@inproceedings{62079, abstract = {{This paper investigates two modeling approaches for the simulation of the deformation and decomposition behavior of preconsolidated rovings above the thermoplastic matrix{\textquoteright} melting temperature. This is crucial for capturing the local material structure after processes introducing highly localized deformation such as mechanical joining processes between metal and fiber reinforced thermoplastics (FRTP). A generic finite element (FE) model is developed, incorporating interfaces discretized through either cohesive zone (CZ) elements or Coulomb friction-based contacts. The material parameters for the FE elements are derived from the initial stiffness of a statistical volume element (SVE) at micro scale modelled with an Arbitrary-Lagrange-Eulerian method for three load cases. The CZ properties calculated are based on the shear viscosity of the composite. The CZ and contact modelling approaches are evaluated using three load cases of the SVE, comparing force-displacement curves. Under simple loading conditions, such as normal pressure tension and bending, both methods produce similar results; however, in complex load cases, the CZ approach shows clear advantages in handling interface interactions and shows robust simulations. The CZ approach thus presents a promising method for simulating roving decomposition in FRTP-metal joining applications above the matrix{\textquoteright} melting temperature.}}, author = {{Gröger, Benjamin and Gerritzen, Johannes and Hornig, Andreas and Gude, Maik}}, booktitle = {{Sheet Metal 2025}}, editor = {{Meschut, G. and Bobbert, M. and Duflou, J. and Fratini, L. and Hagenah, H. and Martins, P. and Merklein, M. and Micari, F.}}, isbn = {{978-1-64490-354-4}}, keywords = {{Finite Element Method (FEM), Process, Thermoplastic Fiber Reinforced Plastic}}, pages = {{268–275}}, publisher = {{Materials Research Forum LLC, Materials Research Foundations}}, title = {{{Modeling approaches for the decomposition behavior of preconsolidated rovings throughout local deformation processes}}}, doi = {{10.21741/9781644903551-33}}, year = {{2025}}, } @article{54847, abstract = {{The widespread adoption of ultra-high strength steels, due to their high bulk resistivity, intensifies expulsion issues in resistance spot welding (RSW), deteriorating both the spot weld and surface quality. This study presents a novel approach to prevent expulsion by employing a preheating current. Through characteristic analysis of joint formation under critical welding current, the importance of plastic material encapsulation around the weld nugget (plastic shell) at high temperatures in preventing expulsion is highlighted. To evaluate the effect of preheating on the plastic shell and understand its mechanism in expulsion prevention, a two-dimensional welding simulation model for dissimilar ultra-high strength steel joints was established. The results showed that optimal preheating enhances the thickness of the plastic shell, improving its ability to encapsulate the weld nugget during the primary welding phase, thereby diminishing expulsion risks. Experimental validation confirmed that by employing the optimal preheating current, the maximum nugget diameter was enhanced to 9.42 mm, marking an increase of 13.4 % and extending the weldable current range by 27.5 %. Under quasi-static cross-tensile loading, joints with preheating demonstrated a 7.9 % enhancement in maximum load-bearing capacity compared to joints without preheating, showing a reproducible and complete pull-out failure mode within the heat-affected zone. This study offers a prevention method based on underlying mechanisms, providing a new perspective for future research on welding parameter optimization with the aim of expulsion prevention.}}, author = {{Yang, Keke and El-Sari, Bassel and Olfert, Viktoria and Wang, Zhuoqun and Biegler, Max and Rethmeier, Michael and Meschut, Gerson}}, issn = {{1526-6125}}, journal = {{Journal of Manufacturing Processes}}, keywords = {{Expulsion Resistance spot welding Finite element modelling Preheating Weldable current range Ultra-high strength steel}}, pages = {{489--502}}, publisher = {{Elsevier BV}}, title = {{{Expulsion prevention in resistance spot welding of dissimilar joints with ultra-high strength steel: An analysis of the mechanism and effect of preheating current}}}, doi = {{10.1016/j.jmapro.2024.06.034}}, volume = {{124}}, year = {{2024}}, } @article{61900, abstract = {{Background Anti-Muslim and anti-Islam attitudes are widespread in contemporary western societies. A grassroots movement of mosques tries to reduce prejudice by organizing guided mosque tours for non-Muslims. While this is an opportunity for intergroup contact in a social psychological sense, contact occurs under sometimes difficult conditions. As yet, its effects have not been investigated empirically. Objective We examine (a) whether visits have an immediate and medium-term effect on prejudice toward Islam and (b) how they change the visitors’ subjective images of Muslims. Methods (a) We survey