TY - JOUR
A1 - Nguyen-Xuan, Hung
A1 - Nguyen, Hiep Vinh
A1 - Bordas, Stéphane Pierre Alain
A1 - Rabczuk, Timon
A1 - Duflot, Marc
T1 - A cell-based smoothed finite element method for three dimensional solid structures
JF - KSCE Journal of Civil Engineering
N2 - This paper extends further the strain smoothing technique in finite elements to 8-noded hexahedral elements (CS-FEM-H8). The idea behind the present method is similar to the cell-based smoothed 4-noded quadrilateral finite elements (CS-FEM-Q4). In CSFEM, the smoothing domains are created based on elements, and each element can be further subdivided into 1 or several smoothing cells. It is observed that: 1) The CS-FEM using a single smoothing cell can produce higher stress accuracy, but insufficient rank and poor displacement accuracy; 2) The CS-FEM using several smoothing cells has proper rank, good displacement accuracy, but lower stress accuracy, especially for nearly incompressible and bending dominant problems. We therefore propose 1) an extension of strain smoothing to 8-noded hexahedral elements and 2) an alternative CS-FEM form, which associates the single smoothing cell issue with multi-smoothing cell one via a stabilization technique. Several numerical examples are provided to show the reliability and accuracy of the present formulation.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
U6 - http://dx.doi.org/10.1007/s12205-012-1515-7
SP - 1230
EP - 1242
ER -
TY - JOUR
A1 - Zhao, Jun-Hua
A1 - Wang, L.
A1 - Jiang, Jin-Wu
A1 - Wang, Z.
A1 - Guo, Wanlin
A1 - Rabczuk, Timon
T1 - A comparative study of two molecular mechanics models based on harmonic potentials
JF - Journal of Applied Physics
N2 - A comparative study of two molecular mechanics models based on harmonic potentials
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
ER -
TY - JOUR
A1 - Bucher, Christian
A1 - Most, Thomas
T1 - A comparison of approximate response functions in structural reliability analysis
JF - Probabilistic Engineering Mechanics
N2 - A comparison of approximate response functions in structural reliability analysis
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2008
SP - 154
EP - 163
ER -
TY - JOUR
A1 - Talebi, Hossein
A1 - Silani, Mohammad
A1 - Bordas, Stéphane Pierre Alain
A1 - Kerfriden, Pierre
A1 - Rabczuk, Timon
T1 - A computational library for multiscale modeling of material failure
JF - Computational Mechanics
N2 - A computational library for multiscale modeling of material failure
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
ER -
TY - JOUR
A1 - Zhuang, Xiaoying
A1 - Huang, Runqiu
A1 - Rabczuk, Timon
A1 - Liang, C.
T1 - A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage
JF - Mathematical Problems in Engineering
N2 - A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
ER -
TY - JOUR
A1 - Zhuang, Xiaoying
A1 - Huang, Runqiu
A1 - Liang, Chao
A1 - Rabczuk, Timon
T1 - A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage
JF - Mathematical Problems in Engineering
N2 - Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES) provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Though CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM) modelling of nonisothermal gas flow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared.
KW - Energiespeicherung
KW - Druckluft
KW - Kaverne
KW - Modellierung
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170428-31726
ER -
TY - JOUR
A1 - Zhang, Chao
A1 - Wang, Cuixia
A1 - Lahmer, Tom
A1 - He, Pengfei
A1 - Rabczuk, Timon
T1 - A dynamic XFEM formulation for crack identification
JF - International Journal of Mechanics and Materials in Design
N2 - A dynamic XFEM formulation for crack identification
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2016
SP - 427
EP - 448
ER -
TY - CHAP
A1 - Brehm, Maik
A1 - Most, Thomas
T1 - A four-node plane EAS-element for stochastic nonlinear materials
N2 - A four-node plane EAS-element for stochastic nonlinear materials
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2003
ER -
TY - JOUR
A1 - Yang, Shih-Wei
A1 - Budarapu, Pattabhi Ramaiah
A1 - Mahapatra, D.R.
A1 - Bordas, Stéphane Pierre Alain
A1 - Zi, Goangseup
A1 - Rabczuk, Timon
T1 - A Meshless Adaptive Multiscale Method for Fracture
JF - Computational Materials Science
N2 - A Meshless Adaptive Multiscale Method for Fracture
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 382
EP - 395
ER -
TY - JOUR
A1 - Most, Thomas
A1 - Bucher, Christian
T1 - A moving least squares weighting function for the element-free Galerkin method which almost fulfills essential boundary conditions
JF - Structural Engineering and Mechanics
N2 - A moving least squares weighting function for the element-free Galerkin method which almost fulfills essential boundary conditions
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2005
SP - 315
EP - 332
ER -
TY - CHAP
A1 - Häfner, Stefan
A1 - Könke, Carsten
T1 - A multigrid finite element method for the mesoscale analysis of concrete
N2 - A multigrid finite element method for the mesoscale analysis of concrete
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2004
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
A1 - Macke, M.
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - A NATURAL NEIGHBOR BASED MOVING LEAST SQUARES APPROACH WITH INTERPOLATING WEIGHTING FUNCTION
N2 - The Element-free Galerkin Method has become a very popular tool for the simulation of mechanical problems with moving boundaries. The internally applied Moving Least Squares approximation uses in general Gaussian or cubic weighting functions and has compact support. Due to the approximative character of this method the obtained shape functions do not fulfill the interpolation condition, which causes additional numerical effort for the imposition of the essential boundary conditions. The application of a singular weighting function, which leads to singular coefficient matrices at the nodes, can solve this problem, but requires a very careful placement of the integration points. Special procedures for the handling of such singular matrices were proposed in literature, which require additional numerical effort. In this paper a non-singular weighting function is presented, which leads to an exact fulfillment of the interpolation condition. This weighting function leads to regular values of the weights and the coefficient matrices in the whole interpolation domain even at the nodes. Furthermore this function gives much more stable results for varying size of the influence radius and for strongly distorted nodal arrangements than classical weighting function types. Nevertheless, for practical applications the results are similar as these obtained with the regularized weighting type presented by the authors in previous publications. Finally a new concept will be presented, which enables an efficient analysis of systems with strongly varying node density. In this concept the nodal influence domains are adapted depending on the nodal configuration by interpolating the influence radius for each direction from the distances to the natural neighbor nodes. This approach requires a Voronoi diagram of the domain, which is available in this study since Delaunay triangles are used as integration background cells. In the numerical examples it will be shown, that this method leads to a more uniform and reduced number of influencing nodes for systems with varying node density than the classical circular influence domains, which means that the small additional numerical effort for interpolating the influence radius leads to remarkable reduction of the total numerical cost in a linear analysis while obtaining similar results. For nonlinear calculations this advantage would be even more significant.
KW - Architektur
KW - CAD
KW - Computerunterstütztes Verfahren
Y1 - 2006
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170327-29943
UR - http://euklid.bauing.uni-weimar.de/ikm2006/index.php_lang=de&what=papers.html
ER -
TY - JOUR
A1 - Most, Thomas
T1 - A natural neighbour-based moving least-squares approach for the element-free Galerkin method
JF - International Journal for Numerical Methods in Engineering
N2 - A natural neighbour-based moving least-squares approach for the element-free Galerkin method
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2007
SP - 224
EP - 252
ER -
TY - JOUR
A1 - Nguyen-Xuan, Hung
A1 - Rabczuk, Timon
A1 - Nguyen-Thanh, Nhon
A1 - Nguyen-Thoi, T.
A1 - Bordas, Stéphane Pierre Alain
T1 - A node-based smoothed finite element method (NS-FEM) for analysis of Reissner-Mindlin plates
JF - Computational Mechanics
N2 - A node-based smoothed finite element method (NS-FEM) for analysis of Reissner-Mindlin plates
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2010
SP - 679
EP - 701
ER -
TY - JOUR
A1 - Jia, Yue
A1 - Zhang, Yongjie
A1 - Rabczuk, Timon
T1 - A Novel Dynamic Multilevel Technique for Image Registration
JF - Computers and Mathematics with Applications
N2 - A Novel Dynamic Multilevel Technique for Image Registration
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
ER -
TY - JOUR
A1 - Nguyen-Tuan, Long
A1 - Lahmer, Tom
A1 - Datcheva, Maria
A1 - Stoimenova, Eugenia
A1 - Schanz, Tom
T1 - A novel parameter identification approach for buffer elements involving complex coupled thermo-hydro-mechanical analyses
JF - Computers and Geotechnics
N2 - A novel parameter identification approach for buffer elements involving complex coupled thermo-hydro-mechanical analyses
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2016
SP - 23
EP - 32
ER -
TY - JOUR
A1 - Kerfriden, Pierre
A1 - Goury, O.
A1 - Rabczuk, Timon
A1 - Bordas, Stéphane Pierre Alain
T1 - A partitioned model order reduction approach to rationalise computational expenses in nonlinear fracture mechanics
JF - Computer Methods in Applied Mechanics and Engineering
N2 - A partitioned model order reduction approach to rationalise computational expenses in nonlinear fracture mechanics
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
SP - 169
EP - 188
ER -
TY - JOUR
A1 - Vu-Bac, N.
A1 - Nguyen-Xuan, Hung
A1 - Chen, Lei
A1 - Lee, C.K.
A1 - Zi, Goangseup
A1 - Zhuang, Xiaoying
A1 - Liu, G.R.
