Christof Eck's research while affiliated with Universität Stuttgart and other places

Publications (71)

Chapter
Thermodynamics is concerned with the definition and relation of notions like temperature, pressure and volume, with the first law of thermodynamics as a basis. The additional notion of entropy is characterized by the second law of thermodynamics. Temperature can be viewed as an integrating factor. Equilibrium conditions can be formulated by means o...
Chapter
The conservation laws of continuum mechanics are motivated with the help of classical point mechanics. Then the conservation laws for mass, momentum, angular momentum in their pointwise form are systematically derived. It is demonstrated how the second law of thermodynamics, the principle of frame difference and symmetries restrict the form of cons...
Chapter
Elements of the theory of partial differential equations that are relevant for the modeling process are discussed. Elliptic, parabolic, hyperbolic equations as well as the Navier-Stokes and the Euler equations are treated. Finally, boundary layer theory is discussed.
Chapter
One-dimensional oscillations are described by linear ordinary differential equations with closed form solutions extendable to forced oscillations. Besides the Lagrangian the Hamiltonian form of mechanics is introduced. Further applications are the motion of space frames (from Chapter 3) and two species models from population dynamics. By means of q...
Chapter
Obstacle and contact problems leading to variational inequalities as well as models for porous media are studied. A main theme is phase transitions appearing in the context of solidification processes. Finally, also free boundary problems in fluid dynamics are considered.
Chapter
Electrical networks and space frames in its stationary state can be described by sets of linear equations of similar structure. This is extendable to alternating current circuits by the use of complex parameters. The set of equations can be written in a form equivalent to a constrained optimization problem, giving rise to a dual form by means of La...
Chapter
Viele Anwendungen in Naturwissenschaften und Technik führen auf Problemstellungen, bei denen die Geometrie des Gebietes, auf dem eine Gleichung gelöst werden soll, a priori unbestimmt ist. Ist eine partielle Differentialgleichung in einem Gebiet zu lösen, von dem ein Teil des Randes unbekannt ist, so spricht man von einem Problem mit freiem Rand.
Chapter
Viele Naturgesetze drücken die Änderung einer Größe als Folge der Wirkung anderer Größen aus. So ist zum Beispiel die Änderung der Geschwindigkeit eines Körpers proportional zu der auf den Körper wirkenden Kraft, aus der Änderung eines elektrischen Feldes erhält man ein Magnetfeld, ein sich änderndes Magnetfeld erzeugt ein elektrisches Feld.
Chapter
Viele einfache Modelle basieren auf linearen Beziehungen zwischen verschiedenen Größen. Problemstellungen mit mehreren Variablen und linearen Beziehungen zwischen diesen Variablen führen auf lineare Gleichungssysteme. Auch kompliziertere Prozesse mit nichtlinearen Beziehungen zwischen den relevanten Parametern lassen sich innerhalb eines für die Pr...
Chapter
Die Thermodynamik befasst sich mit der Untersuchung bestimmter physikalisch beobachtbarer Eigenschaften von Materie, wie zum Beispiel der Temperatur, des Drucks, und des Volumens beziehungsweise der Dichte und deren Beziehungen zueinander. Gemeinsames Merkmal dieser Größen ist es, dass sie die ,,makroskopisch messbare“ Auswirkung von Bewegungen der...
Chapter
In diesem Kapitel werden wir die in der Kontinuumsmechanik aufgetretenen partiellen Differentialgleichungen näher diskutieren. Es werden die Grundzüge der Analysis dieser Gleichungen aufgezeigt, insbesondere mit dem Ziel, Zusammenhänge zwischen den eingesetzten mathematischen Methoden und den Eigenschaften der zugehörigen Anwendungsprobleme zu sehe...
