bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mathematical Modeling of Coolant Flow in Discontinuous Drilling Processes with Temperature Coupling
Authors: Fast Michael , Mierka Otto , Turek Stefan , Wolf Tobias , Biermann Dirk 
Published: March 2023

AbstractNickel‐based alloys, like Inconel 718, are widely used in industrial applications due to their high‐temperature strength and high toughness. However, machining such alloys is a challenging task because of high thermal loads at the cutting edge and thus extensive tool wear is expected. Consequently, the development of new process strategies is needed. We will consider the discontinuous drilling process with coolant. The main idea is to interrupt the drilling process in order to let the coolant to flow around the cutting edge and to reduce thermal loads. Since measurements inside the borehole are (nearly) impossible, simulations are a key tool to analyze and understand the proposed process.In this paper, a 3D fluid flow simulation model with Q2P1 Finite Elements in combination with the Fictitious Boundary Method is presented to simulate the coolant flow around the drill inside the borehole. The underlying equations are transformed into a rotational frame of reference overcoming the challenges of mesh design for high rotational domains inside the fluid domain. Special treatment of Coriolis forces is developed, that modifies the ‘Pressure Poisson’ Problem in the projection step improving the solver for high angular velocities. To further take high velocities into account, a two‐scale artificial diffusion technique is introduced to stabilize the simulation. Finally, Q1 Finite Elements are used to simulate the heating and cooling processes in both the tool and the coolant during the complete discontinuous drilling process. The simulation is split into a ‘contact’ and a ‘no contact’ phase and a coupling strategy between these phases is developed. FBM is utilized to switch between the two configurations, thus only one unified grid for both configurations is needed. The results are used to gain insight into the discontinuous drilling process and to optimize the process design.
Modeling the moving boundary value problem of electrochemical machining
Authors: van der Velden Tim , Ritzert Stephan , Reese Stefanie , Waimann Johanna 
Published: March 2023

AbstractTwo evolving surfaces define the moving boundary value problem in electrochemical machining. On the side of the work piece, the anodic dissolution yields the evolution of the machined surface. A novel approach for modeling the dissolution process of the anode has recently been proposed by [6], which is based on internal variables and effective material parameters that are inserted into the balance equation of electric charge. Thereby, the resulting distributions of the electric current densities ‐ the driving forces of the dissolution process ‐ are accurately captured without the necessity to adapt the finite element mesh in each time step. On the tool side, an efficient methodology to incorporate the movement of the cathode into the simulation without remeshing had been lacking so far. Thus, we proposed to extend the modeling approach of [6] to model the cathode also based on effective material parameters whilst using a constant finite element mesh (see [7]). The procedure allows for the consideration of arbitrarily complex geometries that additionally may possess differently oriented feed vectors. In this paper, a new anisotropic rule of mixture is put forward. The presented example is restricted to a stationary cathode, but focuses on a detailed investigation of the new methodology and a comparison with existing rules of mixture, which are a key component of the methodology and equivalently applicable to moving boundary value problems.
Fast formation and assembly for spline‐based 3D fictitious domain methods
Authors: Marussig Benjamin 
Published: March 2023

AbstractStandard finite element methods employ an element‐wise assembly strategy. The element's contribution to the system matrix is formed by a loop over quadrature points. This concept is also used in fictitious domain methods, which perform simulations on a simple tensor‐product background mesh cut by a boundary representation that defines the domain of interest.Considering such d‐dimensional background meshes based on splines of degree p with maximal smoothness, Cp−1, the cost of setting up the system matrix is 𝒪(p3d) per degree of freedom. Alternative assembly and formation techniques can significantly reduce this cost. In particular, the combination of (1) sum factorization, (2) weighted quadrature, and (3) row‐based assembly yields a cost of 𝒪(pd+1) for non‐cut background meshes. However, applying this fast approach to cut background meshes is an open challenge since they do not have a tensor‐product structure.This work presents techniques that allow the treatment of cut background meshes and thus the application of fast formation and assembly to fictitious domain methods. First, a discontinuous version of weighted quadrature is presented, which introduces a discontinuity into a cut test function's support. The cut region can be treated separately from the non‐cut counterpart; the latter can be assembled by the fast concepts. A three‐dimensional example investigates the accuracy and efficiency of the proposed concept and demonstrates its speed‐up compared to conventional formation and assembly.
Experimental investigation of carbon long fiber reinforced polyamide 6 exposed to environmental conditions
Authors: Christ Nicolas , Montesano John , Hohe Jörg 
Published: March 2023