A1 - Rabczuk, Timon
T1 - A phantom-node method with edge-based strain smoothing for linear elastic fracture mechanics
JF - Journal of Applied Mathematics
N2 - This paper presents a novel numerical procedure based on the combination of an edge-based smoothed finite element (ES-FEM) with a phantom-node method for 2D linear elastic fracture mechanics. In the standard phantom-node method, the cracks are formulated by adding phantom nodes, and the cracked element is replaced by two new superimposed elements. This approach is quite simple to implement into existing explicit finite element programs. The shape functions associated with discontinuous elements are similar to those of the standard finite elements, which leads to certain simplification with implementing in the existing codes. The phantom-node method allows modeling discontinuities at an arbitrary location in the mesh. The ES-FEM model owns a close-to-exact stiffness that is much softer than lower-order finite element methods (FEM). Taking advantage of both the ES-FEM and the phantom-node method, we introduce an edge-based strain smoothing technique for the phantom-node method. Numerical results show that the proposed method achieves high accuracy compared with the extended finite element method (XFEM) and other reference solutions.
KW - Finite-Elemente-Methode
KW - Steifigkeit
KW - Bruchmechanik
KW - Riss
Y1 - 2013
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170426-31676
ER -
TY - JOUR
A1 - Döring, R.
A1 - Hoffmeyer, J.
A1 - Seeger, T.
A1 - Vormwald, M.
T1 - A plasticity model for calculating stress–strain sequences under multiaxial nonproportional cyclic loading
JF - Computational Materials Science
N2 - A plasticity model for calculating stress–strain sequences under multiaxial nonproportional cyclic loading
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2003
SP - 587
EP - 596
ER -
TY - JOUR
A1 - Silani, Mohammad
A1 - Ziaei-Rad, S.
A1 - Talebi, Hossein
A1 - Rabczuk, Timon
T1 - A Semi-Concurrent Multiscale Approach for Modeling Damage in Nanocomposites
JF - Theoretical and Applied Fracture Mechanics
N2 - A Semi-Concurrent Multiscale Approach for Modeling Damage in Nanocomposites
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
ER -
TY - JOUR
A1 - Areias, Pedro
A1 - Rabczuk, Timon
A1 - Cesar de Sa, J.M.
A1 - Jorge, R.N.
T1 - A semi-implicit _nite strain shell algorithm using in-plane strains based on least-squares
JF - Computational Mechanics
N2 - A semi-implicit _nite strain shell algorithm using in-plane strains based on least-squares
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
ER -
TY - CHAP
A1 - Döring, R.
A1 - Hoffmeyer, J.
A1 - Seeger, T.
A1 - Vormwald, M.
T1 - A Short Crack Growth Model for the Prediction of Fatigue Lives under Multiaxial Nonproportional Loading
N2 - A Short Crack Growth Model for the Prediction of Fatigue Lives under Multiaxial Nonproportional Loading
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2001
ER -
TY - JOUR
A1 - Talebi, Hossein
A1 - Zi, Goangseup
A1 - Silani, Mohammad
A1 - Samaniego, Esteban
A1 - Rabczuk, Timon
T1 - A simple circular cell method for multilevel finite element analysis
JF - Journal of Applied Mathematics
N2 - A simple multiscale analysis framework for heterogeneous solids based on a computational homogenization technique is presented. The macroscopic strain is linked kinematically to the boundary displacement of a circular or spherical representative volume which contains the microscopic information of the material. The macroscopic stress is obtained from the energy principle between the macroscopic scale and the microscopic scale. This new method is applied to several standard examples to show its accuracy and consistency of the method proposed.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2012
U6 - http://dx.doi.org/10.1155/2012/526846
ER -
TY - JOUR
A1 - Talebi, Hossein
A1 - Zi, Goangseup
A1 - Silani, Mohammad
A1 - Samaniego, Esteban
A1 - Rabczuk, Timon
T1 - A simple circular cell method for multilevel finite element analysis
JF - Journal of Applied Mathematics
N2 - A simple multiscale analysis framework for heterogeneous solids based on a computational homogenization technique is presented. The macroscopic strain is linked kinematically to the boundary displacement of a circular or spherical representative volume which contains the microscopic information of the material. The macroscopic stress is obtained from the energy principle between the macroscopic scale and the microscopic scale. This new method is applied to several standard examples to show its accuracy and consistency of the method proposed.
KW - Finite-Elemente-Methode
KW - Feststoff
Y1 - 2012
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170426-31639
ER -
TY - JOUR
A1 - Nguyen-Thanh, Nhon
A1 - Thai-Hoang, C.
A1 - Nguyen-Xuan, Hung
A1 - Rabczuk, Timon
T1 - A smoothed finite element method for the static and free vibration analysis of shells
JF - Journal of Civil Engineering and Architecture
N2 - A smoothed finite element method for the static and free vibration analysis of shells
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2010
SP - 13
EP - 25
ER -
TY - CHAP
A1 - Nguyen-Thanh, Nhon
A1 - Rabczuk, Timon
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - A SMOOTHED FINITE ELEMENT METHOD FOR THE STATIC AND FREE VIBRATION ANALYSIS OF SHELLS
N2 - A four-node quadrilateral shell element with smoothed membrane-bending based on Mindlin-Reissner theory is proposed. The element is a combination of a plate bending and membrane element. It is based on mixed interpolation where the bending and membrane stiffness matrices are calculated on the boundaries of the smoothing cells while the shear terms are approximated by independent interpolation functions in natural coordinates. The proposed element is robust, computationally inexpensive and free of locking. Since the integration is done on the element boundaries for the bending and membrane terms, the element is more accurate than the MITC4 element for distorted meshes. This will be demonstrated for several numerical examples.
KW - Angewandte Informatik
KW - Angewandte Mathematik
KW - Architektur
KW - Computerunterstütztes Verfahren
KW - Computer Science Models in Engineering; Multiscale and Multiphysical Models; Scientific Computing
Y1 - 2010
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-28777
UR - http://euklid.bauing.uni-weimar.de/ikm2009/paper.html
SN - 1611-4086
ER -
TY - JOUR
A1 - Vu-Bac, N.
A1 - Lahmer, Tom
A1 - Zhuang, Xiaoying
A1 - Nguyen-Thoi, T.
A1 - Rabczuk, Timon
T1 - A software framework for probabilistic sensitivity analysis for computationally expensive models
JF - Advances in Engineering Software
N2 - A software framework for probabilistic sensitivity analysis for computationally expensive models
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2016
SP - 19
EP - 31
ER -
TY - JOUR
A1 - Jiang, Jin-Wu
A1 - Rabczuk, Timon
A1 - Park, Harold S.
T1 - A Stillinger-Weber Potential for Single-Layer Black Phosphorus, and the Importance of Cross-Pucker Interactions for Negative Poisson's Ratio and Edge Stress-Induced Bending
JF - Nanoscale
N2 - The distinguishing structural feature of single-layered black phosphorus is its puckered structure, which leads to many novel physical properties. In this work, we first present a new parameterization of the Stillinger–Weber potential for single-layered black phosphorus. In doing so, we reveal the importance of a cross-pucker interaction term in capturing its unique mechanical properties, such as a negative Poisson's ratio. In particular, we show that the cross-pucker interaction enables the pucker to act as a re-entrant hinge, which expands in the lateral direction when it is stretched in the longitudinal direction. As a consequence, single-layered black phosphorus has a negative Poisson's ratio in the direction perpendicular to the atomic plane. As an additional demonstration of the impact of the cross-pucker interaction, we show that it is also the key factor that enables capturing the edge stress-induced bending of single-layered black phosphorus that has been reported in ab initio calculations.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
U6 - http://dx.doi.org/10.1039/C4NR07341J
ER -
TY - JOUR
A1 - Ghorashi, Seyed Shahram
A1 - Lahmer, Tom
A1 - Bagherzadeh, Amir Saboor
A1 - Zi, Goangseup
A1 - Rabczuk, Timon
T1 - A stochastic computational method based on goal-oriented error estimation for heterogeneous geological materials
JF - Engineering Geology
N2 - A stochastic computational method based on goal-oriented error estimation for heterogeneous geological materials
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2016
ER -
TY - JOUR
A1 - Jiang, Jin-Wu
A1 - Park, Harold S.
A1 - Gall, K.
A1 - Leach, A.
A1 - Rabczuk, Timon
T1 - A Surface Stacking Fault Energy Approach to Predicting Defect Nucleation in Surface-Dominated Nanostructures
JF - Journal of the Mechanics and Physics of Solids
N2 - A Surface Stacking Fault Energy Approach to Predicting Defect Nucleation in Surface-Dominated Nanostructures
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
ER -
TY - JOUR
A1 - Zhao, Jun-Hua
A1 - Jiang, Jin-Wu
A1 - Jia, Yue
A1 - Guo, Wanlin
A1 - Rabczuk, Timon
T1 - A theoretical analysis of cohesive energy between carbon nanotubes, graphene and substrates
JF - Carbon
N2 - Explicit solutions for the cohesive energy between carbon nanotubes, graphene and substrates are obtained through continuum modeling of the van der Waals interaction between them. The dependence of the cohesive energy on their size, spacing and crossing angles is analyzed. Checking against full atom molecular dynamics calculations and available experimental results shows that the continuum solution has high accuracy. The equilibrium distances between the nanotubes, graphene and substrates with minimum cohesive energy are also provided explicitly. The obtained analytical solution should be of great help for understanding the interaction between the nanostructures and substrates, and designing composites and nanoelectromechanical systems.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
U6 - http://dx.doi.org/10.1016/j.carbon.2013.01.041
SP - 108
EP - 119
ER -
TY - JOUR
A1 - Silani, Mohammad
A1 - Talebi, Hossein
A1 - Ziaei-Rad, S.