Chapter
In der Kontinuumsmechanik studiert man Prozesse, die auf einer Teilmenge des d–dimensionalen euklidischen Raumes ablaufen. Die relevanten Größen, zum Beispiel die Massendichte, die Temperatur, der Druck, das Geschwindigkeitsfeld, sind an jedem Punkt der Menge definiert. Die Zusammensetzung von Materie wie etwa Wasser, Luft oder Metall aus Atomen od...
Chapter
Mit Modellierung bezeichnet man die Umsetzung konkreter Probleme aus Anwendungswissenschaften wie etwa der Physik, der Technik, der Chemie, der Biologie, den Wirtschaftswissenschaften, oder der Verkehrsplanung in eine wohldefinierte mathematische Aufgabenstellung.
Book
Dieses Lehrbuch bietet eine lebendige und anschauliche Einführung in die mathematische Modellierung von Phänomenen aus den Natur- und Ingenieurwissenschaften. Die Leserin und der Leser lernen mathematische Modelle zu verstehen und selbst herzuleiten und finden gleichzeitig eine Fülle von wichtigen Beispielen für die im Mathematikstudium behandelten...
Article
Mathematical models are the decisive tool to explain and predict phenomena in the natural and engineering sciences. With this book readers will learn to derive mathematical models which help to understand real world phenomena. At the same time a wealth of important examples for the abstract concepts treated in the curriculum of mathematics degrees...
Article
This article presents a fast and accurate adaptive algorithm that numerically solves a two-scale model with continuous inter-scale dependencies. The examined sample two-scale model describes a phase transition of a binary mixture with the evolution of equiaxed dendritic microstructures. It consists of a macroscopic heat equation and a family of mic...
Article
We study contact problems with contact models of normal compliance type, where the compliance function tends to infinity for a given finite interpenetration. Such models are physically more realistic than standard normal compliance models, where the interpenetration is not restricted, because the interpenetration is typically justified by deformati...
Article
We present a phase field model which approximates a one-phase Stefan-like problem with a kinetic condition at the moving boundary, and which models a dissolution and precipitation reaction. The concentration of dissolved particles is variable on one side of the free boundary and jumps across the free boundary to a fixed value given by the constant...
Chapter
Full-text available
Viele Naturgesetze drücken die Änderung einer Größe als Folge der Wirkung anderer Größen aus. So ist zum Beispiel die Änderung der Geschwindigkeit eines Körpers proportional zu der auf den Körper wirkenden Kraft, aus der Änderung eines elektrischen Feldes erhält man ein Magnetfeld, ein sich änderndes Magnetfeld erzeugt ein elektrisches Feld. Die Än...
Article
In der Kontinuumsmechanik studiert man Prozesse, die auf einer Teilmenge des d–dimensionalen euklidischen Raumes ablaufen. Die relevanten Größen, zum Beispiel die Massendichte, die Temperatur, der Druck, das Geschwindigkeitsfeld, sind an jedem Punkt der Menge definiert. Die Zusammensetzung von Materie wie etwa Wasser, Luft oder Metall aus Atomen od...
Chapter
Viele einfache Modelle basieren auf linearen Beziehungen zwischen verschiedenen Größen. Problemstellungen mit mehreren Variablen und linearen Beziehungen zwischen diesen Variablen führen auf lineare Gleichungssysteme. Auch kompliziertere Prozesse mit nichtlinearen Beziehungen zwischen den relevanten Parametern lassen sich innerhalb eines für die Pr...
Article
Viele Anwendungen in Naturwissenschaften und Technik führen auf Problemstellungen, bei denen die Geometrie des Gebietes, auf dem eine Gleichung gelöst werden soll, a priori unbestimmt ist. Ist eine partielle Differentialgleichung in einem Gebiet zu lösen, von dem ein Teil des Randes unbekannt ist, so spricht man von einem Problem mit freiem Rand. Z...
Chapter
In diesem Kapitel werden wir die in der Kontinuumsmechanik aufgetretenen partiellen Differentialgleichungen näher diskutieren. Es werden die Grundzüge der Analysis dieser Gleichungen aufgezeigt, insbesondere mit dem Ziel, Zusammenhänge zwischen den eingesetzten mathematischen Methoden und den Eigenschaften der zugehörigen Anwendungsprobleme zu sehe...
