bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of a level set method and the method of moving asymptotes for the topology optimization of flexible components in multibody systems
Authors: Azari Nejat Ali , Held Alexander , Seifried Robert 
Published: March 2023

AbstractThe gradient‐based topology optimization of flexible multibody systems is considered, where the floating frame of reference method is utilized to model the flexible components with an appropriate efficiency. Thereby, the quality of the optimization results depends, among others, on the chosen gradient calculation strategy and the applied optimization algorithm. Here, both a fully‐coupled time‐continuous adjoint sensitivity analysis and a weakly‐coupled equivalent static load method are tested for gradient calculation. Moreover, both the method of moving asymptotes and a level set method are taken to solve the optimization problem. Different combinations of the mentioned gradient strategies and optimization algorithms are applied for the topology optimization of a flexible piston rod in a slider‐crank mechanism. The corresponding results and comparisons shall be used as quality benchmarks for further studies.
Scaled boundary isogeometric analysis with C1 coupling for Kirchhoff‐Love theory
Authors: Arf Jeremias , Reichle Mathias , Klinkel Sven , Simeon Bernd 
Published: March 2023

AbstractScaled boundary isogeometric analysis (SB‐IGA) describes the computational domain by proper boundary NURBS together with a well‐defined scaling center; see [5]. More precisely, we consider star convex domains whose domain boundaries correspond to a sequence of NURBS curves and the interior is determined by a scaling of the boundary segments with respect to a chosen scaling center. However, providing a decomposition into star shaped blocks one can utilize SB‐IGA also for more general shapes. Even though several geometries can be described by a single patch, in applications frequently there appear multipatch structures. Whereas a C0 continuous patch coupling can be achieved relatively easily, the situation becomes more complicated if higher regularity is required. Consequently, a suitable coupling method is inevitably needed for analyses that require global C1 continuity.In this contribution we apply the concept of analysis‐suitable G1 parametrizations [2] to the framework of SB‐IGA for the C1 coupling of planar domains with a special consideration of the scaling center. We obtain globally C1 regular basis functions and this enables us to handle problems such as the Kirchhoff‐Love plate and shell, where smooth coupling is an issue. Furthermore, the boundary representation within SB‐IGA makes the method suitable for the concept of trimming. In particular, we see the possibility to extend the coupling procedure to study trimmed plates and shells.The approach was implemented using the GeoPDEs package [1] and its performance was tested on several numerical examples. Finally, we discuss the advantages and disadvantages of the proposed method and outline future perspectives.
Closed‐form buckling analysis of unsymmetrically laminated plates
Authors: Schreiber Philip , Mittelstedt Christian 
Published: March 2023

AbstractThe local stability of thin‐walled fibre‐reinforced plastic composite beams can be reduced to individual laminates using discrete plate theory. These individual plates receive a supporting effect from their surrounding structure, which is modelled with rotational restraints. In the present investigation, this buckling problem is described by a closed‐form solution. The energy‐based method works with the Rayleigh quotient and the principle of the stationary value of the elastic potential energy. For the analysis of unsymmetrically laminated plates, the classical laminated plate theory (CLPT) considers both the plate deflection and the in‐plane displacements. The first‐order shear deformation theory (FSDT) and third‐order shear deformation theory (TSDT) additionally describe the cross‐sectional rotations and thus take transverse shear deformations into account. In addition to the direct consideration of the bending‐extension couplings, these have also been investigated using the reduced bending stiffness (RBS) method. The investigation shows the influence of bending‐extension coupling on the stability of compressively loaded unsymmetrically laminated plates. Moreover, it is found that the transverse shear stiffness reduces the critical load at relatively high plate thicknesses. The closed‐form analytical solution and the RBS method show good agreement with finite element analyses. The presented closed‐form analytical methods provide explicit solutions for the critical compressive load of unsymmetric laminates under different boundary conditions. Due to the explicit solution, this method is significantly more computationally efficient than numerical, semi‐analytical or exact methods. The present methods are characterised by a simple applicability as well as a very high computational efficiency and are very suitable for preliminary design as well as optimisation of laminated structures.
Dynamic Crack Propagation in a Lattice Boltzmann Method for Solid Mechanics
Authors: Müller Henning , Schlüter Alexander , Müller Ralf 
Published: March 2023

