = {{{Stochastic local FEM for computational homogenization of heterogeneous materials exhibiting large plastic deformations}}}, doi = {{10.1007/s00466-021-02099-x}}, year = {{2021}}, } @article{30642, abstract = {{Sheet metal forming as well as mechanical joining demand increasingly accurate and efficient material modelling to capture large deformations, the inherent sheet orthotropy and even process-induced damage, which is expected to be influential. To account for large strains the additive logarithmic strain space is utilised that enables a straightforward incorporation of plastic anisotropy, herein modelled by a Hill48 yield function. A gradient-enhancement is used to equip the ductile damage model with an internal length scale curing the damage-induced localisation. An affine combination of the local and non-local softening variable is derived enabling a more efficient single surface formulation for the regularised plasticity-damage material model.}}, author = {{Friedlein, J. and Mergheim, J. and Steinmann, P.}}, journal = {{PAMM}}, title = {{{Anisotropic plasticity‐damage material model for sheet metal — Regularised single surface formulation}}}, doi = {{10.1002/pamm.202100068}}, volume = {{21}}, year = {{2021}}, } @inproceedings{20807, author = {{Bielak, Christian Roman and Böhnke, Max and Bobbert, Mathias and Meschut, Gerson}}, location = {{Lüttich}}, title = {{{Further development of a numerical method for analyzing the load capacity of clinched joints in versatile process chains}}}, doi = {{10.25518/esaform21.4298}}, year = {{2021}}, } @article{30650, abstract = {{Due to increasingly strict emission targets and regulatory requirements, especially for companies in the transport industry, the demand for multi-material-systems is continuously rising in order to lower energy consumption. In this context, mechanical joining processes offer an environmentally friendly and flexible alternative to established joining methods, especially in the field of lightweight design. For example, cold-formed cylindrical pin structures show high potentials in joining multi-material-systems without auxiliary elements. The pin structures are joined either by pressing them directly into the joining partner or by caulking with a pre-punched part. However, to evaluate the strength of the joint and to ensure the joining reliability for versatile processes, such as changing joining partners or batch variations, engineering designers currently have only limited design principles available compared to thermal joining processes. Consequently, the design of an optimal pin joint requires cost- and time-intensive experimental investigations and adjustments to design or process parameters. As a solution, data-driven methods offer procedures for structuring data and identifying dependencies between varying process parameters and resulting pin structure characteristics. Motivated by this, the paper presents an approach for the data-driven analysis of cold-formed pin structures and offers a deeper understanding of how versatile processes affect the pin characteristics. Therefore, the application of an intelligent design of experiment in combination with several machine learning methods enable the setup of a best-fitting meta-model. Resulting, the determination of a mathematical model provides the opportunity to accurately estimate the pin height considering only relevant geometrical and process parameters with a prediction quality of 95 %.}}, author = {{Römisch, D. and Zirngibl, C. and Schleich, B. and Wartzack, S. and Merklein, M.}}, journal = {{IOP Conference Series: Materials Science and Engineering}}, pages = {{012077}}, title = {{{Data-driven analysis of cold-formed pin structure characteristics in the context of versatile joining processes}}}, doi = {{10.1088/1757-899X/1157/1/012077}}, volume = {{1157}}, year = {{2021}}, } @article{30648, abstract = {{In clinching, the combinations of requirements, materials, component dimensions and tools influence the resulting joint geometry and the resulting bonding mechanisms. These in turn affect the property profile of the joint. For example, it is possible to use different tools to flexibly adapt clinching points to the respective required load regime. Clinching points dimensioned in this way can be geometrically similar, but have different mechanical stress states, which leads to different properties in terms of load-bearing behavior. Within the scope of this work, the clinching process with different tools in optimal and compromise design and its effect on the force and form-closure component, is investigated in a torsion test of the clinched connection. Clinched steel sheets with two thicknesses and joining directions are analyzed. Virtual experiments are carried out using finite element analyses (FEA) of the joining process and are followed by a springback simulation. Subsequently, the surface pressure between the two joining partners in the clinching points is calculated on the basis of the results from the FEA and the transmittable moment of the connection, as an indicator for the force-closure component, is determined. Finally, the experimental and simulated data are compared and discussed.}}, author = {{Steinfelder, C. and Kalich, J. and Brosius, A. and Füssel, U.