TY - JOUR A1 - Lahmer, Tom A1 - Ilg, J. A1 - Lerch, Reinhard T1 - Variance-based sensitivity analyses of piezoelectric models JF - Computer Modeling in Engineering & Sciences N2 - Variance-based sensitivity analyses of piezoelectric models KW - Angewandte Mathematik KW - Stochastik KW - Strukturmechanik Y1 - 2015 SP - 105 EP - 126 ER - TY - CHAP A1 - Nguyen-Tuan, Long A1 - Lahmer, Tom A1 - Datcheva, Maria A1 - Stoimenova, Eugenia A1 - Schanz, Tom ED - Gürlebeck, Klaus ED - Lahmer, Tom T1 - PARAMETER IDENTIFICATION APPLYING IN COMPLEX THERMO-HYDRO-MECHANICAL PROBLEMS LIKE THE DESIGN OF BUFFER ELEMENTS T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar N2 - This study contributes to the identification of coupled THM constitutive model parameters via back analysis against information-rich experiments. A sampling based back analysis approach is proposed comprising both the model parameter identification and the assessment of the reliability of identified model parameters. The results obtained in the context of buffer elements indicate that sensitive parameter estimates generally obey the normal distribution. According to the sensitivity of the parameters and the probability distribution of the samples we can provide confidence intervals for the estimated parameters and thus allow a qualitative estimation on the identified parameters which are in future work used as inputs for prognosis computations of buffer elements. These elements play e.g. an important role in the design of nuclear waste repositories. KW - Angewandte Informatik KW - Angewandte Mathematik KW - Building Information Modeling KW - Computerunterstütztes Verfahren KW - Data, information and knowledge modeling in civil engineering; Function theoretic methods and PDE in engineering sciences; Mathematical methods for (robotics and) computer vision; Numerical modeling in engineering; Optimization in engineering applications Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-28162 SN - 1611-4086 ER - TY - JOUR A1 - Zhao, Jun-Hua A1 - Lu, Lixin A1 - Zhang, Zhiliang A1 - Guo, Wanlin A1 - Rabczuk, Timon T1 - Continuum modeling of the cohesive energy for the interfaces between _lms, spheres, coats and substrates JF - Computational Materials Science N2 - Continuum modeling of the cohesive energy for the interfaces between _lms, spheres, coats and substrates KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 SP - 432 EP - 438 ER - TY - JOUR A1 - Ben, S. A1 - Zhao, Jun-Hua A1 - Zhang, Yancheng A1 - Rabczuk, Timon T1 - The interface strength and debonding for composite structures: review and recent developments JF - Composite Structures N2 - The interface strength and debonding for composite structures: review and recent developments KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 ER - TY - JOUR A1 - Zhao, Jun-Hua A1 - Jia, Yue A1 - Wei, Ning A1 - Rabczuk, Timon T1 - Binding energy and mechanical stability of two parallel and crossing carbon nanotubes JF - Journal of Applied Mechanics N2 - Binding energy and mechanical stability of two parallel and crossing carbon nanotubes KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 ER - TY - JOUR A1 - Kumar, S. A1 - Singh, I. A1 - Mishra, B.K. A1 - Rabczuk, Timon T1 - Modeling and Simulation of Kinked Cracks by Virtual Node XFEM JF - Computer Methods in Applied Mechanics and Engineering N2 - Modeling and Simulation of Kinked Cracks by Virtual Node XFEM KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 SP - 1425 EP - 1466 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 - Talebi, Hossein A1 - Silani, Mohammad A1 - Rabczuk, Timon T1 - Concurrent Multiscale Modelling of Three Dimensional Crack and Dislocation Propagation JF - Advances in Engineering Software N2 - Concurrent Multiscale Modelling of Three Dimensional Crack and Dislocation Propagation KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 SP - 82 EP - 92 ER - TY - JOUR A1 - Ghasemi, Hamid A1 - Brighenti, Roberto A1 - Zhuang, Xiaoying A1 - Muthu, Jacob A1 - Rabczuk, Timon T1 - Optimum fiber content and distribution in fiber-reinforced solids using a reliability and NURBS based sequential optimization approach JF - Structural and Multidisciplinary Optimization N2 - Optimum _ber content and distribution in _ber-reinforced solids using a reliability and NURBS based sequential optimization approach KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 SP - 99 EP - 112 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 - 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 - Nanthakumar, S.S. A1 - Lahmer, Tom A1 - Zhuang, Xiaoying A1 - Zi, Goangseup A1 - Rabczuk, Timon T1 - Detection of material interfaces using a regularized level set method in piezoelectric structures JF - Inverse Problems in Science and Engineering N2 - Detection of material interfaces using a regularized level set method in piezoelectric structures KW - Angewandte Mathematik KW - Stochastik KW - Strukturmechanik Y1 - 2015 ER - TY - JOUR A1 - Vu-Bac, N. A1 - Rafiee, Roham A1 - Zhuang, Xiaoying A1 - Lahmer, Tom A1 - Rabczuk, Timon T1 - Uncertainty quantification for multiscale modeling of polymer nanocomposites with correlated parameters JF - Composites Part B: Engineering N2 - Uncertainty quantification for multiscale modeling of polymer nanocomposites with correlated parameters KW - Angewandte Mathematik KW - Stochastik KW - Strukturmechanik Y1 - 2015 SP - 446 EP - 464 ER - TY - CHAP A1 - Jaouadi, Zouhour A1 - Lahmer, Tom ED - Gürlebeck, Klaus ED - Lahmer, Tom T1 - Topology optimization of structures subjected to multiple load cases by introducing the Epsilon constraint method T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar N2 - A topology optimization method has been developed for structures subjected