Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Bemerkung Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Zugriffsart Link Abteilungen OPUS4-264 Konferenzveröffentlichung Ballmann, J., ; Raatschen, Hans-Jürgen, raatschen@fh-aachen.de; Staat, Manfred, m.staat@fh-aachen.de High stress intensities in focussing zones of waves The propagation of mechanical waves in plates of isotropic elastic material is investigated. After a short introduction to the understanding of focussing of stress waves in a plate with a curved boundary the method of characteristics is applied to a plate of hyperelastic material. Using this method the propagation of acceleration waves is discussed. Based on this a numerical difference scheme is developed for solving initial-boundary-value problems and applied to two examples: propagation of a point disturbance in a homogeneously finitely strained non-linear elastic plate and geometrical focussing in al linear elastic plate. 1985 10.1016/B978-0-444-42520-1.50015-3 Fachbereich Medizintechnik und Technomathematik OPUS4-174 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de; Ballmann, J., Fundamental aspects of numerical methods for the propagation of multi-dimensional nonlinear waves in solids 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. 1989 14 Nonlinear hyperbolic equations : theory, computations methods, and applications ; proceedings of the 2nd International Conference on Nonlinear Hyperbolic Problems, Aachen 574 588 bezahl http://dx.doi.org/10.1007/978-3-322-87869-4_56 Fachbereich Medizintechnik und Technomathematik OPUS4-203 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de; Heitzer, Michael, Limit and shakedown analysis for plastic design Limit and shakedown theorems are exact theories of classical plasticity for the direct computation of safety factors or of the load carrying capacity under constant and varying loads. Simple versions of limit and shakedown analysis are the basis of all design codes for pressure vessels and pipings. Using Finite Element Methods more realistic modeling can be used for a more rational design. The methods can be extended to yield optimum plastic design. In this paper we present a first implementation in FE of limit and shakedown analyses for perfectly plastic material. Limit and shakedown analyses are done of a pipe-junction and a interaction diagram is calculated. The results are in good correspondence with the analytic solution we give in the appendix. 1997 Fachbereich Medizintechnik und Technomathematik OPUS4-1553 Konferenzveröffentlichung Burgazzi, L., ; Fiorini, F., ; De Magistris, W. (u.a.), ; Lensa, W. von, ; Staat, Manfred, m.staat@fh-aachen.de; Altes, J., Reliability Assessment of Passive Safety Systems New York American Society of Mechanical Engineers 1998 Proceedings of the 6th International Conference on Nuclear Engineering : ICONE : May 10 - 14, 1998, San Diego, Calif. CD-ROM Fachbereich Medizintechnik und Technomathematik OPUS4-200 Konferenzveröffentlichung Heitzer, M., ; Staat, Manfred, m.staat@fh-aachen.de Direct FEM approach to design-by-analysis of pressurized components 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 2000 Fachbereich Medizintechnik und Technomathematik OPUS4-63 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de; Heitzer, Michael, Direct static FEM approach to limit and shakedown analysis Safety and reliability of structures may be assessed indirectly by stress distributions. Limit and shakedown theorems are simplified but exact methods of plasticity that provide safety factors directly in the loading space. These theorems may be used for a direct definition of the limit state function for failure by plastic collapse or by inadaptation. In a FEM formulation the limit state function is obtained from a nonlinear optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error. Moreover, the direct way leads to highly effective and precise reliability analyses. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. 2000 Fachbereich Medizintechnik und Technomathematik OPUS4-62 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de; Heitzer, Michael, The restricted influence of kinematic hardening on shakedown loads Structural design analyses are conducted with the aim of verifying the exclusion of ratcheting. To this end it is important to make a clear distinction between the shakedown range and the ratcheting range. In cyclic plasticity more sophisticated hardening models have been suggested in order to model the strain evolution observed in ratcheting experiments. The hardening models used in shakedown analysis are comparatively simple. It is shown that shakedown analysis can make quite stable predictions of admissible load ranges despite the simplicity of the underlying hardening models. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis. Both give identical or similar shakedown ranges. Structural shakedown analyses show that the loading may have a more pronounced effect than the hardening model. 2002 Fachbereich Medizintechnik und Technomathematik OPUS4-76 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de Design by Analysis of Pressure Components by non-linear Optimization This paper presents the direct route to Design by Analysis (DBA) of the new European pressure vessel standard in the language of limit and shakedown analysis (LISA). This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for some examples from the DBA-Manual. One observation from the examples is, that the optimisation approach gives reliable and close lower bound solutions leading to simple and optimised design decision. 2003 Fachbereich Medizintechnik und Technomathematik OPUS4-158 Konferenzveröffentlichung Staat, Manfred, m.staat@fh-aachen.de Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability. - Überarb. Ausg. In: Technical feasibility and reliability of passive safety systems for nuclear power plants. Proceedings of an Advisory Group Meeting held in Jülich, 21-24 November 1994. - Vienna , 1996. - Seite: 43 - 55 IAEA-TECDOC-920 Abstract: It is shown that the difficulty for probabilistic fracture mechanics (PFM) is the general problem of the high reliability of a small population. There is no way around the problem as yet. Therefore what PFM can contribute to the reliability of steel pressure boundaries is demon­strated with the example of a typical reactor pressure vessel and critically discussed. Although no method is distinguishable that could give exact failure probabilities, PFM has several addi­tional chances. Upper limits for failure probability may be obtained together with trends for design and operating conditions. Further, PFM can identify the most sensitive parameters, improved control of which would increase reliability. Thus PFM should play a vital role in the analysis of steel pressure boundaries despite all shortcomings. 2006 Fachbereich Medizintechnik und Technomathematik OPUS4-191 Konferenzveröffentlichung Tran, Thanh Ngoc, tran@fh-aachen.de; Staat, Manfred, m.staat@fh-aachen.de; Kreißig, R., Calculation of load carrying capacity of shell structures with elasto-plastic material by direct methods Proceedings of the International Conference on Material Theory and Nonlinear Dynamics. MatDyn. Hanoi, Vietnam, Sept. 24-26, 2007, 8 p. In this paper, a method is introduced to determine the limit load of general shells using the finite element method. The method is based on an upper bound limit and shakedown analysis with elastic-perfectly plastic material model. A non-linear constrained optimisation problem is solved by using Newton's method in conjunction with a penalty method and the Lagrangean dual method. Numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm. 2007 Fachbereich Medizintechnik und Technomathematik