Article
Die Thermodynamik befasst sich mit der Untersuchung bestimmter physikalisch beobachtbarer Eigenschaften von Materie, wie zum Beispiel der Temperatur, des Drucks, und des Volumens beziehungsweise der Dichte und deren Beziehungen zueinander. Gemeinsames Merkmal dieser Größen ist es, dass sie die „makroskopisch messbare“ Auswirkung von Bewegungen der...
Article
We consider a dynamic frictional contact problem between an elastic-visco-plastic body and a foundation. The contact is modelled with a normal damped response condition of such a type that the normal velocity is restricted with unilateral constraint, associated with the Coulomb law in which the coefficient of friction may depend on the velocity. We...
Article
The term electrowetting is commonly used for phenom-ena where shape and wetting behaviour of liquid droplets are changed by the application of electric fields. We develop and analyze a model for electrowetting that combines the Navier-Stokes system for fluid flow, a phase-field model of Cahn-Hilliard type for the movement of the interface, a charge...
Article
We calculate an exact upper bound for the magnitude of the coefficient of friction that ensures the existence of a solution to a static contact problem with Coulomb friction. The approach is based on a general existence result that is valid under the assumption that the coefficient of friction is bounded by a certain constant depending on the const...
Chapter
Full-text available
Mit Modellierung bezeichnet man die Umsetzung konkreter Probleme aus Anwendungswissenschaften wie etwa der Physik, der Technik, der Chemie, der Biologie, den Wirtschaftswissenschaften, oder der Verkehrsplanung in eine wohldefinierte mathematische Aufgabenstellung. Bei der mathematischen Aufgabenstellung kann es sich zum Beispiel um eine Gleichung h...
Chapter
Viele einfache Modelle basieren auf linearen Beziehungen zwischen verschiedenen Größen. Problemstellungen mit mehreren Variablen und linearen Beziehungen zwischen diesen Variablen führen auf lineare Gleichungssysteme. Auch kompliziertere Prozesse mit nichtlinearen Beziehungen zwischen den relevanten Parametern lassen sich innerhalb eines für die Pr...
Chapter
Viele Naturgesetze drücken die Änderung einer Größe als Folge der Wirkung anderer Größen aus. So ist zum Beispiel die Änderung der Geschwindigkeit eines Körpers proportional zu der auf den Körper wirkenden Kraft, aus der Änderung eines elektrischen Feldes erhält man ein Magnetfeld, ein sich änderndes Magnetfeld erzeugt ein elektrisches Feld. Die Än...
Chapter
Die Thermodynamik befasst sich mit der Untersuchung bestimmter physikalisch beobachtbarer Eigenschaften von Materie, wie zum Beispiel der Temperatur, des Drucks, und des Volumens beziehungsweise der Dichte und deren Beziehungen zueinander. Gemeinsames Merkmal dieser Größen ist es, dass sie die „makroskopisch messbare“ Auswirkung von Bewegungen der...
Article
Full-text available
Numerical computations are performed for a recently derived phase field model for the interface between two phases. The rigorous results indicate that solutions to this new phase field model should converge more rapidly than traditional ones to solutions of the corresponding sharp interface (free boundary) formulation for sufficiently small values...
Chapter
In diesem Kapitel werden wir die in der Kontinuumsmechanik aufgetretenen partiellen Differentialgleichungen näher diskutieren. Es werden die Grundzüge der Analysis dieser Gleichungen aufgezeigt, insbesondere mit dem Ziel, Zusammenhänge zwischen den eingesetzten mathematischen Methoden und den Eigenschaften der zugehörigen Anwendungsprobleme zu sehe...
