bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient simulation of waves in heterogeneous domains using the scaled boundary finite element method
Authors: Nattoji-Shara Sharath , Birk Carolin , Gravenkamp Hauke 
Published: March 2023

AbstractSimulation of wave propagation phenomena is very challenging due to the restrictions placed on the spatial as well as on the temporal discretization. Image‐based domain discretization using hierarchical meshes (2D polygonal elements) in conjunction with the scaled boundary finite element method provides an efficient numerical simulation tool. In this setting, the computational effort is reduced as only a limited number of unique cell patterns are formed. This is beneficial while computing element matrices in the preprocessing stage. When solving the dynamic system, the advantages of similar elements can only be fully exploited for the explicit time‐stepping schemes in connection with mass lumping when the domain is discretized using low‐order elements (p ≤ 2). On the other hand, the time step size may be limited by the stability criterion. Moreover, high‐order elements require fewer degrees of freedom. Hence for a specific application, it is not straightforward to predict superiority of one time‐stepping scheme over the other. A comparative study of implicit and explicit time‐stepping schemes is presented using an artificial two‐material model.
The concept of unequally and nonlinearly weighted averaging operators as a fundamental homogenization framework in phase‐field modeling
Authors: von Oertzen Vincent , Kiefer Bjoern 
Published: March 2023

AbstractIn recent years, the phase‐field method has gained tremendous potential to serve as a continuum modeling approach of micro structural evolution mechanisms for multiple applications such as alloy solidification, phase transitions, and fracture. By replacing sharp interfaces between phases with a diffusive formulation, additional degrees of freedom, namely order parameters, enter the continuum model to locally describe the current phase composition at each material point. Single phase properties thus need to be interpolated carefully within diffuse interface regions by applying mixture rules subject to specific constraints in an underlying homogenization framework, c.f. [1,2]. However, there exists a variety of well established nonlinear interpolation schemes that can only partially, or not at all, comply with conventional homogenization approaches.To this end, an extension towards unequally and nonlinearly weighted averaging operators is presented, in which conventional unweighted homogenization represents a special case. The embedding of nonlinearly interpolated Reuss‐Sachs, Taylor‐Voigt and rank‐one homogenization models within the given framework is demonstrated by means of energy relaxation. Furthermore, upper and lower energetic bounds are compared between unweighted and nonlinearly weighted averages of order distributions, where the weighted case is shown to yield an improved effective energy description.
Towards modelling of energy storages for use in an intelligent energy management system
Authors: Kappertz Lars , Büskens Christof 
Published: March 2023

AbstractWith the transition towards renewable energy underway, demand‐side management together with the local generation of renewable energy is receiving growing attention. Optimizing the self‐consumption of locally produced renewable energy can not only have financial benefits for the respective household or business (and improve their autarky from increasingly unstable energy markets), but also help improve grid stability against the volatility of some sources of renewable energy. In order to optimize the self‐consumption of a given household or enterprise with an energy management system, the energy demand and generation, as well as the behaviour of all controlled devices have to be forecast. There are many different methods of mathematically modelling these different properties, but the task becomes especially challenging for dynamic systems like energy storage systems. Here, the state of charge at a specific time point depends on both external influences and the previous time point's state of charge, thus modelling errors quickly accumulate. In the context of small and medium agricultural enterprises, examples of such dynamic systems can be electrical storages, like a battery, or thermal storages like a milk cooling tank or a heat pump.In this work, a common way for the modelling of these systems is explored, namely parameter identification. Here, the parameters of an ordinary differential equation representing the assumed physical behaviour of the system are identified from measured data of states and controls in an optimization problem. The success of this approach, and with it the performance of the derived model depends on how well the physical equations actually describe the system, but also on the quality, quantity and content of the measurement data used. In the case of a household battery storage already a simple physical model with parameters identified from measurement data of state of charge and battery power provides useful results. The example of a milk cooling tank provides a situation where external forcing has an important influence on the system's state of charge, its temperature. The cleaning of the tank generates a large heat influx, and raises the temperature, while the filling and emptying of milk influences the heat capacity. While these influences are shown to also be representable by equations based on the physical processes, parameter identification becomes difficult when they are not included in the measurement data. Thus, different approaches to derive these external forcings from the available data are outlined.
Analysis of GMRES for Low‐Rank and Small‐Norm Perturbations of the Identity Matrix
Authors: Carr Arielle K. , de Sturler Eric , Embree Mark 
Published: March 2023

