TY - JOUR A1 - Mühling, Mischa A1 - Sandriesser, Sabrina A1 - Dendorfer, Sebastian A1 - Augat, Peter T1 - Assessment of implant internal stresses under physiological femoral loading: Translation to a simplified bending load model JF - Journal of Biomechanics N2 - The success of surgical treatment for fractures hinges on various factors, notably accurate surgical indication. The process of developing and certifying a new osteosynthesis device is a lengthy and costly process that requires multiple cycles of review and validation. Current methods, however, often rely on predecessor standards rather than physiological loads in specific anatomical locations. This study aimed to determine actual loads experienced by an osteosynthesis plate, exemplified by a standard locking plate for the femoral shaft, utilizing finite elements analysis (FEA) and to obtain the bending moments for implant development standard tests. A protocol was developed, involving the creation and validation of a fractured femur model fixed with a locking plate, mechanical testing, and FEA. The model’s validation demonstrated exceptional accuracy in predicting deformations, and the FEA revealed peak stresses in the fracture bridging zone. Results of a parametric analysis indicate that larger fracture gaps significantly impact implant mechanical behavior, potentially compromising stability. This study underscores the critical need for realistic physiological conditions in implant evaluations, providing an innovative translational approach to identify internal loads and optimize implant designs. In conclusion, this research contributes to enhancing the understanding of implant performance under physiological conditions, promoting improved designs and evaluations in fracture treatments. KW - bone biomechanics KW - finite elements analysis KW - femoral fracture KW - Euler-Bernoulli-Beam-Theory KW - simplified loading model Y1 - 2024 U6 - https://doi.org/10.1016/j.jbiomech.2024.112229 SN - 1873-2380 IS - 112229 PB - Elsevier ER - TY - JOUR A1 - Jahn, Hannes A1 - Böhm, Valter A1 - Zentner, Lena T1 - Analysis of deformation in tensegrity structures with curved compressed members JF - Meccanica N2 - AbstractTensegrity structures are prestressed structures consisting of compressed members connected by prestressed tensioned members. Due to their properties, such as flexibility and lightness, mobile robots based on these structures are an attractive subject of research and are suitable for space applications. In this work, a mobile robot based on a tensegrity structure with two curved members connected by eight tensioned strings is analyzed in terms of deformation in the curved members. Further, the difference in locomotion trajectory between the undeformed and deformed structure after the prestress is analyzed. For that, the theory of large deflections of rod-like structures is used. To determine the relationship between acting forces and the deformation, the structure is optimized using minimization algorithms in Python. The results are validated by parameter studies in FEM. The analysis shows that the distance between the two curved members significantly influences the structure’s locomotion. It can be said that the deformation of the components significantly influences the locomotion of tensegrity structures and should be considered when analyzing highly compliant structures. KW - Rolling locomotion KW - Mobile robot KW - Tensegrity structures KW - Deformation of compressedmembers KW - Finite element simulations Y1 - 2024 U6 - https://doi.org/10.1007/s11012-024-01833-y SN - 0025-6455 PB - Springer Nature ER - TY - JOUR A1 - Tezel, Tugce A1 - Schultheiss, Ulrich A1 - Hornberger, Helga A1 - Kovan, Volkan T1 - Operational wear behaviour of 3D-printed lightweight metal gears: EDS and oil analysis comparison JF - Materials Testing N2 - Additive manufacturing (AM) has come to the fore in recent years among manufacturing techniques. This technique, which has different advantages than traditional ones such as casting, forging and machining, is expected to be widely used in producing machine parts like gears in the coming years. Therefore, experimental data on AM parameters for lightweight metal gears are important for industrial production. In this study, a wear test was applied to AlSi10Mg and Ti6Al4V gears under operational conditions, and the wear behaviour of conventionally and additively manufactured gears was compared. The amount of abrasion elements was determined by analysing the oil in the gearbox. In addition, gear surfaces were analysed using scanning electron microscopy and an energy-dispersive spectrometer before and after wear. Thus, the wear behaviour of gears produced by conventional and AM under service conditions was demonstrated comparatively. KW - additive manufacturing KW - titanium KW - aluminium KW - gear KW - wear Y1 - 2024 U6 - https://doi.org/10.1515/mt-2023-0222 SN - 0025-5300 VL - 66 IS - 6 SP - 830 EP - 834 PB - de Gruyter ER - TY - JOUR A1 - Auer, Simon A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Using markerless motion capture and musculoskeletal models: An evaluation of joint kinematics JF - Technology and Health Care N2 - BACKGROUND: This study presents a comprehensive comparison between a marker-based motion capture system (MMC) and a video-based motion capture system (VMC) in the context of kinematic analysis using musculoskeletal models. OBJECTIVE: Focusing on joint angles, the study aimed to evaluate the accuracy of VMC as a viable alternative for biomechanical research. METHODS: Eighteen healthy subjects performed isolated movements with 17 joint degrees of freedom, and their kinematic data were collected using both an MMC and a VMC setup. The kinematic data were entered into the AnyBody Modelling System, which enables the calculation of joint angles. The mean absolute error (MAE) was calculated to quantify the deviations between the two systems. RESULTS: The results showed good agreement between VMC and MMC at several joint angles. In particular, the shoulder, hip and knee joints showed small deviations in kinematics with MAE values of 4.8∘, 6.8∘ and 3.5∘, respectively. However, the study revealed problems in tracking hand and elbow movements, resulting in higher MAE values of 13.7∘ and 27.7∘. Deviations were also higher for head and thoracic movements. CONCLUSION: Overall, VMC showed promising results for lower body and shoulder kinematics. However, the tracking of the wrist and pelvis still needs to be refined. The research results provide a basis for further investigations that promote the fusion of VMC and musculoskeletal models. KW - biomechanics KW - range of motion KW - musculoskeletal system KW - optical motion capture Y1 - 2024 U6 - https://doi.org/10.3233/THC-240202 SN - 0928-7329 N1 - Corresponding author der OTH Regensburg: Sebastian Dendorfer SP - 1 EP - 10 PB - IOS Press ER - TY - JOUR A1 - Förstl, Nikolas A1 - Adler, Ina A1 - Süß, Franz A1 - Dendorfer, Sebastian T1 - Technologies for Evaluation of Pelvic Floor Functionality: A Systematic Review JF - Sensors N2 - Pelvic floor dysfunction is a common problem in women and has a negative impact on their quality of life. The aim of this review was to provide a general overview of the current state of technology used to assess pelvic floor functionality. It also provides literature research of the physiological and anatomical factors that correlate with pelvic floor health. This systematic review was conducted according to the PRISMA guidelines. The PubMed, ScienceDirect, Cochrane Library, and IEEE databases were searched for publications on sensor technology for the assessment of pelvic floor functionality. Anatomical and physiological parameters were identified through a manual search. In the systematic review, 114 publications were included. Twelve different sensor technologies were identified. Information on the obtained parameters, sensor position, test activities, and subject characteristics was prepared in tabular form from each publication. A total of 16 anatomical and physiological parameters influencing pelvic floor health were identified in 17 published studies and ranked for their statistical significance. Taken together, this review could serve as a basis for the development of novel sensors which could allow for quantifiable prevention and diagnosis, as well as particularized documentation of rehabilitation processes related to pelvic floor dysfunctions. Y1 - 2024 U6 - https://doi.org/10.3390/s24124001 N1 - Die Preprint-Version ist ebenfalls in diesem Repositorium verzeichnet unter: https://opus4.kobv.de/opus4-oth-regensburg/frontdoor/index/index/docId/7306 VL - 24 IS - 12 PB - MDPI ER - TY - JOUR A1 - Wagner, Maria Stella A1 - Kranz, Michael A1 - Krenkel, Lars A1 - Pointner, Daniel A1 - Foltan, Maik A1 - Lubnow, Matthias A1 - Lehle, Karla ED - Becatti, Matteo T1 - Computer based visualization of clot structures in extracorporeal membrane oxygenation and histological clot investigations for understanding thrombosis in membrane lungs JF - Frontiers in Medicine N2 - Extracorporeal membrane oxygenation (ECMO) was established as a treatment for severe cardiac or respiratory disease. Intra-device clot formation is a common risk. This is based on complex coagulation phenomena which are not yet sufficiently understood. The objective was the development and validation of a methodology to capture the key properties of clots deposed in membrane lungs (MLs), such as clot size, distribution, burden, and composition. One end-oftherapy PLS ML was examined. Clot detection was performed using multidetector computed tomography (MDCT), microcomputed tomography (μCT), and photography of fiber mats (fiber mat imaging, FMI). Histological staining was conducted for von Willebrand factor (vWF), platelets (CD42b, CD62P), fibrin, and nucleated cells (4′, 6-diamidino-2-phenylindole, DAPI). The three imaging methods showed similar clot distribution inside the ML. Independent of the imaging method, clot loading was detected predominantly in the inlet chamber of the ML. The μCT had the highest accuracy. However, it was more expensive and time consuming than MDCT or FMI. The MDCT detected the clots with low scanning time. Due to its lower resolution, it only showed clotted areas but not the exact shape of clot structures. FMI represented the simplest variant, requiring little effort and resources. FMI allowed clot localization and calculation of clot volume. Histological evaluation indicated omnipresent immunological deposits throughout the ML. Visually clot-free areas were covered with leukocytes and platelets forming platelet-leukocyte aggregates (PLAs). Cells were embedded in vWF cobwebs, while vWF fibers were negligible. In conclusion, the presented methodology allowed adequate clot identification and histological classification of possible thrombosis markers such as PLAs. KW - ECMO KW - membrane lung KW - µCT KW - MDCT KW - shear induced clotting KW - vWF KW - histological evaluation Y1 - 2024 U6 - https://doi.org/10.3389/fmed.2024.1416319 IS - 11 PB - Frontiers ER - TY - JOUR A1 - Broll, Alexander A1 - Rosentritt, Martin A1 - Schlegl, Thomas A1 - Goldhacker, Markus T1 - A data-driven approach for the partial reconstruction of individual human molar teeth using generative deep learning JF - Frontiers in Artificial Intelligence N2 - Background and objectiveDue to the high prevalence of dental caries, fixed dental restorations are regularly required to restore compromised teeth or replace missing teeth while retaining function and aesthetic appearance. The fabrication of dental restorations, however, remains challenging due to the complexity of the human masticatory system as well as the unique morphology of each individual dentition. Adaptation and reworking are frequently required during the insertion of fixed dental prostheses (FDPs), which increase cost and treatment time. This article proposes a data-driven approach for the partial