bluuebunny/crossref_metadata_2025_split huggingface dataset:
The talar morphology of a hypochondroplasic dwarf: A case study from the Italian Late Antique period
Authors: Sorrentino Rita , Carlson Kristian J. , Figus Carla , Pietrobelli Annalisa , Stephens Nicholas B. , DeMars Lily J. D. , Saers Jaap P. P. , Armando Jessica , Bettuzzi Matteo , Guarnieri Tiziana , Oxilia Gregorio , Vazzana Antonino , Parr William , Turley Kevin , Morigi Maria Pia , Stock Jay T. , Ryan Timothy M. , Benazzi Stefano , Marchi Damiano , Belcastro Maria Giovanna 
Published: December 2021

AbstractThis project aims to test whether geometric morphometric (GM) and trabecular analyses may be useful tools in identifying talar characteristics related to hypochondroplasia. We quantified the external and internal talar morphology of a hypochondroplasic dwarf (T17) from Modena (northern Italy) dated to the sixth century AD. External talar morphology of T17 was compared with a broad sample of modern human tali (n = 159) using GM methods. Additionally, a subsample of these tali (n = 41) was used to investigate whole talar trabecular changes in T17. Our results show that GM and trabecular analyses identify a combination of traits linked to the dwarfing disorder of hypochondroplasia. These traits include decreased scaled talar dimensions compared with normal‐sized individuals, presence of an accessory antero‐lateral talar facet, high bone volume fraction, and high anisotropy values throughout the entire talus. In our case study, hypochondroplasia does not appear to substantially modify external talar morphology probably due to the fast growth of the talus. We suggest that small talar dimensions are associated with hypochondroplasia. An antero‐lateral talar facet may result from the talus and calcaneus coalition (i.e., talocalcaneal abnormal bridging) possibly related to an everted foot posture that was limited by overgrowth of the fibula. We suggest that high talar trabecular density and strut orientation provide insights into pathological development of the trabecular plates in T17. Finally, our study suggests that high talar trabecular density and strut orientation, and small talar dimensions, may be added as possible concomitant talar hallmarks for hypochondroplasia.
Numerical convergence of discrete extensions in a space‐time finite element, fictitious domain method for the Navier–Stokes equations
Authors: Anselmann Mathias , Bause Markus 
Published: December 2021

AbstractA key ingredient of our fictitious domain, higher order space‐time cut finite element (CutFEM) approach for solving the incompressible Navier–Stokes equations on evolving domains (cf. [1]) is the extension of the physical solution from the time‐dependent flow domain Ωtf to the entire, time‐independent computational domain Ω. The extension is defined implicitly and, simultaneously, aims at stabilizing the discrete solution in the case of unavoidable irregular small cuts. Here, the convergence properties of the scheme are studied numerically for variations of the combined extension and stabilization.
Fully Implicit RUNGE‐KUTTA Schemes for Ideal Elastoplasticity
Authors: Schröder Bettina , Kuhl Detlef 
Published: December 2021

AbstractThe present paper derives a multifield formulation of ideal elastoplasticity to enable the consistent application of higher order accurate RUNGE‐KUTTA schemes. With the help of an axisymmetric model problem the appearing time discretization errors of distinct schemes are determined and compared.
High‐order SBFEM solution of the Reynolds equation
Authors: Pfeil Simon , Gravenkamp Hauke , Duvigneau Fabian , Woschke Elmar 
Published: December 2021

AbstractA semi‐analytical solution of the Reynolds equation for hydrodynamic bearings in rotordynamic simulations is investigated, which is based on the Scaled Boundary Finite Element Method (SBFEM). The numerical efficiency of this approach is compared to the Finite Element Method (FEM), considering linear as well as higher‐order shape functions. It is observed that the SBFEM requires significantly less computational time than the FEM, especially with respect to high‐order formulations.
Simulation of granular materials with the discrete element method to investigate their suitability as crash‐absorber in ship collisions
Authors: Kraus Sonja , Woitzik Christian , Dosta Maksym , Düster Alexander 
Published: December 2021

