TY - JOUR A1 - Staat, Manfred A1 - Ballmann, J. T1 - Computation of impacts on elastic solids by methods of bicharacteristics JF - Computational Mechanics '88 : theory and applications ; proceedings of the International Conference on Computational Engineering Science April 10-14, 1988, Atlanta, GA, USA ; vol. 2 N2 - Shock waves, explosions, impacts or cavitation bubble collapses may generate stress waves in solids causing cracks or unexpected dammage due to focussing, physical nonlinearity or interaction with existing cracks. There is a growing interest in wave propagation, which poses many novel problems to experimentalists and theorists. KW - Bicharakteristikenverfahren KW - Elastizität KW - elastic solids KW - bicharacteristics Y1 - 1988 SP - 1719 EP - 1722 ER - TY - JOUR A1 - Staat, Manfred T1 - Basis Reduction for the Shakedown Problem for Bounded Kinematic Hardening Material N2 - Limit and shakedown analysis are effective methods for assessing the load carrying capacity of a given structure. The elasto–plastic behavior of the structure subjected to loads varying in a given load domain is characterized by the shakedown load factor, defined as the maximum factor which satisfies the sufficient conditions stated in the corresponding static shakedown theorem. The finite element dicretization of the problem may lead to very large convex optimization. For the effective solution a basis reduction method has been developed that makes use of the special problem structure for perfectly plastic material. The paper proposes a modified basis reduction method for direct application to the two-surface plasticity model of bounded kinematic hardening material. The considered numerical examples show an enlargement of the load carrying capacity due to bounded hardening. KW - Finite-Elemente-Methode KW - Einspielen KW - Basis Reduktion KW - konvexe Optimierung KW - FEM KW - Druckgeräte KW - Basis reduction KW - Convex optimization KW - FEM KW - Shakedown analysis Y1 - 2000 ER - TY - CHAP A1 - Staat, Manfred A1 - Ballmann, J. T1 - Fundamental aspects of numerical methods for the propagation of multi-dimensional nonlinear waves in solids T2 - Nonlinear hyperbolic equations : theory, computations methods, and applications ; proceedings of the 2nd International Conference on Nonlinear Hyperbolic Problems, Aachen N2 - The nonlinear scalar constitutive equations of gases lead to a change in sound speed from point to point as would be found in linear inhomogeneous (and time dependent) media. The nonlinear tensor constitutive equations of solids introduce the additional local effect of solution dependent anisotropy. The speed of a wave passing through a point changes with propagation direction and its rays are inclined to the front. It is an open question whether the widely used operator splitting techniques achieve a dimensional splitting with physically reasonable results for these multi-dimensional problems. May be this is the main reason why the theoretical and numerical investigations of multi-dimensional wave propagation in nonlinear solids are so far behind gas dynamics. We hope to promote the subject a little by a discussion of some fundamental aspects of the solution of the equations of nonlinear elastodynamics. We use methods of characteristics because they only integrate mathematically exact equations which have a direct physical interpretation. KW - Nichtlineare Welle KW - Nichtlineare Gleichung KW - Festkörper KW - Elastodynamik KW - Multi-dimensional wave propagation KW - nonlinear solids KW - nonlinear tensor constitutive equation Y1 - 1989 SP - 574 EP - 588 ER - TY - JOUR A1 - Staat, Manfred T1 - LISA - a European project for FEM-based limit and shakedown analysis N2 - The load-carrying capacity or the safety against plastic limit states are the central questions in the design of structures and passive components in the apparatus engineering. A precise answer is most simply given by limit and shakedown analysis. These methods can be based on static and kinematic theorems for lower and upper bound analysis. Both may be formulated as optimization problems for finite element discretizations of structures. The problems of large-scale analysis and the extension towards realistic material modelling will be solved in a European research project. Limit and shakedown analyses are briefly demonstrated with illustrative examples. KW - Einspielen KW - Traglast KW - Finite-Elemente-Methode KW - Traglastanalyse KW - Einspielanalyse KW - FEM KW - limit analysis KW - shakedown analysis Y1 - 2001 ER - TY - CHAP A1 - Jung, Alexander A1 - Frotscher, Ralf A1 - Staat, Manfred T1 - Electromechanical model of hiPSC-derived ventricular cardiomyocytes cocultured with fibroblasts T2 - 6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11-15 June 2018, Glasgow, UK N2 - The CellDrum provides an experimental setup to study the mechanical effects of fibroblasts co-cultured