reconstruction of occlusal surfaces based on a data set that comprises 92 3D mesh files of full dental crown restorations.MethodsA Generative Adversarial Network (GAN) is considered for the given task in view of its ability to represent extensive data sets in an unsupervised manner with a wide variety of applications. Having demonstrated good capabilities in terms of image quality and training stability, StyleGAN-2 has been chosen as the main network for generating the occlusal surfaces. A 2D projection method is proposed in order to generate 2D representations of the provided 3D tooth data set for integration with the StyleGAN architecture. The reconstruction capabilities of the trained network are demonstrated by means of 4 common inlay types using a Bayesian Image Reconstruction method. This involves pre-processing the data in order to extract the necessary information of the tooth preparations required for the used method as well as the modification of the initial reconstruction loss.ResultsThe reconstruction process yields satisfactory visual and quantitative results for all preparations with a root mean square error (RMSE) ranging from 0.02 mm to 0.18 mm. When compared against a clinical procedure for CAD inlay fabrication, the group of dentists preferred the GAN-based restorations for 3 of the total 4 inlay geometries.ConclusionsThis article shows the effectiveness of the StyleGAN architecture with a downstream optimization process for the reconstruction of 4 different inlay geometries. The independence of the reconstruction process and the initial training of the GAN enables the application of the method for arbitrary inlay geometries without time-consuming retraining of the GAN. KW - inlay restoration KW - dental prosthesis design KW - StyleGAN KW - machine learning KW - digital dentistry Y1 - 2024 U6 - https://doi.org/10.3389/frai.2024.1339193 SN - 2624-8212 VL - 7 PB - Frontiers Media SA ER - TY - JOUR A1 - Schulz, Carsten A1 - Vogl, Yannick A1 - Geiger, Benjamin A1 - Schaeffer, Thomas T1 - Vor- und Nachteile einer Lumped-Mass-Modellierung von Förderbändern am Beispiel eines Zwei-Walzensystems JF - Forschung im Ingenieurwesen JF - Engineering Research N2 - Im Betrieb von Förderbändern auftretende Phänomene sind das Bandwandern in Achsrichtung der Walzen und die Bandverformung in der Bandebene [1, S. 142]. Das Bandwandern ist bisher detailliert untersucht [2–4], während die Bandverformung Gegenstand weniger Veröffentlichungen ist. Deshalb wird in diesem Artikel eine Methode zur Berechnung der sich im dynamischen Betrieb einstellenden Verformung eines elastischen Förderbandes vorgestellt. Dazu wird ein Mehrkörpersimulations-Modell basierend auf der Lumped-Mass-Modellierung verwendet. Als Untersuchungsbeispiel dient ein Zwei-Walzensystem mit flexiblen und zylindrischen Walzen, sowie ein flexibles Förderband. Es zeigt sich, dass mit der Lumped-Mass-Modellierung eine dynamische Bandverformung, die von der gewählten Diskretisierung abhängt, berechnet werden kann. Aufgrund dieser Abhängigkeit ist es notwendig eine Konvergenzanalyse durchzuführen. Zusätzlich ist darauf zu achten, dass die künstliche Anregung aufgrund der Lumped-Mass-Modellierung nicht mit einer Eigenfrequenz des Modells zusammenfällt. N2 - Phenomena occurring in the operation of conveyor belts are belt walking in the axial direction of the rollers and belt deformation in the belt plane [1, S. 142]. Whereas [2,3,4] investigate the first effect in detail [2,3,4], the latter is mostly neglected. The authors therefore focus on the calculation of the deformation of the elastic conveyor belt during dynamic operation using a flexible multibody approach. To consider the flexibility of the belt in an efficient way, the model uses the well-known Lumped-Mass-Approach. The discretization of the model (number and distance of masses) thereby impacts the shape of the band deformation. The article investigates the minimum required discretization for two dimensions, the effect on the system response and the influence on the computation time. As an example, a two-roller system with flexible, cylindrical rolls and a flexible conveyor belt is used. The results of the model will be compared with theoretical expectations and show very promising results. T2 - Pros and cons of Lumped Mass Modelling of conveyor belts using a two-roller system Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-72891 SN - 0015-7899 N1 - Corresponding author der OTH Regensburg: Carsten Schulz VL - 88 IS - 1 PB - Springer Vieweg CY - Belrin ; Heidelberg ER - TY - JOUR A1 - Schulz, Carsten A1 - Kieß, Benjamin A1 - Graneß, Henry T1 - Einfluss der Modellierungsstrategie des Zahnfußes auf den Drehwegfehler JF - Schwingungen 2023 : 4. VDI-Fachtagung : 27. und 28. November 2023, Würzburg N2 - Bei der Untersuchung und Optimierung der Getriebedynamik, im Sinne der Akustik und Lastverteilung, wird oftmals der Drehwegfehler als Bewertungskriterium herangezogen. Zahlreiche Forschungsvorhaben haben sich in diesem Zusammenhang intensiv mit dem Drehwegfehler als parametererregte Schwingungsanregung auseinandergesetzt, um diesen im Hinblick auf das Systemverhalten zu optimieren. Dabei bleibt der Zahnfußbereich, welcher außerhalb der Evolvente liegt, und dessen Einfluss auf den Drehwegfehler oftmals unberücksichtigt. Dieser Artikel untersucht daher den Einfluss des Zahnfußbereiches auf den statischen Drehwegfehler, indem relevante Größen wie das spezifische Kopfspiel und der Fußrundungsradius an einer typischen und real eingesetzten Stirnradverzahnung variiert werden. Ferner wird betrachtet, inwiefern der Drehwegfehler durch unterschiedliche Geometriedefinitionen (Fertigungssimulation, Zahngeometrie mit vereinfachter sowie stark vereinfachter Modellierung des Zahnfußbereichs) beeinflusst wird. Die Autoren nutzen hierfür zwei FE-Ansätze (adaptives und nicht-adaptives Netz) und bewerten diese hinsichtlich ihrer Gültigkeit, Modellgüte und Praktikabilität. Die Ergebnisse der Untersuchungen werden hinsichtlich einer minimal erforderlichen Geometrie des Zahnfußbereiches interpretiert. Für den Praxistransfer wird einerseits der maximale Fehler bei Nichtberücksichtigung des gesamten Zahnfußbereichs beziffert. Andererseits wird eine Empfehlung zur Anpassung einer vereinfachten Geometrie, an eine Geometrie, ähnlich der aus einer Fertigungssimulation, gegeben. Weiterhin wird der Artikel diskutieren, ob man ein vereinfachtes Zahnmodell zur Berechnung der Getriebedynamik nutzen kann, wenn der Fertigungsprozess noch nicht definiert ist. KW - Verzahnungsanregung KW - Getriebedynamik KW - Drehwegfehler Y1 - 2023 SN - 978-3-18-102429-4 U6 - https://doi.org/10.51202/9783181024294-57 SN - 0083-5560 SP - 57 EP - 70 PB - VDI Verlag CY - Düsseldorf ER - TY - JOUR A1 - Broll, Alexander A1 - Goldhacker, Markus A1 - Hahnel, Sebastian A1 - Rosentritt, Martin T1 - Generative deep learning approaches for the design of dental restorations: A narrative review JF - Journal of Dentistry N2 - Objectives: This study aims to explore and discuss recent advancements in tooth reconstruction utilizing deep learning (DL) techniques. A review on new DL methodologies in partial and full tooth reconstruction is conducted. Data/Sources: PubMed, Google Scholar, and IEEE Xplore databases were searched for articles from 2003 to 2023. Study selection: The review includes 9 articles published from 2018 to 2023. The selected articles showcase novel DL approaches for tooth reconstruction, while those concentrating solely on the application or review of DL methods are excluded. The review shows that data is acquired via intraoral scans or laboratory scans of dental plaster models. Common data representations are depth maps, point clouds, and voxelized point clouds. Reconstructions focus on single teeth, using data from adjacent teeth or the entire jaw. Some articles include antagonist teeth data and features like occlusal grooves and gap distance. Primary network architectures include Generative Adversarial Networks (GANs) and Transformers. Compared to conventional digital methods, DL-based tooth reconstruction reports error rates approximately two times lower. Conclusions: Generative DL models analyze dental datasets to reconstruct missing teeth by extracting insights into patterns and structures. Through specialized application, these models reconstruct morphologically and functionally sound dental structures, leveraging information from the existing teeth. The reported advancements facilitate the feasibility of DL-based dental crown reconstruction. Beyond GANs and Transformers with point clouds or voxels, recent studies indicate promising outcomes with diffusion-based architectures and innovative data representations like wavelets for 3D shape completion and inference problems. Clinical significance: Generative network architectures employed in the analysis and reconstruction of dental structures demonstrate notable proficiency. The enhanced accuracy and efficiency of DL-based frameworks hold the potential to enhance clinical outcomes and increase patient satisfaction. The reduced reconstruction times and diminished requirement for manual intervention may lead to cost savings and improved accessibility of dental services. KW - Tooth reconstruction KW - Dental prosthesis design KW - Deep Learning KW - Digital dentistry Y1 - 2024 U6 - https://doi.org/10.1016/j.jdent.2024.104988 SN - 0300-5712 VL - 145 PB - Elsevier ER - TY - JOUR A1 - Franke, Markus A1 - Wagner, Marcus T1 - Transient surrogate modeling of modally reduced structures with discontinuous loads and damping JF - Archive of Applied Mechanics N2 - In this work, a surrogate model for structural, transient and discontinuously excited finite element method simulations is developed. This allows to reduce the computational effort of repeated calculations of identical models under different load cases. The architecture of the surrogate combines fully connected neural network layers with long short-term memory layers. For the reproduction of different damping ratios, a categorical variable is added to the continuous input data. Based on a recursive flow of the predicted data back to the input layer, long-term dependencies do not vanish due to short-input sequences. The system dimension is reduced by applying the model-order reduction technique for modal decomposition. The high accuracy of the surrogate and the reduction of computational costs are shown on an academic example of a cantilever beam and a real-world example of a robot. The advantages of our approach are illustrated in comparison with state-of-the-art surrogates for transient finite element analysis. By using the surrogate proposed in this study, oscillations due to discontinuous excitation of mechanical structures can be reproduced. For this purpose, only short-input sequences are necessary since the excitation of the oscillations does not have to be part of the input sequence during the whole duration of the oscillations. Due to the categorical variable for the damping ratio, the surrogate can account for the influence of different damping in parameter studies. KW - Discontinuous loads KW - Modal decomposition KW - Surrogate modeling KW - Long short-term memory KW - Finite element method Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-72834 N1 - Corresponding author der OTH Regensburg: Markus Franke VL - 94 IS - 5 PB - Springer Nature ER - TY - JOUR A1 - Lehrer, Tobias A1 - Kaps, Arne A1 - Lepenies, Ingolf A1 - Raponi, Elena A1 - Wagner, Marcus A1 - Duddeck, Fabian T1 - Complementing Drawability Assessment of Deep-Drawn Components with Surrogate-Based Global Sensitivity Analysis JF - ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part B: Mechanical Engineering N2 - In the early-stage development of sheet metal parts, key design properties of new structures must be specified. As these decisions are made under significant uncertainty regarding drawing configuration changes, they sometimes