@phdthesis{Haefner2006,
author = {H{\"a}fner, Stefan},
title = {Grid-based procedures for the mechanical analysis of heterogeneous solids},
doi = {10.25643/bauhaus-universitaet.858},
url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20070830-9185},
school = {Bauhaus-Universit{\"a}t Weimar},
year = {2006},
abstract = {The importance of modern simulation methods in the mechanical analysis of heterogeneous solids is presented in detail. Thereby the problem is noted that even for small bodies the required high-resolution analysis reaches the limits of today's computational power, in terms of memory demand as well as acceptable computational effort. A further problem is that frequently the accuracy of geometrical modelling of heterogeneous bodies is inadequate. The present work introduces a systematic combination and adaption of grid-based methods for achieving an essentially higher resolution in the numerical analysis of heterogeneous solids. Grid-based methods are as well primely suited for developing efficient and numerically stable algorithms for flexible geometrical modeling. A key aspect is the uniform data management for a grid, which can be utilized to reduce the effort and complexity of almost all concerned methods. A new finite element program, called Mulgrido, was just developed to realize this concept consistently and to test the proposed methods. Several disadvantages which generally result from grid discretizations are selectively corrected by modified methods. The present work is structured into a geometrical model, a mechanical model and a numerical model. The geometrical model includes digital image-based modeling and in particular several methods for the theory-based generation of inclusion-matrix models. Essential contributions refer to variable shape, size distribution, separation checks and placement procedures of inclusions. The mechanical model prepares the fundamentals of continuum mechanics, homogenization and damage modeling for the following numerical methods. The first topic of the numerical model introduces to a special version of B-spline finite elements. These finite elements are entirely variable in the order k of B-splines. For homogeneous bodies this means that the approximation quality can arbitrarily be scaled. In addition, the multiphase finite element concept in combination with transition zones along material interfaces yields a valuable solution for heterogeneous bodies. As the formulation is element-based, the storage of a global stiffness matrix is superseded such that the memory demand can essentially be reduced. This is possible in combination with iterative solver methods which represent the second topic of the numerical model. Here, the focus lies on multigrid methods where the number of required operations to solve a linear equation system only increases linearly with problem size. Moreover, for badly conditioned problems quite an essential improvement is achieved by preconditioning. The third part of the numerical model discusses certain aspects of damage simulation which are closely related to the proposed grid discretization. The strong efficiency of the linear analysis can be maintained for damage simulation. This is achieved by a damage-controlled sequentially linear iteration scheme. Finally a study on the effective material behavior of heterogeneous bodies is presented. Especially the influence of inclusion shapes is examined. By means of altogether more than one hundred thousand random geometrical arrangements, the effective material behavior is statistically analyzed and assessed.},
subject = {B-Spline},
language = {en}
}
@misc{Bock2004,
type = {Master Thesis},
author = {Bock, Sebastian},
title = {Approximation mit polynomialen L{\"o}sungen der Lam{\´e}schen Differentialgleichung},
doi = {10.25643/bauhaus-universitaet.640},
url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-6409},
school = {Bauhaus-Universit{\"a}t Weimar},
year = {2004},
abstract = {Grundidee der Arbeit ist es, L{\"o}sungen von Randwertaufgaben durch Linearkombinationen exakter klassischer L{\"o}sungen der Differentialgleichung zu approximieren. Die freien Koeffizienten werden dabei durch die Bestimmung der besten Approximation der Randwerte berechnet. Als Basis der Approximation werden vollst{\"a}ndige orthogonale und nahezu orthogonale Funktionensysteme verwendet. Anhand ausgew{\"a}hlter Beispiele mit Randvorgaben unterschiedlicher Glattheit wird am Beispiel der Kugel die prinzipielle Anwendbarkeit der Methode getestet und hinsichtlich der Entwicklung des Fehlers der N{\"a}herungsl{\"o}sung, der Stabilit{\"a}t des Verfahrens und des numerischen Aufwandes untersucht. Die erhaltenen Resultate geben einen begr{\"u}ndeten Anlass, die Anwendung der Methode als Bestandteil einer hybriden analytisch-numerischen Methode, insbesondere der Verkn{\"u}pfung mit der FEM, weiterzuverfolgen.},
subject = {Legendre-Funktion},
language = {de}
}
@article{Lizounov1997,
author = {Lizounov, P. P.},
title = {Dynamics of solid and deformable Bodies Systems at complex Movements},
doi = {10.25643/bauhaus-universitaet.541},
url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-5410},
year = {1997},
abstract = {Analytical models, describing oscillations of systems of interconnected solid and deformable bodies,making a complex movement in fields of inertia forces and gravitation forces, are resulted. Method of numerical investigation of dynamics of the specified systems, based on sharing of parameter prolongation method, Newton-Kantorovich algorithm, Flocke and Liapunov hteories, is developed. On the basis of constructed analytical models and numerical techniques a new, practically important problems of dynamics of systems, consisting of solid bodies, flexible rods, membranes and soft shells, which make a complex movement in fields of forces of inertia and gravity are solved. The received results are used during designing of responsible elements of structures, making a complex movement, which find application in construction and mechanical engineering.},
subject = {Festk{\"o}rpermechanik},
language = {en}
}
@article{TolokTolokGomenyuk1997,
author = {Tolok, V. A. and Tolok, A. V. and Gomenyuk, S. I.},
title = {The instrumental System of Mechanics Problems Analysis of the deformed Solid Body},
doi = {10.25643/bauhaus-universitaet.536},
url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20111215-5361},
year = {1997},
abstract = {In the abstract proposed is the Instrumental System of mechanics problems analysis of the deformed solid body. It supplies the researcher with the possibility to describe the input data on the object under analyses and the problem scheme based upon the variational principles within one task. The particular feature of System is possibility to describe the information concerning the object of any geometrical shape and the computation sheme according to the program defined for purpose. The Methods allow to compute the tasks with indefinite functional and indefinite geometry of the object (or the set of objects). The System provides the possibility to compute the tasks with indefinite sheme based upon the Finite Element Method (FEM). The restrictions of the System usage are therefore determined by the restrictions of the FEM itself. It contrast to other known programms using FEM (ANSYS, LS-DYNA and etc) described system possesses more universality in defining input data and choosing computational scheme. Builtin is an original Subsytem of Numerical Result Analuses. It possesses the possibility to visualise all numerical results, build the epures of the unknown variables, etc. The Subsystem is approved while solving two- and three-dimensional problems of Elasticiti and Plasticity, under the conditions of Geometrical Unlinearity. Discused are Contact Problems of Statics and Dynamics.},
subject = {Festk{\"o}rpermechanik},
language = {en}
}