AbstractIn recent years, the idea of increasing the crash‐worthiness of ships by filling their double hull structure with granules has been studied. To this end, different granular materials have been investigated in [1, 2] with the result, that expanded glass materials are best suited for this purpose. Based on this work, it is important to gain deeper insights into the breakage behavior of expanded glass particles performing numerical investigations. The corresponding simulation procedure as well as the computational results are presented in this contribution.
Efficient modeling of material dissolution in electrochemical machining
Authors: van der Velden Tim , Rommes Bob , Klink Andreas , Reese Stefanie , Waimann Johanna 
Published: December 2021

AbstractThe manufacturing process of electrochemical machining (ECM) allows for the precise machining of high‐strength materials. In order to save time and reduce experimental costs, one depends on efficient simulation tools. Numerous modeling approaches consider the anodic material dissolution in ECM based on a high resolution of the material (see e.g. [2], [3]). However, these models require computationally expensive remeshing after every time step. Therefore, we propose a novel approach that describes the dissolution process based on effective material parameters (see [5]). Faraday's law of electrolysis provides the evolution of the dissolution level which is described by an internal variable that relates the dissolved volume to a reference volume. The dissolution level in turn controls the effective material parameters. This procedure allows for the simulation of the entire process with a fixed finite element mesh. Moreover, the model considers the full coupling of the thermoelectric boundary value problem to accurately account for the electric current density distribution. The comparison of the model with analytical and experimental reference solutions yields realistic results and, hence, motivates the model's application to predict the surface roughness evolution in a pulsed electrochemical machining process.
Macroscopic modelling of stress driven anisotropic growth in bioengineered tissues
Authors: Lamm Lukas , Holthusen Hagen , Böhm Christian , Jockenhövel Stefan , Reese Stefanie 
Published: December 2021

AbstractWithin this contribution we present a new approach to macroscopically describe stress‐driven volumetric growth occurring in soft tissues. To overcome the limitations of an a‐priori prescribed structure of the growth tensor, the existence of a general growth potential is postulated. Such a potential aims to describe a homeostatic stress state that is ultimately reached as a result of the growth process. Similar to well established methods from the field of visco‐plasticity, we formulate the evolution of the growth related right Cauchy‐Green tensor as a time dependent associative evolution law with respect to the given growth potential. This approach is not restricted to describe either isotropic or anisotropic growth related changes in geometry, but can cover both, which gives the model a flexibility that many other established models are lacking. Besides the main aspects of the theoretical development, we also show numerical examples comparing the newly derived model with a standard formulation of isotropic growth.
Consideration of rubber bushings in a multi‐body simulation by detailed finite element models
Authors: Marter Paul , Daniel Christian , Duvigneau Fabian , Woschke Elmar , Juhre Daniel 
Published: December 2021

AbstractWithin a multi‐body simulation (MBS) a three‐dimensional FE model is employed to represent the nonlinear properties of rubber bushings. This is implemented via a sequential force‐displacement coupling between the two solvers. For a first material modelling approach of the elastomer, the modified Neo Hooke model is used in conjunction with the generalized Maxwell model. Later, however, a physically motivated material model will be used. First results for a single‐mass oscillator are presented and show the general functionality of the coupled approach. Since the use of FE models in MBS causes a significantly higher computational effort, it is necessary to realize the coupling between FEM and MBS as efficient as possible, which is also a future task.
Schur‐type preconditioning of a phase‐field fracture model in mixed form
Authors: Heister Timo , Mang Katrin , Wick Thomas 
Published: December 2021