AbstractIn recent years, Lattice Boltzmann methods (LBMs) have been adapted and developed to simulate the behavior of solids. They have already been applied to fractures as well. However, until now, our previous work has been restricted to stationary cracks.In this work, we regard the reduced 2D case of anti‐plane shear deformation with mode III crack opening. The wave equation is the governing equation for this problem, which is solved via an LBM.The main contribution of this work is the introduction of an algorithm to handle crack growth in an LBM for solids. The underlying scheme is based on geometric assumptions, which is well suited for the regular lattice used by the LBM. A fracture criterion based on the stress intensity factor is implemented and illustrated by a numerical example.
A new shape optimization approach for fracture propagation
Authors: Suchan Tim , Welker Kathrin , Wollner Winnifried 
Published: March 2023

AbstractWithin this work, we present a novel approach to fracture simulations based on shape optimization techniques. Contrary to widely‐used phase‐field approaches in literature the proposed method does not require a specified ‘length‐scale’ parameter defining the diffused interface region of the phase‐field. We provide the formulation and discuss the used solution approach. We conclude with some numerical comparisons with well‐established single‐edge notch tension and shear tests.
Homogenisation for macroscopic shell structures with application to textile‐reinforced mesostructures
Authors: Mester Leonie , Klarmann Simon , Klinkel Sven 
Published: March 2023

AbstractIn the analysis of textile‐reinforced shell structures full‐scale models are often impractical due to the complex nature of the meso‐structure. The structure is assumed to be globally periodic which allows the definition of a representative volume element (RVE). In this contribution, the RVE is embedded within a first‐order homogenisation framework, where the meso‐to‐macro transition is governed by the Hill‐Mandel condition. In a coupled multiscale approach the macroscopic scale is analysed using shell elements. Each macroscopic integration point is linked to an RVE which accounts for the total thickness of the shell. The macroscopic shell strains are applied on the RVE by means of suitable boundary conditions. On the mesoscopic scale, a boundary value problem is solved in order to obtain equivalent material parameters which are returned to the macroscopic scale. Here, a discrete model of the textile‐reinforcement on the mesostructure is obtained by adapting the approach from the scaled boundary finite element method (SBFEM) in which solids are described by means of their boundary surfaces. These are scaled into one central point, the so‐called scaling center. The required star‐shaped domains are obtained by subdivision. Combination with the isogeometric analysis (IGA) allows to directly facilitate the NURBS (Non‐Uniform Rational B‐Splines) functions describing the boundaries in commonly used CAD software. A key point is the choice of suitable boundary conditions for the RVE. In this contribution a set of periodic boundary conditions will be presented. The proposed method for the analysis of textile‐reinforced shell structures is validated by means of numerical examples.
Linear and nonlinear thermoviscoelastic behavior of polyamide 6
Authors: Keursten Johannes , Kehrer Loredana , Böhlke Thomas 
Published: March 2023

AbstractThermoplastic polyamides are used in many industrial areas due to their potential in lightweight applications. Polyamides serve as matrix material in fiber reinforced thermoplastics, for instance. The mechanical behavior of polyamides is characterized by pronounced viscoelastic effects that are strongly affected by environmental conditions like temperature or humidity. In this work, linear thermoviscoelastic behavior of polyamide 6 is considered. Viscoelastic behavior is modeled by the generalized Maxwell model while extended time‐temperature superposition is used to model temperature dependency. A temperature‐frequency sweep conducted by dynamic mechanical analysis serves as input for the model. By horizontal and vertical shifting, master curves of the loss factor, storage modulus, and loss modulus are obtained. Based on this, limitations of time‐temperature superposition and linear thermoviscoelastic modeling are discussed. Furthermore, it is shown that the horizontal shifts can be well approximated by the Williams‐Landel‐Ferry equation for temperatures above and below the glass transition temperature.
Hybrid Digital Twins: A Proof of Concept for Reinforced Concrete Beams
Authors: von Danwitz Max , Kochmann Thank Thank , Sahin Tarik , Wimmer Johannes , Braml Thomas , Popp Alexander 
Published: March 2023