A1 - Hamouda, A.M.S.
A1 - Zi, Goangseup
A1 - Rabczuk, Timon
T1 - A three dimensional Extended Arlequin Method for Dynamic Fracture
JF - Computational Materials Science
N2 - A three dimensional Extended Arlequin Method for Dynamic Fracture
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 425
EP - 431
ER -
TY - JOUR
A1 - Vu-Bac, N.
A1 - Silani, Mohammad
A1 - Lahmer, Tom
A1 - Zhuang, Xiaoying
A1 - Rabczuk, Timon
T1 - A unified framework for stochastic predictions of Young's modulus of clay/epoxy nanocomposites (PCNs)
JF - Computational Materials Science
N2 - A unified framework for stochastic predictions of Young's modulus of clay/epoxy nanocomposites (PCNs)
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2015
SP - 520
EP - 535
ER -
TY - JOUR
A1 - Msekh, Mohammed Abdulrazzak
A1 - Sargado, M.
A1 - Jamshidian, M.
A1 - Areias, Pedro
A1 - Rabczuk, Timon
T1 - ABAQUS implementation of phase_field model for brittle fracture
JF - Computational Materials Science
N2 - ABAQUS implementation of phase_field model for brittle fracture
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 472
EP - 484
ER -
TY - JOUR
A1 - Jiang, Jin-Wu
A1 - Wang, Bing-Shen
A1 - Rabczuk, Timon
T1 - Acoustic and breathing phonon modes in bilayer graphene with Moire-acute patterns
JF - Applied Physics Letters
N2 - The lattice dynamics properties are investigated for twisting bilayer graphene. There are big jumps for the inter-layer potential at twisting angle θ=0° and 60°, implying the stability of Bernal-stacking and the instability of AA-stacking structures, while a long platform in [8,55]° indicates the ease of twisting bilayer graphene in this wide angle range. Significant frequency shifts are observed for the z breathing mode around θ=0° and 60°, while the frequency is a constant in a wide range [8,55]°. Using the z breathing mode, a mechanical nanoresonator is proposed to operate on a robust resonant frequency in terahertz range.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2012
U6 - http://dx.doi.org/10.1063/1.4735246
ER -
TY - THES
A1 - Luther, Torsten
T1 - Adaptation of atomistic and continuum methods for multiscale simulation of quasi-brittle intergranular damage
N2 - The numerical simulation of damage using phenomenological models on the macroscale was state of the art for many decades. However, such models are not able to capture the complex nature of damage, which simultaneously proceeds on multiple length scales. Furthermore, these phenomenological models usually contain damage parameters, which are physically not interpretable. Consequently, a reasonable experimental determination of these parameters is often impossible. In the last twenty years, the ongoing advance in computational capacities provided new opportunities for more and more detailed studies of the microstructural damage behavior. Today, multiphase models with several million degrees of freedom enable for the numerical simulation of micro-damage phenomena in naturally heterogeneous materials. Therewith, the application of multiscale concepts for the numerical investigation of the complex nature of damage can be realized. The presented thesis contributes to a hierarchical multiscale strategy for the simulation of brittle intergranular damage in polycrystalline materials, for example aluminum. The numerical investigation of physical damage phenomena on an atomistic microscale and the integration of these physically based information into damage models on the continuum meso- and macroscale is intended. Therefore, numerical methods for the damage analysis on the micro- and mesoscale including the scale transfer are presented and the transition to the macroscale is discussed. The investigation of brittle intergranular damage on the microscale is realized by the application of the nonlocal Quasicontinuum method, which fully describes the material behavior by atomistic potential functions, but reduces the number of atomic degrees of freedom by introducing kinematic couplings. Since this promising method is applied only by a limited group of researchers for special problems, necessary improvements have been realized in an own parallelized implementation of the 3D nonlocal Quasicontinuum method. The aim of this implementation was to develop and combine robust and efficient algorithms for a general use of the Quasicontinuum method, and therewith to allow for the atomistic damage analysis in arbitrary grain boundary configurations. The implementation is applied in analyses of brittle intergranular damage in ideal and nonideal grain boundary models of FCC aluminum, considering arbitrary misorientations. From the microscale simulations traction separation laws are derived, which describe grain boundary decohesion on the mesoscale. Traction separation laws are part of cohesive zone models to simulate the brittle interface decohesion in heterogeneous polycrystal structures. 2D and 3D mesoscale models are presented, which are able to reproduce crack initiation and propagation along cohesive interfaces in polycrystals. An improved Voronoi algorithm is developed in 2D to generate polycrystal material structures based on arbitrary distribution functions of grain size. The new model is more flexible in representing realistic grain size distributions. Further improvements of the 2D model are realized by the implementation and application of an orthotropic material model with Hill plasticity criterion to grains. The 2D and 3D polycrystal models are applied to analyze crack initiation and propagation in statically loaded samples of aluminum on the mesoscale without the necessity of initial damage definition.
N2 - Strukturmechanische Ermüdungs- und Lebensdaueranalysen basieren meist auf der Anwendung phänomenologischer Modelle der Schädigungs- und Bruchmechanik zur numerischen Simulationen des makroskopischen Schädigungsverhaltens. Ausgehend von einer definierten Anfangsschädigung sind diese Modelle nicht in der Lage, die tatsächlichen Vorgänge der Rissinitiierung und unterschiedlichen Rissausbreitung zu erfassen. Eine physikalische Interpretation der phänomenologisch eingeführten Schädigungsparameter ist oftmals nicht möglich und deren experimentelle Bestimmung schwierig. Die Berücksichtigung des mikrostrukturellen Aufbaus von Materialien in numerischen Modellen der Schädigungs- und Bruchmechanik bietet neue Möglichkeiten, die für die Rissinitiierung und Rissausbreitung ursächlichen physikalischen Phänomene abzubilden. Zunehmende Erkenntnisse über gleichzeitig auftretende Mikro- und Makroschädigungsvorgänge resultieren in verbesserten numerischen Modellen, mit denen aufwändige und kostenintensive Experimente in der Materialentwicklung zum Teil ersetzt werden können. In Kenntnis einer Vielfalt von unterschiedlichen Schädigungsphänomenen in technischen Materialien fokussiert die vorliegende Dissertation auf die Entwicklung und Verbesserung numerischer Methoden der Atomistik und der Kontinuumsmechanik zur Mehrskalenuntersuchung quasi-spröder Korngrenzenschädigung in polykristallinen Werkstoffen, z.B. Aluminium. Die kombinierte Anwendung dieser Methoden ist Teil eines hierarchischen Mehrskalenansatzes zur Integration des physikalisch beschriebenen Materialverhaltens der Atomistik in ein ingenieurmäßiges Kontinuumsschädigungsmodell. Ziel der Dissertation ist die Entwicklung einer Methodik, die es erlaubt, den Verlust atomarer Bindungen als physikalische Ursache spröder Schädigung zu simulieren und Ergebnisse aus diesen atomistischen Mikroskalen-Simulationen zur Parametrisierung von kohäsiven Materialmodellen der Kontinuumsmechanik zu nutzen. Diese beschreiben den intergranularen Sprödbruch in heterogenen Polykristallmodellen der Mesoskala. Der Einfluss der Heterogenität wird in nichtlinearen Finite-Elemente-Simulationen durch explizite Abbildung der Kornstruktur im mesoskopischen Polykristallmodell berücksichtigt. Durch den Einsatz des kohäsiven Interface-Gesetzes erlaubt das auf der Mesoskala angewandte Kontinuumsmodell die Simulation spröder Korngrenzenschädigung in statisch belasteten 2D und 3D Modellen ohne die Notwendigkeit der Definition einer Anfangsschädigung, wie dies in klassischen Modellen der linear-elastischen Bruchmechanik notwendig ist. Zur effizienten Realisierung der atomistischen Mikroskalen-Simulationen wird eine Implementation der nichtlokalen 3D Quasikontinuumsmethode angewandt. Diese Methode basiert auf einem atomistischen Ansatz und beschreibt das Materialverhalten auf Grundlage atomarer Bindungskräfte. In Modellgebieten mit gleichmäßigem Verformungsfeld werden kinematische Kopplungen atomarer Freiheitsgrade eingeführt, sodass sich die Zahl unabhängiger Freiheitsgrade stark reduziert. Deren effizienter Einsatz erlaubt Simulationen an größeren Modellen ohne Kopplung mit kontinuumsmechanischen Methoden. Eine verbesserte Vernetzung, ein robuster Optimierungsalgorithmus und die vorgenommene Parallelisierung machen die implementierte nichtlokale 3D Quasikontinuumsmethode zu einem effizienten Werkzeug für die robuste Simulation von physikalischen Schädigungsphänomenen in beliebigen atomistischen Konfigurationen. In quasistatischen Simulationen wird eine deutliche Beschleunigung gegenüber der Methode der Gitterstatik bei vergleichbarer Qualität der Ergebnisse erreicht.
T2 - Weiterentwicklung numerischer Methoden der Atomistik und Kontinuumsmechanik zur Multiskalen-Simulation quasi-spröder intergranularer Schädigung
T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2010,2
KW - Mechanik
KW - Computersimulation
KW - Mikro-Scale
KW - Meso-Scale
KW - Polykristall
KW - intergranular damage
KW - atomistic simulation methods
KW - continuum mechanics
KW - quasicontinuum method
KW - scale transition
Y1 - 2010
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20101101-15245
ER -
TY - CHAP
A1 - Unger, Jörg F.