result in the development of new parts that, at a later design stage, will not be drawable. As a result, there is a need to increase the certainty of experience-driven drawing configuration decisions. Complementing this process with a global sensitivity analysis can provide insight into the impact of various changes in drawing configurations on drawability, unveiling cost-effective strategies to ensure the drawability of new parts. However, when quantitative global sensitivity approaches, such as Sobol's method, are utilized, the computational requirements for obtaining Sobol indices can become prohibitive even for small application problems. To circumvent computational limitations, we evaluate the applicability of different surrogate models engaged in computing global design variable sensitivities for the drawability assessment of a deep-drawn component. Here, we show in an exemplary application problem, that both a standard kriging model and an ensemble model can provide commendable results at a fraction of the computational cost. Moreover, we compare our surrogate models to existing approaches in the field. Furthermore, we show that the error introduced by the surrogate models is of the same order of magnitude as that from the choice of drawability measure. In consequence, our surrogate models can improve the cost-effective development of a component in the early design phase. KW - sheet metal forming KW - deep drawing KW - global sensitivity analysis KW - variance-based sensitivity analysis KW - metamodeling Y1 - 2024 U6 - https://doi.org/10.1115/1.4065143 SN - 2332-9025 SP - 1 EP - 10 PB - ASME ER - TY - JOUR A1 - Schuderer, Matthias A1 - Rill, Georg A1 - Schaeffer, Thomas A1 - Schulz, Carsten T1 - Friction modeling from a practical point of view JF - Multibody System Dynamics N2 - AbstractRegularized static friction models have been used successfully for many years. However, they are unable to maintain static friction in detail. For this reason, dynamic friction models have been developed and published in the literature. However, commercial multibody simulation packages such as Adams, RecurDyn, and Simpack have developed their own specific stick-slip models instead of adopting one of the public domain approaches. This article introduces the fundamentals of these commercial models and their behavior from a practical point of view. The stick-slip models were applied to a simple test model and a more sophisticated model of a festoon cable system using their standard parameters. KW - Multibody dynamics KW - Friction KW - Stick-slip effect KW - Adams KW - RecurDyn KW - Simpack Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-72513 SN - 1384-5640 N1 - Corresponding author: Matthias Schuderer PB - Springernature ER - TY - JOUR A1 - Tauwald, Sandra Melina A1 - Erzinger, Florian A1 - Quadrio, Maurizio A1 - Rütten, Markus A1 - Stemmer, Christian A1 - Krenkel, Lars T1 - Tomo-PIV in a patient-specific model of human nasal cavities: a methodological approach JF - Measurement Science and Technology N2 - The human nose serves as the primary gateway for air entering the respiratory system and plays a vital role in breathing. Nasal breathing difficulties are a significant health concern, leading to substantial healthcare costs for patients. Understanding nasal airflow dynamics is crucial for comprehending respiratory mechanisms. This article presents a detailed study using tomo-Particle Image Velocimetry (PIV) to investigate nasal airflow dynamics while addressing its accuracy. Embedded in the OpenNose project, the work described aims to provide a validation basis for different numerical approaches to upper airway flow. The study includes the manufacturing of a transparent silicone model based on a clinical CT scan, refractive index matching to minimize optical distortions, and precise flow rate adjustments based on physiological breathing cycles. This method allows for spatial high-resolution investigations in different regions of interest within the nasopharynx during various phases of the breathing cycle. The results demonstrate the accuracy of the investigations, enabling detailed analysis of flow structures and gradients. This spatial high-resolution tomo-PIV approach provides valuable insights into the complex flow phenomena occurring during the physiological breathing cycle in the nasopharynx. The study's findings contribute to advancements in non-free-of-sight experimental flow investigation of complex cavities under nearly realistic conditions. Furthermore, reliable and accurate experimental data is crucial for properly validating numerical approaches that compute this patient-specific flow for clinical purposes. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-70393 N1 - Corresponding author: Sandra Melina Tauwald VL - 35 IS - 5 PB - IOP Publishing ER - TY - JOUR A1 - Pongratz, Christian A1 - Tix, Janek A1 - Wolfrum, Johannes A1 - Gerke, Steffen A1 - Ehrlich, Ingo A1 - Brünig, Michael T1 - Test Setup for Investigating the Impact Behavior of Biaxially Prestressed Composite Laminates JF - Experimental Techniques N2 - Instrumented impact testing and compression-after-impact testing are important to adequately qualify material behavior and safely design composite structures. However, the stresses to which fiber-reinforced plastic components are typically subjected in practice are not considered in the impact test methods recommended in guidelines or standards. In this paper, a test setup for investigating the impact behavior of composite specimens under plane uniaxial and biaxial preloading is presented. For this purpose, a special test setup consisting of a biaxial testing machine and a specially designed drop-weight tower was developed. The design decisions were derived from existing guidelines and standards with the aim of inducing barely visible impact damage in laminated carbon fiber-reinforced plastic specimens. Several measurement systems have been integrated into the setup to allow comprehensive observation of the impact event and specimen behavior. A feasibility test was performed with biaxially prestressed carbon fiber-reinforced plastic specimens in comparison with unstressed reference tests. The compressive-tensile prestressing resulted in lower maximum contact forces, higher maximum deflections, higher residual deflections and a different damage pattern, which was investigated by light microscopic analysis. Finally, the functionality of the experimental setup is discussed, and the results seem to indicate that the test setup and parameters were properly chosen to investigate the effect of prestresses on the impacts behavior of composite structures, in particular for barely visible subsequent damages. KW - Mechanical Engineering KW - Mechanics of Materials KW - Faserverbundwerkstoff KW - Schlagprüfung Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-70355 SN - 0732-8818 N1 - Corresponding authors: Christian Pongratz und Ingo Ehrlich PB - Springer Nature ER - TY - JOUR A1 - Walter, Stefanie A1 - Schwanzer, Peter A1 - Hagen, Gunter A1 - Rabl, Hans-Peter A1 - Dietrich, Markus A1 - Moos, Ralf T1 - Combined Ash and Soot Monitoring for Gasoline Particulate Filters Using a Radio-Frequency-Based Sensor JF - Emission Control Science and Technology N2 - Increasingly stringent emission limits have made particulate filters necessary for gasoline engines. Similar to diesel applications, gasoline particulate filters (GPFs) can be monitored by differential pressure measurement or by the radio-frequency-based filter diagnosis (RF sensor). In addition to measuring the soot loading, ash detection is critical for monitoring the GPF over the entire vehicle lifetime. Because the RF sensor detects the filter loading through a change in the dielectric properties of the GPF, it can detect not only soot but also ash. In diesel applications, the RF sensor has already demonstrated its potential for ash detection. To verify the feasibility of simultaneous ash and soot monitoring for GPFs, filters were loaded with ash on an engine test bench and measured on a lab test bench under defined synthetic exhaust gas conditions. By evaluating resonant modes, soot and ash could be clearly distinguished, as ash mainly affects the resonant frequency, while soot also changes the quality factor due to its high dielectric losses. However, higher soot loadings could not be detected by the resonant parameters, but instead by a frequency-averaged transmission signal. While the presence of ash caused an offset in this signal, its sensitivity to soot was not affected. Thus, the influence of ash can be corrected if the signal in the soot-free filter state is known, e.g., from the behavior of the resonant parameters. Therefore, even with a continuously increasing ash loading over the lifetime of a vehicle, an accurate soot detection is possible with the RF sensor. KW - Gasoline particulate flter KW - Radio-frequency KW - Soot mass determination KW - Ash detection Y1 - 2023 U6 - https://doi.org/10.1007/s40825-023-00235-y PB - Springer ER - TY - JOUR A1 - Schaeffer, Leon A1 - Herrmann, David A1 - Schratzenstaller, Thomas A1 - Dendorfer, Sebastian A1 - Böhm, Valter T1 - Preliminary theoretical considerations on the stiffness characteristics of a tensegrity joint for the use in dynamic orthoses JF - Journal of Medical Robotics Research N2 - Early motion therapy plays an important role for effective long-term healing of joint injuries. In many cases, conventional dynamic orthoses fail to address the intricate movement possibilities of the underlying joints, limited by their simplistic joint representations, often represented by revolute joints, enabling rotations by only one axis. In this paper, a two-dimensional compliant tensegrity joint for use in biomedical applications is investigated. It consists of two compressed members and five compliant tensioned members. Relative movement possibilities are realized by the intrinsic compliance of the structure. In the development of these systems, the first step is the determination of the static stable equilibrium. This analysis is conducted in this paper by considering the potential energy approach or by using the geometric nonlinear finite element method. The mechanical behavior of the structure is assessed with a specific emphasis on its mechanical compliance. The primary objective of this study is the investigation of the influence of structural parameters on the overall stiffness and movability of the structure. The results underscore the significant effect of member parameters on the stiffness and movability of the compliant tensegrity joint, particularly under varying load magnitudes. These findings provide insights for optimizing the joint’s performance, contributing to its potential application in advanced orthotic and exoskeleton devices. KW - mechanical compliance KW - flexibility ellipsis KW - form-finding KW - tensegrity joint Y1 - 2023 U6 - https://doi.org/10.1142/S2424905X23400081 PB - World Scientific ER - TY - JOUR A1 - Nonn, Aida A1 - Kiss, Bálint A1 - Pezeshkian, Weria A1 - Tancogne-Dejean, Thomas A1 - Cerrone, Albert R. A1 - Kellermayer, Miklos A1 - Bai, Yuanli A1 - Li, Wei A1 - Wierzbicki, Tomasz T1 - Inferring mechanical properties of the SARS-CoV-2 virus particle with nano-indentation tests and numerical simulations JF - Journal of the mechanical behavior of biomedical materials N2 - The pandemic caused by the SARS-CoV-2 virus has claimed more than 6.5 million lives worldwide. This global challenge has led to accelerated development of highly effective vaccines tied to their ability to elicit a sustained immune response. While numerous studies have focused primarily on the spike (S) protein, less is known about the interior of the virus. Here we propose a methodology that combines several experimental and simulation techniques to elucidate the internal structure and mechanical properties of the SARS-CoV-2 virus. The mechanical response of the virus