AbstractIn the context of phase‐field modeling of fractures in incompressible materials, a mixed form of the elasticity equation can overcome possible volume locking effects. The drawback is that a coupled variational inequality system with three unknowns (displacements, pressure and phase‐field) has to be solved, which increases the overall workload. Efficient preconditioning at this point is an indispensable tool. In this work, a problem‐specific iterative solver is proposed leveraging the saddle‐point structure of the displacement and pressure variable. A Schur‐type preconditioner is developed to avoid ill‐conditioning of the phase‐field fracture problem. Finally, we show numerical results of a pressure‐driven benchmark which to confirm the robustness of the solver.
Constitutive artificial neural networks: a general anisotropic constitutive modeling framework utilizing machine learning
Authors: Hillgärtner Markus , Linka Kevin , Abdolazizi Kian P. , Aydin Roland C. , Itskov Mikhail , Cyron Christian J. 
Published: December 2021

AbstractIn this contribution, a novel machine learning architecture for data‐driven modeling of the mechanical constitutive behavior of materials, constitutive artificial neural networks (CANNs) [1], will be introduced. CANNs incorporate basic material modeling fundamentals from continuum mechanics while relying on artificial neural networks for material‐specific relations. Their architecture allows them to process stress‐strain curves and arbitrary additional information (e.g., about the microstructure or manufacturing parameters). With only a low‐to‐moderate amount of training data and training time, they can predict the constitutive behavior of complex nonlinear and anisotropic materials. The ability to utilize additional material‐specific information enables CANNs to predict the mechanical behavior of previously unseen materials if the CANN was sufficiently trained with many similar materials.
Symplectic Partitioned Runge‐Kutta Methods for High‐Order Approximation in Linear‐Quadratic Optimal Control of Hamiltonian Systems
Authors: Herrmann-Wicklmayr Markus , Flaßkamp Kathrin 
Published: December 2021

AbstractSymplectic partitioned Runge‐Kutta (SPRK) methods are known to be a good choice in forward simulations of Hamiltonian systems due to their structure‐preserving properties. Recent works study the application of SPRK methods to nonlinear and linear‐quadratic optimal control problems howing various advantages of these methods compared to standard non‐symplectic integration schemes. Now, our focus is on extending the comparison to SPRK and RK methods of higher orders. For linear‐quadratic optimal control problems, we consider the discrete‐time Riccati feedback as well as the feedforward control implementation. For applications in which computational power or computation time is limited, low sampling rates are of particular interest. Hence we study this case for the n‐fold harmonic oscillator.
Reanalysis for local quantities of interest
Authors: Materna Daniel 
Published: December 2021

AbstractIn this contribution a method for the prediction of the change in a quantity of interest due to structural modifications is considered. The approach is based on a goal‐oriented method by using the primal and dual problems. The method can be used in order to reduce the overall computational cost in the numerical simulation. Furthermore, the proposed method is easily to implement in existing finite element programs, because no derivatives with respect to the design variables are necessary.
Application of variable excitation frequency for amplitude reduction
Authors: Simader Victoria , Holl Helmut J. 
Published: December 2021

AbstractDynamic systems are faced with large vibration amplitudes if they operate near the resonance frequency of the system or while passing through the resonance. With a suitable external excitation a reduction of the amplitude of the oscillation can be achieved. The analysis of a variable excitation frequency was first carried out on the force driven single degree of freedom harmonic oscillator. The influence of various excitation parameters can be seen after a mathematical transformation of the excitation signal. The elimination of the natural frequency of the system from the excitation signal is possible with specially selected parameters. It is demonstrated that suitable numerical values, correlations between the parameters and functions allow to reduce the oscillation of the amplitude of the system if the operation takes place near the resonance frequency and also during the resonance passage. The theoretical assertions are validated with an experimental setup and a parameter identification has been made. In addition a worst case scenario is analysed on the test rig. The developed requirements are extended to force driven harmonic oscillators with multi degree of freedom.
Approximate computational model for shear loaded stiffened composite panels
Authors: Schilling Jakob C. , Mittelstedt Christian 
Published: December 2021

