bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling fluid‐driven fractures for partially saturated porous materials
Authors: Sonntag Alixa , Wagner Arndt , Ehlers Wolfgang 
Published: January 2021

AbstractThis contribution aims to study the influence of the saturation degree on the fracturing process. Therefore, a continuum‐mechanical model for fluid‐driven fracturing in partially saturated porous material is presented on the basis of the Theory of Porous Media and the phase‐field approach to fracture. The material is described on the macroscopic scale as an immiscible mixture of three phases, i.e. a solid phase, representing the solid skeleton, and two fluid phases percolating the pore space. Hereby, capillarity effects between the fluid phases are taken into account. The fracturing process is modelled with a phase‐field approach, characterising a diffuse crack pattern. The crack propagation in the solid skeleton is driven by the pressure field of the injected fluid. Finally, a numerical example showing the coupled process of crack propagation in partially saturated porous materials is discussed.
A higher order fictitious domain method for the Navier–Stokes equations
Authors: Bause Markus , Anselmann Mathias 
Published: January 2021

AbstractWe present a higher order approach for the numerical approximation of the Navier–Stokes equations of incompressible viscous flow on time‐dependent domains. A fictitious domain method using non body‐fitted finite element meshes for immersed and moving boundaries along with cut cell techniques is applied. Higher order discontinuous Galerkin time discretization schemes and inf‐sup stable pairs of finite elements for the discretization in space are further ingredients of the approach.
Experimental Investigation of non‐periodic oscillations in a surface tension driven flow around a bubble
Authors: Tadrous Ebram , Wozniak Günter 
Published: January 2021

AbstractThermocapillary convection around an air bubble under a heated wall is experimentally investigated under gravitational conditions. The flow is basically studied through temperature fluctuation plots near the bubble periphery, which is subjected to an upward flow driving temperature gradient. This study illuminates the thermocapillary‐buoyancy convective flow behaviour within the regime of non‐periodic oscillations. Moreover, the fluid flow is qualitatively categorized according to the transient behaviour of the thermocapillary vortex boundary line around the bubble using the shadowgraph technique. A low viscous silicone oil as test fluid restricts reaching higher temperature gradients to avoid the formation of undesired vapour bubbles. However, pursuing the experiments under high pressures allowed reaching higher temperature gradients in order to achieve the non‐periodic flow regime. Both periodic and chaotic oscillations of the liquid flow around the bubble were recorded. They were distinguished from each other through the periodicity of the visualized thermocapillary vortex boundary line movements. The recording of temperature fluctuations at positions near the bubble during a time period Δt demonstrated the thermocapillary fluid flow behaviour at different Marangoni‐numbers Mg.
Integral jump conditions for singular problems – applied to Debye‐layer phenomena
Authors: Marthaler Philipp G. , Class Andreas G. 
Published: January 2021

AbstractIn numerical simulations boundary layers can be treated as jump conditions inheriting detailed physical effects that emerge inside the thin layer. The presented approach, first applied by Class et al. [3], is used to determine such jump conditions in integral form. It is applied to an electro‐hydrodynamic problem with a Debye‐layer in direct vicinity to a charged solid wall.
Inverse Identification of Material Properties of the Human Eye Using Optical Deformation Measurements
Authors: Muench Stefan , Roellig Mike , Balzani Daniel 
Published: January 2021

AbstractThe aim of the study presented here is the non‐invasive and in‐vivo measurement of material parameters of the eye. For this purpose, we propose a method for the construction of full‐field displacements from 2D deformation contours to enable a fast identification of material parameters, which could be used as advanced diagnostic tool for a broad range of diseases of the human eye. First results are presented here based on virtual test setups which should be confirmed through the use of real medical data in the future.
Influence of lubricant film cavitation on the rotor dynamic system behaviour of an exhaust gas turbocharger rotor
Authors: Ziese Christian , Irmscher Cornelius , Woschke Elmar 
Published: January 2021