Chapter
Viele Anwendungen in Naturwissenschaften und Technik führen auf Problemstellungen, bei denen die Geometrie des Gebietes, auf dem eine Gleichung gelöst werden soll, a priori unbestimmt ist. Ist eine partielle Differentialgleichung in einem Gebiet zu lösen, von dem ein Teil des Randes unbekannt ist, so spricht man von einem Problem mit freiem Rand. Z...
Chapter
In der Kontinuumsmechanik studiert man Prozesse, die auf einer Teilmenge des d-dimensionalen euklidischen Raumes ablaufen. Die relevanten Größen, zum Beispiel die Massendichte, die Temperatur, der Druck, das Geschwindigkeitsfeld, sind an jedem Punkt der Menge definiert, es wird also angenommen, dass an jedem Punkt „Materie“ vorhanden ist. Die Zusam...
Article
The term electrowetting is commonly used for some techniques to change the shape and wetting behaviour of liquid droplets by the application of electric fields and charges. We developand analyze a model for electrowetting that combines the Navier-Stokes system for fluid flow, a phase-field model of Cahn-Hilliard type for the movement of the interfa...
Article
We present finite element error estimates for discretizations of a phase field model and a two-scale model. Both models describe solidification with equiaxed dendritic microstructure. The two-scale model is a homogenization limit of the phase field model for periodic initial conditions of scale ε > 0 under the assumption of a suitable scaling of ph...
Chapter
Imposed by the crystal lattice, at the surface of a crystal, there exist atomic steps, which separate exposed lattice planes that differ in height by a single lattice spacing. These steps are long-living lattice defects, which make them suitable as a basis for the description of surface morphology on a mesoscopic length scale and thus are an ideal...
Article
Full-text available
We propose a phase field model that approximates its limiting sharp interface model (free boundary problem) up to second order in interface thickness. A broad range of double-well potentials can be utilized so long as the dynamical coefficient in the phase equation is adjusted appropriately. This model thereby assures that computation with particul...
Article
Spiral surface growth is well understood in the limit where motion of the spiral ridge is controlled by the local supersaturation of adatoms in its surrounding. In liquid epitaxial growth, however, spirals can form governed by both, transport of heat as well as solute. We propose for the first time a two-scale model of epitaxial growth which takes...
Article
Full-text available
Our objective is to describe solidification phenomena in alloy systems. In the classical approach, balance equations in the phases are coupled to conditions on the phase boundaries which are modelled as moving hypersurfaces. The Gibbs-Thomson condition ensures that the evolution is consistent with thermodynamics. We present a derivation of that con...
Book
The mathematical analysis of contact problems, with or without friction, is an area where progress depends heavily on the integration of pure and applied mathematics. This book presents the state of the art in the mathematical analysis of unilateral contact problems with friction, along with a major part of the analysis of dynamic contact problems...
Article
The aim of this article is the derivation of a two-scale model that describes the evolution of equiaxed dendritic microstructure in liquid-solid phase transitions of binary mixtures. The approach is based on a phase field model proposed by G. Caginalp and W. Xie [Arch. Ration. Mech. Anal. 142, No. 4, 293–329 (1998; Zbl 0906.73008)]. Assuming a peri...
Article
We study a two-scale phase field model for liquid-solid phase transitions with equiaxed dendritic microstructure in binary mixtures. The model consists of a macroscopic heat equation and microscopic problems that describe the evolution of single equiaxed crystals. It is the formal homogenization limit of a phase field model under the assumption of...
Article
We consider phase field models with the objective of approximating sharp interface models. By using second order asymptotics in the interface thickness parameter, ε, we develop models in which the order ε term is eliminated, suggesting more rapid convergence to the ε = 0 (sharp interface) limit. In addition we use non-smooth potentials with a non-z...
Article
We develop an a posteriori error estimate for boundary element solutions of static contact problems without friction. The presented result is based on an error estimate for linear pseudodifferential equations and on a certain commutator property for pseudodifferential operators. A heuristic extension of the obtained error estimate to frictional con...