N = 324 secondary school students in a three-wave panel study in 6 guided mosque tours in different parts of Germany, including a control sample. The tour programme was in line with common practice in the mosques. Standardized measurements were taken immediately before and after the tour and again several months later. (b) We asked about subjective images of Muslims and had subjects report their spontaneous associations with the term Muslim. Results (a) Most, but not all, mosque visits significantly alleviate anti-Islam prejudice in the short term. The effects fall off after several months. (b) After the visit, the image of Muslims possessed more concrete religious content, while negative and menacing associations, such as oppression of women, threat, or so-called Islamic State have decreased. Conclusions Outgroup contact in a mosque works as predicted by the intergroup contact research, even under less than optimal conditions. However, there is potential for improvement of the setup of tours in the interest of a more sustainable impact.}}, author = {{Janzen, Olga and Diekmann, Isabell and Tsolak, Dorian and Salentin, Kurt}}, issn = {{2510-1226}}, journal = {{Zeitschrift für Religion, Gesellschaft und Politik}}, keywords = {{Intergroup contact, Anti-Islam attitudes, Anti-Muslim attitudes, Prejudice, Youth}}, number = {{1}}, pages = {{ 129–159}}, publisher = {{Springer VS}}, title = {{{Do Guided Mosque Tours Alleviate the Prejudice of Non-Muslims against Islam and Muslims? Evidence from a Quasi-Experimental Panel Study from Germany}}}, doi = {{10.1007/s41682-023-00161-4}}, volume = {{8}}, year = {{2024}}, } @inproceedings{50479, abstract = {{Verifying assertions is an essential part of creating and maintaining knowledge graphs. Most often, this task cannot be carried out manually due to the sheer size of modern knowledge graphs. Hence, automatic fact-checking approaches have been proposed over the last decade. These approaches aim to compute automatically whether a given assertion is correct or incorrect. However, most fact-checking approaches are binary classifiers that fail to consider the volatility of some assertions, i.e., the fact that such assertions are only valid at certain times or for specific time intervals. Moreover, the few approaches able to predict when an assertion was valid (i.e., time-point prediction approaches) rely on manual feature engineering. This paper presents TEMPORALFC, a temporal fact-checking approach that uses multiple sources of background knowledge to assess the veracity and temporal validity of a given assertion. We evaluate TEMPORALFC on two datasets and compare it to the state of the art in fact-checking and time-point prediction. Our results suggest that TEMPORALFC outperforms the state of the art on the fact-checking task by 0.13 to 0.15 in terms of Area Under the Receiver Operating Characteristic curve and on the time-point prediction task by 0.25 to 0.27 in terms of Mean Reciprocal Rank. Our code is open-source and can be found at https://github.com/dice-group/TemporalFC.}}, author = {{Qudus, Umair and Röder, Michael and Kirrane, Sabrina and Ngomo, Axel-Cyrille Ngonga}}, booktitle = {{The Semantic Web – ISWC 2023}}, editor = {{R. Payne, Terry and Presutti, Valentina and Qi, Guilin and Poveda-Villalón, María and Stoilos, Giorgos and Hollink, Laura and Kaoudi, Zoi and Cheng, Gong and Li, Juanzi}}, isbn = {{9783031472398}}, issn = {{0302-9743}}, keywords = {{temporal fact checking · ensemble learning · transfer learning · time-point prediction · temporal knowledge graphs}}, location = {{Athens, Greece}}, pages = {{465–483}}, publisher = {{Springer, Cham}}, title = {{{TemporalFC: A Temporal Fact Checking Approach over Knowledge Graphs}}}, doi = {{10.1007/978-3-031-47240-4_25}}, volume = {{14265}}, year = {{2023}}, } @phdthesis{41971, abstract = {{Ultraschall-Drahtbonden ist eine Standardtechnologie im Bereich der Aufbau- und Verbindungstechnik von Leistungshalbleitermodulen. Um Prozessschritte und damit wertvolle Zeit zu sparen, sollen die Kupferdickdrähte für die Leistungshalbleiter auch für die Kontaktierung von eingespritzten Anschlusssteckern im Modulrahmen verwendet werden. Das Kontaktierungsverfahren mit diesen Drähten auf Steckern in dünnwandigen Kunststoffrahmen führt häufig zu unzureichender Bondqualität. In dieser Arbeit wird das Bonden von Anschlusssteckern experimentell und anhand von Simulationen untersucht, um die Prozessstabilität zu steigern. Zunächst wurden Experimente auf Untergründen mit hoher Steifigkeit durchgeführt, um Störgrößen von Untergrundeigenschaften zu verringern. Die gewonnenen Erkenntnisse erlaubten die Entwicklung eines Simulationsmodells für die Vorhersage der Bondqualität. Dieses basiert auf einer flächenaufgelösten Reibarbeitsbestimmung im Fügebereich unter Berücksichtigung des Ultraschallerweichungseffektes und der hierdurch entstehenden hohen Drahtverformung. Experimente an den Anschlusssteckern im Modulrahmen zeigten eine verringerte Relativverschiebung zwischen Draht und Stecker, was zu einer deutlichen Verringerung der Reibarbeit führt. Außerdem wurden verminderte Schwingamplituden des Bondwerkzeugs nachgewiesen. Dies führt zu einer weiteren Reduktion der Reibarbeit. Beide Effekte wurden mithilfe eines Mehrmassenschwingers modelliert. Die gewonnenen Erkenntnisse und die erstellten Simulationsmodelle ermöglichen die Entwicklung von Klemmvorrichtungen, welche die identifizierten Störgrößen gezielt kompensieren und so ein verlässliches Bonden der Anschlussstecker im gleichen Prozessschritt ermöglichen, in dem auch die Leistungshalbleiter kontaktiert werden.