A1 - Most, Thomas
A1 - Bucher, Christian
A1 - Könke, Carsten
T1 - Adaptation of the natural element method for crack growth simulations
N2 - Adaptation of the natural element method for crack growth simulations
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2004
ER -
TY - JOUR
A1 - Eckardt, Stefan
A1 - Könke, Carsten
T1 - Adaptive damage simulation of concrete using heterogeneous multiscale models
JF - Journal of Algorithms & Computational Technology
N2 - Adaptive damage simulation of concrete using heterogeneous multiscale models
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2008
SP - 275
EP - 297
ER -
TY - CHAP
A1 - Pham, Hoang Anh
T1 - Adaptive excitation for selective sensitivity-based structural identification
N2 - Adaptive excitation for selective sensitivity-based structural identification
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - CHAP
A1 - Pham, Hoang Anh
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - ADAPTIVE EXCITATION FOR SELECTIVE SENSITIVITY-BASED STRUCTURAL IDENTIFICATION
N2 - Major problems of applying selective sensitivity to system identification are requirement of precise knowledge about the system parameters and realization of the required system of forces. This work presents a procedure which is able to deriving selectively sensitive excitation by iterative experiments. The first step is to determine the selectively sensitive displacement and selectively sensitive force patterns. These values are obtained by introducing the prior information of system parameters into an optimization which minimizes the sensitivities of the structure response with respect to the unselected parameters while keeping the sensitivities with respect to the selected parameters as a constant. In a second step the force pattern is used to derive dynamic loads on the tested structure and measurements are carried out. An automatic control ensures the required excitation forces. In a third step, measured outputs are employed to update the prior information. The strategy is to minimize the difference between a predicted displacement response, formulated as function of the unknown parameters and the measured displacements, and the selectively sensitive displacement calculated in the first step. With the updated values of the parameters a re-analysis of selective sensitivity is performed and the experiment is repeated until the displacement response of the model and the actual structure are conformed. As an illustration a simply supported beam made of steel, vibrated by harmonic excitation is investigated, thereby demonstrating that the adaptive excitation can be obtained efficiently.
KW - Architektur
KW - CAD
KW - Computerunterstütztes Verfahren
Y1 - 2006
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170327-30015
UR - http://euklid.bauing.uni-weimar.de/ikm2006/index.php_lang=de&what=papers.html
ER -
TY - THES
A1 - Eckardt, Stefan
T1 - Adaptive heterogeneous multiscale models for the nonlinear simulation of concrete
N2 - The nonlinear behavior of concrete can be attributed to the propagation of microcracks within the heterogeneous internal material structure. In this thesis, a mesoscale model is developed which allows for the explicit simulation of these microcracks. Consequently, the actual physical phenomena causing the complex nonlinear macroscopic behavior of concrete can be represented using rather simple material formulations. On the mesoscale, the numerical model explicitly resolves the components of the internal material structure. For concrete, a three-phase model consisting of aggregates, mortar matrix and interfacial transition zone is proposed. Based on prescribed grading curves, an efficient algorithm for the generation of three-dimensional aggregate distributions using ellipsoids is presented. In the numerical model, tensile failure of the mortar matrix is described using a continuum damage approach. In order to reduce spurious mesh sensitivities, introduced by the softening behavior of the matrix material, nonlocal integral-type material formulations are applied. The propagation of cracks at the interface between aggregates and mortar matrix is represented in a discrete way using a cohesive crack approach. The iterative solution procedure is stabilized using a new path following constraint within the framework of load-displacement-constraint methods which allows for an efficient representation of snap-back phenomena. In several examples, the influence of the randomly generated heterogeneous material structure on the stochastic scatter of the results is analyzed. Furthermore, the ability of mesoscale models to represent size effects is investigated. Mesoscale simulations require the discretization of the internal material structure. Compared to simulations on the macroscale, the numerical effort and the memory demand increases dramatically. Due to the complexity of the numerical model, mesoscale simulations are, in general, limited to small specimens. In this thesis, an adaptive heterogeneous multiscale approach is presented which allows for the incorporation of mesoscale models within nonlinear simulations of concrete structures. In heterogeneous multiscale models, only critical regions, i.e. regions in which damage develops, are resolved on the mesoscale, whereas undamaged or sparsely damage regions are modeled on the macroscale. A crucial point in simulations with heterogeneous multiscale models is the coupling of sub-domains discretized on different length scales. The sub-domains differ not only in the size of the finite elements but also in the constitutive description. In this thesis, different methods for the coupling of non-matching discretizations - constraint equations, the mortar method and the arlequin method - are investigated and the application to heterogeneous multiscale models is presented. Another important point is the detection of critical regions. An adaptive solution procedure allowing the transfer of macroscale sub-domains to the mesoscale is proposed. In this context, several indicators which trigger the model adaptation are introduced. Finally, the application of the proposed adaptive heterogeneous multiscale approach in nonlinear simulations of concrete structures is presented.
N2 - Das nichtlineare Materialverhalten von Beton ist durch die Entwicklung von Mikrorissen innerhalb der heterogenen Materialstruktur gekennzeichnet. In dieser Arbeit wird ein Mesoskalenmodell entwickelt, welches die einzelnen Bestandteile der Materialstruktur explizit auflöst und somit die Simulation dieser Mikrorisse erlaubt. Dadurch können die wirklichen physikalischen Vorgänge, welche das komplexe nichtlineare Verhalten von Beton verursachen, durch relativ einfache Materialformulierungen abgebildet werden. Für Beton wird auf der Mesoskala ein 3-Phasenmodell vorgeschlagen, bestehend aus groben Zuschlägen, Mörtelmatrix und Übergangszone zwischen Zuschlag und Matrix. In diesem Zusammenhang wird ein effizienter Algorithmus vorgestellt, welcher ausgehend von einer gegebenen Sieblinie dreidimensionale Kornstrukturen mittels Ellipsoiden simuliert. Im Mesoskalenmodell wird das Zugversagen der Mörtelmatrix durch einen Kontinuumsansatz beschrieben. Um Netzabhängigkeiten, welche durch das Entfestigungsverhalten des Materials hervorgerufen werden, zu reduzieren, kommen nichtlokale Materialformulierungen zum Einsatz. Risse innerhalb der Übergangszone zwischen Zuschlag und Matrix werden, basierend auf einem kohäsiven Modell, mittels eines diskreten Rissansatzes abgebildet. Die Verwendung einer neuen Nebenbedingung innerhalb der Last-Verschiebungs-Zwangsmethode führt zu einer Stabilisierung des iterativen Lösungverfahrens, so dass eine effiziente Simulation von Snap-back Phänomenen möglich wird. Anhand von Beispielen wird gezeigt, dass Mesoskalenmodelle die stochastische Streuung von Ergebnissen und Maßstabseffekte abbilden können. Da auf der Mesoskala die Diskretisierung der inneren Materialstruktur erforderlich ist, steigt im Vergleich zu Simulationen auf der Makroskala der numerische Aufwand erheblich. Aufgrund der Komplexität des numerischen Modells sind Mesoskalensimulationen in der Regel auf kleine Probekörper beschränkt. In dieser Arbeit wird ein adaptiver heterogener Mehrskalenansatz vorgestellt, welcher die Verwendung von Mesoskalenmodellen in nichtlinearen Simulationen von Betonstrukturen erlaubt. In heterogenen Mehrskalenmodellen werden nur kritische Bereiche auf der Mesoskala aufgelöst, während ungeschädigte Bereiche auf der Makroskala abgebildet werden. Ein wichtiger Aspekt in Simulationen mit heterogenen Mehrskalenmodellen ist die Kopplung der auf unterschiedlichen Längenskalen diskretisierten Teilgebiete. Diese unterscheiden sich nicht nur in der Größe der finiten Elemente sondern auch in der Beschreibung des Materials. Verschiedene Methoden zur Kopplung nicht übereinstimmender Vernetzungen - Kopplungsgleichungen, die Mortar-Methode und die Arlequin-Methode - werden untersucht und ihre Anwendung in heterogenen Mehrskalenmodellen wird gezeigt. Ein weiterer wichtiger Aspekt ist die Bestimmung kritischer Regionen. Eine adaptive Lösungsstrategie wird entwickelt, welche die Umwandlung von Makroskalengebieten auf die Mesoskala erlaubt. In diesem Zusammenhang werden Indikatoren vorgestellt, die eine Modellanpassung auslösen. Anhand nichtlinearer Simulationen von Betonstrukturen wird die Anwendung des vorgestellten adaptiven heterogenen Mehrskalenansatzes demonstriert.
T2 - Adaptive heterogene Mehrskalenmodelle zur nichtlinearen Simulation von Beton
T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2010,1
KW - Beton
KW - Mehrskalenanalyse
KW - Finite-Elemente-Methode
KW - Nichtlineare Finite-Elemente-Methode
KW - Schadensmechanik
KW - Mehrskalenmodell
KW - Adaptives Verfahren
KW - concrete
KW - multiscale method
KW - finite element method
KW - continuum damage mechanics
KW - adaptive simulation
Y1 - 2009
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20100317-15023
ER -
TY - THES
A1 - Budarapu, Pattabhi Ramaiah
T1 - Adaptive multiscale methods for fracture
T1 - Adaptive Multiskalen-Methoden zur Modellierung von Materialversagen
N2 - One major research focus in the Material Science and Engineering Community in the past decade has been to obtain a more fundamental understanding on the phenomenon 'material failure'. Such an understanding is critical for engineers and scientists developing new materials with higher strength and toughness, developing robust designs against failure, or for those concerned with an accurate estimate of a component's design life. Defects like cracks and dislocations evolve at
nano scales and influence the macroscopic properties such as strength, toughness and ductility of a material. In engineering applications, the global response of the system is often governed by the behaviour at the smaller length scales. Hence, the sub-scale behaviour must be computed accurately for good predictions of the full scale behaviour.