}}, journal = {{IOP Conference Series: Materials Science and Engineering}}, pages = {{012003}}, title = {{{Numerical and experimental investigation of the transmission moment of clinching points}}}, doi = {{10.1088/1757-899x/1157/1/012003}}, volume = {{1157}}, year = {{2021}}, } @article{30653, abstract = {{Continuous Fiber Reinforced Thermoplastic (CFRT) hybrid parts offer interesting possibilities for lightweight application, which can exceed the capabilities of mono material metal or CFRT parts. In this case, the joining technology oftentimes is the limiting factor. This study investigates a joining operation with metal pin structures which are additively manufactured via powder bed fusion featuring different diameters and tip geometries, which are inserted into the locally infrared heated CFRT part. The resulting fiber rearrangement is assessed using transmitted light microscopy, confocal laser scanning microscopy as well as micro-computer-tomography. It could be shown that for all assessed pin variants a similar distinct fiber displacement can be seen and that the pin diameter has a significant effect on the resulting fiber orientation with smaller pin diameters being advantageous because of gentle fiber displacement and reduced undulation. The tip geometry has only minor effect on the fiber orientation. Especially in the X/Y plane no systematic influence of the tip geometry on the fiber displacement could be observed. Based on the gained insights a three-stage model of the fiber orientation processes is proposed.}}, author = {{Popp, J. and Kleffel, T. and Römisch, D. and Papke, T. and Merklein, M. and Drummer, D.}}, journal = {{Applied Composite Materials}}, pages = {{951–972}}, title = {{{Fiber Orientation Mechanism of Continuous Fiber Reinforced Thermoplastics Hybrid Parts Joined with Metallic Pins}}}, doi = {{10.1007/s10443-021-09892-0}}, volume = {{28}}, year = {{2021}}, } @article{30652, abstract = {{Clinching continuous fibre reinforced thermoplastic composites and metals is challenging due to the low ductility of the composite material. Therefore, a number of novel clinching technologies has been developed specifically for these material combinations. A systematic overview of these advanced clinching methods is given in the present paper. With a focus on process design, three selected clinching methods suitable for different joining tasks are described in detail. The clinching processes including equipment and tools, observed process phenomena and the resultant material structure are compared. Process phenomena during joining are explained in general and compared using computed tomography and micrograph images for each process. In addition the load bearing behaviour and the corresponding failure mechanisms are investigated by means of single-lap shear tests. Finally, the new joining technologies are discussed regarding application relevant criteria.}}, author = {{Gröger, B. and Troschitz, J. and Vorderbrüggen, J. and Vogel, C. and Kupfer, R. and Meschut, G. and Gude, M.}}, journal = {{Materials}}, pages = {{2286}}, title = {{{Clinching of Thermoplastic Composites and Metals—A Comparison of Three Novel Joining Technologies}}}, doi = {{10.3390/ma14092286X}}, volume = {{14}}, year = {{2021}}, } @article{30662, abstract = {{Industrial X-ray computed tomography (XCT) is a tool for non-destructive testing and a volumetric analysis method with the ability to measure dimensions and geometry inside a component without destroying it. However, XCT is a relatively young technology in the field of dimensional metrology and thus faces several challenges. The achievement of a high measurement resolution, which is re-quired to detect small geometrical features, depends on a variety of influencing factors. In this arti-cle, the interface structural resolution (ISR) as one of the key challenges will be investigated. The two-sphere standard called the hourglass standard allows the determination of the structural resolu-tion by evaluation of the surrounding area of an ideal point contact of two spheres after the CT re-construction in form of a neck-shaped transition. Close to the contact point of the two spheres two opposing surfaces exist. Their distances from each other increase as the distance from the contact point of the two spheres increase. The determination of the distances between the spheres’ surface allows a statement about the ISR. A new developed specimen or standard with a variable gap size consisting of calibrated parallel gauge blocks allows statements about the ISR, too. Because of the higher number of probing points of the gauge block standard the results of the determined ISR are more stable compared to the hourglass standard. This paper compares the results of the computed tomography measurements for the designed interface structural resolution standard with those of the hourglass standard. }}, author = {{Busch, M. and Hausotte, T.}}, journal = {{Key Engineering Materials}}, pages = {{41--48}}, title = {{{Determination of the Interface Structural Resolution of an Industrial X-Ray Computed Tomograph Using a Spherical Specimen and a Gap Specimen Consisting of Gauge Blocks}}}, doi = {{10.4028/www.scientific.net/kem.883.41}}, volume = {{883}}, year = {{2021}}, } @inproceedings{30725, abstract = {{Several algorithms for finding the best arm in the dueling bandits setting assume the existence of a Condorcet winner (CW), that is, an arm that uniformly dominates all other arms. Yet, by simply relying on this assumption but not verifying it, such algorithms may produce doubtful results in cases where it actually fails to hold. Even worse, the problem may not be noticed, and an alleged CW still be produced. In this paper, we therefore address the problem as a ”testification” task, by which we mean a combination of testing and identification: The online identification of the CW is combined with the statistical testing of the CW assumption. Thus, instead of returning a supposed CW at some point, the learner has the possibility to stop sampling and refuse an answer in case it feels confident that the CW assumption is violated. Analyzing the testification problem formally, we derive lower bounds on the expected sample complexity of any online algorithm solving it. Moreover, a concrete algorithm is proposed, which achieves the optimal sample complexity up to logarithmic terms.