}}, author = {{Althoff, Simon}}, isbn = {{978-3-8440-8903-5}}, keywords = {{heavy copper bonding, wire bonding, quality prediction, friction model, point-contact-element}}, pages = {{192}}, publisher = {{Shaker}}, title = {{{Predicting the Bond Quality of Heavy Copper Wire Bonds using a Friction Model Approach}}}, volume = {{15}}, year = {{2023}}, } @inproceedings{33509, abstract = {{In this publication a novel method for far-field prediction from magnetic Huygens box data based on the boundary element method (BEM) is presented. Two examples are considered for the validation of this method. The first example represents an electric dipole so that the obtained calculations can be compared to an analytical solution. As a second example, a printed circuit board is considered and the calculated far-field is compared to a fullwave simulation. In both cases, the calculations for different field integral equations are under comparison, and the results indicate that the presented method performs very well with a combined field integral equation, for the specified problem, when only magnetic Huygens box data is given.}}, author = {{Marschalt, Christoph and Schroder, Dominik and Lange, Sven and Hilleringmann, Ulrich and Hedayat, Christian and Kuhn, Harald and Sievers, Denis and Förstner, Jens}}, booktitle = {{2022 Smart Systems Integration (SSI)}}, keywords = {{Near-Field Scanning, Huygens Box, Boundary Element Method, Method of Moments, tet_topic_hf, tet_enas}}, location = {{Grenoble, France}}, publisher = {{IEEE}}, title = {{{Far-field Calculation from magnetic Huygens Box Data using the Boundary Element Method}}}, doi = {{10.1109/ssi56489.2022.9901431}}, year = {{2022}}, } @inproceedings{27652, abstract = {{Aufgrund der Fortschritte der Digitalisierung finden Systeme zur Zustandsüberwachung vermehrt Einsatz in der Industrie, um durch eine zustandsbasierte oder eine prädiktive Instandhaltung Vorteile, wie eine verbesserte Zuverlässigkeit und geringere Kosten zu erzielen. Dabei beruhen Zustandsüberwachungssysteme auf den folgenden Bausteinen: Sensorik, Datenvorverarbeitung, Merkmalsextraktion und -auswahl, Diagnose bzw. Prognose sowie einer Entscheidungsfindung basierend auf den Ergebnissen. Jeder dieser Bausteine erfordert individuelle Einstellungen, um ein geeignetes Zustandsüberwachungssystem für die jeweilige Anwendung zu entwickeln. Eine offene Fragestellung im Bereich der Zustandsüberwachung ergibt sich aufgrund der Unsicherheit der Zukunft, die sich in den zukünftigen Betriebs- und Umgebungsbedingungen zeigt. Diese Unsicherheit gilt es in allen Bausteinen zu berücksichtigen. Dieser Beitrag konzentriert sich auf den Baustein Merkmalsextraktion und -selektion, mit dem Ziel anhand geeigneter Merkmale eine Prognose der nutzbaren Restlebensdauer mit hoher Genauigkeit realisieren zu können. Daher werden geeignete Merkmale aus dem Zeitbereich und daraus abgeleitete Zustandsindikatoren für die Restlebensdauerprognose von technischen Systemen vorgestellt. Dabei sind Zustandsindikatoren Kenngrößen zur Beobachtung des Zustands der kritischen Systemkomponenten. Anhand dreier Anwendungsbeispiele wird ihre Eignung evaluiert. Dabei werden Daten aus Lebensdauerversuchen unter instationären Betriebs- und Umgebungsbedingungen ausgewertet. Die auftretenden Unsicherheiten der Zukunft werden somit berücksichtigt. Die Beispielsysteme beruhen auf Gummi-Metall-Elementen und Wälzlagern. Aus den generierten Ergebnissen lässt sich schließen, dass die Zustandsindikatoren aus der betrachteten Zeitreihen-Toolbox auch unter unbekannten Betriebs- und Umgebungsbedingungen robust sind. }}, author = {{Aimiyekagbon, Osarenren Kennedy and Bender, Amelie and Sextro, Walter}}, booktitle = {{VDI-Berichte 2391}}, isbn = {{978-3-18-092391-8}}, issn = {{0083-5560 }}, keywords = {{run-to-failure, rubber-metal element, bearing prognostics, non-stationary operating conditions, varying operating conditions, feature extraction, feature selection}}, location = {{Würzburg}}, pages = {{197 -- 210}}, publisher = {{VDI Verlag GmbH}}, title = {{{Extraktion und Selektion geeigneter Merkmale für die Restlebensdauerprognose von technischen Systemen trotz aleatorischen Unsicherheiten }}}, year = {{2021}}, } @article{32559, abstract = {{This investigation concentrates on value similarity between parents and their children during adulthood. The interplay between gender, age, relationship quality, and frequency of contact on value similarity was analyzed. A total of 600 adult German children (53.8% women) and their parents took part in a questionnaire study. Value orientation was measured with a short version of Schwartz’s Portrait Values Questionnaire, and relationship quality with the Network of Relationships Inventory (Furman & Buhrmeister, 1992).Value similarity was higher in mother–daughter dyads compared to mother–son dyads, but in the other dyads, no significant differences were found. Regarding relationship quality, verbal intimacy was not related to value similarity. Parental satisfaction was associated with value similarity in the father–child dyads. Satisfaction, as perceived by adult children, was linked to value similarity in mother–child and father–son dyads. Furthermore, the frequency of contact related to value similarity between mothers and sons.