Molecular Dynamics (MD) simulations promise to reveal the fundamental mechanics of material failure by modeling the atom to atom interactions. Since the atomistic dimensions are of the order of Angstroms ( A), approximately 85 billion atoms are required to model a 1 micro- m^3 volume of Copper. Therefore, pure atomistic models are prohibitively expensive with everyday engineering computations involving macroscopic cracks and shear bands, which are much larger than the atomistic length and time scales. To reduce the computational effort, multiscale methods are required, which are able to couple a continuum description of the structure with an atomistic description. In such paradigms, cracks and dislocations are explicitly modeled at the atomistic scale, whilst a self-consistent continuum model elsewhere.
Many multiscale methods for fracture are developed for "fictitious" materials based on "simple" potentials such as the Lennard-Jones potential. Moreover, multiscale methods for evolving cracks are rare. Efficient methods to coarse grain the fine scale defects are missing. However, the existing multiscale methods for fracture do not adaptively adjust the fine scale domain as the crack propagates. Most methods, therefore only "enlarge" the fine scale domain and therefore drastically increase computational cost. Adaptive adjustment requires the fine scale domain to be refined and coarsened. One of the major difficulties in multiscale methods for fracture is to up-scale fracture related material information from the fine scale to the coarse scale, in particular for complex crack problems. Most of the existing approaches therefore were applied to examples with comparatively few macroscopic cracks.
Key contributions
The bridging scale method is enhanced using the phantom node method so that cracks can be modeled at the coarse scale. To ensure self-consistency in the bulk, a virtual atom cluster is devised providing the response of the intact material at the coarse scale. A molecular statics model is employed in the fine scale where crack propagation is modeled by naturally breaking the bonds. The fine scale and coarse scale models are coupled by enforcing the displacement boundary conditions on the ghost atoms. An energy criterion is used to detect the crack tip location. Adaptive refinement and coarsening schemes are developed and implemented during the crack propagation. The results were observed to be in excellent agreement with the pure atomistic simulations. The developed multiscale method is one of the first adaptive multiscale method for fracture.
A robust and simple three dimensional coarse graining technique to convert a given atomistic region into an equivalent coarse region, in the context of multiscale fracture has been developed. The developed method is the first of its kind. The developed coarse graining technique can be applied to identify and upscale the defects like: cracks, dislocations and shear bands. The current method has been applied to estimate the equivalent coarse scale models of several complex fracture patterns arrived from the pure atomistic simulations. The upscaled fracture pattern agree well with the actual fracture pattern. The error in the potential energy of the pure atomistic and the coarse grained model was observed to be acceptable.
A first novel meshless adaptive multiscale method for fracture has been developed. The phantom node method is replaced by a meshless differential reproducing kernel particle method. The differential reproducing kernel particle method is comparatively more expensive but allows for a more "natural" coupling between the two scales due to the meshless interpolation functions. The higher order continuity is also beneficial. The centro symmetry parameter is used to detect the crack tip location. The developed multiscale method is employed to study the complex crack propagation. Results based on the meshless adaptive multiscale method were observed to be in excellent agreement with the pure atomistic simulations.
The developed multiscale methods are applied to study the fracture in practical materials like Graphene and Graphene on Silicon surface. The bond stretching and the bond reorientation were observed to be the net mechanisms of the crack growth in Graphene. The influence of time step on the crack propagation was studied using two different time steps. Pure atomistic simulations of fracture in Graphene on Silicon surface are presented. Details of the three dimensional multiscale method to study the fracture in Graphene on Silicon surface are discussed.
T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2015,1
KW - Material
KW - Strukturmechanik
KW - Materialversagen
KW - material failure
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20150507-23918
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
T1 - Adaptive response surface approach for reliability analysis using advanced meta-models
N2 - Adaptive response surface approach for reliability analysis using advanced meta-models
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2007
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
T1 - Adaptive response surface approach using artificial neural networks and Moving Least Squares
N2 - Adaptive response surface approach using artificial neural networks and Moving Least Squares
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - ADAPTIVE RESPONSE SURFACE APPROACH USING ARTIFICIAL NEURAL NETWORKS AND MOVING LEAST SQUARES
N2 - In engineering science the modeling and numerical analysis of complex systems and relations plays an important role. In order to realize such an investigation, for example a stochastic analysis, in a reasonable computational time, approximation procedure have been developed. A very famous approach is the response surface method, where the relation between input and output quantities is represented for example by global polynomials or local interpolation schemes as Moving Least Squares (MLS). In recent years artificial neural networks (ANN) have been applied as well for such purposes. Recently an adaptive response surface approach for reliability analyses was proposed, which is very efficient concerning the number of expensive limit state function evaluations. Due to the applied simplex interpolation the procedure is limited to small dimensions. In this paper this approach is extended for larger dimensions using combined ANN and MLS response surfaces for evaluating the adaptation criterion with only one set of joined limit state points. As adaptation criterion a combination by using the maximum difference in the conditional probabilities of failure and the maximum difference in the approximated radii is applied. Compared to response surfaces on directional samples or to plain directional sampling the failure probability can be estimated with a much smaller number of limit state points.
KW - Architektur
KW - CAD
KW - Computerunterstütztes Verfahren
Y1 - 2006
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170327-29922
UR - http://euklid.bauing.uni-weimar.de/ikm2006/index.php_lang=de&what=papers.html
ER -
TY - CHAP
A1 - Roos, Dirk
A1 - Bucher, Christian
T1 - Adaptive Response Surfaces for Structural Reliability of Nonlinear Finite Element Structures
N2 - Adaptive Response Surfaces for Structural Reliability of Nonlinear Finite Element Structures
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2003
ER -
TY - CHAP
A1 - Eckardt, Stefan
A1 - Könke, Carsten
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - ADAPTIVE SIMULATION OF THE DAMAGE BEHAVIOR OF CONCRETE USING HETEROGENEOUS MULTISCALE MODELS
N2 - In this paper an adaptive heterogeneous multiscale model, which couples two substructures with different length scales into one numerical model is introduced for the simulation of damage in concrete. In the presented approach the initiation, propagation and coalescence of microcracks is simulated using a mesoscale model, which explicitly represents the heterogeneous material structure of concrete. The mesoscale model is restricted to the damaged parts of the structure, whereas the undamaged regions are simulated on the macroscale. As a result an adaptive enlargement of the mesoscale model during the simulation is necessary. In the first part of the paper the generation of the heterogeneous mesoscopic structure of concrete, the finite element discretization of the mesoscale model, the applied isotropic damage model and the cohesive zone model are briefly introduced. Furthermore the mesoscale simulation of a uniaxial tension test of a concrete prism is presented and own obtained numerical results are compared to experimental results. The second part is focused on the adaptive heterogeneous multiscale approach. Indicators for the model adaptation and for the coupling between the different numerical models will be introduced. The transfer from the macroscale to the mesoscale and the adaptive enlargement of the mesoscale substructure will be presented in detail. A nonlinear simulation of a realistic structure using an adaptive heterogeneous multiscale model is presented at the end of the paper to show the applicability of the proposed approach to large-scale structures.
KW - Architektur
KW - CAD
KW - Computerunterstütztes Verfahren
Y1 - 2006
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170327-29478
UR - http://euklid.bauing.uni-weimar.de/ikm2006/index.php_lang=de&what=papers.html
ER -
TY - JOUR
A1 - Rafiee, Roham
A1 - Rabczuk, Timon
A1 - Milani, Abbas S.
A1 - Tserpes, Konstantinos I.
T1 - Advances in Characterization and Modeling of Nanoreinforced Composites
JF - JOURNAL OF NANOMATERIALS
N2 - This special issue deals with a range of recently developed characterization and modeling techniques employed to better understand and predict the response of nanoreinforced composites at different scales.
KW - Physikalische Eigenschaft
KW - Werkstoff
KW - nanoreinforced composites
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170411-31134
ER -
TY - CHAP
A1 - De Roeck, G.
A1 - Zabel, Volkmar
A1 - Brehm, Maik
A1 - Liu, K.
A1 - Reynders, E.
T1 - Algorithms for structural identification and damage detection of steel-concrete composite bridges
N2 - Algorithms for structural identification and damage detection of steel-concrete composite bridges
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2009
ER -
TY - CHAP
A1 - Zabel, Volkmar
A1 - Brehm, Maik
T1 - Algorithms for vibration-based structural identification and damage detection
N2 - Algorithms for vibration-based structural identification and damage detection
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2010
ER -
TY - CHAP
A1 - Cantieni, Reto
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Rauert, T.
A1 - Hoffmeister, B.
T1 - Ambient modal analysis and model updating of a twin composite filler beam railway bridge for high-speed trains with continuous ballast
N2 - Ambient modal analysis and model updating of a twin composite filler beam railway bridge for high-speed trains with continuous ballast
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2008
ER -
TY - CHAP
A1 - Cantieni, Reto
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Rauert, T.
A1 - Hoffmeister, B.