to multiple load cases (Example of a bridge pier subjected to wind loads, traffic, superstructure...). We formulate the problem as a multi-criterial optimization problem, where the compliance is computed for each load case. Then, the Epsilon constraint method (method proposed by Chankong and Haimes, 1971) is adapted. The strategy of this method is based on the concept of minimizing the maximum compliance resulting from the critical load case while the other remaining compliances are considered in the constraints. In each iteration, the compliances of all load cases are computed and only the maximum one is minimized. The topology optimization process is switching from one load to another according to the variation of the resulting compliance. In this work we will motivate and explain the proposed methodology and provide some numerical examples. KW - Angewandte Informatik KW - Angewandte Mathematik KW - Building Information Modeling KW - Computerunterstütztes Verfahren KW - Data, information and knowledge modeling in civil engineering; Function theoretic methods and PDE in engineering sciences; Mathematical methods for (robotics and) computer vision; Numerical modeling in engineering; Optimization in engineering applications Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-28042 SN - 1611-4086 ER - TY - THES A1 - Vu, Bac Nam T1 - Stochastic uncertainty quantification for multiscale modeling of polymeric nanocomposites N2 - Nanostructured materials are extensively applied in many fields of material science for new industrial applications, particularly in the automotive, aerospace industry due to their exceptional physical and mechanical properties. Experimental testing of nanomaterials is expensive, timeconsuming,challenging and sometimes unfeasible. Therefore,computational simulations have been employed as alternative method to predict macroscopic material properties. The behavior of polymeric nanocomposites (PNCs) are highly complex. The origins of macroscopic material properties reside in the properties and interactions taking place on finer scales. It is therefore essential to use multiscale modeling strategy to properly account for all large length and time scales associated with these material systems, which across many orders of magnitude. Numerous multiscale models of PNCs have been established, however, most of them connect only two scales. There are a few multiscale models for PNCs bridging four length scales (nano-, micro-, meso- and macro-scales). In addition, nanomaterials are stochastic in nature and the prediction of macroscopic mechanical properties are influenced by many factors such as fine-scale features. The predicted mechanical properties obtained by traditional approaches significantly deviate from the measured values in experiments due to neglecting uncertainty of material features. This discrepancy is indicated that the effective macroscopic properties of materials are highly sensitive to various sources of uncertainty, such as loading and boundary conditions and material characteristics, etc., while very few stochastic multiscale models for PNCs have been developed. Therefore, it is essential to construct PNC models within the framework of stochastic modeling and quantify the stochastic effect of the input parameters on the macroscopic mechanical properties of those materials. This study aims to develop computational models at four length scales (nano-, micro-, meso- and macro-scales) and hierarchical upscaling approaches bridging length scales from nano- to macro-scales. A framework for uncertainty quantification (UQ) applied to predict the mechanical properties of the PNCs in dependence of material features at different scales is studied. Sensitivity and uncertainty analysis are of great helps in quantifying the effect of input parameters, considering both main and interaction effects, on the mechanical properties of the PNCs. To achieve this major goal, the following tasks are carried out: At nano-scale, molecular dynamics (MD) were used to investigate deformation mechanism of glassy amorphous polyethylene (PE) in dependence of temperature and strain rate. Steered molecular dynamics (SMD)were also employed to investigate interfacial characteristic of the PNCs. At mico-scale, we developed an atomistic-based continuum model represented by a representative volume element (RVE) in which the SWNT’s properties and the SWNT/polymer interphase are modeled at nano-scale, the surrounding polymer matrix is modeled by solid elements. Then, a two-parameter model was employed at meso-scale. A hierarchical multiscale approach has been developed to obtain the structure-property relations at one length scale and transfer the effect to the higher length scales. In particular, we homogenized the RVE into an equivalent fiber. The equivalent fiber was then employed in a micromechanical analysis (i.e. Mori-Tanaka model) to predict the effective macroscopic properties of the PNC. Furthermore, an averaging homogenization process was also used to obtain the effective stiffness of the PCN at meso-scale. Stochastic modeling and uncertainty quantification consist of the following ingredients: - Simple random sampling, Latin hypercube sampling, Sobol’ quasirandom sequences, Iman and Conover’s method (inducing correlation in Latin hypercube sampling) are employed to generate independent and dependent sample data, respectively. - Surrogate models, such as polynomial regression, moving least squares (MLS), hybrid method combining polynomial regression and MLS, Kriging regression, and penalized spline regression, are employed as an approximation of a mechanical model. The advantage of the surrogate models is the high computational efficiency and robust as they