AbstractIn many applications, linear systems arise where the coefficient matrix takes the special form I + K + E, where I is the identity matrix of dimension n, rank(K) = p ≪ n, and ∥E∥ ≤ ϵ < 1. GMRES convergence rates for linear systems with coefficient matrices of the forms I+K and I+E are guaranteed by well‐known theory, but only relatively weak convergence bounds specific to matrices of the form I + K + E currently exist. In this paper, we explore the convergence properties of linear systems with such coefficient matrices by considering the pseudospectrum of I + K. We derive a bound for the GMRES residual in terms of ϵ when approximately solving the linear system (I + K + E)x = b and identify the eigenvalues of I + K that are sensitive to perturbation. In particular, while a clustered spectrum away from the origin is often a good indicator of fast GMRES convergence, that convergence may be slow when some of those eigenvalues are ill‐conditioned. We show there can be at most 2p eigenvalues of I + K that are sensitive to small perturbations. We present numerical results when using GMRES to solve a sequence of linear systems of the form (I + Kj + Ej)xj = bj that arise from the application of Broyden's method to solve a nonlinear partial differential equation.
Implementation of a surrogate model for a novel path‐based finite element simulation for additive manufacturing processes in construction
Authors: Ekanayaka Virama , Hürkamp André 
Published: March 2023

AbstractAdditive manufacturing in large‐scale construction is an ongoing research topic that shows significant potential to overcome the challenges in terms of efficient material usage and process automation in construction. A large challenge in deposition based additive manufacturing processes of concrete material is to ensure the structural stability while printing. Due to the weak material properties of the fresh concrete, it has to be ensured that during the printing process the not fully cured printed structure is able to carry its own weight. This requires process stabilization and a proper process control to prevent a collapse of the structure. Therefore, a numerical model of the printing process that takes into account the time dependent material behavior of the applied concrete as well as the printing path and the process parameters is necessary to support the process planning. Within the framework of project B04 of the collaborative research center TRR277 – Additive Manufacturing in Construction, a novel path‐based finite element simulation was developed in which the simulated geometry is constructed directly from the printing trajectory. Additionally, this approach allows the time‐dependent material properties of fresh concrete to be modeled directly and efficiently into the mesh of the printed structure. Since the computation of large scale printing processes with finite element simulations is quite expensive, there exists a need for a much faster computational model. In this contribution, the implementation of a surrogate model based on a neural network and its deployment to optimize the interlayer waiting time is presented.
Optimization of Mirror Positioning for Single‐Camera 3D Displacement Measurements
Authors: Gille Max , Maierhofer Johannes , Rixen Daniel J. 
Published: March 2023

AbstractCamera‐based 3D displacement measurements are only possible when two different viewing angles of the respective measurement point are available. We earlier introduced a simplified 3D reconstruction algorithm for camera‐mirror measurements where the mirror reflects the second view onto the camera sensor to eliminate the need for a second (costly) high speed camera. In this study, we concentrate on formulating guidelines on how to position the mirror with respect to the camera and the measured structure, the goal being to minimize errors arising in the 3D reconstruction procedure. The focus lies on the angle between the optical axes of both camera views. We hereby also take into account limitations in the experimental setup that the special camera‐mirror‐setup brings with it. This study is conducted in terms of simulations using the animation software BLENDER as well as real experiments on a simple vibrating structure.
A procedure for determination of the microstructural probabilistic characteristics from micrographs and their impact on subsequent results
Authors: Klatt Eduard , Widera Ilona M. , Rauter Natalie 
Published: March 2023

AbstractIn this study a methodology for the experimental determination of the probabilistic characteristics induced by injection molding of short‐fibre reinforced composites is presented. This approach is based on a pattern recognition algorithm for the fibre detection on the two‐dimensional micrograph. Since the fibres are of elliptic shape when dealing with a two‐dimensional arbitrary oriented cross‐section, the method of ellipses is used. The stochastic characteristics of the microstructure are described by probability density functions of the fibre length, diameter, and orientation, which are extracted from the two‐dimensional micrograph. For accurate results, sample preparation is of major significance, otherwise the microstructural characteristics are not captured correctly. The result of the fibre orientation over the cross‐section shows a typical layered structure of the microstructure. Furthermore, the extracted probability density function of the fibre diameter present as expected a normal distribution. In general, the results are in good agreement with literature and other scientific works.
Coupled thermo‐viscoplastic fracture model for ductile‐brittle failure of amorphous glassy polymers with phase‐field approach
Authors: Başdemir Selçuk , Gültekin Osman , Dal Hüsnü 
Published: March 2023