AbstractThe vibration behaviour of fast rotating rotors is significantly influenced by the bearing properties. Lubricant film induced excitations can cause sub‐synchronous rotor oscillations known as oil‐whirl and oil‐whip phenomena. The non‐linear bearing properties depend primarily on the lubricant properties, kinematics of bearing partners and especially on the occurrence of cavitation. Outgassing processes lead to a two‐phase flow consisting of gas and oil, which can influence the bearing stiffness and damping respectively and consequently the rotor response behaviour. In this contribution, the oscillations of a semi‐floating ring supported turbocharger rotor are investigated under the influence of lubricant film cavitation. For this purpose, run‐up simulations are carried out under the assumption of mass‐conserving cavitation according to the two‐phase model and compared with measurements. In order to illustrate the influence of outgassing processes, a comparison is made with non‐mass‐conserving cavitation theory according to the assumptions of Half‐Sommerfeld.
Modelling stress‐state dependent nonlocal damage and failure of ductile metals
Authors: Nahrmann Marvin , Matzenmiller Anton 
Published: January 2021

AbstractDamage and failure of ductile metals is highly influenced by the stress state. In fact, void growth takes place under hydrostatic tensile loading and void coalescence leads eventually to ductile failure. A completely different damage mechanism occurs for shear dominated loading that results in void elongation within a narrow shear band. In order to account for both failure mechanisms, a stress state dependent damage model is proposed. The model is based on a continuum damage mechanics approach, whereby nonlinear damage evolution is taken into account. The influence of the stress triaxiality and the LODE parameter on damage initiation and failure is considered by the Hosford‐Coulomb model. Pathological mesh sensitivity is prevented by an integral type nonlocal formulation. Finally, the proposed stress‐state dependent nonlocal damage model is verified by test data for the microalloyed high strength steel HX340LAD for a wide range of stress states.
Statistical Analysis of Missile's Trajectory Deviation Due to Production Errors
Authors: Trzun Zvonko , Vrdoljak Milan , Cajner Hrvoje 
Published: January 2021

AbstractThe paper describes the model for assessing the effect that manufacturing errors have on the missile's trajectory and the position of its impact point. Manufacturing errors are considered to be non‐deterministic variables. One typical error is analyzed: the erroneously manufactured missile's warhead. To test the resulting trajectory deviation, a realistic 3D CAD model of a missile is built and linked to the improved 6DOF model. A simulation using the Monte‐Carlo method shows the resulting dispersion of missile's impact points.
The legacy of Coulomb and generalized laws of friction
Authors: Popova Elena , Popov Valentin L. 
Published: January 2021

AbstractThe simple formulation of “Coulomb's law of friction” which can be found in most textbooks—the force of friction is proportional to the normal force and does not depend on the contact area and velocity—has little to do with the real work of Coulomb. On the contrary, Coulomb found that Amontons' law, as well as the independence of the coefficient of friction on velocity, normal force, contact area and roughness are only a first, very rough approximation. He differentiated between material couples (e.g. metal‐metal), where Amontons' law is a good approximation, and other (wood on metal or wood on wood), where there are significant deviations from Amontons' law. In all cases, however, the dependencies are relatively weak. In contemporary language, we would say they are of logarithmic character: the geometric and loading parameters have to be changed by several orders of magnitude to achieve a change in the coefficient of friction by a factor of two. Coulomb also gives simple two‐term relations, which empirically summarize these experimental findings.
MLMC method to estimate propagation of uncertainties in electromagnetic fields scattered from objects of uncertain shapes
Authors: Litvinenko Alexander , Yucel Abdulkadir , Bagci Hakan , Oppelstrup Jesper , Michielssen Eric , Tempone Raúl 
Published: January 2021