can be constructed from a limited amount of available data. - Global sensitivity analysis (SA) methods, such as variance-based methods for models with independent and dependent input parameters, Fourier-based techniques for performing variance-based methods and partial derivatives, elementary effects in the context of local SA, are used to quantify the effects of input parameters and their interactions on the mechanical properties of the PNCs. A bootstrap technique is used to assess the robustness of the global SA methods with respect to their performance. In addition, the probability distribution of mechanical properties are determined by using the probability plot method. The upper and lower bounds of the predicted Young’s modulus according to 95 % prediction intervals were provided. The above-mentioned methods study on the behaviour of intact materials. Novel numerical methods such as a node-based smoothed extended finite element method (NS-XFEM) and an edge-based smoothed phantom node method (ES-Phantom node) were developed for fracture problems. These methods can be used to account for crack at macro-scale for future works. The predicted mechanical properties were validated and verified. They show good agreement with previous experimental and simulations results. KW - Polymere KW - nanocomposite KW - Nanoverbundstruktur KW - stochastic KW - multiscale Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20160322-25551 ER - TY - CHAP ED - Gürlebeck, Klaus ED - Lahmer, Tom T1 - International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar T1 - Internationales Kolloquium über Anwendungen der Informatik und Mathematik in Architektur und Bauwesen : 20. bis 22.7. 2015, Bauhaus-Universität Weimar T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar N2 - The 20th International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering will be held at the Bauhaus University Weimar from 20th till 22nd July 2015. Architects, computer scientists, mathematicians, and engineers from all over the world will meet in Weimar for an interdisciplinary exchange of experiences, to report on their results in research, development and practice and to discuss. The conference covers a broad range of research areas: numerical analysis, function theoretic methods, partial differential equations, continuum mechanics, engineering applications, coupled problems, computer sciences, and related topics. Several plenary lectures in aforementioned areas will take place during the conference. We invite architects, engineers, designers, computer scientists, mathematicians, planners, project managers, and software developers from business, science and research to participate in the conference! KW - Angewandte Informatik KW - Angewandte Mathematik KW - Computerunterstütztes Verfahren KW - Building Information Modeling KW - Optimization in engineering applications KW - Data, information and knowledge modeling in civil engineering KW - Function theoretic methods and PDE in engineering sciences KW - Mathematical methods for (robotics and) computer vision KW - Numerical modeling in engineering Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20150828-24515 SN - 1611-4086 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 - Zhao, Jiyun A1 - Lu, Lixin A1 - Rabczuk, Timon T1 - The tensile and shear failure behavior dependence on chain length and temperature in amorphous polymers JF - Computational Materials Science N2 - The tensile and shear failure behavior dependence on chain length and temperature in amorphous polymers KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2015 SP - 567 EP - 572 ER - TY - CHAP A1 - Tan, Fengjie A1 - Lahmer, Tom A1 - Siddappa, Manju Gyaraganahalll ED - Gürlebeck, Klaus ED - Lahmer, Tom T1 - SECTION OPTIMIZATION AND RELIABILITY ANALYSIS OF ARCH-TYPE DAMS INCLUDING COUPLED MECHANICAL-THERMAL AND HYDRAULIC FIELDS T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar N2 - From the design experiences of arch dams in the past, it has significant practical value to carry out the shape optimization of arch dams, which can fully make use of material characteristics and reduce the cost of constructions. Suitable variables need to be chosen to formulate the objective function, e.g. to minimize the total volume of the arch dam. Additionally a series of constraints are derived and a reasonable and convenient penalty function has been formed, which can easily enforce the characteristics of constraints and optimal design. For the optimization method, a Genetic Algorithm is adopted to perform a global search. Simultaneously, ANSYS is used to do the mechanical analysis under the coupling of thermal and hydraulic loads. One of the constraints of the newly designed dam is to fulfill requirements on the structural safety. Therefore, a reliability analysis is applied to offer a good decision supporting for matters concerning predictions of both safety and service life of the arch dam. By this, the key factors which would influence the stability and safety of arch dam significantly can be acquired, and supply a good way to take preventive measures to prolong ate the service life of an arch dam and enhances the safety of structure. KW - Angewandte Informatik KW - Angewandte Mathematik KW - Building Information Modeling KW - Computerunterstütztes Verfahren KW - Data, information and knowledge modeling in civil engineering; Function theoretic methods and PDE in engineering sciences; Mathematical methods for (robotics and) computer vision; Numerical modeling in engineering; Optimization in engineering applications Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-28212 SN - 1611-4086 ER - TY - JOUR A1 - Anitescu, Cosmin 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 -