AbstractDigital twins map physical objects, processes, and further entities from the real (physical) world into digital space. Going one step further, hybrid digital twins combine physics‐based modeling with data‐based techniques to form a simulation tool with predictive power. In the light of an increasing digitalization of our built world, such digital twins have great potential to contribute to the protection of critical technical infrastructures. In case of bridges, digital twins can have a key role in structural health monitoring. This contribution outlines a path to approach these goals and provides a proof of concept of a hybrid digital twin for steel‐reinforced concrete beams as a representative component in civil engineering structures.Four model components are combined to form the hybrid digital twin, namely, a physics‐based full‐order model, a fast‐to‐evaluate reduced‐order model, a purely data‐driven model, and a baseline model. Applied to the concrete beam, the full‐order model is based on a novel finite element formulation allowing for efficient modeling of slender structures embedded into solid bodies. We use this method to capture the interaction between reinforcement components and concrete matrix of the beam. As reduced‐order model, a physics‐informed neural network is trained with parts of the available measurement data and with the governing equations of a simplified physical model. The data‐driven model localizes cracks in the concrete in a statistical outlier analysis of fiber‐optical strain measurement data. In completion, the baseline model estimates the system behavior based on a closed‐from expression from civil engineering literature.The proposed hierarchy of four models with decreasing model complexity allows to select an appropriate model according to an application specific trade‐off between model accuracy and cost. We demonstrate the combination of physics‐based modeling with data‐driven techniques based on sensor data measured in a physical four‐point bending test of the reinforced concrete beam.
Electrostatic Body Forces and their Implications for Cracks
Authors: Schlosser Alexander , Ricoeur Andreas 
Published: March 2023

AbstractA Griffith‐type crack in a dielectric solid under electromechanical loading is investigated by numerically solving the combined boundary value problem. The focus is on the contribution of electrostatically induced body forces, coming along with the still controversially discussed Maxwell stress tensor, to the crack tip loading. A 1/r‐singularity of compressive stress is found to evolve at the crack tip, however, just being dominant over the mechanically induced 1/√r‐behavior within a very small region.
Approximate computational model for the local postbuckling of omega‐stringer‐stiffened composite panels
Authors: Schilling Jakob C. , Mittelstedt Christian 
Published: March 2023

AbstractTypical thin‐walled structures are found in applications like aircraft, spacecraft and marine vessels. For this type of structure, stability behaviour is crucial. The better this behaviour is understood, the better the full lightweight potential can be exploited. For composite structures especially, new fast analysis tools for preliminary design are required to address this issue. Therefore, the local postbuckling of omega‐stringer‐stiffened composite panels is the subject of a new computational model. The analysis method is computationally highly efficient because it is based on a closed‐form analytical approach. The explicit solution is derived based on the principle of the minimum of the total elastic potential. Furthermore, the solution assumes that the initial eigenform does not substantially change in the early postbuckling regime. In this way, the plates of the skin and stringer can be included explicitly in the analysis. Compared to finite element analysis and a closed‐form computational model found in the literature, the new analysis tool is assessed. The results indicate excellent agreement for panels, where the bay plate is the most critical element of the panel. The new computational model promises to be a highly efficient tool in the preliminary design framework.
Phase‐field modeling of chemically reactive multi‐component and multi‐phase systems
Authors: Seupel Andreas , Roth Stephan , Kiefer Bjoern 
Published: March 2023