}}, author = {{Hoellger, Christian and Sommer, Sabrina and Albert, Isabelle and Buhl, Heike M.}}, issn = {{0192-513X}}, journal = {{Journal of Family Issues}}, keywords = {{Adult child–parent dyads, value similarity, relationship quality, frequency of contact, parent-child-relationship}}, number = {{6}}, pages = {{1234--1257}}, publisher = {{SAGE Publications}}, title = {{{Intergenerational Value Similarity in Adulthood}}}, doi = {{10.1177/0192513x20943914}}, volume = {{42}}, year = {{2020}}, } @article{9972, abstract = {{The transportation of dry fine powders is an emerging technologic task, as in biotechnology, pharmaceu-tical and coatings industry the particle sizes of processed powders get smaller and smaller. Fine powdersare primarily defined by the fact that adhesive and cohesive forces outweigh the weight forces, leadingto mostly unwanted agglomeration (clumping) and adhesion to surfaces. Thereby it gets more difficult touse conventional conveyor systems (e.g. pneumatic or vibratory conveyors) for transport. A rather newmethod for transporting these fine powders is based on ultrasonic vibrations, which are used to reducefriction between powder and substrate. Within this contribution an experimental set-up consisting of apipe, a solenoid actuator for axial vibration and an annular piezoelectric actuator for the high frequencyradial vibration of the pipe is described. Since amplitudes of the radial pipe vibration should be as large aspossible to get high effects of friction reduction, the pipe is excited to vibrate in resonance. To determinethe optimum excitation frequency and actuator position the vibration modes and resonance frequenciesof the pipe are calculated and measured. Results are in good accordance.}}, author = {{Dunst, Paul and Hemsel, Tobias and Sextro, Walter}}, journal = {{elsevier}}, keywords = {{Powder transport Piezoelectrics Ultrasonics Pipe vibration Finite element simulation Fine powder}}, pages = {{733--736}}, title = {{{Analysis of pipe vibration in an ultrasonic powder transportationsystem}}}, volume = {{Sensors and Actuators A 263}}, year = {{2017}}, } @inproceedings{9955, abstract = {{Wire bonding has been an established packaging technology for decades. When introducing copper as wire material for high power applications, adaptations to the bonding process and to machines became necessary. Here, challenges occur due to the stiffer wire material and changing oxide layers on the contact partners. To achieve sufficient process stability, a clean bond area is required, which can only be achieved with high shear stresses in the contact partners surfaces. These necessitate high normal forces to plastically deform the wire and substrate. To achieve such high stresses in the contact area, the bonding tool needs to be able to transmit the needed tangential forces to the top side of the wire. The wire itself performs a shear movement and transmits the force into the contact area to clean the contaminant and oxide layers and to level the desired bond surfaces. The main function of the tool is to transmit these forces. If the bond tool can only transmit low forces in the direction of excitation, the parameter space for a stable bond process is severely restricted. Here, a modeling approach to estimate how well different tool shapes meet the demand of transmitting high tangential forces is presented. The model depends on wire deformation and thus on the ultrasonic softening effect.}}, author = {{Althoff, Simon and Meyer, Tobias and Unger, Andreas and Sextro, Walter and Eacock, Florian}}, booktitle = {{IEEE 66th Electronic Components and Technology Conference}}, keywords = {{finite element simulation, wire bonding, tool geometry}}, pages = {{2103--2110}}, title = {{{Shape-Dependent Transmittable Tangential Force of Wire Bond Tools}}}, doi = {{10.1109/ECTC.2016.234}}, year = {{2016}}, } @inproceedings{9963, abstract = {{Tire-wheel assembly is the only connection between road and vehicle. Contacting directly with road within postcard size of contact area, it is mounted and guided by the suspension system. Therefore kinematics and compliances of suspension system greatly influence the frictional coupling of tire tread elements and road surface asperities by affecting pressure and sliding velocity distribution in the contact zone. This