was analyzed by nanoindentation tests using a novel flat indenter and evaluated in comparison to a conventional sharp tip indentation. The elastic properties of the viral membrane were estimated by analytical solutions, molecular dynamics (MD) simulations on a membrane patch and by a 3D Finite Element (FE)-beam model of the virion's spike protein and membrane molecular structure. The FE-based inverse engineering approach provided a reasonable reproduction of the mechanical response of the virus from the sharp tip indentation and was successfully verified against the flat tip indentation results. The elastic modulus of the viral membrane was estimated in the range of 7-20 MPa. MD simulations showed that the presence of proteins significantly reduces the fracture strength of the membrane patch. However, FE simulations revealed an overall high fracture strength of the virus, with a mechanical behavior similar to the highly ductile behavior of engineering metallic materials. The failure mechanics of the membrane during sharp tip indentation includes progressive damage combined with localized collapse of the membrane due to severe bending. Furthermore, the results support the hypothesis of a close association of the long membrane proteins (M) with membrane-bound hexagonally packed ribonucleoproteins (RNPs). Beyond improved understanding of coronavirus structure, the present findings offer a knowledge base for the development of novel prevention and treatment methods that are independent of the immune system. Y1 - 2023 U6 - https://doi.org/10.1016/j.jmbbm.2023.106153 SN - 1751-6161 VL - 148 PB - Elsevier ER - TY - JOUR A1 - Thumann, Philipp A1 - Buchner, Stefan A1 - Marburg, Steffen A1 - Wagner, Marcus T1 - A comparative study of Glinka and Neuber approaches for fatigue strength assessment on 42CrMoS4-QT specimens JF - Strain N2 - In fatigue strength assessment, the methods based on ideal elastic stresses according to Basquin and the less established method based on elastic-plastic stress quantities according to Manson, Coffin and Morrow are applied. The former calculates loads using linear-elastic stresses, the latter requires elasticplastic evaluation parameters, such as stresses and strains. These can be determined by finite element analysis (FEA) with a linear-elastic constitutive law, and subsequent conversion to elastic-plastic loads, using the macro support formula by Neuber. In this contribution, an alternative approach to approximate elastic-plastic parameters proposed by Glinka is compared to the the strain-life method using Neuber's formula, as well as the stress-life method of Basquin. Several component tests on 42CrMoS4-QT specimens are investigated. To determine the input data for the fatigue strength evaluations, the entire test setup is computed by FEA. The nodal displacements from these validated full-model simulations are used as boundary conditions for a submodel simulation of a notch, whose results serve as input for the fatigue strength assessments. It is shown that all approaches provide a reliable assessment of components. Our key result is that the strain-life method using the concept by Glinka for notch stress computation, yields improved results in fatigue strength assessments. KW - 42CrMoS4-QT KW - fatigue strength KW - stress-life method KW - Glinka KW - strain-life method Y1 - 2023 U6 - https://doi.org/10.1111/str.12470 SN - 1475-1305 N1 - Corresponding author: Marcus Wagner VL - 2023 IS - e12470 PB - Wiley ER - TY - JOUR A1 - Kloiber, Jessica A1 - Schultheiß, Ulrich A1 - Sotelo, Lamborghini A1 - Sarau, George A1 - Christiansen, Silke H. A1 - Gavras, Sarkis A1 - Hort, Norbert A1 - Hornberger, Helga T1 - Corrosion behaviour of electropolished magnesium materials JF - Materials Today Communications N2 - Although magnesium and its alloys are promising candidates as biodegradable implant materials, the tendency for localized corrosion mechanism in physiological environment limit their biomedical application. Electropolishing is an attractive strategy for improving the corrosion behaviour of metals, but it is still largely unexplored in magnesium materials. In this study, the characterization of electropolished surfaces of AM50 and pure magnesium was performed, focussing on their in vitro degradation behaviour in cell medium. Corrosion rates were evaluated using potentiodynamic polarisation. The surface morphology before and after the onset of corrosion was investigated by scanning electron microscopy and confocal laser scanning microscopy. The presented electropolishing process led to improved surface performances, observable by significantly lower corrosion rates (0.08 mm·year-1 in Dulbecco's modified Eagle's medium), lower arithmetical mean height (0.05 µm), lower water contact angle (25-35°) and lower micro hardness (35-50 HV 0.1) compared to mechanically and chemically treated surfaces. MgO/Mg(OH)2 could be detected on electropolished surfaces. The localized corrosion mode could be reduced, but not entirely prevented. Electropolishing shows great potential as post-treatment of magnesium-based components, but detailed tests of the long-term corrosion behaviour are an important area of future research. KW - biomedical application KW - corrosion behaviour KW - electropolishing KW - magnesium alloy KW - pure magnesium KW - surface characterization Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-68254 N1 - Corresponding author: Helga Hornberger PB - Elsevier ET - Journal Pre-proof ER - TY - JOUR A1 - Galka, Stefan A1 - Wappler, Mona T1 - Integration of cash flow management and further aspects of the supply chain management in production system design JF - IFAC-PapersOnLine N2 - One major goal of production system design is to decide on space requirements in the plant. In this phase, detailed information about the supply chain network (e.g. which suppliers deliver which parts) is often unavailable. Nevertheless, typical decisions in supply chain management, like the definition of replenishment processes and quantities or make-or-buy decisions, impact space requirements and the capital investment in raw materials. Therefore, it should be considered in factory and production planning. This research article proposes a simulation approach for a production simulation in which raw material replenishment is integrated to evaluate the capital investment and space requirements for raw materials. Y1 - 2023 U6 - https://doi.org/10.1016/j.ifacol.2023.10.1687 VL - 56 IS - 2 SP - 947 EP - 952 PB - IFAC / Elsevier ER - TY - JOUR A1 - Grad, Marius A1 - Honig, Lars-Hauke A1 - Diemar, Andreas A1 - Flock, Dominik A1 - Spieß, Lothar T1 - Complex material analysis of a TiC coating produced by hot pressing with optical light microscopy, EDS, XRD, GDOES and EBSD JF - Surface & Coatings Technology N2 - The present study investigates the interface between carbon steel and titanium samples annealed at different temperatures (𝜗1 = 800 ◦C and 𝜗2 = 1050 ◦C). In both cases, an observable layer forms at the interface, with its thickness increasing from t𝜗1= 2.75 ± 0.15 μm at 800 ◦C to t𝜗2= 8.86 ± 0.29 μm at 1050 ◦C. The layer’s composition and thickness evolve with temperature. Analysis reveals approximately 40 at.-% carbon concentration in the exterior region, indicating likely titanium carbide creation. X-ray diffraction identifies titanium carbide peaks, while microscopy and elemental mapping confirm compositional gradients at the interface. Electron Backscatter Diffraction (EBSD) shows a gradient in grain size near the TiC surface, reflecting TiC nucleation rates. XRD data detect both titanium carbide and titanium phases, with TiC becoming more prominent at 1050 ◦C. Rietveld analysis further confirms TiC formation. Notably, distinct diffraction patterns on the contact and rear sides suggest a Ti(C, O, N) presence. Depth profiles exhibit varying surface and depth carbon concentrations, attributed to temperature effects. The study successfully demonstrates TiC coating fabrication through hot pressing, wherein Ti(C, O, N) coatings arise from titanium’s affinity for reacting with oxygen and nitrogen. This research contributes to the understanding of phase transformations and interfacial properties in titanium-carbon steel systems. Y1 - 2024 U6 - https://doi.org/10.1016/j.surfcoat.2023.130265 VL - 476 PB - Elsevier ER - TY - JOUR A1 - Noster, Ulf A1 - Scholtes, Berthold T1 - Isothermal strain-controlled quasi-static and cyclic deformation behavior of magnesium wrought alloy AZ31 JF - International Journal of Materials Research / Zeitschrift für Metallkunde N2 - The low-cycle and high-cycle fatigue behavior of the Mg-base wrought alloy AZ31 is investigated in the temperature range 20– 300 °C using total-strain-controlled push – pull tests. It is shown that the mechanical properties of the material are substantially influenced by the direction dependent formation of deformation twins and resulting deformation asymmetry. As a consequence tensile mean stresses develop during total-strain-controlled fatigue tests without mean strain. Y1 - 2003 U6 - https://doi.org/10.1515/ijmr-2003-0098 VL - 94 IS - 5 SP - 559 EP - 563 ER - TY - JOUR A1 - Kastenmeier, Andreas A1 - Siegl, Marco A1 - Ehrlich, Ingo A1 - Gebbeken, Norbert T1 - Review of elasto-static models for three-dimensional analysis of thick-walled anisotropic tubes JF - Journal of Composite Materials N2 - Most shell or beam models of anisotropic tubes under bending have no validity for thick-walled structures. As a result, the need to develop three-dimensional formulations which allow a change in the stress, strain and displacement distributions across the radial component arises. Basic formulations on three-dimensional anisotropic elasticity were made either stressor displacement-based by Lekhnitskii or Stroh on plates. Lekhnitskii also was the first to expand these analytical formulations to tubes under various loading conditions. This paper presents a review of the stress and strain analysis of tube models using three-dimensional anisotropic elasticity. The focus lies on layered structures, like fiber-reinforced plastics, under various bending loads, although the basic formulations and models regarding axisymmetric loads are briefly discussed. One section is also dedicated to the determination of an equivalent bending stiffness of tubes. KW - composite tube bending KW - layered structrues KW - anisotropy KW - Analytical modelling KW - elasticity Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67521 N1 - Corresponding author: Andreas Kastenmeier PB - Sage ER - TY - JOUR A1 - Morag, Sarah A1 - Kieninger, Martin A1 - Eissnert, Christoph A1 - Auer, Simon A1 - Dendorfer, Sebastian A1 - Popp, Daniel A1 - Hoffmann, Johannes A1 - Kieninger, Bärbel T1 - Comparison of different techniques for prehospital cervical spine immobilization: Biomechanical measurements with a wireless motion capture system JF - PLOS ONE Y1 - 2023 U6 - https://doi.org/10.1371/journal.pone.0292300 VL - 18 IS - 11 SP - 1 EP - 14 PB - PLOS CY - San Francisco, California ER - TY - JOUR A1 - Bartsch, Alexander A1 - Beham, Daniela A1 - Gebhardt, Jakob A1 - Ehrlich, Ingo A1 - Schratzenstaller, Thomas A1 - Monkman, Gareth J. T1 - Mechanical Properties of NdPrFeB Based Magnetoactive Bisphenol-Free Boron-Silicate Polymers JF - Journal of Nanomedicine and Nanotechnology N2 - Following a ban on many materials containing bisphenol-A, new bisphenol-free Boron silicates have been found as substitutes. The purpose of this study is to describe the mechanical properties of these bisphenol-free magnetoactive borosilicate polymers containing hard magnetic particles. Samples of 0%, 33% and 66% by wt. were loaded for compression using a universal testing machine. The maximum forces occurring for different travel speeds were compared before and after post-magnetization treatments. The post-magnetization included 2 stages. In addition, the change in mechanical properties within 24 hours after the post-magnetization process was investigated. Furthermore, the influence of speed and particle content were investigated. In general, there is a correlation between the required compressive force and, the level of post-magnetization stress, the increase in travel speed and particle content in the boron silicate. Comparison of the non-post-magnetized and post-magnetized samples using two-tailed t-tests shows that the p-values for all weight fraction changes in NdPrFeB particles and travel speeds are less than 0.001. Also, a comparison between tests in which the traverse speed was varied also showed significant changes in the resulting compression forces. The same is valid for changes in the weight ratio of the NdPrFeB particles in the samples. For post-magnetized samples, no significant difference can be observed in the first 24 hours following magnetization. In summary, the material presents viscoelastic, plastic force-displacement behavior, which can be well recognized by its bi-linear curve shape. The investigation shows that borosilicate polymers based on NdPrFeB can have their mechanical behavior modified and controlled by post-magnetization processes. This opens new possibilities for many future applications. Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67425 UR - https://www.walshmedicalmedia.com/open-access/mechanical-properties-of-ndprfeb-based-magnetoactive-bisphenolfree-boronsilicate-polymers-124385.html SN - 2157-7439 N1 - Corresponding author: Alexander Bartsch VL - 14 IS - 6 PB - Walsh Medical Media ER - TY - JOUR A1 - Lingel, Maximilian P. A1 - Haus, Moritz A1 - Paschke, Lukas A1 - Foltan, Maik A1 - Lubnow, Matthias A1 - Gruber, Michael A1 - Krenkel, Lars A1 - Lehle, Karla T1 - Clinical relevance of cell-free DNA during venovenous extracorporeal membrane oxygenation JF - Artificial organs N2 - BACKGROUND: Thrombosis remains a critical complication during venovenous extracorporeal membrane oxygenation (VV ECMO). The involvement of neutrophil extracellular traps (NETs) in thrombogenesis has to be discussed. The aim was to verify NETs in the form of cell-free DNA (cfDNA) in the plasma of patients during ECMO. METHODS: A fluorescent DNA-binding dye (QuantifFluor®, Promega) was used to detect cell-free DNA in plasma samples. cfDNA concentrations from volunteers (n = 21) and patients (n = 9) were compared and correlated with clinical/technical data before/during support, ECMO end and time of a system exchange. RESULTS: Before ECMO, patients with a median (IQR) age of 59 (51/63) years, SOFA score of 11 (10/15), and ECMO run time of 9.0 (7.0/19.5) days presented significantly higher levels of cfDNA compared to volunteers (6.4 (5.8/7.9) ng/μL vs. 5.9 (5.4/6.3) ng/μL; p = 0.044). Within 2 days after ECMO start, cfDNA, inflammatory, and hemolysis parameters remained unchanged, while platelets decreased (p = 0.005). After ECMO removal at the end of therapy, cfDNA, inflammation, and coagulation data (except antithrombin III) remained unchanged. The renewal of a system resulted in known alterations in fibrinogen, d-dimers, and platelets, while cfDNA remained unchanged. CONCLUSION: Detection of cfDNA in plasma of ECMO patients was not an indicator of acute and circuit-induced thrombogenesis. KW - blood KW - cell- free DNA KW - coagulation KW - ECMO KW - inflammation KW - neutrophil extracellular traps Y1 - 2023 U6 - https://doi.org/10.1111/aor.14616 SN - 1525-1594 VL - 47 IS - 11 SP - 1720 EP - 1731 PB - Wiley ER - TY - JOUR A1 - Dendorfer, Sebastian A1 - Gschoßman, Lukas T1 - Hightech in der Rehabiliation JF - BVOU Infobrief: Hightech in Orthopädie und Unfallchirurgie N2 - Aufgrund der steigenden Lebenserwartung und dem damit einhergehenden demographischen Wandel wird der Bedarf an Rehabilitations-Behandlungen in absehbarer Zukunft stark ansteigen. Ein Beispiel für diesen Trend ist die physiotherapeutische Behandlung nach Erhalt einer Knie-Totalendoprothese (Knie-TEP). So gehen Modellrechnungen basierend auf dem Bevölkerungswachstum und der bisherigen Prävalenz von Knie-TEPs davon aus, dass die Anzahl an durchgeführten Eingriffen in einkommensstarken Ländern wie Deutschland weiter zunehmen wird. Weiterhin stoßen traditionelle Rehabilitationsverfahren, gerade in strukturschwachen Regionen, schon heute an ihre Grenzen. Deutlich zu sehen war das während den Hochphasen der aktuellen Covid-19-Pandemie, als der Kontakt zwischen Therapeut*in und Patient*in flächendeckend eingeschränkt war. Eine erhöhte Nachfrage nach neuartigen Reha-Angeboten ist die logische Konsequenz. Innovative Konzepte sind daher dringend notwendig, um die daraus resultierenden technischen, sozialen und ökonomischen Herausforderungen zu bewältigen. Y1 - 2023 UR - https://www.bvou.net/infobrief-1-23/ SN - 2747-5913 IS - 1 SP - 9 EP - 11 PB - BVOU – Berufsverband für Orthopädie und Unfallchirurgie e.V. CY - Berlin ER - TY - JOUR A1 - Tauwald, Sandra Melina A1 - Michel, Johanna A1 - Brandt, Marie A1 - Vielsmeier, Veronika A1 - Stemmer, Christian A1 - Krenkel, Lars T1 - Experimental studies and mathematical modeling of the viscoelastic rheology of tracheobronchial mucus from respiratory healthy patients JF - Multidisciplinary Respiratory Medicine N2 - BACKGROUND: Tracheobronchial mucus plays a crucial role in pulmonary function by providing protection against inhaled pathogens. Due to its composition of water, mucins, and other biomolecules, it has a complex viscoelastic rheological behavior. This interplay of both viscous and elastic properties has not been fully described yet. In this study, we characterize the rheology of human mucus using oscillatory and transient tests. Based on the transient tests, we describe the material behavior of mucus under stress and strain loading by mathematical models. METHODS: Mucus samples were collected from clinically used endotracheal tubes. For rheological characterization, oscillatory amplitude-sweep and frequency-sweep tests, and transient creep-recovery and stress-relaxation tests were performed. The results of the transient test were approximated using the Burgers model, the Weibull distribution, and the six-element Maxwell model. The three-dimensional microstructure of the tracheobronchial mucus was visualized using scanning electron microscope imaging. RESULTS: Amplitude-sweep tests showed storage moduli ranging from 0.1 Pa to 10000 Pa and a median critical strain of 4 %. In frequency-sweep tests, storage and loss moduli increased with frequency, with the median of the storage modulus ranging from 10 Pa to 30 Pa, and the median of the loss modulus from 5 Pa to 14 Pa. The Burgers model approximates the viscoelastic behavior of tracheobronchial mucus during a constant load of stress appropriately (R2 of 0.99), and the Weibull distribution is suitable to predict the recovery of the sample after the removal of this stress (R2 of 0.99). The approximation of the stress-relaxation test data by a six-element Maxwell model shows a larger fit error (R2 of 0.91). CONCLUSIONS: This study provides a detailed description of all process steps of characterizing the rheology of tracheobronchial mucus, including sample collection, microstructure visualization, and rheological investigation. Based on this characterization, we provide mathematical models of the rheological behavior of tracheobronchial mucus. These can now be used to simulate mucus flow in the respiratory system through numerical approaches. KW - tracheobronchial mucus KW - rheological model KW - viscoelasticity Y1 - 2023 U6 - https://doi.org/10.4081/mrm.2023.923 SN - 2049-6958 N1 - Corresponding author: Sandra Melina Tauwald VL - 18 IS - 1 PB - PAGEPress CY - Pavia, Italy ER - TY - JOUR A1 - Rill, Georg A1 - Schaeffer, Thomas A1 - Schuderer, Matthias T1 - LuGre or not LuGre JF - Multibody System Dynamics N2 - The LuGre model is widely used in the analysis and control of systems with friction. Recently, it has even been made available in the commercial multibody dynamics simulation software system Adams. However, the LuGre model exhibits well-known drawbacks like too low and force rate-dependent break-away forces, drift problems during sticking periods, and significant differences in non-stationary situations between the pre-defined friction law and the one produced by the LuGre model. In the present literature, these problems are supposed to come from the model dynamics or its nonlinear nature. However, most of these drawbacks are not simple side effects of a dynamic friction model but are caused in the LuGre approach, as shown here, by a too simple and inconsistent model of the bristle dynamics. Standard examples and a more practical application demonstrate that the LuGre model is not a “what you see is what you get” approach. A dynamic friction model with accurate bristle dynamics and consistent friction force is set up here. It provides insight into the physical basis of the LuGre model dynamics. However, it results in a nonlinear and implicit differential equation, whose solution will not be easy because of the ambiguity of the friction characteristics. The standard workaround, a static model based on simple regularized characteristics, produces reliable and generally satisfactory results but definitely cannot maintain a stick. The paper presents a second-order dynamic friction model, which may serve as an alternative. It can maintain a stick and produces realistic and reliable results. KW - Dynamic friction model KW - LuGre model KW - Asymmetric regularization KW - Break-away force KW - Stick-slip KW - Multibody dynamics Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-65653 N1 - Corresponding author: Georg Rill PB - Springer ER - TY - JOUR A1 - Bartsch, Alexander A1 - Burger, Moritz A1 - Grad, Marius A1 - Esper, Lukas A1 - Schultheiß, Ulrich A1 - Noster, Ulf A1 - Schratzenstaller, Thomas T1 - Enhancement of laser cut edge quality of ultra-thin titanium grade 2 sheets by applying an in-process approach using modulated Yb:YAG continuous wave fiber laser JF - Discover Mechanical Engineering N2 - Titanium is used in many areas due to its excellent mechanical, biological and corrosion-resistant properties. Implants often have thin and filigree structures, providing an ideal application for fine cutting with laser. In the literature, the main focus is primarily on investigating and optimizing the parameters for titanium sheets with thicknesses greater than 1 mm. Hence, in this study, the basic manufacturing parameters of laser power, cutting speed and laser pulse of a 200 W modulated fiber laser are investigated for 0.15 mm thick grade 2 titanium sheets. A reproducible, continuous cut could be achieved using 90 W laser-power and 2 mm/s cutting-speed. Pulse pause variations between 85 and 335 μs in 50 μs steps and a fixed pulse width of 50 μs show that a minimum kerf width of 23.4 μm, as well as a minimum cut edge roughness Rz of 3.59 μm, is achieved at the lowest pulse pause duration. An increase in roughness towards the laser exit side, independent of the laser pulse pause duration, was found and discussed. The results provide initial process parameters for cutting thin titanium sheets and thus provide the basis for further investigations, such as the influence of cutting gas pressure and composition on the cut edge. KW - Laser cutting KW - Titanium sheet KW - Kerf Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-65647 N1 - Corresponding author: Alexander Bartsch IS - 10 PB - Springer ER - TY - JOUR A1 - Rill, Georg A1 - Schuderer, Matthias T1 - A Second-Order Dynamic Friction Model Compared to Commercial Stick–Slip Models JF - Modelling N2 - Friction has long been an important issue in multibody dynamics. Static friction models apply appropriate regularization techniques to convert the stick inequality and the non-smooth stick–slip transition of Coulomb’s approach into a continuous and smooth function of the sliding velocity. However, a regularized friction force is not able to maintain long-term stick. That