AbstractThe present phase‐field approach is based on a mixture theory for multiple components and phases within the framework of non‐equilibrium thermodynamics of internal state variables. More specifically, diffuse interfaces are included in the state potential by terms depending on spatial gradients of the component mass fractions as well as order parameters representing different phases. Coupled field equations of generalized Cahn‐Hilliard and Allen‐Cahn type are derived directly from a local entropy balance, under the assumption of a localized Gibbs fundamental equation. Additionally, thermodynamically consistent kinetics for equilibrium reactions are formulated. The field equations are recast into a mixed variational formulation, which allows a discretization by finite elements with low‐order ansatz functions. The numerical implementation is discussed by means of a benchmark problem for reactive binary systems, of which the thermodynamic equilibrium solution is known.
Numerical investigation of hot bulk forming processes with respect to the resulting residual stress distribution
Authors: Hellebrand Sonja , Brands Dominik , Scheunemann Lisa , Schröder Jörg 
Published: March 2023

AbstractThe cost‐ and time‐efficient design of today's manufacturing processes is closely linked to numerical simulations. By developing and applying suitable simulation models, component properties can be specifically predicted and, if necessary, modified according to the customer's specifications. One important aspect of this is the adjustment towards advantageous residual stress profiles, for example to increase service life or wear resistance. Hot forming processes offer the advantage of the interaction of thermal, mechanical and metallurgical effects. In particular, cooling after prior heating and forming, in this case upsetting, results in a phase transformation on the microscale in the material. The residual stress state, which arises from dislocations in the atomic lattice, will be considered in more detail in this contribution.Here, the focus lies on the analysis of microscopic characteristics utilizing a multi‐scale Finite Element model in terms of a FE2 approach.
Sensitivity of predicted stresses in thick‐walled steel/ceramics spherical FGM‐structures to parameter uncertainties
Authors: Arslan Eray , Mack Werner 
Published: March 2023

AbstractThe effects of both material data uncertainties of the constituents and of volume fraction deviations from the design values caused by the manufacturing process on the forecasted stresses in a spherical container of functionally graded material (FGM) are investigated. Specifically, a steel/alumina hollow sphere subject to internal pressure and homogeneous heating is studied. It is shown that even moderate uncertainties and deviations may cause large expectation ranges of von Mises equivalent stresses, and this issue may yet predominate over the question for the most reasonable homogenization scheme(s).
Bonded particle models for discrete element simulation of porous granules
Authors: Rotter Sonja , Woitzik Christian , Düster Alexander 
Published: March 2023

AbstractThe growing interest in granular materials used in mechanical applications, for example as crash absorbers in ship collisions, leads to an increased need for numerical models to simulate such granules. Since, in the case of an application as a crash absorber, the fracture behaviour of the granules is of particular interest, the numerical models must be able to simulate the breakage and predict, for example, the energy dissipation during fracture. For this purpose, a discrete element method is used together with a bonded particle model. Since the bond model mainly affects the fracture of particles, this work focuses on new models and their influence on the breaking behaviour of granules.
Efficient simulation of cables with anisotropic high‐order solid finite elements
Authors: Hildebrandt André , Sharma Prateek , Diebels Stefan , Düster Alexander 
Published: March 2023

AbstractCables are slender structures with a complex geometry, that can undergo large deformations during their installation or in dynamic environments. In combination with their complex inner structure they pose a challenging problem for finite element simulations. In this article a simplified approach is presented to model cables by using an effective material and a homogeneous cross‐section, which is anisotropic in the elastic and inelastic domain. For the high‐order hierarchic shape functions with quasi‐regional mapping, anisotropic ansatz spaces are applied in tension, torsion and bending simulations. The identification of material parameters is conducted based on experimental results for a tension and a torsion test using the particle swarm optimization algorithm. Finally, the identified parameters are validated for a combined load case with torsion and free bending, showing a promising approach regarding the simulation of cable structures.
Sparse signals on hypergraphs
Authors: Emmrich Tarek , Juhnke-Kubitzke Martina , Kunis Stefan 
Published: March 2023