study emphasizes the development of a numerical methodology for frictional rolling contact analysis with focus on interaction of suspension system dynamics and tire-road contact using ADAMS. For this purpose a comprehensive flexible multibody system of the multi-link rear suspension is established, where both flexible and rigid bodies are modeled to allow large displacements with included elastic effects. To meet accuracy requirements for the high frequency applications, such as road excitations, the amplitude- and frequency-dependency of rubber-metal bushings is included. Furthermore the proposed flexible viscoelastic suspension model is enhanced by a Flexible Ring Tire Model (FTire), which describes a 3D tire dynamic response and covers any road excitations by tread submodel connected to road surface model. Concerning the verification and validation procedure numerous experiments are carried out to confirm the validity and the accuracy of both the developed submodels and the entire model. The devised approach makes it possible to investigate the influence of suspension system design on dynamical rolling contact and to evaluate tire tread wear. Therefore it can be a useful tool to predict frictional power distribution within the contact area under more realistic conditions.}}, author = {{Kohl, Sergej and Sextro, Walter and Schulze, Sebastian}}, booktitle = {{The 2nd International Conference on Automotive Innovation and Green Energy Vehicle (AiGEV 2016), Cyberjaya, Malaysia, 2016.}}, keywords = {{Kinematics and compliances, flexible viscoelastic suspension model, frictional rolling contact analysis, frictional power distribution.}}, pages = {{1--12}}, title = {{{Aspects of Flexible Viscoelastic Suspension Modeling for Frictional Rolling Contact Analysis using ADAMS}}}, year = {{2016}}, } @inproceedings{9952, abstract = {{The contact between viscoelastic materials e.g. elastomers and a rough surface leads to a special friction characteristic, which differs greatly in its properties comparing to other materials like metals. In practice, this friction combination occurs for example in the tire-road contact, or in the use of rubber gaskets. Due to the frictional forces a system is significantly influenced in its vibrational properties. The friction force is composed of two main components adhesion and hysteresis. The adhesion results from molecular bounds between the contact partners, while the deformation of the viscoelastic material by the roughness of the counter body leads to power loss. This internal friction results in an additional frictional force, which is described by the hysteresis. To simulate the frictional behaviour of elastomers on rough surfaces and thus to determine the energy dissipation in contact, it is necessary to develop a mechanical model which considers the roughness of the contact partners, as well as dynamic effects and the dependence on normal pressure and sliding speed. The viscoelastic material behaviour must also be considered. The contact between two rough surfaces is modelled as a rough rigid layer contacting a rough elas- tic layer. The elastic layer is modelled by point masses connected by Maxwell-elements. This allows the viscoelastic properties of the elastomer to be considered. The behaviour of whole system can be described by equations of motion with integrated constraints. The degrees of freedom of the model depends on the varying contact conditions. A point mass not in contact has two degrees of freedom. A point mass in contact moving along the roughness path can be described by only one degree of freedom. For each Maxwell-Element also an inner coordinate and thus a further degree of freedom is needed. Because of varying contact conditions dur- ing the simulation, the simulation interrupts in case the contact conditions change. Then the equations of motions are adapted with respect to the contact constraints. As a result of the simulation one obtain the energy dissipation and thus the friction char- acteristic during the friction process. It is possible to use these results in three dimensional point-contact elements in order to model contact surfaces on lager length scales.}}, author = {{Schulte, Frank and Neuhaus, Jan and Sextro, Walter}}, booktitle = {{Proceedings of ICoEV 2015 International Conference on Engineering Vibration}}, keywords = {{Contact Mechanics, Viscoelastic Material, Adhesive Friction, Hysteresis Friction, Energy Dissipation, Vibration}}, pages = {{1109--1117}}, title = {{{A Mechanical Model for the Dynamical Contact of Elastic Rough Bodies with Viscoelastic Properties}}}, year = {{2015}}, } @article{13893, abstract = {{In this contribution, we present an efficient approach for the transient and time-causal modeling of guided waves in viscoelastic cylindrical waveguides in the context of ultrasonic material characterization. We use the scaled boundary finite element method (SBFEM) for efficient computation of the phase velocity dispersion. Regarding the viscoelastic behavior of the materials under consideration, we propose a decomposition