is why dynamic friction models were developed in recent decades. The friction force depends herein not only on the sliding velocity but also on internal states. The probably best-known representative, the LuGre friction model, is based on a fictitious bristle but realizes a too-simple approximation. The recently published second-order dynamic friction model describes the dynamics of a fictitious bristle more accurately. It is based on a regularized friction force characteristic, which is continuous and smooth but can maintain long-term stick due to an appropriate shift in the regularization. Its performance is compared here to stick–slip friction models, developed and launched not long ago by commercial multibody software packages. The results obtained by a virtual friction test-bench and by a more practical festoon cable system are very promising. Thus, the second-order dynamic friction model may serve not only as an alternative to the LuGre model but also to commercial stick–slip models. KW - commercial stick–slip friction models KW - dynamic friction model KW - long-term stick KW - multibody dynamics Y1 - 2023 U6 - https://doi.org/10.3390/modelling4030021 SN - 2673-3951 N1 - Corresponding author: Georg Rill VL - 4 IS - 3 SP - 366 EP - 381 PB - MDPI ER - TY - JOUR A1 - Walter, Stefanie A1 - Schwanzer, Peter A1 - Hagen, Gunter A1 - Rabl, Hans-Peter A1 - Dietrich, Markus A1 - Moos, Ralf T1 - Soot Monitoring of Gasoline Particulate Filters Using a Radio-Frequency-Based Sensor JF - Sensors N2 - Owing to increasingly stringent emission limits, particulate filters have become mandatory for gasoline-engine vehicles. Monitoring their soot loading is necessary for error-free operation. The state-of-the-art differential pressure sensors suffer from inaccuracies due to small amounts of stored soot combined with exhaust gas conditions that lead to partial regeneration. As an alternative approach, radio-frequency-based (RF) sensors can accurately measure the soot loading, even under these conditions, by detecting soot through its dielectric properties. However, they face a different challenge as their sensitivity may depend on the engine operation conditions during soot formation. In this article, this influence is evaluated in more detail. Various soot samples were generated on an engine test bench. Their dielectric properties were measured using the microwave cavity perturbation (MCP) method and compared with the corresponding sensitivity of the RF sensor determined on a lab test bench. Both showed similar behavior. The values for the soot samples themselves, however, differed significantly from each other. A way to correct for this cross-sensitivity was found in the influence of exhaust gas humidity on the RF sensor, which can be correlated with the engine load. By evaluating this influence during significant humidity changes, such as fuel cuts, it could be used to correct the influence of the engineon the RF sensor. KW - dielectric properties KW - engine test bench KW - gasoline particulate filter (GPF) KW - microwave cavity perturbation KW - radio-frequency (RF) KW - soot mass determination Y1 - 2023 U6 - https://doi.org/10.3390/s23187861 SN - 1424-8220 N1 - This research work was funded by the Bavarian Research Foundation (Bayerische Forschungsstiftung, BFS) as part of the project “Load Sensor for GPF” (AZ-1288-17). VL - 23 IS - 18 SP - 1 EP - 19 PB - MDPI ER - TY - JOUR A1 - Gamisch, Bernd A1 - Ettengruber, Stefan A1 - Gaderer, Matthias A1 - Dawoud, Belal T1 - Dynamic simulation of isothermal and non-isothermal reduction and oxidation reactions of iron oxide for a hydrogen storage process JF - Renewable and Sustainable Energy N2 - This work aims first to develop a dynamic lumped model for the isothermal reactions of hydrogen/steam with a single iron oxide/iron pellet inside a tubular reactor and to validate the model results against the experimental reaction kinetic data with the help of our STA device. To describe the temporal change in mass, and consequently, the temporal heat of reaction, the shrinking core model, based on the geometrical contracting sphere, is applied. It turned out that, the simulation model can reproduce the experimental, temporal concentration and temperature-dependent conversion rates with a maximum deviation of 4.6% during the oxidation reactions and 3.1% during the reduction reactions. In addition, a measured isothermal storage process comprising one reduction and one oxidation phase with a holding phase in between on a single reacting pellet could be reproduced with a maximum absolute deviation in the conversion rate of 1.5%. Moreover, a lumped, non-isothermal simulation model for a pelletized tubular redox-reactor including 2kg of iron oxide pellets has been established, in which the heat of reaction, heat transfer to the ambient and heat transfer between the solid and gas phases are considered. The temporal courses of the outlet gas concentration as well as the temperatures of the gas stream and the solid material at a constant input gas flow rate and a constant reacting gas inlet concentration but different input gas temperatures are estimated. Because of the endothermic nature of the reduction reaction, the inlet reacting gas temperature shall be kept high to prevent the severe temperature drop in the solid phase and, consequently, the significant reduction of the reaction rate. Contrary to that, the oxidation process requires lower input gas temperatures to avoid the excessive overheating of the reaction mass and, consequently, the sintering of the reacting pellets. Finally, five of the previous reactors have been connected in series to explore the influence of the changing inlet gas temperatures and concentrations on the dynamic performance of each storage mass. KW - hydrogen storage KW - iron/iron oxide KW - redox reactions KW - lumped model KW - isothermal reactions KW - non-isothermal reactions KW - kinetics of reactions KW - Aspen Custom Modeler Y1 - 2023 U6 - https://doi.org/10.55092/rse20230004 N1 - Corresponding author: Belal Dawoud VL - 1 IS - 1 PB - ELSP, International Open Science Platform ER - TY - JOUR A1 - Auer, Simon A1 - Kubowitsch, Simone A1 - Dendorfer, Sebastian T1 - Kombinierter Einfluss von psychologischen und biomechanischen Faktoren auf die muskulären Belastungen beim Fußballspielen JF - Die Orthopädie N2 - When mental stress and musculoskeletal loading interact, the risk for injury increases due to altered body kinematics and increased muscle tension. These changes can be detected with musculoskeletal models, and mental loading and stress must be analyzed at emotional, cognitive, and behavioral levels. To investigate these kinematic and loading changes under stress, competitive athletes were subjected to mental stress during highly dynamic movements, and musculoskeletal models were used to analyze the biomechanical loading. It was shown that under mental stress, independent of the subjective perception, a strong change in muscle forces can occur. Accordingly, competitive athletes should undergo screenings to assess individual movement patterns and promote general stress resilience. N2 - Für Fußballer:innen stellen muskuläre Verletzungen der unteren Extremitäten ein großes Problem dar. Ein Beispiel hierfür liefert die Nationalmannschaftsstürmerin Alexandra Popp, die aufgrund muskulärer Probleme das EM-Finale 2022 in Wembley kurzfristig verpasste. Oftmals stehen gerade hohe Anspannungssituationen in zeitlichem Zusammenhang mit Verletzungen, der Einfluss der psychischen Beanspruchung auf die biomechanischen Belastungen wird jedoch meist nur wenig beachtet. KW - Biologische Modelle KW - Biomechanik KW - Leistungssportler KW - Bewegung KW - Resilienz, psychologische KW - Biological models KW - Biomechanics KW - Elite athletes KW - Movement KW - Resilience, psychological Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-65113 N1 - Corresponding author: Sebastian Dendorfer VL - 52 IS - 11 SP - 1 EP - 6 PB - Springer ER - TY - JOUR A1 - Förstl, Nikolas A1 - Süß, Franz A1 - Englert, Carsten A1 - Dendorfer, Sebastian T1 - Design of a reverse shoulder implant to measure shoulder stiffness during implant component positioning JF - Medical Engineering & Physics N2 - To avoid dislocation of the shoulder joint after reverse total shoulder arthroplasty, it is important to achieve sufficient shoulder stability when placing the implant components during surgery. One parameter for assessing shoulder stability can be shoulder stiffness. The aim of this research was to develop a temporary reverse shoulder implant prototype that would allow intraoperative measurement of shoulder stiffness while varying the position of the implant components. Joint angle and torque measurement techniques were developed to determine shoulder stiffness. Hall sensors were used to measure the joint angles by converting the magnetic flux densities into angles. The accuracy of the joint angle measurements was tested using a test bench. Torques were determined by using thin-film pressure sensors. Various mechanical mechanisms for variable positioning of the implant components were integrated into the prototype. The results of the joint angle measurements showed measurement errors of less than 5° in a deflection range of ±15° adduction/abduction combined with ±45° flexion/extension. The proposed design provides a first approach for intra-operative assessment of shoulder stiffness. The findings can be used as a technological basis for further developments. Y1 - 2023 U6 - https://doi.org/10.1016/j.medengphy.2023.104059 N1 - Corresponding author: Sebstian Dendorfer VL - 121 PB - Elsevier ET - Journal Pre-proof ER - TY - JOUR A1 - Salama, Amgad A1 - Kou, Jisheng A1 - Dawoud, Belal A1 - Simonson, Carey T1 - A modeling approach for capillary-driven flow of a wetting fluid in a rectangular open microchannel of arbitrary axisymmetric width profile BT - Application to heat pipes JF - International Journal of Thermal Sciences N2 - Microchips are intensively used in almost all nowadays electronic devices. With the continuous advancement of our technologies, they get smaller in size than ever before. They generate high-intensity heat loads that need to be transported effectively such that they may function properly. Heat pipes have proven to be very effective in transporting relatively large heat loads from miniature components. They are of seamless structure that involves a working fluid capable of evaporation and condensation at the working temperature of the electronic chips. The working fluid is derived to move from the condenser to the evaporator via multiple microgrooves using capillary forces. It is important that the condensate reaches the evaporator at a proper rate such that no dry-out or flooding occur. In this work, we are particularly interested in the case of capillary-driven flows in rectangular microchannels. A generalized model is developed that works for axe-symmetric rectangular channels of arbitrary, moderately varying width profiles. It also accounts for any contrast of viscosity between the liquid and the vapor under isothermal conditions. The model shows to reduce to the special case of imbibition in straight and uniform microchannels, for which comparisons with experimental and modeling works show an excellent match. Cases representing linearly and quadratically varying converging/diverging width profiles have been explored. It is found that the viscosity ratio has a significant influence on the rate at which the meniscus advances. The model also negates the common practice found in the literature of using the formula developed for imbibition rates in capillary tubes for rectangular microchannels by replacing the diameter of the tube with the hydraulic diameter. It is also found that the channel profile has an influential effect on the imbibition rates. For tapered microchannels, the capillary force increases along the channel length while it decreases for