AbstractAmorphous glassy polymers have an extensive use in the industrial sectors including micro‐electronics, medical industry and aerospace, therefore their design and usage have become a significant task nowadays. The fracture response of these polymers may vary from ductile to brittle depending on several factors such as entanglement density, temperature level and external loading rate. The ductile response is driven by diffuse shear zones exhibiting volume–preserving inelastic deformations while the brittle response is manifested by very small crack‐like defects composed of a sequence of fibrillar bridges separated by micro‐voids, thereby connotating void formation consisting of nucleation and propagation steps. The presents study is focused on the description of shear yielding and crazing phenomenon in terms of their respective evolution equations. In addition, an extension towards the modelling of the fracture is employed via the crack phase–field approach, considering ductile and brittle failure simultaneously. This is provided by the novel failure criterion that features a critical amount of plastic strain and void volume fraction. Since the proposed approach unitedly models the macroscopic crack initiation and propagation for ductile or brittle failure, it is asserted to be more physically grounded compared to present models in the literature. Constitutive formulations for shear yielding, crazing, and void volume fraction are derived with their specific forms starting with the local and conductive component of the dissipation inequality. The performance of model is evaluated after developing the local and global Newton–type update algorithms for the dissipative internal and primary field variables, respectively and it has been analysed by fitting of several experimental data of homogeneous and inhomogeneous tests. The findings reveal the remarkable temperature dependency on the type of failure as well as the interaction between loading rate and temperature change owing to dissipative heating in the solid.
Tracking of fracture‐state displacement data generated by cohesive zone modeling using shape optimization
Authors: Suchan Tim , Najafi Koopas Rasoul , Rauter Natalie , Welker Kathrin 
Published: March 2023

AbstractMany infrastructure objects made from concrete like bridges are in bad condition. Different types of damage like corrosion and fractures reduce the stiffness and strength significantly. Knowledge of the fracture propagation is essential to predict the remaining life time and to guarantee a safe operation. There are different approaches to solve this problem. On the one hand finite element simulations including cohesive zone modeling are commonly used to determine the current condition and to predict the fracture propagation in a component. In addition, mathematical optimization techniques like shape optimization can be used to predict the fracture growth. In this work, fracture‐state displacement data generated by cohesive zone modeling is tracked using shape optimization techniques, which leads to the imitation of fracture growth. It is shown that the techniques lead to comparable results for the fracture propagation in concrete.
Consideration of chemically‐induced damage in a thermo‐electrically coupled system
Authors: Waimann Johanna , van der Velden Tim , Schmidt Annika , Ritzert Stephan , Reese Stefanie 
Published: March 2023

AbstractElectro‐chemical machining (ECM) allows the removal of material based on the effect of anodic dissolution and without mechanical contact. Thus, it avoids tool abrasion as well as influencing the surface quality, for instance due to formed dislocations and/or damage. Due to that, ECM is a very attractive machining process for high strength materials such as titanium.The effect of anodic dissolution is a result of a present electric current in combination with the contact with an electrolyte. We show a material model, which enables to predict the mentioned effect by use of a chemically motivated damage of the material based on Faraday's law. After the approach's introduction, we will address its consideration within a thermo‐electrically coupled finite element method by using effective material parameters that differ between metal and electrolyte. The presentation is completed by the numerical results, which show the method's ability to simulate the ECM process.
Experiments on the dynamic Poisson's ratio of PUR foams
Authors: Bogunia Lukas , Buchen Stefan , Fischbach Marcel , Weinberg Kerstin 
Published: March 2023

AbstractPolyurethane (PUR) foams are used in various industrial applications, including vibration damping and noise reduction. Because the effective mechanical properties are needed for the engineering design process, this work presents a method to measure the dynamic Poisson's ratio for the typical range of sound frequencies. A hydraulic pulse testing machine is used to apply the harmonic displacement excitation of the cylindrical specimens for 1 − 100 Hz. The analysis of the time‐dependent deformation data is based on video recordings of a high‐speed camera and a specially derived image processing algorithm.For the Poisson's ratios of the measured foams no significant frequency dependence was found. For PUR foam with an open‐cell or mixed‐cell microstructure the dynamic Poisson's ratio is approximately 0.3. Poisson's ratios of about 0.4 were measured for PUR foams with a high density and a closed‐cell microstructure.
Large Data Limit of the MBO Scheme for Data Clustering
Authors: Laux Tim , Lelmi Jona 
Published: March 2023

AbstractThe MBO scheme is a highly performant scheme used for data clustering and other applications in machine learning. We report on the first theoretical studies of the scheme in the large data limit. Our results relate (i) the final state of the scheme to minimal surfaces in the data manifold and (ii) the dynamics of the scheme to the steepest descent for surfaces, which is mean curvature flow. The tools employed are variational methods for (i) and viscosity solution techniques for (ii).
FE‐based modeling of a mesoscale piezoelectric motor
Authors: Marter Paul , Duvigneau Fabian , Orszulik Ryan , Juhre Daniel 
Published: March 2023