approach that considers the real-valued frequency dependence of the (visco-)elastic moduli and, separately, of their attenuation. The modal expansion approach is utilized to take the transmitting and receiving transducers into account and to propagate the excited waveguide modes through a waveguide of finite length. The effectiveness of the proposed simulation model is shown by comparison with a standard transient FEM simulation as well as simulation results based on the exact solution of the complex-valued viscoelastic guided wave problem. Two material models are discussed, namely the fractional Zener model and the anti-Zener model; we re-interpret the latter in terms of the Rayleigh damping model. Measurements are taken on a polypropylene sample and the proposed transient simulation model is used for inverse material characterization. The extracted material properties may then be used in computer-aided design of ultrasonic systems.}}, author = {{Bause, Fabian and Gravenkamp, Hauke and Rautenberg, Jens and Henning, Bernd}}, issn = {{0957-0233}}, journal = {{Measurement Science and Technology}}, keywords = {{viscoelasticity, ultrasonics, guided waves, inverse problem, scaled boundary finite element method}}, number = {{095602 (17pp)}}, title = {{{Transient modeling of ultrasonic guided waves in circular viscoelastic waveguides for inverse material characterization}}}, doi = {{10.1088/0957-0233/26/9/095602}}, volume = {{26}}, year = {{2015}}, } @inproceedings{9868, abstract = {{In order to increase mechanical strength, heat dissipation and ampacity and to decrease failure through fatigue fracture, wedge copper wire bonding is being introduced as a standard interconnection method for mass production. To achieve the same process stability when using copper wire instead of aluminum wire a profound understanding of the bonding process is needed. Due to the higher hardness of copper compared to aluminum wire it is more difficult to approach the surfaces of wire and substrate to a level where van der Waals forces are able to arise between atoms. Also, enough friction energy referred to the total contact area has to be generated to activate the surfaces. Therefore, a friction model is used to simulate the joining process. This model calculates the resulting energy of partial areas in the contact surface and provides information about the adhesion process of each area. The focus here is on the arising of micro joints in the contact area depending on the location in the contact and time. To validate the model, different touchdown forces are used to vary the initial contact areas of wire and substrate. Additionally, a piezoelectric tri-axial force sensor is built up to identify the known phases of pre-deforming, cleaning, adhering and diffusing for the real bonding process to map with the model. Test substrates as DBC and copper plate are used to show the different formations of a wedge bond connection due to hardness and reaction propensity. The experiments were done by using 500 $\mu$m copper wire and a standard V-groove tool.}}, author = {{Althoff, Simon and Neuhaus, Jan and Hemsel, Tobias and Sextro, Walter}}, booktitle = {{Electronic Components and Technology Conference (ECTC), 2014 IEEE 64th}}, keywords = {{adhesion, circuit reliability, deformation, diffusion, fatigue cracks, friction, interconnections, lead bonding, van der Waals forces, Cu, adhering process, adhesion process, ampacity improvement, bond quality improvement, cleaning process, diffusing process, fatigue fracture failure, friction energy, friction model, heat dissipation, mechanical strength, piezoelectric triaxial force sensor, predeforming process, size 500 mum, total contact area, van der Waals forces, wedge copper wire bonding, Bonding, Copper, Finite element analysis, Force, Friction, Substrates, Wires}}, pages = {{1549--1555}}, title = {{{Improving the bond quality of copper wire bonds using a friction model approach}}}, doi = {{10.1109/ECTC.2014.6897500}}, year = {{2014}}, } @inproceedings{9887, abstract = {{A model to calculate the locally resolved tangential contact forces of the wheel rail contact with respect to contact kinematics, material and surface properties as well as temperature is introduced. The elasticity of wheel and rail is modeled as an elastic layer consisting of point contact elements connected by springs to each other and to the wheel. Each element has two degrees of freedom in tangential directions. The resulting total stiffness matrix is reduced to calculate only the position of the elements in contact. Friction forces as well as contact stiffnesses are incorporated by a nonlinear force-displacement characteristic, which originates from a detailed contact model. The contact elements are transported through the contact zone in discrete time steps. After each time step an equilibrium is calculated. For all elements, their temperature and its influence on local friction are regarded by calculating friction power and temperature each time step.