}}, author = {{Haddenhorst, Björn and Bengs, Viktor and Brandt, Jasmin and Hüllermeier, Eyke}}, booktitle = {{Proceedings of the Thirty-Seventh Conference on Uncertainty in Artificial Intelligence}}, editor = {{de Campos, Cassio and Maathuis, Marloes H.}}, pages = {{1195–1205}}, publisher = {{PMLR}}, title = {{{Testification of Condorcet Winners in dueling bandits}}}, volume = {{161}}, year = {{2021}}, } @article{30659, abstract = {{In lightweight design, clinching is a cost-efficient solution as the joint is created through localized cold-forming of the joining parts. 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 control 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). However, a clinching tool made of steel would cause strong artefacts and a high attenuation in the CT measurement, reducing the significance of this method. Additionally, when joining parts of the same material, the sheet-sheet interface is hardly detectable. This work aims at identifying, firstly, tool materials that allow artefact-reduced CT measurements during clinching, and, secondly, radiopaque materials that can be applied between the joining parts to enhance the detectability of the sheet-sheet interface. Therefore, both CT-suitable tool materials and radiopaque materials are selected and experimentally investigated. In the clinching process, two aluminium sheets with radiopaque material in between are clinched in a single-step (rotationally symmetric joint without cut section). It is shown that e.g. silicon nitride is suited as tool material and a tin layer is suitable to enhance the detectability of the sheet-sheet interface. }}, author = {{Köhler, D. and Kupfer, R. and Troschitz, J. and Gude, M.}}, journal = {{ESAFORM 2021}}, title = {{{Clinching in In-situ CT – Experimental Study on Suitable Tool Materials}}}, doi = {{10.25518/esaform21.2781}}, year = {{2021}}, } @article{30661, abstract = {{As lightweight design gains more and more attention, time and cost-efficient joining methods such as clinching are becoming more popular. A clinch point’s quality is usually determined by ex situ destructive analyses such as microsectioning. However, these methods do not yield the detection of phenomena occurring during loading such as elastic deformations and cracks that close after unloading. Alternatively, in situ computed tomography (in situ CT) can be used to investigate the loading process of clinch points. In this paper, a method for in situ CT analysis of a single-lap shear test with clinched metal sheets is presented at the example of a clinched joint with two 2 mm thick aluminum sheets. Furthermore, the potential of this method to validate numerical simulations is shown. Since the sheets’ surfaces are locally in contact with each other, the interface between both aluminum sheets and therefore the exact contour of the joining partners is difficult to identify in CT analyses. To compensate for this, the application of copper varnish between the sheets is investigated. The best in situ CT results are achieved with both sheets treated. It showed that with this treatment, in situ CT is suitable to properly observe the three-dimensional deformation behavior and to identify the failure modes.}}, author = {{Köhler, D. and Kupfer, R. and Troschitz, J. and Gude, M.}}, journal = {{Materials}}, pages = {{1859}}, title = {{{In Situ Computed Tomography—Analysis of a Single-Lap Shear Test with Clinch Points}}}, doi = {{10.3390/ma14081859}}, volume = {{14}}, year = {{2021}}, } @article{30719, abstract = {{Due to increasing demands regarding ecological and economic specifications in vehicle design, the effort required for production is continuously increasing. One trend is the increased use of multi-material systems, which are characterised by the use of different materials such as high-strength steels or aluminium alloys. In addition to the varying mechanical properties of the components, an increased number of variants accompanied by different geometries is leading to increasing challenges on body construction. For the assembly and connection of the individual components, conventional joining methods reach their limitations. Therefore, new joining methods are necessary, which feature properties of versatility and can adapt to process and disturbance variables. One way of achieving tailored joints is to use a tumbling self-piercing riveting process. For the design of the process route, numerical investigations are necessary for which a characterisation of the friction properties is necessary. This paper therefore investigates the contact and friction conditions that occur in a tumbling self-piercing riveting process. The individual contacts between the process components are identified and based on this, suitable processes for the characterisation of the friction factors - and coefficients are selected and performed.}}, author = {{Wituschek, S. and Lechner, M.}}, journal = {{Key Engineering Materials}}, pages = {{27--34}}, title = {{{Friction Characterisation for a Tumbling Self-Piercing Riveting Process}}}, doi = {{10.4028/www.scientific.net/kem.883.27}}, volume = {{883}}, year = {{2021}}, } @inproceedings{30723, author = {{Haddenhorst, Björn and Bengs, Viktor and Hüllermeier, Eyke}}, booktitle = {{Advances in Neural Information Processing Systems}}, editor = {{Beygelzimer, A. and Dauphin, Y. and Liang, P. and Vaughan, J. Wortman}}, title = {{{Identification of the Generalized Condorcet Winner in Multi-dueling Bandits}}}, year = {{2021}}, } @misc{17751, author = {{Peckhaus, Volker}}, booktitle = {{Staatslexikon. Recht, Wirtschaft, Gesellschaft, Bd. 5: Schule - Virtuelle Realität}}, pages = {{983--991 (Spalten)}}, publisher = {{Herder Verlag}}, title = {{{Technikphilosophie}}}, year = {{2021}}, }