AbstractWe estimate the propagation of uncertainties in electromagnetic wave scattering problems. The computational domain is a dielectric object with uncertain shape. Since classical Monte Carlo (MC) method is too expensive, we suggest to use a modified multilevel Monte Carlo (MLMC) method. This method uses a hierarchy of spatial meshes and optimally balances the statistical and discretisation errors. MLMC performs most of the simulations using low‐fidelity models and only a few simulations using high‐fidelity models. As a result, the final computational cost is becoming significantly smaller.
Simulation of absorption processes in nanoparticle catalysts
Authors: Köhler Maximilian , Junker Philipp , Balzani Daniel 
Published: January 2021

AbstractIn this contribution, we present a novel modeling approach for mass transport problems that connects the microscale with the macroscale. It is based on a proper investigation of the diffusion process in the catalytic pellets from which, after semi‐analytic considerations, a source term for the macroscopic advection‐diffusion process can be identified. For the special case of a spherical catalyst pellet, the parabolic partial differential equation at the microscale can be reduced to a single ordinary differential equation in time through the proposed semi‐analytic approach. After the presentation of our model, we show results for its calibration against the macroscopic response of a mass transport experiment. Based thereon, the effective diffusion parameters of the catalyst pellet can be identified. Furthermore, we test the model's robustness by applying significant noise to virtual experimental datasets.
Analysis of model and data uncertainties for the failure of adhesive bonds in composite materials
Authors: Drieschner Martin , Gruhlke Robert , Petryna Yuri , Eigel Martin , Hömberg Dietmar 
Published: January 2021

AbstractThis study has been performed within the research project MuScaBlaDes “Multi‐scale failure analysis with polymorphic uncertainties for optimal design of rotor blades" as part of the DFG Priority Programme (SPP 1886) “Polymorphic Uncertainty Modelling for the Numerical Design of Structures" started in 2016. Stress concentrations in adhesive bonds of a composite structure influence the structural integrity and can initiate the overall failure. Their numerical prediction always depends on present model and data uncertainties. For that, the development of an efficient numerical model and the role of the quality of data is presented. The assessment of the numerical models is shown by comparing predicted strains to measured ones.
Influence of the geometric nonlinearity on the wave propagation properties of periodic lattice frame structures
Authors: Mellmann Marius , Zhang Chuanzeng 
Published: January 2021

AbstractThe elastic wave propagation and vibration characteristics of periodic lattice frame structures can be tuned by changing the density or the stiffness of the structural components, adding certain local resonators or pre‐deforming some structural members [1, 2]. In this way, it is possible to generate the so‐called band‐gaps, which are certain frequency ranges, in which the propagation of elastic or acoustic waves is prohibited. In this paper, the influence of the geometric nonlinearity on the wave propagation properties of two‐dimensional (2D) periodic lattice frame structures is analyzed.
Analysis of the remote laser cutting process induced damage in carbon fibre reinforced polymers with cutting process simulations
Authors: Schmidt Benjamin , Rose Michael , Zimmermann Martina , Kästner Markus 
Published: January 2021

AbstractRemote laser cutting in carbon fibre reinforced polymers is a promising machining technology, which can reduce the main drawback in laser cutting, the heat affected zone. As the heat affected zone has a strong influence on the mechanical behaviour of the composite, an exact characterisation is a key challenge for the simulation and design of fibre reinforced polymers. In order to reach this goal, a laser cutting process model is introduced. Based on the finite difference method, the heat transport is modelled on a macroscopic scale. The macroscopic material parameters are calculated with a rule of mixture. Matrix and fibre evaporation, which cause the formation of the matrix evaporation zone and the gap, are modelled with phase transitions and an adaption in the rule of mixture.The simulation results are validated with micro‐sections of the cutting gap.
The Virtual Element Method for the numerical homogenization of electro‐mechanical responses
Authors: Böhm Christoph , Hudobivnik Blaž , Marino Michele , Wriggers Peter 
Published: January 2021