}}, author = {{Neuhaus, Jan and Sextro, Walter}}, booktitle = {{Proceedings of the 5th International Conference on Computational Methods}}, editor = {{Liu, G.R. and Guan, Z.W.}}, keywords = {{Rolling Contact, Discrete Elements, Contact Stiffness, Temperature}}, publisher = {{ScienTech Publisher}}, title = {{{Thermo-Mechanical Model for Wheel Rail Contact using Coupled Point Contact Elements}}}, year = {{2014}}, } @inproceedings{9895, abstract = {{Power semiconductor modules are used to control and switch high electrical currents and voltages. Within the power module package wire bonding is used as an interconnection technology. In recent years, aluminum wire has been used preferably, but an ever-growing market of powerful and efficient power modules requires a material with better mechanical and electrical properties. For this reason, a technology change from aluminum to copper is indispensable. However, the copper wire bonding process reacts more sensitive to parameter changes. This makes manufacturing reliable copper bond connections a challenging task. The aim of the BMBF funded project Itsowl-InCuB is the development of self-optimizing techniques to enable the reliable production of copper bond connections under varying conditions. A model of the process is essential to achieve this aim. This model needs to include the dynamic elasto-plastic deformation, the ultrasonic softening effect and the proceeding adhesion between wire and substrate. This paper focusses on the pre-deformation process. In the touchdown phase, the wire is pressed into the V-groove of the tool and a small initial contact area between wire and substrate arise. The local characteristics of the material change abruptly because of the cold forming. Consequently, the pre-deformation has a strong effect on the joining process. In [1], a pre-cleaning effect during the touchdown process of aluminum wires by cracking of oxide layers was presented. These interactions of the process parameters are still largely unknown for copper. In a first step, this paper validates the importance of modeling the pre-deformation by showing its impact on the wire deformation characteristic experimentally. Creating cross-section views of pre-deformed copper wires has shown a low deformation degree compared to aluminum. By using a digital microscope and a scanning confocal microscope an analysis about the contact areas and penetration depths after touchdown has been made. Additionally, it has to be taken into account that the dynamical touchdown force depends on the touchdown speed and the touchdown force set in the bonding machine. In order to measure the overshoot in the force signals, a strain gauge sensor has been used. Subsequently, the affecting factors have been interpreted independently Furthermore, the material properties of copper wire have been investigated with tensile tests and hardness measurements. In a second step, the paper presents finite element models of the touchdown process for source and destination bonds. These models take the measured overshoot in the touchdown forces into account. A multi-linear, isotropic material model has been selected to map the material properties of the copper. A validation of the model with the experimental determined contact areas, normal pressures and penetration depths reveals the high model quality. Thus, the simulation is able to calculate and visualize the three dimensional pre-deformation with an integrated material parameter of the wire if the touchdown parameters of the bonding machine are known. Based on the calculated deformation degrees of wire and substrate, it is probably possible to investigate the effect of the pre-deformation on the pre-cleaning phase in the copper wire bonding.}}, author = {{Unger, Andreas and Sextro, Walter and Althoff, Simon and Eichwald, Paul and Meyer, Tobias and Eacock, Florian and Brökelmann, Michael}}, booktitle = {{Proceedings of the 47th International Symposium on Microelectronics (IMAPS)}}, keywords = {{pre-deformation, copper wire bonding, finite element model}}, pages = {{289--294}}, title = {{{Experimental and Numerical Simulation Study of Pre-Deformed Heavy Copper Wire Wedge Bonds}}}, year = {{2014}}, } @article{34442, abstract = {{Radial shaft seals are used in a variety of applications, where rotating shafts in steady housings have to be sealed. Typical examples are crankshafts, camshafts, differential gear or hydraulic pumps. In the operating state the elastomeric seal ring and the shaft are separated by a lubrication film of just a few micrometers. Due to shear strain and fluid friction the contact area is subject to a higher temperature than the rest of the seal ring. The stiffness of the elastomeric material is intensely influenced by this temperature and thus contact pressure, friction and wear also strongly depend on the contact temperature. In order to simulate the contact behavior of elastomer seal rings it is essential to use a comprehensive approach which takes into consideration the interaction of temperature, friction and wear. Based on this idea a macroscopic simulation model has been developed at the MEGT. It combines a finite element approach for the simulation of contact pressure at different wear states, a semi-analytical approach for the calculation of contact temperature and an empirical approach for the calculation of friction. In this paper the model setup is presented, as well as simulation and experimental results.