AbstractThe stability behavior is critical for thin‐walled composite structures. This type of structures is for example employed in aircraft, spacecraft and marine vessels, where weight is an important factor in the design. For stiffened panels of, e.g. a fuselage structure, shear is a relevant load case. A new approximate computational model for the local buckling behavior of omega‐stringer‐stiffened panels under shear loading is presented that is based on energy methods. To assess the quality of the derived solution, the results of suitable parameter studies are discussed. In comparison to numerical methods, the new model reduces the computational effort necessary for the preliminary design of omega‐stringer‐stiffened composite panels. Thus, it contributes to increase the performance of structures and consequently reduces the weight of the mentioned applications.
On the Correspondence between Replicator Dynamics and Assignment Flows
Authors: Boll Bastian , Schwarz Jonathan , Schnörr Christoph 
Published: December 2021

AbstractAssignment flows are smooth dynamical systems for data labeling on graphs. Although they exhibit structural similarities with the well‐studied class of replicator dynamics, it is nontrivial to apply existing tools to their analysis. We propose an embedding of the underlying assignment manifold into the interior of a single probability simplex. Under this embedding, a large class of assignment flows are pushed to much higher‐dimensional replicator dynamics. We demonstrate the applicability of this result by transferring a spectral decomposition of replicator dynamics to assignment flows.
Analysis of the remote laser cutting process induced damage in carbon fibre reinforced polymers
Authors: Schmidt Benjamin , Husert Markus , Rose Michael , Zimmermann Martina , Kästner Markus 
Published: December 2021

AbstractIn this contribution a modelling approach for the laser cutting process simulation of carbon fibre reinforced polymers is introduced. The cutting process is modelled in a 3D thermal simulation, the material is modelled layer‐wise orthotropically. For the evaporation of matrix and fibre phase transitions are utilised. The laser spot is modelled with its gaussian distribution as a heat input on the upper side.
Exploring the interplay between cellular development and mechanics in the developing human brain
Authors: Zarzor M. S. , Kaessmair S. , Steinmann P. , Blümcke I. , Budday S. 
Published: December 2021

AbstractThe human brain has a complex structure on both cellular and organ scales. This structure is closely related to the brain's abilities and functions. Disruption of one of the biological processes occurring during brain development on the cellular scale may affect the cortical folding pattern of the brain on the organ scale. However, the link between disruptions in cellular brain development and associated cortical malformation remains largely unknown. From a mechanical perspective, the forces generated during development lead to mechanical instability and, eventually, the mergence of cortical folds. To fully understand mechanism underlying malformations of cortical development, it is key to consider both the events that occur on the cellular scale and the mechanical forces generated on the organ scale. Here we present a computational model describing cellular division and migration on the cellular scale, as well as growth and cortical folding on the tissue or organ scale, in a continuous way by a coupled finite growth and advection‐diffusion model. We introduce the cell density as an independent field controlling the volumetric growth. Furthermore, we formulate a positive relation between cell density and cortical layer stiffness. This allows us to study the influence of the migration velocity, the cell diffusivity, the local stiffness, and the local connectivity of cells on the cortical folding process and mechanical properties during normal and abnormal brain development numerically. We show how an increase in the density of the neurons increases the layer's mechanical stiffness. Moreover, weWe validate our simulation results through the comparison with histological sections of the fetal human brain. The current model aims to be a first step towards providing a reliable platform to systematically evaluate the role of different cellular events on the cortical folding process and vice versa.
Numerical simulation of low cycle fatigue behavior, combining the phase‐field method and the Armstrong‐Frederick model
Authors: Wiegold Tillmann , Aygün Serhat , Klinge Sandra 
Published: December 2021