with hiPSC-derived ventricular cardiomyocytes. Multi-scale computational models based on the Finite Element Method are developed. Coupled electrical cardiomyocyte-fibroblast models (cell level) are embedded into reaction-diffusion equations (tissue level) which compute the propagation of the action potential in the cardiac tissue. Electromechanical coupling is realised by an excitation-contraction model (cell level) and the active stress arising during contraction is added to the passive stress in the force balance, which determines the tissue displacement (tissue level). Tissue parameters in the model can be identified experimentally to the specific sample. Y1 - 2018 ER - TY - GEN A1 - Staat, Manfred A1 - Barry, Steve T1 - Continuum Mechanics with an Introduction to the Finite Element Method / Steve Barry; Manfred Staat. With extensions by Manfred Staat. N2 - Contents: 1 Introduction 2 One Dimensional Continuum Mechanics 3 Tensors 4 Three Dimensional Stress and Strain 5 Conservation Laws 6 Contiunuum Modelling 7 Plain Problems 8 Questions 9 Reference Information KW - Technische Mechanik KW - Finite-Elemente-Methode Y1 - 2006 ER - TY - CHAP A1 - Jung, Alexander A1 - Staat, Manfred A1 - Müller, Wolfram ED - Onate, E. T1 - Optimization of the flight style in ski jumping T2 - 11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20 - 25, 2014, Barcelona Y1 - 2014 N1 - Das Paper wurde nach der Konferenz überarbeitet. SP - 799 EP - 810 ER - TY - CHAP A1 - Staat, Manfred A1 - Duong, Minh Tuan T1 - Smoothed Finite Element Methods for Nonlinear Solid Mechanics Problems: 2D and 3D Case Studies T2 - Proceedings of the National Science and Technology Conference on Mechanical - Transportation Engineering (NSCMET 2016), 13th October 2016, Hanoi, Vietnam, Vol.2 N2 - The Smoothed Finite Element Method (SFEM) is presented as an edge-based and a facebased techniques for 2D and 3D boundary value problems, respectively. SFEMs avoid shortcomings of the standard Finite Element Method (FEM) with lower order elements such as overly stiff behavior, poor stress solution, and locking effects. Based on the idea of averaging spatially the standard strain field of the FEM over so-called smoothing domains SFEM calculates the stiffness matrix for the same number of degrees of freedom (DOFs) as those of the FEM. However, the SFEMs significantly improve accuracy and convergence even for distorted meshes and/or nearly incompressible materials. Numerical results of the SFEMs for a cardiac tissue membrane (thin plate inflation) and an artery (tension of 3D tube) show clearly their advantageous properties in improving accuracy particularly for the distorted meshes and avoiding shear locking effects. Y1 - 2016 SP - 440 EP - 445 ER - TY - JOUR A1 - Staat, Manfred A1 - Heitzer, M. T1 - Limit and Shakedown Analysis Using a General Purpose Finite Element Code JF - Proceedings of NAFEMS World Congress '97 on Design, Simulation & Optimisation : reliability & applicability of computational methods ; Stuttgart, Germany, 9 - 11 April 1997 Y1 - 1997 SN - 1-87437-620-4 SP - 522 EP - 533 PB - NAFEMS CY - Glasgow ER - TY - CHAP A1 - Heitzer, M. A1 - Staat, Manfred T1 - Direct FEM approach to design-by-analysis of pressurized components N2 - Abstracts of the ACHEMA 2000 - International Meeting on Chemical Engineering, Environmental Protection and Biotechnology, May 22 - 27, 2000. Frankfurt am Main. Achema 2000 : special edition / Linde. [Ed.: Linde AG. Red.: Volker R. Leski]. - Wiesbaden : Linde AG, 2000. - 56 p. : Ill., . - pp: 79 - 81 N2 - Abstracts der ACHEMA 2000 - International Meeting on Chemical Engineering, Environmental Protection and Biotechnology, May 22 - 27, 2000. Frankfurt am Main. KW - Finite-Elemente-Methode KW - Finite-Elemente-Methode KW - limit analysis KW - shakedown analysis Y1 - 2000 ER - TY - CHAP A1 - Frotscher, Ralf A1 - Staat, Manfred ED - Nithiarasu, Perumal T1 - Homogenization of a cardiac tissue construct T2 - CMBE15 : 4th International Conference on Computational & Mathematical Biomedical Engineering ; 29th June - 1st July 2015 ; École Normale Supérieure de Cachan ; Cachan (Paris), France Y1 - 2015 SN - 2227-9385 N1 - Konferenzband unter: http://www.compbiomed.net/getfile.php?type=12/site_documents&id=Proceedings_2227-9385_compressed.pdf SP - 645 EP - 648 PB - CMBE CY - [s.l.] ER - TY - CHAP A1 - Tran, Thanh Ngoc A1 - Staat, Manfred ED - Onate, E. T1 - Uncertain multimode failure and limit analysis of shells T2 - 11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona Y1 - 2014 SP - 1 EP - 12 ER - TY - JOUR A1 - Staat, Manfred T1 - An extension strain type Mohr–Coulomb criterion JF - Rock mechanics and rock engineering N2 - Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion. Y1 - 2021 U6 - https://doi.org/10.1007/s00603-021-02608-7 SN - 1434-453X N1 - Corresponding author: Manfred Staat VL - 54 IS - 12 SP - 6207 EP - 6233 PB - Springer Nature CY - Cham ER -