}}, author = {{Frölich, D. and Magyar, Balázs and Sauer, B.}}, issn = {{0043-1648}}, journal = {{Wear}}, keywords = {{Radial shaft seal ring, Contact temperature, Wear, Friction torque, Finite element simulation}}, number = {{1}}, pages = {{71--80}}, title = {{{A comprehensive model of wear, friction and contact temperature in radial shaft seals}}}, doi = {{https://doi.org/10.1016/j.wear.2013.12.030}}, volume = {{311}}, year = {{2014}}, } @inproceedings{36918, abstract = {{This paper presents an advanced eight levels spanning SystemC based virtual platform methodology and framework - referred to as HeroeS 3 - providing smooth application to platform mapping and continuous co-refinement of a virtual prototype with its physical environment model. For heterogeneity support, various SystemC extensions are combined covering continuous/discrete models of computation and different communication abstractions, such as analog mixed-signal models, abstract RTOS/HAL/middleware models, TLM bus models, and QEMU wrappers. We enable dependability assessment by Fault Effect Modeling (FEM) at the virtual prototype in order to avoid risking physical injury or damage. Also, simulation results are deterministic and can be evaluated interactively or offline. We apply FEM to both the physical environment model and the different abstractions of the virtual prototype. Currently, we focus on sensor failures and application control flow errors.}}, author = {{Becker, Markus and Kuznik, Christoph and Müller, Wolfgang}}, keywords = {{Computational modeling, Finite element analysis, Prototypes, Abstracts, Software, Fault tolerance, Fault tolerant systems}}, location = {{Berlin}}, publisher = {{IEEE}}, title = {{{Fault Effect Modeling in a Heterogeneous SystemC Based Virtual Platform Framework for Cyber Physical Systems}}}, doi = {{10.1109/ICCPS.2014.6843726}}, year = {{2014}}, } @inproceedings{9797, abstract = {{A model approach for wedge/wedge bonding copper wire is presented. The connection between wire and substrate is based on a variety of physical effects, but the dominant one is the friction based welding while applying ultrasound. Consequently, a friction model was used to investigate the welding process. This model is built up universal and can be used to describe the formation of micro welds in the time variant contact area between wire and substrate. Aim of the model is to identify the interactions between touchdown, bond normal force, ultrasonic power and bonding time. To do so, the contact area is discretized into partial areas where a Point Contact Model is applied. Based on this approach it is possible to simulate micro and macro slip inside the contact area between wire and substrate. The work done by friction force is a main criterion to define occurring micro joints which influence the subsequent welding.}}, author = {{Althoff, Simon and Neuhaus, Jan and Hemsel, Tobias and Sextro, Walter}}, booktitle = {{IMAPS 2013, 46th International Symposium on Microelectronics}}, keywords = {{Wire bonding, friction modeling, wire bond quality, contact element modeling}}, title = {{{A friction based approach for modeling wire bonding}}}, doi = {{10.4071/isom-2013-TA67}}, year = {{2013}}, } @article{17204, abstract = {{In a longitudinal naturalistic study, we observed German mothers interacting with their infants when they were 3 and 6 months old. Pursuing the idea that infants’ attention is socialized in everyday interactions, we explored whether eye contact is reinforced selectively by behavioral modification in the input provided to infants. Applying a microanalytical approach focusing on the sequential organization of interaction, we explored how the mother draws the infant’s attention to herself and how she tries to maintain attention when the infant is looking at her. Results showed that eye contact is reinforced by specific infant-directed practices: interrogatives and conversational openings, multimodal stimulation, repetition, and imitation. In addition, these practices are contingent on the infant’s own behavior. By comparing the two data points (3 and 6 months), we showed how the education of attention evolves hand-in-hand with the developing capacities of the infant.}}, author = {{Nomikou, Iris and Rohlfing, Katharina and Szufnarowska, Joanna}}, issn = {{1572-0381}}, journal = {{Interaction Studies}}, keywords = {{interactional adaptation, multimodal input, social learning, ecology of attention, eye contact}}, number = {{2}}, pages = {{240--267}}, publisher = {{John Benjamins Publishing Company}}, title = {{{Educating attention: recruiting, maintaining, and framing eye contact in early natural mother-infant interactions}}}, doi = {{10.1075/is.14.2.05nom}}, volume = {{14}}, year = {{2013}}, }