AbstractThe present work couples the phase field method of fracture to the Armstrong‐Frederick model of plasticity with the kinematic hardening. The chosen approach inherits the advantages of both techniques and is aimed at the study of low cycle fatigue effects in ductile materials. However, the numerical implementation of this promising concept brings with it several challenges, such as the definition of a unique framework for both setups, the derivation of coupled evolution equations, the distinction between tension and compression mode and the development of a computationally efficient algorithm. In the approach developed, the derivation of evolution equations uses the minimum principle of the dissipation potential. This step requires the expression of the dissipation potential of the classic Armstrong‐Frederick model in terms of the internal variable rates by using the Legendre transformation. The model is eventually implemented in the FE‐program and applied in order to investigate the life‐time of the cold‐formed carbon steel and the cold‐formed stainless steel.
Long‐term stability and debonding of cementless implants
Authors: Immel Katharina , Nguyen Vu-Hieu , Haiat Guillaume , Sauer Roger A. 
Published: December 2021

AbstractThis work presents a three‐dimensional FE frictional contact formulation with NURBS‐enriched contact elements for the debonding of partially osseointegrated, cementless implants. The contact model is based on a modified Coulomb's friction law [1] that can model the tangential debonding of partially osseointegrated implants. Here, a smooth transition function between the two friction coefficients is used to model the decrease of friction due to debonding of the implant. The model is applied to simulate the debonding of a hip implant to determine the influence of partial osseointegration on the stability of the implant.
Thermomechanical analysis of actuation mechanism of a microgripper fabricated with direct laser writing
Authors: Huang Wenjie , de Payrebrune Kristin M. 
Published: December 2021

AbstractWith direct laser writing micro structures can be manufactured by solidifying a photo resist when the laser beam triggers a photochemical reaction in the focal voxel. We have used direct laser writing to fabricate a thermally actuated microgripper, which can move its two cantilever like arms to grip micro‐objects. One cantilever consists thereby of two strips with different coefficients of thermal expansion such that both cantilevers bends towards each other for an increasing temperature like a welded bimetal.This work investigates the impact of each cantilever's geometry on the gripping performance of the micro gripper theoretically. The tip deflection of the gripper is calculated by the analytical model of Timoshenko's theory of elasticity. After fabricaiton of the microgripper, its gripping performance is observed under the microscope while heated by a heating element.
On a hybrid approximation concept for self‐excited periodic oscillations of large‐scale dynamical systems
Authors: Kappauf Jonas , Hetzler Hartmut 
Published: December 2021

AbstractWhen approximating periodic solutions in the context of large‐scale dynamical systems involving strong local nonlinearities, efficiency is of special interest. Hence, the literature suggests a combination of two approximation methods for increasing the ratio of computational cost to accuracy. Within this contribution, a combination of Finite Difference and Harmonic Balance method is proposed. Due to the usage of Harmonic Balance it is shown, that the resulting equations only depend on the degrees of freedom that are affected by nonlinear forces. As an application, a self‐excited limit cycle of a chain of oscillators is approximated and results are compared against numerical time integration to highlight qualitative accuracy.
Experimental investigations on rising bubbles in stagnant water in vertical capillaries
Authors: Grünendahl Sabrina , Danila Kevin , Brandner Dean Martin , Ehrhard Peter 
Published: December 2021

AbstractWe investigate how the walls of cylindrical capillaries affect the velocity of rising gas bubbles of various diameters. Of course, as the capillary diameter increases, the velocity of the rising bubble will approach the case of free rising. Such systematic experiments on the bubble rise in capillaries, in which the ratio of bubble diameter and capillary diameter is varied from one towards smaller values, can hardly be found in literature. Experiments within the system water/air have been conducted in stagnant water and will be discussed in this paper.
Macroscopic model for steel fiber reinforced high performance concrete based on unit cell calculations
Authors: Pise Mangesh , Brands Dominik , Schröder Jörg , Gebuhr Gregor , Anders Steffen 
Published: December 2021

AbstractThe influence of reinforced steel fiber on the failure behavior of high performance concrete (HPC) is mainly characterized by the complex fiber‐matrix interaction at microscale. A phenomenological material model is developed for more efficient simulation of the overall material behavior of fiber reinforced HPC. For the calibration of the material parameters and to verify the efficiency of the presented phenomenological material model the simulation results of a virtual experiment using an ellipsoidal RVE and a macroscopic boundary value problem (BVP) are compared.