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Item type:Publication, Access status: without files , Partitioned solution strategies for electro-thermo-mechanical problems applied to the field-assisted sintering technologyPublicationtype: Doctoral Thesis60 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Partitioned coupling strategies for multi-physically coupled radiative heat transfer problems(2015-11-01); ; This article aims to propose new aspects concerning a partitioned solution strategy for multi-physically coupled fields including the physics of thermal radiation. Particularly, we focus on the partitioned treatment of electro-thermo-mechanical problems with an additional fourth thermal radiation field. One of the main goals is to take advantage of the flexibility of the partitioned approach to enable combinations of different simulation software and solvers. Within the frame of this article, we limit ourselves to the case of nonlinear thermoelasticity at finite strains, using temperature-dependent material parameters. For the thermal radiation field, diffuse radiating surfaces and gray participating media are assumed. Moreover, we present a robust and fast partitioned coupling strategy for the fourth field problem. Stability and efficiency of the implicit coupling algorithm are improved drawing on several methods to stabilize and to accelerate the convergence. To conclude and to review the effectiveness and the advantages of the additional thermal radiation field several numerical examples are considered to study the proposed algorithm. In particular we focus on an industrial application, namely the electro-thermo-mechanical modeling of the field-assisted sintering technology.Publicationtype: Journal Article68 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Monolithic and partitioned coupling schemes for thermo-viscoplasticity(2015-08-05); ; ; In this article we investigate a fully, thermo-mechanically coupled viscoplasticity model in view of various numerical aspects. First, we develop the entire system of differential-algebraic equations resulting from the spatially discretized principle of virtual displacements, the principle of virtual temperatures, and the evolution equations of the internal variables provided by the constitutive model. In the time-integration step this system is solved both using a fully monolithic approach based on a Backward-Euler scheme in combination with the Multilevel-Newton algorithm as well as a partitioned approach solving the fully coupled system. The latter is treated by means of a combination of a Backward-Euler method and an accelerated Gauss-Seidel/Multilevel-Newton scheme to solve the resulting system of algebraic equations within each time-integration step. Additionally, we consider a specific treatment of the interpolation between different meshes within the partitioned approach. This is shown for p-version finite elements based on hierarchical shape functions. Finally, it turns out that the specific constitutive model of small-strain thermo-viscoplasticity, which is based on the decomposition into kinematic hardening and energy storing strains, yields a problem-adapted stress algorithm. This allows to reduce the stress algorithm on Gauss-point level to the solution of one scalar equation. Numerical examples serve to elucidate the behavior and properties of the proposed methods.Publicationtype: Journal Article98 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A partitioned solution approach for electro-thermo-mechanical problemsThe purposes of this article are to present new aspects of modeling multi-physically coupled fields, focusing particularly on the partitioned treatment of electro-thermo-mechanical problems. Coupled problems of this kind occur in many industrial applications, such as micro-electrical devices, field-assisted sintering processes or electrical fuses. In this paper, we restrict ourselves to the case of nonlinear thermo-elasticity at finite strains and a heat source resulting from the electrical field. Plasticity effects are not taken into consideration. The objective is to ascertain the coupling of the algorithm relating to the fields involved individually and to demonstrate a global partitioned solution strategy. We also introduce several methods that increase algorithmic stability and accelerate the iterative coupling process. This article aims to present an efficient partitioned coupling strategy for different coupling levels between the fields. To this end, we study the proposed algorithm with the help of several numerical examples ranging from linear to highly nonlinear problems, involving substantial geometric changes and finite strains.Publicationtype: Journal Article138 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Accelerated staggered coupling schemes for problems of thermoelasticity at finite strainsThis paper introduces a fully implicit partitioned coupling scheme for problems of thermoelasticity at finite strains utilizing the -version of the finite element method. The mechanical and the thermal fields are partitioned into symmetric subproblems where algorithmic decoupling has been obtained by means of an isothermal operator-split. Numerical relaxation methods have been implemented to accelerate the convergence of the algorithm. Such methods are well-known from coupled fluid-structure interaction problems leading to highly efficient algorithms. Having studied the influence of three different strategies: polynomial prediction methods, numerical relaxation with constant relaxation coefficients, its dynamic variant with a residual based relaxation coefficient and a variant of a reduced order model - quasi-Newton method, we present several numerical simulations of quasi-static problems investigating the performance of accelerated coupling schemes.Publicationtype: Journal Article139