AbstractTo enhance the possibilities in lightweight constructions in terms of processability and recyclability, fiber reinforced thermoplastics are a promising class of materials. In this context, the fiber‐matrix interface has a major influence on the mechanical properties of the composite. With polyamide 6 (PA6) being a hygroscopic thermoplastic, the effects of elevated humidity and temperature on the mechanical behavior must be considered [1]. This study aims to characterize the micro‐mechanical material properties of carbon long fiber reinforced PA6 in quasi‐static tensile tests after exposure to elevated temperature and humidity levels. Therefore, the specimens are conditioned in different climates and tested afterwards. In order to determine the initiation and propagation of matrix cracks, interface failure, and fiber fracture, the experiments are conducted on a micro‐scale with an average cross‐section of 0.03 mm2. The damage patterns are captured using optical microscopy and SEM images. The effects of conditioning at various temperature and humidity levels are discussed. The main results are the qualitative description of the degradation of mechanical properties due to hydrothermal effects.
FFT‐based simulation of evolving microstructures utilizing an adapting reduced set of Fourier modes
Authors: Gierden Christian , Waimann Johanna , Svendsen Bob , Reese Stefanie 
Published: March 2023

AbstractThe mechanical behavior of a periodic heterogeneous microstructure may be predicted by using a fast Fourier transform (FFT) based simulation approach. To reduce the computational effort of this method, we introduced a model order reduction (MOR) technique utilizing a reduced set of Fourier modes for the computations in Fourier space. To increase the accuracy of this MOR technique we developed a geometrically adapted sampling pattern for choosing the considered Fourier modes based on the representation of phases within the microstructure. Since the phase distribution of, for example, martensite and austenite in a polycrystalline microstructure evolves with increasing mechanical or thermal loads, the set of considered Fourier modes should also evolve according to the underlying micromechanical fields. We present the accuracy and the adaptability of this adaptive reduced set of Fourier modes by investigating the micromechanical fields of a polycrystal considering such phase transformations.
Mechanical Characterisation of Cables in Different Loading Directions
Authors: Sharma Prateek , Hildebrandt André , Düster Alexander , Diebels Stefan 
Published: March 2023

AbstractThe mechanical characterisation of cables can help improving the production and lifetime of various products, for example a robotic arm. Cables however form a class of composite structures, that is highly anisotropic and dissipates energy due to the reorientation of its constituents which is superimposed by the dissipation due to the deformation of the polymer components. Cables also have a degree of randomness in their structure. Moreover, the stiffness in one loading direction is coupled to the stiffness in another loading direction.In this work, experimental investigations on the mechanical properties of the cables are presented. An experimental setup has been constructed to test the cables in tensile, torsion and the bending directions individually as well as coupled to each other. Free bending tests were conducted where axial forces were compensated during the bending to dissociate the tensile and the bending properties of the cables. To apply larger tensile and torsional loads on cables a commercial testing device was also used. To characterise the influence of bending on torsion, free bending tests were conducted with a combination of torsional load. Thus, a complete mechanical characterisation of a cable is presented.
Remarks on rank‐one convexity and quasiconvexity for planar functions with an additive volumetric–isochoric split
Authors: Martin Robert J. , Voss Jendrik , Sander Oliver , Neff Patrizio 
Published: March 2023

AbstractWe study convexity properties of isotropic energy functions in planar nonlinear elasticity in the context of Morrey's conjecture, which states that rank‐one convexity does not imply quasiconvexity in the two‐dimensional case. Recently, it has been shown that for the special case of isochoric energy functions on GL+(2) = {F ∈ ℝ2×2 | det F > 0}, i.e. for any isotropic function W : GL+(2) → ℝ with W(aF) = W(F) for all a > 0, these two notions of generalized convexity are, in fact, equivalent. Here, we consider the more general case of functions on GL+(2) with an additive volumetric–isochoric split of the form

urn:x-wiley:16177061:media:PAMM202200185:pamm202200185-math-0001

with an isochoric function Wiso on GL+(2) and a function Wvol on (0, ∞). In particular, we investigate the importance of the function

urn:x-wiley:16177061:media:PAMM202200185:pamm202200185-math-0002

and its convexity properties; here, λmax ≥ λmin > 0 are the ordered singular values of the deformation gradient F ∈ GL+(2). This function arises naturally as an “extremal” case in the class of volumetric–isochorically split energies with respect to rank‐one convexity.
Closed‐loop adaptive model predictive control of a bluff body wake
Authors: Gaina Ghiroaga Calin , Morton Chris , Martinuzzi Robert 
Published: March 2023