Article
By using the fixed point index theory, the author obtains the existence of two positive solutions for a boundary value problem of first-order nonlinear integro-differential equations on an infinite interval in a real Banach space.
Article
Contact problems with friction have many applications in mechanics and represent an important task of applied mathematics. Despite this fact, there are still many open problems. The main reason for this situation is the non-compact, non-monotone and non-smooth character of the friction term. The aim of this survey is both to overview available theo...
Article
We study an iteration for the solution of two{body contact problems without friction based on one-sided contact problems for one body and Neumann problems for the other one. The convergence of this iteration is proved in the continuous setting by reformulating it as a xed point iteration for a contractive operator. Then the application of the metho...
Article
A two-scale model for liquid–solid phase transitions with equiaxed dendritic microstructure in binary material in the case of slow solute diffusion is presented. The model consists of a macroscopic energy transport equation and, for each point of the macroscopic domain, a local cell problem describing the evolution of the microstructure and the mic...
Article
The solvability of a coupled thermo-viscoelastic system including contact and friction is outlined. The nonlinear growth of the viscous, frictional and deformation heat occuring in the system is compensated by a certain superlinear growth of the solution-dependent diffusion coefficients.
Article
The solvability of a coupled thermoviscoelastic contact problem with Coulomb friction is investigated. The heat generated by friction is described by a boundary term of quadratic order. The tensor of thermal conductivity is dependent on the temperature gradient and satisfies a certain growth condition.
Chapter
In many liquid-solid phase transitions, a specific dendritic microstructure of the phase interface is observed. In this contribution we present two-scale models capable to describe the evolution of equiaxed microstructure. The models are based either on a sharp interface model or on a phase field model for phase transitions in binary alloys. In bot...
Article
The variational solution of the nonlinear Signorini contact problem determines also the active contact zone Γ c . If the latter is known, then the elastic field is a solution of a linear mixed boundary value problem in which on Γ c the normal displacement and tangential traction are given, while on the non-contact part the total traction is zer...
Article
Full-text available
A short survey of available existence results for dynamic contact problems, including heat generation and heat transfer, is presented.
Article
A survey about existence theorems both for static and for dynamic signorini contact problems with Coulomb—type friction is presented.
Article
We prove the existence of solutions to the static contact problem with Coulomb friction, provided that the coefficient of friction is small enough. The proof employs the penalty method and a certain smoothing procedure for the friction functional. Using optimal trace estimates for the solutions of the Lamé equations, we calculate an upper bound for...
Article
We present a boundary integral formulation for quasistatic elastoplastic contact with Coulomb friction. The used model is valid for material satisfying a general flow law including hardening in the framework of the theory of small deformations. Our approach is based on a penalization and smoothing of Coulomb friction law, and on a symmetric represe...
Article
A symmetric boundary element method for the static contact problem with Coulomb friction is presented. The method is based on the penalty approximation, a smooth approximation of the Coulomb law of friction and a symmetric discretization of the Steklov–Poincaré operator. The convergence of the proposed algorithm is proved and a numerical example is...
Article
A coupled thermoviscoelastic frictional contact problem is investigated. The contact is modelled by the Signorini condition for the displacement velocities and the friction by the Coulomb law. The heat generated by friction is described by a non-linear boundary condition with at most linear growth. The weak formulation of the problem consists of a...
Article
The existence of solutions to the dynamic contact problem with Coulomb friction for viscoelastic bodies is proved with the use of penalization and regularization methods. The contact condition, which describes the nonpenetrability of mass, is formulated in velocities. The coefficient of friction may depend on the solution but is assumed to be bound...
Article
We present some formulations of the static and dynamic contact problem with friction by means of boundary integral equations, which include domain integrals. After stating the equations of motion and the boundary conditions to the dynamic contact problem, we use a time stepping algorithm to transform this problem into a sequence of static problems,...