T1 - Ambient Testing and Model Updating of a Filler Beam Bridge for High-Speed Trains
N2 - Ambient Testing and Model Updating of a Filler Beam Bridge for High-Speed Trains
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2008
ER -
TY - JOUR
A1 - Budarapu, Pattabhi Ramaiah
A1 - Gracie, Robert
A1 - Bordas, Stéphane Pierre Alain
A1 - Rabczuk, Timon
T1 - An adaptive multiscale method for quasi-static crack growth
JF - Computational Mechanics
N2 - This paper proposes an adaptive atomistic- continuum numerical method for quasi-static crack growth. The phantom node method is used to model the crack in the continuum region and a molecular statics model is used near the crack tip. To ensure self-consistency in the bulk, a virtual atom cluster is used to model the material of the coarse scale. The coupling between the coarse scale and fine scale is realized through ghost atoms. The ghost atom positions are interpolated from the coarse scale solution and enforced as boundary conditions on the fine scale. The fine scale region is adaptively enlarged as the crack propagates and the region behind the crack tip is adaptively coarsened. An energy criterion is used to detect the crack tip location. The triangular lattice in the fine scale region corresponds to the lattice structure of the (111) plane of an FCC crystal. The Lennard-Jones potential is used to model the atom–atom interactions. The method is implemented in two dimensions. The results are compared to pure atomistic simulations; they show excellent agreement.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
U6 - http://dx.doi.org/10.1007/s00466-013-0952-6
SP - 1129
EP - 1148
ER -
TY - CHAP
A1 - Most, Thomas
T1 - An adaptive response surface approach for reliability analyses of high-dimensional problems
N2 - An adaptive response surface approach for reliability analyses of high-dimensional problems
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2008
ER -
TY - CHAP
A1 - Most, Thomas
T1 - An adaptive response surface approach for structural reliability analyses based on support vector machines
N2 - An adaptive response surface approach for structural reliability analyses based on support vector machines
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2007
ER -
TY - JOUR
A1 - Nguyen-Xuan, Hung
A1 - Liu, G.R.
A1 - Bordas, Stéphane Pierre Alain
A1 - Natarajan, S.
A1 - Rabczuk, Timon
T1 - An adaptive singular ES-FEM for mechanics problems with singular field of arbitrary order
JF - Computer Methods in Applied Mechanics and Engineering
N2 - An adaptive singular ES-FEM for mechanics problems with singular field of arbitrary order
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
SP - 252
EP - 273
ER -
TY - JOUR
A1 - Nguyen-Thanh, Nhon
A1 - Muthu, Jacob
A1 - Zhuang, Xiaoying
A1 - Rabczuk, Timon
T1 - An adaptive three-dimensional RHT-splines formulation in linear elasto-statics and elasto-dynamics
JF - Computational Mechanics
N2 - An adaptive three-dimensional RHT-splines formulation in linear elasto-statics and elasto-dynamics
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
SP - 369
EP - 385
ER -
TY - JOUR
A1 - Nguyen-Thanh, Nhon
A1 - Rabczuk, Timon
A1 - Nguyen-Xuan, Hung
A1 - Bordas, Stéphane Pierre Alain
T1 - An alternative alpha finite element method (A?FEM) free and forced vibration analysis of solids using triangular meshes
JF - Journal of Computational and Applied Mathematics
N2 - An alternative alpha finite element method (A?FEM) free and forced vibration analysis of solids using triangular meshes
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2009
SP - 2112
EP - 2135
ER -
TY - JOUR
A1 - Nguyen-Thanh, Nhon
A1 - Rabczuk, Timon
A1 - Nguyen-Xuan, Hung
A1 - Bordas, Stéphane Pierre Alain
T1 - An alternative alpha finite element method with stabilized discrete shear gap technique for analysis of Mindlin-Reissner plates
JF - Finite Elements in Analysis & Design
N2 - An alternative alpha finite element method with stabilized discrete shear gap technique for analysis of Mindlin-Reissner plates
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2011
SP - 519
EP - 535
ER -
TY - JOUR
A1 - Areias, Pedro
A1 - Pinto da Costa, A.
A1 - Rabczuk, Timon
A1 - Queiros de Melo, F. J. M.
A1 - Dias-da-Costa, D.
T1 - An alternative formulation for quasi-static frictional and cohesive contact problems
JF - Computational Mechanics
N2 - An alternative formulation for quasi-static frictional and cohesive contact problems
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
SP - 807
EP - 824
ER -
TY - JOUR
A1 - Zhao, Jun-Hua
A1 - Guo, Wanlin
A1 - Rabczuk, Timon
T1 - An analytical molecular mechanics model for the elastic properties of crystalline polyethylene
JF - Journal of Applied Physics
N2 - We present an analytical model to relate the elastic properties of crystalline polyethylene based on a molecular mechanics approach. Along the polymer chains direction, the united-atom (UA) CH2-CH2 bond stretching, angle bending potentials are replaced with equivalent Euler-Bernoulli beams. Between any two polymer chains, the explicit formulae are derived for the van der Waals interaction represented by the linear springs of different stiffness. Then, the nine independent elastic constants are evaluated systematically using the formulae. The analytical model is finally validated by present united-atom molecular dynamics (MD) simulations and against available all-atom molecular dynamics results in the literature. The established analytical model provides an efficient route for mechanical characterization of crystalline polymers and related materials.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2012
U6 - http://dx.doi.org/10.1063/1.4745035
ER -
TY - JOUR
A1 - Zhang, Yancheng
A1 - Zhao, Jun-Hua
A1 - Jia, Yue
A1 - Mabrouki, Tarek
A1 - Gong, Yadong
A1 - Wei, Ning
A1 - Rabczuk, Timon
T1 - An analytical solution on the interface debonding for large diameter carbon nanotube-reinforced composite with functionally graded variation interphase
JF - Composite Structures
N2 - An analytical solution on the interface debonding for large diameter carbon nanotube-reinforced composite with functionally graded variation interphase
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
SP - 261
EP - 269
ER -
TY - JOUR
A1 - Zabel, Volkmar
T1 - An application of discrete wavelet analysis and connection coefficients to parametric system identification
JF - Structural Health Monitoring
N2 - An application of discrete wavelet analysis and connection coefficients to parametric system identification
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2005
SP - 5
EP - 18
ER -
TY - JOUR
A1 - Nguyen-Thoi, T.
A1 - Phung-Van, P.
A1 - Rabczuk, Timon
A1 - Nguyen-Xuan, Hung
A1 - Le-Van, C.
T1 - An application of the ES-FEM in solid domain for dynamic analysis of 2D fluid-solid interaction problems
JF - International Journal of Computational Methods
N2 - An application of the ES-FEM in solid domain for dynamic analysis of 2D fluid-solid interaction problems
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
ER -
TY - JOUR
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Bucher, Christian
T1 - An automatic mode pairing strategy using an enhanced modal assurance citerion based on modal strain energies
JF - Journal of Sound and Vibration
N2 - In the context of finite element model updating using output-only vibration test data, natural frequencies and mode shapes are used as validation criteria. Consequently, the correct pairing of experimentally obtained and numerically derived natural frequencies and mode shapes is important. In many cases, only limited spatial information is available and noise is present in the measurements. Therefore, the automatic selection of the most likely numerical mode shape corresponding to a particular experimentally identified mode shape can be a difficult task. The most common criterion for indicating corresponding mode shapes is the modal assurance criterion. Unfortunately, this criterion fails in certain cases and is not reliable for automatic approaches. In this paper, the purely mathematical modal assurance criterion will be enhanced by additional physical information from the numerical model in terms of modal strain energies. A numerical example and a benchmark study with experimental data are presented to show the advantages of the proposed energy-based criterion in comparison to the traditional modal assurance criterion.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2010
U6 - http://dx.doi.org/10.1016/j.jsv.2010.07.006
SP - 5375
EP - 5392
ER -
TY - CHAP
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Bucher, Christian
A1 - Ribeiro, D.
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - AN AUTOMATIC MODE SELECTION STRATEGY FOR MODEL UPDATING USING THE MODAL ASSURANCE CRITERION AND MODAL STRAIN ENERGIES
N2 - In the context of finite element model updating using vibration test data, natural frequencies and mode shapes are used as validation criteria. Consequently, the order of natural frequencies and mode shapes is important. As only limited spatial information is available and noise is present in the measurements, the automatic selection of the most likely numerical mode shape corresponding to a measured mode shape is a difficult task. The most common criterion to indicate corresponding mode shapes is the modal assurance criterion. Unfortunately, this criterion fails in certain cases. In this paper, the pure mathematical modal assurance criterion will be enhanced by additional physical information of the numerical model in terms of modal strain energies. A numerical example and a benchmark study with real measured data are presented to show the advantages of the enhanced energy based criterion in comparison to the traditional modal assurance criterion.
KW - Angewandte Informatik
KW - Angewandte Mathematik
KW - Architektur
KW - Computerunterstütztes Verfahren
KW - Computer Science Models in Engineering; Multiscale and Multiphysical Models; Scientific Computing
Y1 - 2010
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-28330
UR - http://euklid.bauing.uni-weimar.de/ikm2009/paper.html
SN - 1611-4086
ER -
TY - CHAP
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Ribeiro, D.
T1 - An Automatic Mode Tracking Strategy for Model Updating Using the Modal Assurance Criterion and Modal Strain Energies
N2 - An Automatic Mode Tracking Strategy for Model Updating Using the Modal Assurance Criterion and Modal Strain Energies
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2009
ER -
TY - JOUR
A1 - Phan-Dao, H.
A1 - Nguyen-Xuan, Hung
A1 - Thai-Hoang, C.
A1 - Nguyen-Thoi, T.