diverging ones. It is interestingly demonstrated that, for quadratically tapered microchannel, the speed of the meniscus increases towards the end of the microchannel compared with linearly varying microchannels. On the other hand, for diverging microchannels, the speed of the meniscus decreases due to the increase in the cross-sectional area. Computational fluid dynamics (CFD) analysis has been conducted to provide a framework for confirmation and verification for which very good match has been established, which builds confidence in the modeling approach. KW - Microfluidics KW - Miniature devices KW - Capillary-driven flows KW - Microchannels KW - Heat pipes Y1 - 2024 U6 - https://doi.org/10.1016/j.ijthermalsci.2023.108622 SN - 1290-0729 VL - 195 PB - Elsevier ER - TY - JOUR A1 - Lehrer, Tobias A1 - Kaps, Arne A1 - Lepenies, Ingolf A1 - Duddeck, Fabian A1 - Wagner, Marcus T1 - 2S-ML: A simulation-based classification and regression approach for drawability assessment in deep drawing JF - International Journal of Material Forming N2 - New structural sheet metal parts are developed in an iterative, time-consuming manner. To improve the reproducibility and speed up the iterative drawability assessment, we propose a novel low-dimensional multi-fidelity inspired machine learning architecture. The approach utilizes the results of low-fidelity and high-fidelity finite element deep drawing simulation schemes. It hereby relies not only on parameters, but also on additional features to improve the generalization ability and applicability of the drawability assessment compared to classical approaches. Using the machine learning approach on a generated data set for a wide range of different cross-die drawing configurations, a classifier is trained to distinguish between drawable and non-drawable setups. Furthermore, two regression models, one for drawable and one for non-drawable designs are developed that rank designs by drawability. At instantaneous evaluation time, classification scores of high accuracy as well as regression scores of high quality for both regressors are achieved. The presented models can substitute low-fidelity finite element models due to their low evaluation times while at the same time, their predictive quality is close to high-fidelity models. This approach may enable fast and efficient assessments of designs in early development phases at the accuracy of a later design phase in the future. KW - One-step KW - Deep drawing KW - Drawability KW - Meta-modeling KW - Machine learning Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-64664 N1 - Corresponding author: Tobias Lehrer VL - 16 SP - 1 EP - 17 PB - Springer ER - TY - JOUR A1 - Kuettner, Andreas A1 - Raths, Max A1 - Fischer, Samuel A1 - Laumer, Tobias T1 - Heat staking of polymer parts generated by fused layer modeling JF - The International Journal of Advanced Manufacturing Technology N2 - Heat staking is a joining technology by which thermoplastic pins are formed by force and temperature to create a form- and force-fitting connection between components. This paper examines the characteristics of 3D printed pins in comparison to conventionally turned pins for heat staking applications. The 3D printed pins are created using fused layer modeling, with variations in horizontal and vertical building directions, as well as different layer thicknesses. The study investigates the impact of significant factors on the heat staking process, including the forming force and temperature. Tensile tests, micrographs, and micro-CT measurements were conducted to determine the properties of the heat-staked joints. Additionally, a stage plan was developed to enhance the understanding of the forming process of both printed and conventionally turned materials. The findings suggest that, under specific process parameters, 3D printed pins exhibit comparable strength to conventionally manufactured pins. The research also demonstrates that the anisotropy resulting from the layer-by-layer construction of the pins significantly influences the strength of the connection. Furthermore, the study reveals that 3D printed pins exhibit good forming accuracy during the heat staking process, and the cavities formed during printing can be substantially reduced. KW - Heat staking KW - Additive manufacturing KW - 3D printing KW - Material qualification KW - Polycarbonate (PC) KW - Fused layer modeling (FLM) Y1 - 2023 U6 - https://doi.org/10.1007/s00170-023-11850-y VL - 128 SP - 547 EP - 562 PB - Springer Nature ER - TY - JOUR A1 - Keiner, Dominik A1 - Thoma, Christian A1 - Bogdanov, Dmitrii A1 - Breyer, Christian T1 - Seasonal hydrogen storage for residential on- and off-grid solar photovoltaics prosumer applications: Revolutionary solution or niche market for the energy transition until 2050? JF - Applied Energy N2 - Appropriate climate change mitigation requires solutions for all actors of the energy system. The residential sector is a major part of the energy system and solutions for the implementation of a seasonal hydrogen storage system in residential houses has been increasingly discussed. A global analysis of prosumer systems including seasonal hydrogen storage with water electrolyser, hydrogen compressor, storage tank, and a fuel cell studying the role of such a seasonal household storage in the upcoming decades is not available. This study aims to close this research gap via the improved LUT-PROSUME model, which models a fully micro sector coupled residential photovoltaic prosumer system with linear optimisation for 145 regions globally. The modelling of the cost development of hydrogen storage components allows for the simulation of a residential system from 2020 until 2050 in 5-year steps in hourly resolution. The systems are cost-optimised for either on- or off-grid operation in eight scenarios including battery electric vehicles, which can act as an additional vehicle-to-home electricity storage for the system. Results show that implementation of seasonal hydrogen systems only occurs in least cost solutions in high latitude countries when the system is forced to run in off-grid mode. In general, a solar photovoltaic plus battery system including technologies that can cover the heat demand is the most economic choice and can even achieve lower cost than a full grid supply in off-grid operation for most regions until 2050. Additional parameters including the self-consumption ratio, the demand cover ratio, and the heat cover ratio can therefore not be improved by seasonal storage systems if economics is the main deciding factor for a respective system. Further research opportunities and possible limitations of the system are then identified. KW - Battery KW - Electrolyser KW - Fuel Cell KW - Hydrogen KW - ProsumerIridium KW - Residential seasonal storage KW - Rooftop solar photovoltaics Y1 - 2023 U6 - https://doi.org/10.1016/j.apenergy.2023.121009 VL - 340 PB - Elsevier ER - TY - JOUR A1 - Bitsche, Robert A1 - Noster, Ulf A1 - Peterlechner, Christian T1 - Fügepartner schlüssig zu Leichtbaukomponenten verbinden? JF - Lightweight Design N2 - Kombinationen aus kraft- und formschlüssigen Verbindungen erhöhen die Leistung bei im Hybridguss verbundenen Gussteilen mit Anbau- oder Einlegeteilen und machen separate Fügeprozesse überflüssig. Simulations-Methoden unterstützen das Design kraft- und formschlüssiger Verbindungen. Ergebnisse eines Ausdrückversuchs zeigen eine relativ gute Übereinstimmung zwischen gemessenen und mittels Simulation ermittelten Kraft-Weg-Kurven. Y1 - 2008 U6 - https://doi.org/10.1007/BF03223528 VL - 1 IS - 2 SP - 30 EP - 34 PB - Springer ER - TY - JOUR A1 - Nalla, Ravi K. A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Liu, G.Y. A1 - Scholtes, Berthold A1 - Ritchie, Robert O. T1 - On the influence of mechanical surface treatments—deep rolling and laser shock peening—on the fatigue behavior of Ti–6Al–4V at ambient and elevated temperatures JF - Materials Science and Engineering: A N2 - It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Deep rolling (DR) is particularly attractive since it is possible to generate, near the surface, deep compressive residual stresses and work hardened layers while retaining a relatively smooth surface finish. In the present investigation, the effect of DR on the low-cycle fatigue (LCF) and high-cycle fatigue (HCF) behavior of a Ti–6Al–4V alloy is examined, with particular emphasis on the thermal and mechanical stability of the residual stress states and the near-surface microstructures. Preliminary results on laser shock peened Ti–6Al–4V are also presented for comparison. Particular emphasis is devoted to the question of whether such surface treatments are effective for improving the fatigue properties at elevated temperatures up to ∼450 °C, i.e. at a homologous temperature of ∼0.4T/Tm (where Tm is the melting temperature). Based on cyclic deformation and stress/life (S/N) fatigue behavior, together with the X-ray diffraction and in situ transmission electron microscopy (TEM) observations of the microstructure, it was found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti–6Al–4V at such higher temperatures, despite the almost complete relaxation of the near-surface residual stresses. In the absence of such stresses, it is shown that the near-surface microstructures, which in Ti–6Al–4V consist of a layer of work hardened nanoscale grains, play a critical role in the enhancement of fatigue life by mechanical surface treatment. KW - Deep rolling KW - Elevated temperature behavior KW - Fatigue KW - Laser shock peening KW - Residual stress KW - Surface treatment KW - Ti–6Al–4V Y1 - 2003 U6 - https://doi.org/10.1016/S0921-5093(03)00069-8 SN - 1873-4936 VL - 355 IS - 1-2 SP - 216 EP - 230 PB - Elsevier ER - TY - JOUR A1 - Noster, Ulf A1 - Scholtes, Berthold T1 - Bauschingerefekt und mechanische Zwillingsbildung der Magnesiumlegierung AZ31 JF - Härterei-technische Mitteilungen : HTM ; Zeitschrift für Werkstoffe, Wärmebehandlung, Fertigung Y1 - 2003 UR - https://www.researchgate.net/publication/285130307_Bauschingerefekt_und_mechanische_Zwillingsbildung_der_Magnesiumlegierung_AZ31 VL - 58 SP - 322 EP - 327 PB - Hanser ER - TY - JOUR A1 - Huber, Lea A1 - Heindl, Melanie A1 - Schlosser, Marc A1 - Pfitzner, Arno A1 - Dawoud, Belal T1 - On the Cycle Stability and Macroscopic Structure of Iron Oxide Pellets for Thermochemical Hydrogen Storage: Influence of Water Content during the Pelletizing Process JF - Applied Sciences N2 - Hydrogen storage based on the repeated reduction and oxidation (redox) reactions of iron oxide/iron composites represents a promising technology. This work is dedicated to studying the influence of the amount of water added during the pelletizing process on the cycle stability and structure of iron oxide pellets. The storage composites were prepared from iron oxide (Fe2O3) and 10 wt.-% support material (cement) with different amounts of water (18 and 33 wt.-%) in a laboratory-scale pelletizing disk. To evaluate the cycle stability of the composites, the kinetics of the redox reactions were experimentally measured at 800 ∘ C in an atmosphere of 50% N2 and 50% H2 (reduction) or 50% steam (oxidation), respectively. Moreover, the structure of the pellets was analyzed by micro-computed tomography scans. It turned out that pellets with higher water contents attained faster kinetics and a higher cycle stability. The sample with the least water content (18 wt.-%) needed about 26 min and 19 min to reach a conversion rate of 80% during the reduction and oxidation reactions of the sixth redox cycle, respectively. In contrast, the sample with the highest water content (33 wt.