Article
The existence of a solution to the dynamic contact problem with Coulomb friction is proved for a particular domain and homogeneous isotropic material. The proof is based on the penalization and regularization methods and on explicit calculation of the solution to a certain auxiliary problem.

Citations

... Models play a crucial role in the scientific process by providing a representation of complex systems, processes, and phenomena. Models help scientists to make predictions, test hypotheses, and gain a deeper understanding of the behavior of these systems [1,2]. By using mathematical models, such as physical, statistical, or simulation models, scientists can study the relationships between variables, estimate uncertainties, and explore scenarios without having to perform expensive or dangerous experiments [3,Ch. ...
... Moreover, it turns out that, apart from differences in boundary conditions and source terms, the mathematical formu- lation of the problem is more or less identical with that of a number of problems in porous medium flow [2], [3] (actually, our problem is a problem in porous medium flow), Hele Shaw flows [9], [10], [14], electrochemical machining [8] and heat conduction (degenerate one-phase Stefan problems) [6], [7], [1]. Since the -2- literature on these problems is now fairly extensive and easily available (e.g. in [ 1 0] , [12], [16] f [24]) there is no need to give here an exhaustive treatment of the problem. ...
... is based on continuum mechanical modelling concepts and comprises two nonlinear equations derived from mass balance considerations and the Reynolds transport theorem, [45,Satz 5.4]; Equation (1.1) models the wetting fluid phase and (1.2) models the nonwetting phase. We briefly sum up the meaning of the appearing entities and touch on a few modelling concepts. ...
... Therefore, currently, continuum mechanical simulations enable engineers to simulate the behavior of solids on much larger time and length scales than employing molecular dynamical simulations. In the present thesis, we aim at the (dynamic) continuum mechanical simulation of a solid's reaction to large external forces basically following the monographs [Cia88,EGK08]. Therefore, in the presented model, all physical quantities, for instance, mass, linear momentum, velocity and energy, are considered as mean values. ...
... Farah et al. [16] proposed a new hybrid scheme which beneficially combines the advantages of segment-based and element-based mortar integration. These contact constraint methods have been combined with discrete numerical methods, such as boundary element method [17][18][19], meshless method [20,21], and finite element method [3,4]. With the application of the finite element method (FEM), the FEM has occurred frequently in contact analysis in the past decades [22][23][24]. ...
... are reaction rates according to mass action law, cf. [3, 14, 45, 53, 55]. More precisely, from these references we recall that provided the stoichiometry of a chemical reaction reads as˜s ...
... The dependence of this approximation of the sharp interface velocity on the choice of µ was only clarified in a further publication [2]. Similar approaches can be found in [76], [43] and [34]. ...
... The physical models describing phase transformations, with or without mechano-chemical coupling, can be classified into two main approaches: i) the two-field approaches [31][32][33][34][35][36][37], in which the mass transport is resolved within each phase separately, with a condition at the interface for mass conservation which induces the interface movement; ii) the one-field approaches in which mass transport and transfer are modelled by a unique equation for the overall system [38][39][40]. Phase field modelling belong to the latter since it is based on a free energy functional defined at every point of the multi-phase systems [41][42][43][44][45][46]. They present great advantages for modelling the evolution of complex 3D microstructures. ...
... Although phase field models are widely used and have many applications, there exists only little work on them in homogenization settings. The earliest work known to the author is on a phase field model for the liquid-solid phase transition of binary mixtures ( [Eck and Knabner, 2002], [Eck, 2004], and [Eck, 2005]). The phase field model under consideration is a generalized Caginalp phase field model and describes the dendritic evolution of microscopic crystals. ...
... We now describe the physical setting of the contact problem and provide its classical formulation. We follow the exposition of the model described in [1,8,23,[36][37][38] and employ the thermoviscoelastic version of the Kelvin-Voigt constitutive law. Thus, the thermomechanical behavior of the material is assumed to be linear while the nonlinear effects occur only in the contact boundary conditions. ...