A1 - Rabczuk, Timon
T1 - An edge-based smoothed finite element method for analysis of laminated composite plates
JF - International Journal of Computational Methods
N2 - An edge-based smoothed finite element method for analysis of laminated composite plates
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
ER -
TY - THES
A1 - Alalade, Muyiwa
T1 - An Enhanced Full Waveform Inversion Method for the Structural Analysis of Dams
N2 - Since the Industrial Revolution in the 1700s, the high emission of gaseous wastes into the atmosphere from the usage of fossil fuels has caused a general increase in temperatures globally. To combat the environmental imbalance, there is an increase in the demand for renewable energy sources. Dams play a major role in the generation of “green" energy. However, these structures require frequent and strict monitoring to ensure safe and efficient operation. To tackle the challenges faced in the application of convention dam monitoring techniques, this work proposes the inverse analysis of numerical models to identify damaged regions in the dam. Using a dynamic coupled hydro-mechanical Extended Finite Element Method (XFEM) model and a global optimization strategy, damage (crack) in the dam is identified. By employing seismic waves to probe the dam structure, a more detailed information on the distribution of heterogeneous materials and damaged regions are obtained by the application of the Full Waveform Inversion (FWI) method. The FWI is based on a local optimization strategy and thus it is highly dependent on the starting model. A variety of data acquisition setups are investigated, and an optimal setup is proposed. The effect of different starting models and noise in the measured data on the damage identification is considered. Combining the non-dependence of a starting model of the global optimization strategy based dynamic coupled hydro-mechanical XFEM method and the detailed output of the local optimization strategy based FWI method, an enhanced Full Waveform Inversion is proposed for the structural analysis of dams.
T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2019,1
KW - Talsperre
KW - Staumauer
KW - Damage identification
KW - Inverse analysis
KW - Dams
KW - Full waveform inversion
KW - Wave propagation
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20190813-39566
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
T1 - An enhanced moving least squares interpolation for the element-free Galerkin method
N2 - An enhanced moving least squares interpolation for the element-free Galerkin method
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - JOUR
A1 - Nguyen-Thanh, Nhon
A1 - Valizadeh, N.
A1 - Nguyen, Manh Hung
A1 - Nguyen-Xuan, Hung
A1 - Zhuang, Xiaoying
A1 - Areias, Pedro
A1 - Zi, Goangseup
A1 - Bazilevs, Yuri
A1 - De Lorenzis, Laura
A1 - Rabczuk, Timon
T1 - An extended isogeometric thin shell analysis based on Kirchhoff-Love theory
JF - Computer Methods in Applied Mechanics and Engineering
N2 - An extended isogeometric thin shell analysis based on Kirchho_-Love theory
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 265
EP - 291
ER -
TY - CHAP
A1 - Winkel, B.
T1 - An F-element, composite stress formulation to model muscular tissue in 3D
N2 - An F-element, composite stress formulation to model muscular tissue in 3D
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2004
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Eckardt, Stefan
A1 - Schrader, Kai
A1 - Deckner, T.
T1 - An improved cohesive crack model for combined crack opening and sliding under cyclic loading
N2 - An improved cohesive crack model for combined crack opening and sliding under cyclic loading
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Eckardt, Stefan
A1 - Schrader, Kai
A1 - Deckner, T.
ED - Gürlebeck, Klaus
ED - Könke, Carsten
T1 - AN IMPROVED COHESIVE CRACK MODEL FOR COMBINED CRACK OPENING AND SLIDING UNDER CYCLIC LOADING
N2 - The modeling of crack propagation in plain and reinforced concrete structures is still a field for many researchers. If a macroscopic description of the cohesive cracking process of concrete is applied, generally the Fictitious Crack Model is utilized, where a force transmission over micro cracks is assumed. In the most applications of this concept the cohesive model represents the relation between the normal crack opening and the normal stress, which is mostly defined as an exponential softening function, independently from the shear stresses in tangential direction. The cohesive forces are then calculated only from the normal stresses. By Carol et al. 1997 an improved model was developed using a coupled relation between the normal and shear damage based on an elasto-plastic constitutive formulation. This model is based on a hyperbolic yield surface depending on the normal and the shear stresses and on the tensile and shear strength. This model also represents the effect of shear traction induced crack opening. Due to the elasto-plastic formulation, where the inelastic crack opening is represented by plastic strains, this model is limited for applications with monotonic loading. In order to enable the application for cases with un- and reloading the existing model is extended in this study using a combined plastic-damage formulation, which enables the modeling of crack opening and crack closure. Furthermore the corresponding algorithmic implementation using a return mapping approach is presented and the model is verified by means of several numerical examples. Finally an investigation concerning the identification of the model parameters by means of neural networks is presented. In this analysis an inverse approximation of the model parameters is performed by using a given set of points of the load displacement curves as input values and the model parameters as output terms. It will be shown, that the elasto-plastic model parameters could be identified well with this approach, but require a huge number of simulations.
KW - Architektur
KW - CAD
KW - Computerunterstütztes Verfahren
Y1 - 2006
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170327-29933
UR - http://euklid.bauing.uni-weimar.de/ikm2006/index.php_lang=de&what=papers.html
ER -
TY - JOUR
A1 - Mosavi, Amir
A1 - Najafi, Bahman
A1 - Faizollahzadeh Ardabili, Sina
A1 - Shamshirband, Shahaboddin
A1 - Rabczuk, Timon
T1 - An Intelligent Artificial Neural Network-Response Surface Methodology Method for Accessing the Optimum Biodiesel and Diesel Fuel Blending Conditions in a Diesel Engine from the Viewpoint of Exergy and Energy Analysis
JF - Energies
N2 - Biodiesel, as the main alternative fuel to diesel fuel which is produced from renewable and available resources, improves the engine emissions during combustion in diesel engines. In this study, the biodiesel is produced initially from waste cooking oil (WCO). The fuel samples are applied in a diesel engine and the engine performance has been considered from the viewpoint of exergy and energy approaches. Engine tests are performed at a constant 1500 rpm speed with various loads and fuel samples. The obtained experimental data are also applied to develop an artificial neural network (ANN) model. Response surface methodology (RSM) is employed to optimize the exergy and energy efficiencies. Based on the results of the energy analysis, optimal engine performance is obtained at 80% of full load in presence of B10 and B20 fuels. However, based on the exergy analysis results, optimal engine performance is obtained at 80% of full load in presence of B90 and B100 fuels. The optimum values of exergy and energy efficiencies are in the range of 25–30% of full load, which is the same as the calculated range obtained from mathematical modeling.
KW - Biodiesel
KW - ANN modeling
KW - biodiesel
KW - Artificial Intelligence
KW - diesel engines
KW - energy, exergy
KW - mathematical modeling
Y1 - 2018
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20180507-37467
UR - http://www.mdpi.com/1996-1073/11/4/860
VL - 2018
IS - 11, 4
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Simpson, R.
A1 - Bordas, Stéphane Pierre Alain
A1 - Trevelyan, J.
A1 - Kerfriden, Pierre
A1 - Rabczuk, Timon
T1 - An Isogeometric Boundary Element Method for elastostatic analysis
JF - Computer Methods in Applied Mechanics and Engineering
N2 - The concept of isogeometric analysis, where functions that are used to describe geometry in CAD software are used to approximate the unknown fields in numerical simulations, has received great attention in recent years. The method has the potential to have profound impact on engineering design, since the task of meshing, which in some cases can add significant overhead, has been circumvented. Much of the research effort has been focused on finite element implementations of the isogeometric concept, but at present, little has been seen on the application to the Boundary Element Method. The current paper proposes an Isogeometric Boundary Element Method (BEM), which we term IGABEM, applied to two-dimensional elastostatic problems using Non-Uniform Rational B-Splines (NURBS). We find it is a natural fit with the isogeometric concept since both the NURBS approximation and BEM deal with quantities entirely on the boundary. The method is verified against analytical solutions where it is seen that superior accuracies are achieved over a conventional quadratic isoparametric BEM implementation.
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2012
U6 - http://dx.doi.org/10.1016/j.cma.2011.08.008
ER -
TY - JOUR
A1 - Anitescu, C.
A1 - Jia, Yue
A1 - Zhang, Yongjie
A1 - Rabczuk, Timon
T1 - An isogeometric collocation method using superconvergent points
JF - Computer Methods in Applied Mechanics and Engineer-ing
N2 - An isogeometric collocation method using superconvergent points
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 1073
EP - 1097
ER -
TY - CHAP
A1 - Pham, Hoang Anh
A1 - Bucher, Christian
T1 - An iterative procedure for model updating based on selective sensitivity
N2 - An iterative procedure for model updating based on selective sensitivity
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - CHAP
A1 - Luther, Torsten
A1 - Könke, Carsten
T1 - Analysis of crack initiation and propagation in polyctystalline meso- and microstructures of metal materials
N2 - Analysis of crack initiation and propagation in polyctystalline meso- and microstructures of metal materials
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - INPR
A1 - Rezakazemi, Mashallah
A1 - Mosavi, Amir
A1 - Shirazian, Saeed
T1 - ANFIS pattern for molecular membranes separation optimization
N2 - In this work, molecular separation of aqueous-organic was simulated by using combined soft computing-mechanistic approaches. The considered separation system was a microporous membrane contactor for separation of benzoic acid from water by contacting with an organic phase containing extractor molecules. Indeed, extractive separation is carried out using membrane technology where complex of solute-organic is formed at the interface. The main focus was to develop a simulation methodology for prediction of concentration distribution of solute (benzoic acid) in the feed side of the membrane system, as the removal efficiency of the system is determined by concentration distribution of the solute in the feed channel. The pattern of Adaptive Neuro-Fuzzy Inference System (ANFIS) was optimized by finding the optimum membership function, learning percentage, and a number of rules. The ANFIS was trained using the extracted data from the CFD simulation of the membrane system. The comparisons between the predicted concentration distribution by ANFIS and CFD data revealed that the optimized ANFIS pattern can be used as a predictive tool for simulation of the process. The R2 of higher than 0.99 was obtained for the optimized ANFIS model. The main privilege of the developed methodology is its very low computational time for simulation of the system and can be used as a rigorous simulation tool for understanding and design of membrane-based systems.