-%) could achieve the same conversion rate after 18 min (reduction) and 13 min (oxidation) during the ninth redox cycle. KW - hydrogen storage KW - redox reactions KW - iron/iron oxide KW - pelletizing process KW - cycle stability KW - water content Y1 - 2023 U6 - https://doi.org/10.3390/app13116408 N1 - Corresponding author: Belal Dawoud VL - 13 IS - 11 PB - MDPI CY - 16 ER - TY - JOUR A1 - Kaps, Arne A1 - Lehrer, Tobias A1 - Lepenies, Ingolf A1 - Wagner, Marcus A1 - Duddeck, Fabian T1 - Multi-fidelity optimization of metal sheets concerning manufacturability in deep-drawing processes JF - Structural and Multidisciplinary Optimization N2 - Multi-fidelity optimization, which complements an expensive high-fidelity function with cheaper low-fidelity functions, has been successfully applied in many fields of structural optimization. In the present work, an exemplary cross-die deep-drawing optimization problem is investigated to compare different objective functions and to assess the performance of a multi-fidelity efficient global optimization technique. To that end, hierarchical kriging is combined with an infill criterion called variable-fidelity expected improvement. Findings depend significantly on the choice of objective function, highlighting the importance of careful consideration when defining an objective function. We show that one function based on the share of bad elements in a forming limit diagram is not well suited to optimize the example problem. In contrast, two other definitions of objective functions, the average sheet thickness reduction and an averaged limit violation in the forming limit diagram, confirm the potential of a multi-fidelity approach. They significantly reduce computational cost at comparable result quality or even improve result quality compared to a single-fidelity optimization. KW - Multi-fidelity optimization KW - Efficient global optimization KW - Sheet metal forming KW - Deep drawing Y1 - 2023 U6 - https://doi.org/10.1007/s00158-023-03631-8 VL - 66 PB - Springer Nature ER - TY - JOUR A1 - Salama, Amgad A1 - Kou, Jisheng A1 - Dawoud, Belal A1 - Rady, Mohamed A1 - El Morshedy, Salah T1 - Investigation of the self-propulsion of a wetting/nonwetting ganglion in tapered capillaries with arbitrary viscosity and density contrasts JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects N2 - The movement of a meniscus inside a capillary tube has been extensively studied in the context of displacing one fluid with another immiscible one. This phenomenon exists in many applications including pharmaceutical, oil production, filtration and separation processes, and others. When one of the phases is entrapped inside a capillary tube, it forms what is called a ganglion with two menisci between the two fluids. In a straight uniform capillary tube, a stagnant entrapped ganglion is symmetric. The situation is different if the capillary tube is tapered in which case the two menisci assume different curvatures. Such inhomogeneity of the capillary pressure self-propels the ganglion to move. The fate of the ganglion inside the tapered tube depends on whether it is wetting or nonwetting to the tube wall. That is, after the initial movement, a wetting ganglion accelerates towards the tapered end of the tube while a nonwetting one decelerates towards the wider end before reaching a terminal configuration. Such fates are linked to the variations of the capillary pressure, which continuously increases for a wetting ganglion and decreases for the nonwetting one. In this work, a generalized model is developed that not only describes capillary-driven dynamics over a wide range of viscosity and density contrasts but also pressure-driven scenarios with/without gravity. The model, however, neglects the inertial effect of the two fluids on account of the fact that it is confined to the very early time of the movement process. A first-order nonlinear ordinary differential equation is developed that describes the dynamic behavior of both the wetting and nonwetting ganglions. A fourth-order Runge-Kutta algorithm is developed to solve the model equations. Furthermore, a computational fluid dynamics (CFD) analysis was used to provide a comparison and verification framework. KW - Ganglion KW - Tapered capillary tubes KW - Self-propulsion KW - Surface tension KW - Contact angle Y1 - 2023 U6 - https://doi.org/10.1016/j.colsurfa.2023.131151 SN - 0927-7757 VL - 664 PB - Elsevier ER - TY - JOUR A1 - Köck, Hannah A1 - Striegl, Birgit A1 - Kraus, Annalena A1 - Zborilova, Magdalena A1 - Christiansen, Silke H. A1 - Schäfer, Nicole A1 - Grässel, Susanne A1 - Hornberger, Helga T1 - In Vitro Analysis of Human Cartilage Infiltrated by Hydrogels and Hydrogel-Encapsulated Chondrocytes JF - Bioengineering N2 - Osteoarthritis (OA) is a degenerative joint disease causing loss of articular cartilage and structural damage in all joint tissues. Given the limited regenerative capacity of articular cartilage, methods to support the native structural properties of articular cartilage are highly anticipated. The aim of this study was to infiltrate zwitterionic monomer solutions into human OA-cartilage explants to replace lost proteoglycans. The study included polymerization and deposition of methacryloyloxyethyl-phosphorylcholine- and a novel sulfobetaine-methacrylate-based monomer solution within ex vivo human OA-cartilage explants and the encapsulation of isolated chondrocytes within hydrogels and the corresponding effects on chondrocyte viability. The results demonstrated that zwitterionic cartilage–hydrogel networks are formed by infiltration. In general, cytotoxic effects of the monomer solutions were observed, as was a time-dependent infiltration behavior into the tissue accompanied by increasing cell death and penetration depth. The successful deposition of zwitterionic hydrogels within OA cartilage identifies the infiltration method as a potential future therapeutic option for the repair/replacement of OA-cartilage extracellular suprastructure. Due to the toxic effects of the monomer solutions, the focus should be on sealing the OA-cartilage surface, instead of complete infiltration. An alternative treatment option for focal cartilage defects could be the usage of monomer solutions, especially the novel generated sulfobetaine-methacrylate-based monomer solution, as bionic for cell-based 3D bioprintable hydrogels. KW - osteoarthritis KW - human articular cartilage KW - chondrocytes KW - hydrogels KW - zwitterionic monomers KW - infiltration Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-61235 N1 - Corresponding author: Helga Hornberger VL - 10 SP - 1 EP - 21 PB - MDPI ER - TY - JOUR A1 - Wiesent, Lisa A1 - Stocker, Felix A1 - Nonn, Aida T1 - Investigating the influence of geometric parameters on the deformation of laser powder bed fused stents using low-fidelity thermo-mechanical analysis JF - Materialia N2 - Maintaining dimensional accuracy is a major challenge of laser powder bed fusion (L-PBF) preventing its application for more complex and filigree L-PBF structures in industrial practice. Previous studies have shown that residual stresses and distortion of benchmark L-PBF components may be predicted by sequential thermo-mechanical analyses. However, the reliability of these analyses for more complex structures must be critically questioned, as comprehensive validation and sensitivity analyses are scarce. In this paper, we present a calibrated and validated low-fidelity sequential thermo-mechanical finite element analysis (FEA) of a tubular L-PBF lattice structure, i.e., an aortic stent, where pronounced local deformation is expected. As a first step, the finite element model was extensively calibrated using experimental data to ensure reproducibility of the simulation results. Thereupon, geometric features critical to the distortion of L-PBF lattice structures and measures to compensate for the distortion, such as inversion of the distorted L-PBF structure, were investigated. It was found that the distortion of the L-PBF lattice structures can be reduced, but not completely prevented, by increasing the strut angles, increasing the strut thickness, and decreasing the transition radius in the area of merging struts. FEA-based inversion of the numerically predicted deformed structure minimized distortion, resulting in the L-PBF aortic stent approximating the intended CAD geometry even with a small strut thickness. This work shows that low-fidelity sequential thermo-mechanical FEA can be used not only for the analysis and deformation compensation of reference structures, but also for the analysis of more complex filigree structures with pronounced local deformation. Y1 - 2023 U6 - https://doi.org/10.1016/j.mtla.2023.101774 VL - 28 PB - Elsevier ER - TY - JOUR A1 - Mikhaeil, Makram A1 - Nowak, Sebastian A1 - Palomba, Valeria A1 - Frazzica, Andrea A1 - Gaderer, Matthias A1 - Dawoud, Belal T1 - Experimental and analytical investigation of applying an asymmetric plate heat exchanger as an evaporator in a thermally driven adsorption appliance JF - Applied Thermal Engineering N2 - This communication presents an experimental and analytical study on the evaporation mechanism in a closed-structured asymmetric plate heat exchanger (PHE) employed as a stagnant water evaporator for the application in an adsorption heat transformation appliance. To this aim, an experimental unit is constructed, which comprises two identical PHEs, one acting as an vaporator/condenser and the second, as an adsorber/desorber. Two endoscopes are mounted inside the investigated evaporator to visualize the evaporation mechanism when performing adsorption-evaporation processes under different boundary conditions. It turned out that the evaporation mechanism is a partially covered, thin film evaporation. A heat transfer analysis is performed to evaluate the heat transfer coefficient of the thin film evaporation () inside the investigated evaporator, resulting in -values between 1330 and 160 [W∙m−2∙K−1] over the investigated adsorption-evaporation time. Correlating the obtained () to the film thickness and the wetted area results in -values between 0.34 and 0.78 [mm] and wetted to total area ratios of 0.78 to 0.16. Besides, an analytical model has been developed and introduced to correlate the overall evaporator heat transfer coefficient with the adsorption potential and the time rate of change of the water uptake. KW - Adsorption-evaporation KW - Evaporator KW - Plate heat exchanger KW - Thin film evaporation Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-61115 N1 - Corresponding author: Belal Dawoud IS - 228 PB - Elsevier ER - TY - JOUR A1 - Reindl, Thomas A1 - Meisner, Dennis A1 - Hierl, Stefan T1 - Benchmarking of plastic-based Additive Manufacturing Processes JF - RTejournal - Forum für Rapid Technologie N2 - Additive Manufacturing (AM) is a future-oriented manufacturing technology that is experiencing an enormous boom in the times of Industry 4.0. As a result, various AM technologies and printer models from different manufacturers are entering the market over a short time span. With the advancing establishment of this manufacturing technology for series applications, the expectations and requirements of the fabricated components are also increasing. However, a major challenge is the application-specific selection of the most suitable AM process due to a lack of comparable data. Furthermore, there needs to be more know-how regarding the geometrical and mechanical characteristics of AM parts. This paper addresses this problem by comparing the three most common plasticbased AM processes in the areas of surface quality, dimensional accuracy, and mechanical properties. Roughness measurements, evaluation of a benchmark artifact, tensile tests, and load increase tests are carried out. Based on the results, the individual possibilities and limitations of the compared AM processes can be detected. KW - Additive Manufacturing KW - benchmark artifact KW - dimensional accuracy KW - Fused Layer Modeling KW - mechanical properties KW - Multi Jet Fusion KW - process benchmark KW - Selective Laser Sintering KW - surface quality Y1 - 2023 U6 - https://doi.org/https://doi.org/10.58134/fh-aachen-rte_2023_002 PB - Fachhochschule Aachen ER -