TY - JOUR
A1 - Staat, Manfred
T1 - Shakedown and ratchetting under tension-torsion loadings: analysis and experiments
N2 - Structural design analyses are conducted with the aim of verifying the exclusion of ratchetting. To this end it is important to make a clear distinction between the shakedown range and the ratchetting range. The performed experiment comprised a hollow tension specimen which was subjected to alternating axial forces, superimposed with constant moments. First, a series of uniaxial tests has been carried out in order to calibrate a bounded kinematic hardening rule. The load parameters have been selected on the basis of previous shakedown analyses with the PERMAS code using a kinematic hardening material model. It is shown that this shakedown analysis gives reasonable agreement between the experimental and the numerical results. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis.
KW - Einspielen
KW - Einspielen
KW - Ratchetting
KW - Zug-Druck Belastung
KW - shakedown
KW - ratchetting
KW - tension–torsion loading
Y1 - 2003
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 - JOUR
A1 - Staat, Manfred
T1 - Direct finite element route for design-by-analysis of pressure components
N2 - In the new European standard for unfired pressure vessels, EN 13445-3, there are two approaches for carrying out a Design-by-Analysis that cover both the stress categorization method (Annex C) and the direct route method (Annex B) for a check against global plastic deformation and against progressive plastic deformation. This paper presents the direct route in the language of limit and shakedown analysis. This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for mechanical and thermal actions. One observation from the examples is that the so-called 3f (3Sm) criterion fails to be a reliable check against progressive plastic deformation. Precise conditions are given, which greatly restrict the applicability of the 3f criterion.
KW - Einspielen
KW - Plastizität
KW - Deformation
KW - Analytischer Zulaessigkeitsnachweis
KW - Einspiel-Analyse
KW - fortschreitende plastische Deformation
KW - alternierend Verformbarkeit
KW - Einspiel-Kriterium
KW - Design-by-analysis
KW - Shakedown analysis
KW - Progressive plastic deformation
KW - Alternating plasticity
KW - Shakedown criterion
Y1 - 2005
ER -
TY - JOUR
A1 - Staat, Manfred
T1 - Direct FEM Limit and Shakedown Analysis with Uncertain Data
N2 - The structural reliability with respect to plastic collapse or to inadaptation is formulated on the basis of the lower bound limit and shakedown theorems. A direct definition of the limit state function is achieved which permits the use of the highly effective first order reliability methods (FORM) is achieved. The theorems are implemented into a general purpose FEM program in a way capable of large-scale analysis. The limit state function and its gradient are obtained from a mathematical optimization problem. This direct approach reduces considerably the necessary knowledge of uncertain technological input data, the computing time, and the numerical error, leading to highly effective and precise reliability analyses.
KW - Finite-Elemente-Methode
KW - Einspielen
KW - FEM
KW - Einspielanalyse
KW - shakedown
KW - limit load
KW - reliability analysis
KW - FEM
KW - direct method
Y1 - 2000
ER -
TY - JOUR
A1 - Staat, Manfred
T1 - Cyclic plastic deformation tests to verify FEM-based shakedown analyses
N2 - Fatigue analyses are conducted with the aim of verifying that thermal ratcheting is limited. To this end it is important to make a clear distintion between the shakedown range and the ratcheting range (continuing deformation). As part of an EU-supported research project, experiments were carried out using a 4-bar model. The experiment comprised a water-cooled internal tube, and three insulated heatable outer test bars. The system was subjected to alternating axial forces, superimposed with alternating temperatures at the outer bars. The test parameters were partly selected on the basis of previous shakedown analyses. During the test, temperatures and strains were measured as a function of time. The loads and the resulting stresses were confirmed on an ongoing basis during performance of the test, and after it. Different material models were applied for this incremental elasto-plastic analysis using the ANSYS program. The results of the simulation are used to verify the FEM-based shakedown analysis.
KW - Materialermüdung
KW - Einspielen
KW - Materialermüdung
KW - shakedown analyses
KW - thermal ratcheting
KW - fatigue analyses
Y1 - 2001
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 - JOUR
A1 - Vu, Duc-Khoi
A1 - Staat, Manfred
T1 - An algorithm for shakedown analysis of structure with temperature dependent yield stress
N2 - This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithmfor shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools.
KW - Einspielen
KW - Temperaturabhängigkeit
KW - Fließgrenze
KW - Shakedown
KW - shakedown analysis
KW - yield stress
Y1 - 2004
ER -