Highlights are, Molecular separation using microporous membranes. Developing hybrid model based on ANFIS-CFD for the separation process, Optimization of ANFIS structure for prediction of separation process
KW - Fluid
KW - Simulation
KW - Molecular Liquids
KW - optimization
KW - machine learning
KW - Membrane contactors
KW - CFD
Y1 - 2018
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20181122-38212
N1 - This is the pre-peer reviewed version of the following article:
https://www.sciencedirect.com/science/article/pii/S0167732218345008, which has been published in final form at https://doi.org/10.1016/j.molliq.2018.11.017.
VL - 2018
SP - 1
EP - 20
ER -
TY - CHAP
A1 - Most, Thomas
T1 - Anwendung netzfreier Diskretisierungsverfahren zur stochastischen Rissfortschrittsberechnung
N2 - Anwendung netzfreier Diskretisierungsverfahren zur stochastischen Rissfortschrittsberechnung
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2003
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Eckardt, Stefan
T1 - Application of a hybrid parallelisation technique to accelerate the numerical simulation of nonlinear mechanical problems
N2 - Application of a hybrid parallelisation technique to accelerate the numerical simulation of nonlinear mechanical problems
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2004
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
T1 - Application of an adaptive response surface approach for efficient structural reliability analysis
N2 - Application of an adaptive response surface approach for efficient structural reliability analysis
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - CHAP
A1 - Luther, Torsten
A1 - Könke, Carsten
T1 - Application of an Atom Continuum Model in Process of Damage Simulation on Multiple Length Scales
N2 - Application of an Atom Continuum Model in Process of Damage Simulation on Multiple Length Scales
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2008
ER -
TY - CHAP
A1 - Bucher, Christian
A1 - Most, Thomas
T1 - Application of approximate response functions in structural reliability analysis
N2 - Application of approximate response functions in structural reliability analysis
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2006
ER -
TY - CHAP
A1 - Markwardt, Klaus
T1 - Application of fast wavelet transformation in parametric system identification
N2 - Application of fast wavelet transformation in parametric system identification
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2005
ER -
TY - JOUR
A1 - Rabizadeh, E.
A1 - Saboor Bagherzadeh, Amir
A1 - Rabczuk, Timon
T1 - Application of goal-oriented error estimation and adaptive mesh refinement on thermo-mechanical multifield problems
JF - Computational Materials Science
N2 - Application of goal-oriented error estimation and adaptive mesh re_nement on thermo-mechanical multi_eld problems
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2015
SP - 27
EP - 44
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Bucher, Christian
T1 - Application of the "Fictitious Crack Model" to meshless crack growth simulations
N2 - Application of the "Fictitious Crack Model" to meshless crack growth simulations
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2003
ER -
TY - CHAP
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Markwardt, Klaus
T1 - Applications of biorthogonal wavelets in system identification
N2 - Applications of biorthogonal wavelets in system identification
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2004
ER -
TY - CHAP
A1 - Brehm, Maik
A1 - Zabel, Volkmar
A1 - Markwardt, Klaus
T1 - Applications of Wavelet Packets in System Identifikation
N2 - Applications of Wavelet Packets in System Identifikation
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2005
ER -
TY - CHAP
A1 - Most, Thomas
A1 - Hofstetter, G.
A1 - Hofmann, Markus
A1 - Novák, D.
A1 - Lehký, D.
T1 - Approximation of constitutive parameters for material models using artificial neural networks
N2 - Approximation of constitutive parameters for material models using artificial neural networks
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2007
ER -
TY - THES
A1 - Udrea, Mihai-Andrei
T1 - Assessment of Data from Dynamic Bridge Monitoring
N2 - The focus of the thesis is to process measurements acquired from a continuous
monitoring system at a railway bridge. Temperature, strain and ambient vibration
records are analysed and two main directions of investigation are pursued.
The first and the most demanding task is to develop processing routines able to extract modal parameters from ambient vibration measurements. For this purpose, reliable experimental models are achieved on the basis of a stochastic system identification(SSI) procedure. A fully automated algorithm based on a three-stage clustering is implemented to perform a modal parameter estimation for every single measurement. After selecting a baseline of modal parameters, the evolution of eigenfrequencies is
studied and correlated to environmental and operational factors.
The second aspect deals with the structural response to passing trains. Corresponding
triggered records of strain and temperature are processed and their assessment is
accomplished using the average strains induced by each train as the reference parameter.
Three influences due to speed, temperature and loads are distinguished and treated individually. An attempt to estimate the maximum response variation due to each factor is also carried out.
KW - automatic modal analysis
KW - stochastic subspace identification
KW - modal tracking
KW - modal parameter estimation
KW - clustering
KW - Messtechnik
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140429-21742
ER -
TY - THES
A1 - Abbas, Tajammal
T1 - Assessment of Numerical Prediction Models for Aeroelastic Instabilities of Bridges
N2 - The phenomenon of aerodynamic instability caused by the wind is usually a major design criterion for long-span cable-supported bridges. If the wind speed exceeds the critical flutter speed of the bridge, this constitutes an Ultimate Limit State. The prediction of the flutter boundary, therefore, requires accurate and robust models. The complexity and uncertainty of models for such engineering problems demand strategies for model assessment. This study is an attempt to use the concepts of sensitivity and uncertainty analyses to assess the aeroelastic instability prediction models for long-span bridges. The state-of-the-art theory concerning the determination of the flutter stability limit is presented. Since flutter is a coupling of aerodynamic forcing with a structural dynamics problem, different types and classes of structural and aerodynamic models can be combined to study the interaction. Here, both numerical approaches and analytical models are utilised and coupled in different ways to assess the prediction quality of the coupled model.
T3 - Schriftenreihe des DFG Graduiertenkollegs 1462 Modellqualitäten // Graduiertenkolleg Modellqualitäten - 16
KW - Brücke
KW - Flattern
KW - Unsicherheit
KW - Flutter
KW - Bridges
KW - Sensitivity
KW - Uncertainty
KW - Model assessment
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20180515-27161
UR - https://asw-verlage.de/katalog/assessment_of_numerical_prediction_models_for_aeroelastic_instabilities_of_bridges-1897.html
PB - Jonas Verlag
CY - Weimar
ER -
TY - JOUR
A1 - Areias, Pedro
A1 - Rabczuk, Timon
A1 - Dias-da-Costa, D.
T1 - Assumed-metric spherically-interpolated quadrilateral shell element
JF - Finite Elements in Analysis and Design
N2 - Assumed-metric spherically-interpolated quadrilateral shell element
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
SP - 53
EP - 67
ER -
TY - JOUR
A1 - Areias, Pedro
A1 - Rabczuk, Timon
A1 - Dias-da-Costa, D.
T1 - Asymmetric Shell Elements Based on a Corrected Updated-Lagrangian Approach
JF - CMES: Computer Modeling in Engineering and Sciences
N2 - Asymmetric Shell Elements Based on a Corrected Updated-Lagrangian Approach
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2013
ER -
TY - CHAP
A1 - Bucher, Christian
A1 - Pham, Hoang Anh
T1 - Bayesian reliability updating using system identification based on selective sensitivity
N2 - Bayesian reliability updating using system identification based on selective sensitivity
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2004
ER -
TY - THES
A1 - Will, Johannes
T1 - Beitrag zur Standsicherheitsberechnung im geklüfteten Fels in der Kontinuums- und Diskontinuumsmechanik unter Verwendung impliziter und expliziter Berechnungsstrategien
T1 - Structural safety analysis for jointed rock with continuum and discontinuum mechanics in implizit and explizit codes
KW - Staumauer
KW - Standsicherheit
KW - Klüftung
KW - Finite-Elemente-Methode
KW - Diskrete-Elemente-Methode
KW - Kontinuumsmechanik
KW - Diskontinuumsmechanik
KW - jointed rock
KW - continuum mechanics
KW - diskontinuum mechanics
Y1 - 1999
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20040310-613
ER -
TY - CHAP
A1 - Markwardt, Klaus
A1 - Zabel, Volkmar
T1 - Betrachtungen zur Anwendung der Wavelet- Transformation in der Systemidentifikation
N2 - Betrachtungen zur Anwendung der Wavelet- Transformation in der Systemidentifikation
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2000
ER -
TY - JOUR
A1 - Lahmer, Tom
A1 - Knabe, Tina
A1 - Nikulla, Susanne
A1 - Reuter, Markus
T1 - Bewertungsmethoden für Modelle des konstruktiven Ingenieurbaus
BT - Sonderdruck‐DFG Graduiertenkolleg
JF - Bautechnik
N2 - Bewertungsmethoden für Modelle des konstruktiven Ingenieurbaus
KW - Angewandte Mathematik
KW - Stochastik
KW - Strukturmechanik
Y1 - 2011
SP - 60
EP - 64
ER -
TY - JOUR
A1 - Zhao, Jun-Hua
A1 - Lu, Lixin
A1 - Rabczuk, Timon
T1 - Binding energy and mechanical stability of single- and multi-walled carbon nanotube serpentines
JF - The Journal of Chemical Physics
N2 - Binding energy and mechanical stability of single- and multi-walled carbon nanotube serpentines
KW - Angewandte Mathematik
KW - Strukturmechanik
Y1 - 2014
U6 - http://dx.doi.org/10.1063/1.4878115
ER -