AbstractThe manufacturing of systems at the mesoscale on the order of millimeters to centimeters is costly and challenging. To simplify the development process, the finite element method (FEM) can be used to compare and evaluate different design variations at an early stage. This method also allows for gaining a more precise understanding of the system's behavior. In robotic applications it is the torque that is of the greatest interest as a sufficiently high torque mitigates the need for a gearbox, which is very difficult to manufacture and integrate at small scales. Given this background, the present work aims to develop a finite element model for the numerical representation of a class of rotational piezoelectric motors based on multiple unimorph arms. The influence of different design parameters on the resulting torque is analyzed utilizing this model. The motor design consists of a planar rotor and a flat spring, a stator with three unimorph arms, as well as a shaft. With a total integrated motor thickness of 0.8 mm, the weight is approximately 200 milligrams. The rotation is mainly caused by the tip contact between the arms of the stator and the rotor itself. Experiments with prototypes have shown that bidirectional rotation is possible with the design, which is then investigated in more detail using the numerical model. There are several challenges here in the non‐linearity due to the contact between the individual components and the high‐frequency excitation of the motor in the kHz range.The modeling also requires validation experiments to determine the resulting properties for the coupled system of structural and piezoelectric components. This includes both the measurement of the unimorph arms and the measurement of the natural frequencies of the stator with the piezoelectric unimorphs by a laser scanning vibrometer and displacement sensors. The scanning vibrometer also provides the opportunity to compare the vibration modes, as an important non‐local output quantity, in order to achieve good agreement between the numerical and experimental results.In the next stage, the model is to serve as the basis for multi‐objective optimization to achieve maximum torque in the smallest possible volume. Further miniaturization possibilities will also be investigated in future studies.
Vibration analysis on newly designed painting supports for the Cranach exhibition 2022 at Herzogin Anna Amalia Bibliothek
Authors: Hartlieb Eva , Ziegler Pascal , Eberhard Peter 
Published: March 2023

AbstractThe effect of vibration on the condition of sensitive works of art continues to be of great importance to museums. Vibrations contribute to irreversible changes in the complex materiality of art and cultural heritage. In cooperation with the Klassik Stiftung Weimar, the Institute of Engineering and Computational Mechanics at the University of Stuttgart accompanied an exhibition setup. The museum and partners designed free‐standing columns in the exhibition hall to support valuable works of art. Due to their original design, these are susceptible to vibrations. Thus, the question arises as to what extent these columns should be modified in order to reduce these vibrations. In this study, measurements were taken on the floor and on the columns using a variety of measuring techniques. It was investigated which excitations from the environment propagate to the artwork. It was confirmed that vibrations from the environment, such as road traffic and museum visitors in the exhibition room, are sources of excitation.Experimental modal analysis was used to identify the characteristic vibration behaviour of these columns. By using finite element methods, a simulation model was set up allowing to investigate modifications to the columns in order to predict the change in vibration behaviour. Based on the simulation modifications, structural changes were made to the system through stiffening of individual components and redistribution of masses.
Investigation into the genetics of fetal congenital lymphatic anomalies
Authors: Rogerson Daniella , Alkelai Anna , Giordano Jessica , Pantrangi Madhulatha , Hsiao Meng‐Chang , Nhan‐Chang Chia‐Ling , Motelow Joshua E. , Aggarwal Vimla , Goldstein David , Wapner Ron , Shawber Carrie J. 
Published: March 2023

AbstractObjectiveCongenital lymphatic anomalies (LAs) arise due to defects in lymphatic development and often present in utero as pleural effusion, chylothorax, nuchal and soft tissue edema, ascites, or hydrops. Many LAs are caused by single nucleotide variants, which are not detected on routine prenatal testing.MethodsDemographic data were compared between two subcohorts, those with clinically significant fetal edema (CSFE) and isolated fetal edema. A targeted variant analysis of LA genes was performed using American College of Medical Genetics criteria on whole exome sequencing (WES) data generated for 71 fetal edema cases who remained undiagnosed after standard workup.ResultsCSFE cases had poor outcomes, including preterm delivery, demise, and maternal preeclampsia. Pathogenic and likely pathogenic variants were identified in 7% (5/71) of cases, including variants in RASopathy genes, RASA1, SOS1, PTPN11, and a novel PIEZO1 variant. Variants of uncertain significance (VOUS) were identified in 45% (32/71) of cases. In CSFEs, VOUS were found in CELSR1, EPHB4, TIE1, PIEZO1, ITGA9, RASopathy genes, SOS1, SOS2, and RAF1.ConclusionsWES identified pathogenic and likely pathogenic variants and VOUS in LA genes in 51% of fetal edema cases, supporting WES and expanded hydrops panels in cases of idiopathic fetal hydrops and fluid collections.