AbstractThe virtual element method (VEM) has been attracting interest for applications in micromechanical homogenization. This work aims to introduce and analyze multiphysical formulations in a VEM‐based numerical homogenization scheme. Addressing electromechanical polycrystalline materials, the performance of a VEM‐based approach with respect to FEM‐based approaches is investigated. Results show the outperformance of VEM with respect to FEM models (with the same number of degrees of freedom) on the obtained value of homogenized quantities. The coarse mesh permitted by the VEM rationale, where each grain might represent one element, allows to maintain a low computational cost with a high accuracy.
A Scaled Boundary Approach for Inelasticity of Fibre‐Reinforced Composites
Authors: Eisenträger Johanna , Zhang Junqi , Song Chongmin 
Published: January 2021

AbstractAs versatile materials with elevated mechanical properties, short fibre reinforced composites (SFRCs) are currently used in many applications. To enhance the mechanical properties, e.g. the ductility, or to reduce crack propagation, short fibres are added to a matrix material, such as polymers or concrete. In the case of concrete, for example, the composite might contain additional aggregates as well. Although the addition of fibres improves the mechanical properties in general, it is well‐known that many matrix materials exhibit creep deformations under constant long‐term loads.The contribution at hand discusses a scaled boundary approach to model the inelastic behaviour of SFRCs. To allow for an efficient and automated mesh generation, the scaled boundary finite element method (SBFEM) is used in conjunction with the quadtree/octree decomposition algorithm. Within this framework, the fibres are modelled in a discrete manner, and the mesh of the matrix is generated independently of the fibres. Applying a novel embedding method, the meshes of the matrix and the fibres are combined, which results in a compatible mesh without requiring additional constraints. Furthermore, it is straightforward to combine the discussed techniques with image‐based mesh generation, e.g. based on computed tomography scans. The current contribution presents various 2D and 3D examples illustrating the efficiency and adaptability of the proposed framework.In addition, we present a methodology to incorporate non‐linear constitutive models into the SBFEM. Separate constitutive equations are formulated for the matrix, aggregates, and fibres. Whereas the mechanical behaviour of the aggregates and the fibres can be modelled within the framework of elasticity, one must make use of non‐linear approaches to account for the rate‐dependent inelastic deformation of the matrix under multiaxial stress and deformation states. Overall, this method allows for the simulation of creep in SFRCs, while considering the complex microstructure of these materials in detail. This provides the basis for a realistic estimation of the effect of long‐term loading on SFRC components.
About the influence of neglecting locking effects on the failure behavior at the interface
Authors: Bayat Hamid Reza , Rezaei Shahed , Rajaei Harandi Ali , Brepols Tim , Reese Stefanie 
Published: January 2021

AbstractIn the present work, a novel cohesive discontinuous Galerkin (CDG) method is proposed to model interfacial failure of brittle materials. Before the failure, an incomplete interior penalty Galerkin (IIPG) variant of discontinuous Galerkin (DG) family is applied for the linear elasticity. Once the failure criterion is met, an extrinsic cohesive zone (CZ) model captures the failure behavior of the interface. Through application of the DG method in combination with reduced integration on the boundary terms, the locking problem of the bulk elements is solved as well as a realistic propagation of the crack is obtained. In addition, due to the presence of the DG elements prior to failure, remeshing of the interface during crack propagation is not required for the proposed extrinsic CZ model. Delamination of a composite structure is simulated in a numerical example. Furthermore, the performance of the CDG element formulation in comparison to a conventional intrinsic CZ element is discussed and conclusions are drawn.
Tensile Strength Simulations of Nonwoven Fiber Materials
Authors: Harmening Marc , Marheineke Nicole , Wegener Raimund 
Published: January 2021

AbstractFor airlay manufactured nonwoven materials we present a model which enables efficient tensile strength simulations using virtually generated fiber structure samples. Therefore, we model the fiber structures as truss which yields a family of large‐scale, non‐linear equation systems that has to be solved in order to simulate the elastic material behavior. The assembly and regularization of these non‐linear systems are discussed in this paper.
The maximal angle condition on finite elements: useful or not?
Authors: Apel Thomas , Eckardt Leon , Haubner Christof , Kempf Volker 
Published: January 2021