AbstractA machine learning methodology is outlined to achieve robust closed‐loop feedback control of a bluff body turbulent wake. A Long Short‐Term Memory (LSTM) Neural Network is implemented with Model Predictive Control (MPC) to achieve closed‐loop flow control. The LSTM model is trained using actuation and pressure sensor data to forecast future pressure states. The candidate system is a square cross‐sectional cylinder with two modulated moving surface actuators embedded in the windward face leading corners. The controller performance is tested experimentally for three objective functions: recovery of mean‐base pressure set‐point after perturbation; and minimization of drag or wake fluctuation intensity. An adaptive learning strategy is implemented to adjust the model to new Reynolds number (Re) conditions without user intervention, thereby extending the controller performance and achieving more robust control. The identified minimum drag and wake fluctuation cases are analysed using velocity field data measured with particle image velocimetry.
Reduced order modeling of modular parameter dependent structures based on proper orthogonal decomposition and mesh tying
Authors: Ritzert Stephan , Macek Domen , Simon Jaan-Willem , Reese Stefanie 
Published: March 2023

AbstractA model order reduction technique in combination with mesh tying is used to efficiently simulate many different structures that are assembled from a set of substructures. The stiffness matrices of the substructures are computed separately and assembled into a global stiffness matrix with tied contact formulation. Reducing the degrees of freedom of each substructure with a projection‐based model order reduction technique further decreases the computational time. The mode matrices that project the system into the low‐dimensional subspace are computed for each module separately with proper orthogonal decomposition and the method of snapshots. For the development and optimization of new construction strategies for fiber‐reinforced concrete, many different combinations of the modules have to be tested. The mechanical behavior of these modules depends on a set of parameters. Here the parameters are the fiber directions for transversely isotropic material behavior and parameters that describe the shape of the module. The sensitivity of the model order reduction technique to parameter changes requires a mode adaption technique to obtain reasonable results. Mode matrices for any parameters are computed by interpolating in a tangent space to the Grassmann manifold.
Study on an hp‐Adaptive Finite Element Solver for a Chemo‐Mechanical Battery Particle Model
Authors: Castelli Giuseppe Fabian , Dörfler Willy 
Published: March 2023

AbstractWe consider a Cahn–Hilliard‐type phase‐field model for phase separation and large deformations in battery electrode particles. For the numerical solution we employ an hp‐adaptive finite element solution algorithm coupled to a variable‐step, variable‐order time stepping scheme. Numerical experiments show the adaptive meshing and distribution of the locally varying polynomial degrees of the finite element method. In particular, for a sufficient large range of polynomial degrees we achieve significant computational savings compared to an h‐adaptive algorithm.
Injection molding of semi‐crystalline polymers in a space‐time framework
Authors: Ferrer Fabón Blanca , Alms Jonathan , Behr Marek , Hopmann Christian 
Published: March 2023

AbstractThe challenges in the numerical simulation of the polymer injection molding process are manifold. Such simulation involves a two‐phase flow formulation and the physical modeling of complex material, i.e., molten polymer. This paper presents a complete macroscale simulation approach for the filling stage of injection molding with semi‐crystalline polymers, applied on polypropylene as example. Accurate and efficient results are obtained using a space‐time finite‐element discretization. Heading towards more efficient computations, we search for a reduction of the polymer's physical model, which includes variable viscosity, density, and several crystallization models. The final contribution of the present work is a model sensitivity analysis, which evaluates the relevance of each material model during the filling stage of injection molding.
Objectivity and accuracy enhancement within ANN‐based multiscale material modeling
Authors: Heider Yousef , Sun WaiChing 
Published: March 2023

AbstractNowadays, supervised machine learning (ML) via artificial neural network (ANN) is increasingly applied within multiscale material modeling and homogenization to generate data‐based, physics‐informed material models as an alternative to conventional material models. This application is associated with many benefits, such as increasing of computational efficiency and accuracy. However, the establishment of a reliable data‐based or ML‐based material model requires the availability of a proper and sufficiently large database from small‐scale simulations and appropriate processing of these data as part of the model building steps. In this connection, this contribution discusses the method to generate ML‐based material models, which strictly fulfill a number of restrictions, such as objectivity (or material frame‐indifference) and thermodynamic consistency (second‐law of thermodynamics) for an elasto‐plastic material response. While focusing in this contribution on anisotropic crystal plasticity, the two aforementioned restrictions can be fulfilled via the utilization of informed‐graph NN and the application of data representation in spectral form. The numerical results show that learning the ML model to explicitly predict the plastic strain as an intermediate step not only enhances the fulfillment of thermodynamic consistency but also improves the accuracy of the final prediction.
Aggregated type handling in CoDiPack
Authors: Sagebaum Max , Gauger Nicolas R. 
Published: March 2023

AbstractThe development of algorithmic differentiation (AD) tools focuses mostly on handling floating point types in the target language. Taping optimizations in these tools mostly focus on specific operations like matrix vector products. Aggregated types like std::complex are usually handled by specifying the AD type as a template argument. This approach provides exact results, but prevents the use of expression templates. If AD tools are extended and specialized such that aggregated types can be added to the expression framework, then this will result in reduced memory utilization and improve the timing for applications where aggregated types such as complex number or matrix vector operations are used. Such an integration requires a reformulation of the stored data per expression and a rework of the tape evaluation process. We will demonstrate the overheads on a synthetic benchmark and show the improvement when aggregated types are handled properly by the expression framework of the AD tool.
Modelling of time‐dependent fatigue crack growth of hydrogels
Authors: Liu Dongxu , Ma Songyun , Markert Bernd 
Published: March 2023