AbstractSignals with a sparse representation in a given basis as well as Laplacian eigenvectors of graphs play a big role in signal processing and machine learning. We put these topics together and look at signals on graphs that have a sparse representation in the basis of eigenvectors of the Laplacian matrix, which may appear after convolution with an unknown sparse filter. We give explicit algorithms to recover those sums by sampling the signal only on few vertices, i.e., the number of required samples is independent of the total size of the graph and takes only local properties of the graph into account. We generalize these methods to simplicial complexes.
Influence of a transient bubble dynamics cavitation model for squeeze film dampers on the run‐up behaviour of a turbocharger rotor
Authors: Drapatow Thomas , Woschke Elmar 
Published: March 2023

AbstractThe force response of squeeze film dampers and hydrodynamic bearings is significantly influenced by the occurence of cavitation inside the lubricant films. The viscosity of the occuring mixture of oil and air bubbles is vastly different than that of pure lubricant and therefore changes the pressure build‐up and thereby the stiffness and damping properties of the lubrication films. To accurately predict the force response of a squeeze film damper, the cavitation and its effect on the pressure build‐up therefore has to be taken into account. Well known cavitation algorithms for lubrication problems, like the Elrod algorithm or the two‐phase‐model, neglect the transient nature of outgassing and assume instantaneous bubble formation and collapse. In the presented paper, a transient bubble dynamics model based on the Rayleigh‐Plesset‐Scriven equation is utilised instead and its effect on the rotordynamic behaviour of a turbocharger rotor is examined based on fully transient multi body dynamics simulations.
Modeling of Growth using an Immersed Finite Element Method
Authors: Ebrahem Adnan , Hiemstra René R. , Stoter Stein K. F. , Schillinger Dominik 
Published: March 2023

AbstractTo prevent remeshing, we explore the use of a non‐boundary‐fitted finite element method for the computational modeling of growth including contact mechanics. Accordingly, we utilize a mesh‐related mapping procedure for the use of implicit geometry description by a level set function within the framework of immersed methods. Hence, our framework provides a setting to include patient‐specific geometries based on imaging data as we use a level set function for the implicit geometry description. In this contribution, we show that the proposed approach is a viable alternative for problems with mesh‐related obstacles, in particular when large growth simulations on complex patient‐specific geometries are of primary interest.
Numerical simulation of fluid flow with a fast Boundary‐Domain Integral Method
Authors: Tibaut Jan , Ravnik Jure , Schanz Martin 
Published: March 2023

AbstractFor the simulation of fluid flow the velocity‐vorticity formulation of the Navier‐Stokes equations can be used. Approximating the first order time derivative in these equations by finite differences, essentially, the Yukawa equation for the velocity has to be solved with an inhomogeneity governed by the vorticity. Applying the Boundary Element Method to such problems is not straightforward. However, the Boundary‐Domain Integral Method (BDIM) can be used, which requires to solve beside the boundary integrals as well a domain integral due to the inhomogeneity. Classical BEM formulations have a quadratic complexity with respect to the unknowns on the boundary and, for the BDIM additionally, for the unknowns in the domain. This prevents the BDIM from being applied to real‐world problems.To reduce the quadratic complexity in BEM, approximation methods like the fast multipole method, ℋ‐matrices in combination with the adaptive cross approximation or the ℋ2 ‐matrix technique can be used. All these methods reduce the complexity to an almost linear order. Here, the ℋ2 ‐matrix technique is applied to reduce storage and computing time for the right hand side, i.e., for the matrix of the domain integrals. Based on interpolatory kernel expansions and an heuristic criterium for too small matrix entries an almost linear complexity can be achieved. The numerical studies focus on a lid‐driven cavity. The complexity reduction is demonstrated.