AbstractThe finite element method may converge in situations where the interpolation error does not; in particular meshes violating the maximal angle condition were discussed in the literature recently. However, there is also an example where the finite element method does not converge to the exact solution of the problem on these types of meshes. With a numerical study we stress that the finite element method converges; it converges to a function which is not the exact solution. A carefully designed a posteriori error estimator indicates this behavior. But a numerical test with the error measure as the difference to a solution on a very fine mesh of the same family leads to completely wrong conclusions: one observes a convergence order.
A first Model of Fatigue Corrosion of a Metal through Hydrogen Embrittlement
Authors: Hofmann Martin , Shi Yuhao , Wallmersperger Thomas 
Published: January 2021

AbstractPredicting the durability of components under mechanical loading combined with environmental conditions leading to corrosion is one of the most challenging tasks in mechanical engineering. Precise predictions are neccesary for lightweight design in transportation due to environmental protection. During corrosion often hydrogen is produced by electrochemical reactions. Hydrogen embrittlement is one of the most feared damage mechanisms for metal constructions leading to early and unexpected failure. Until now predictions are mostly done through costly experiments. In the present research, a first simple simulation model based on the fundamentals of electrochemistry and continuum damage mechanics is developed to couple the damage induced by the mechanical stress with the hydrogen embrittlement. Results of the durability are presented for the case of uniaxial cyclic loading for varying testing frequency.
Electrohydrodynamic‐enhanced internal pipe flows from a One‐Dimensional Turbulence perspective
Authors: Medina Méndez Juan A. , Schmidt Heiko , Bacher Christian , Riebel Ulrich 
Published: January 2021

AbstractThe One‐Dimensional Turbulence (ODT) model is applied for the evaluation of internal pipe flows subject to electrohydrodynamic (EHD) forces. The ODT formulation presented here incorporates the effects of the electrostatic potential energy transfer to the kinetic energy of the flow due to EHD instabilities in the presence of a corona discharge. Results for integral quantities such as the skin friction coefficient Cf and the Nusselt number Nu are obtained from ODT simulations and compared to available experimental data [1,2]. The results demonstrate the capabilities of ODT for simulating EHD flows.
Combined continuum mechanics and molecular dynamics approach for uniaxial deformation of a thermoplastic polymer
Authors: Bauer Christof , Pfaller Sebastian 
Published: January 2021

AbstractA hybrid molecular dynamics (MD)‐continuum mechanics (CM) method for calculating a molecular system of an amorphous polymer under uniaxial tensile load was developed. In this contribution, the operating principle of this method is introduced and applied to a sample system. Furthermore, the practicability of the hybrid MD‐CM approach is examined.
Predeformed geometrically exact beam model for a dynamic‐response prosthesis
Authors: Scheiterer Eduard S. , Leyendecker Sigrid 
Published: January 2021

AbstractClinical trials have shown that the storage and release of energy in prosthetic feet plays a major role in the resulting walking comfort for the patient. In comparison to rigid multi‐axis prosthetic feet, dynamic‐response prosthetic feet show good energy storage and release capabilities and thereby increase the walking comfort of the patient. To accurately simulate such a prosthesis in a gait cycle simulation, its model has to represent the deformation energy as accurately as possible.Based on the theory of predeformed geometrically exact beams [1], this work proposes a model for a carbon spring foot prosthesis, continuing the work from [3]. The model is based on the Össur Vari‐Flex®, which has been non destructively reverse engineered resulting in a CAD representation and various parameters. Additionally, the parameters for density and elasticity and shear modulus were refined with parameter optimisation [4]. The geometrically exact beam model of the prosthesis offers a good representation of the deformation energy for large deformations occurring during the gait cycle while reducing the computational cost. The model's implementation is validated numerically and a brief mesh study is performed.The next step is the consideration of epistemic uncertainty and to investigate its influence on the prediction of the energy storage and release capabilities of the prosthesis.