AbstractThe service life of hydrogel‐based devices is strongly influenced by the anti‐fatigue capability of hydrogels. While recent advancements in the synthesis of hydrogels have improved their fatigue resistance, the underlying mechanisms that dominate the time‐dependent fatigue crack growth of hydrogels are still poorly understood. In this study, a computational method is developed to predict the fatigue crack of hydrogels. A physics‐based poro‐visco‐hyperelastic model is developed within the framework of the Theory of Porous Media at finite strains to describe the mechanical behaviour of hydrogels. A Bell model‐based chain evolution law is adopted to describe the time‐dependent breaking/reforming kinetics of physical chains. An energy‐based fatigue crack growth model is proposed to predict the fatigue crack growth of hydrogels. The averaged elastic energy density surrounding the crack tip is calculated as the driving force of fatigue crack growth. The effects of viscoelasticity, physical chain kinetics and fluid transport on the fatigue crack growth are analysed. The results indicate that these time‐dependent mechanisms cannot be ignored in predicting the fatigue crack behaviour of hydrogels.
A partitioned computational framework for damage evolution in stress corrosion cracking utilizing phase‐field
Authors: Kandekar Chaitanya , Ravikumar Aravinth , Höche Daniel , Weber Wolfgang E. 
Published: March 2023

AbstractDissolution‐driven stress corrosion cracking is a complicated multi‐physics phenomenon consisting of coupling between mechanical stress and corrosion. In this coupled electro‐chemo‐mechanical problem, the combined effects of mechanical field, localised corrosion and the microstructure with the effects of grain boundaries are investigated. Therein, corrosion kinetics are accelerated by mechanical straining and also affected by the different material properties along the grain boundaries. A phase‐field modelling approach, a method for regularizing sharp interfaces with smooth gradients, is utilized to describe the metal‐electrolyte interface during localized metal dissolution. The current contribution presents a partitioned computational framework, as an extension of recently published works for solving pitting corrosion and stress corrosion cracking at the micro‐scale. In this extension, mechanically assisted corrosion is coupled bi‐directionally and solved on two software instances facilitating simulation at different time scales, using an open‐source coupling software. The performance of the proposed computational framework is demonstrated through various deterioration model system situations in 2D.
Influence of the correlation length on the probabilistic material modeling of short fiber‐reinforced composites on the component level
Authors: Widera Ilona M. , Klatt Eduard , Rauter Natalie 
Published: March 2023

AbstractIn this study, an approach to numerical modeling of short fiber‐reinforced composites is presented. Based on the multi‐scale approach, elastic material parameters are transferred from the mesoscale to the macroscale, while maintaining their stochastic properties. For this, a complete description of the stochastic properties, consisting of mean, standard deviation and correlation structure in the mesoscale is determined. This information provides a basis for the creation of second order Gaussian random fields, which are used for a FEM simulation. An analysis of the numerical simulation, including a comparison with experimental values, shows the influence of the correlation length on the global material behavior. What is more, it can be demonstrated that the standard deviation is a function of the correlation length, while the mean value remains independent of it.
Analysis of viscous incompressible flows of micropolar fluidswith thermal convection and mixed boundary conditions
Authors: Beneš Michal 
Published: March 2023

AbstractThe Navier‐Stokes equations do not take into account the microstructure of the fluid in the sense that they do not consider the angular momentum of small particles of the fluid due to their rotation. The model of micropolar fluid represents a generalization of the well‐established Navier‐Stokes equations, in such a way that it introduces a new kinematic vector field called microrotation (the angular velocity field of rotation of particles) and adds a new vectorial equation, expressing the conservation of the angular momentum. We will be concerned with the initial boundary value problem for the flow of micropolar heat conducting fluids in a two‐dimensional channel with mixed boundary conditions. The considered boundary conditions are of three types: the Dirichlet boundary conditions on the inflow, the Navier type conditions on solid surfaces and Neumann‐type boundary conditions on the outflow of the channel. The homogeneous Dirichlet boundary conditions on solid surfaces for the microrotation is commonly used in practice. However, imposing such condition is doubtful from the physical point of view. For that reason, more general boundary conditions for the microrotation were proposed throughout the engineering literature to take into account the rotation of the microelements on the solid boundary, linking the velocity and microrotation through the so‐called boundary viscosity. The well‐posedness of problems with different types of boundary conditions for microrotation are completely unexplored. The present contribution is devoted to the analysis of the existence and uniqueness of the solution.