@article{VuStaat2004, author = {Vu, Duc-Khoi and Staat, Manfred}, title = {An algorithm for shakedown analysis of structure with temperature dependent yield stress}, year = {2004}, abstract = {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.}, subject = {Einspielen }, language = {en} } @article{KuehnHaugnerStaatetal.2004, author = {K{\"u}hn, Raoul-Roman and Haugner, Werner and Staat, Manfred and Sponagel, Stefan}, title = {A Two Phase Mixture Model based on Bone Observation}, year = {2004}, abstract = {An optimization method is developed to describe the mechanical behaviour of the human cancellous bone. The method is based on a mixture theory. A careful observation of the behaviour of the bone material leads to the hypothesis that the bone density is controlled by the principal stress trajectories (Wolff's law). The basic idea of the developed method is the coupling of a scalar value via an eigenvalue problem to the principal stress trajectories. On the one hand this theory will permit a prediction of the reaction of the biological bone structure after the implantation of a prosthesis, on the other hand it may be useful in engineering optimization problems. An analytical example shows its efficiency.}, subject = {Knochen}, language = {en} } @article{BaroudWuBohneretal.2003, author = {Baroud, G. and Wu, J.Z. and Bohner, M and Sponagel, Stefan and Steffen, T.}, title = {How to determine the permeability for cement infiltration into osteoporotic cancellous bone}, series = {Medical Engineering \& Physics. 25 (2003), H. 4}, journal = {Medical Engineering \& Physics. 25 (2003), H. 4}, issn = {1350-4533}, pages = {283 -- 288}, year = {2003}, abstract = {Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm4/N.s) reduced to approximately 63\% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice.}, subject = {Osteoporose}, language = {en} } @misc{Staat2006, author = {Staat, Manfred}, title = {Technische Mechanik. Vorlesungsmitschrift. Korrigierter Nachdr. der 3. Aufl.}, year = {2006}, abstract = {{\"U}berarbeitete, korrigierte und erg{\"a}nzte Version einer Vorlesungsmitschrift von Sebastian Kr{\"a}mer. 172 S. Inhaltsverzeichnis 0 Einf{\"u}hrung in die Mechanik 1 Statik starrer K{\"o}rper 2 Elastostatik (Festigkeitslehre) 3 Kinematik 4 Kinetik Literatur}, subject = {Technische Mechanik}, language = {de} } @misc{Staat2006, author = {Staat, Manfred}, title = {Engineering Mechanics. Lecture Notes. 2nd edition, translation of the 3rd corrected and extended German edition of "Technische Mechanik"}, year = {2006}, abstract = {English translation of the corrected lectures notes of Sebastian Kr{\"a}mer. Contents 0 Introduction to Mechanics 1 Statics of Rigid Bodies 2 Elastostatics (Strength of Materials) 3 Kinematics 4 Kinetics Literature}, subject = {Technische Mechanik}, language = {en} } @misc{StaatBarry2006, author = {Staat, Manfred and Barry, Steve}, title = {Continuum Mechanics with an Introduction to the Finite Element Method / Steve Barry; Manfred Staat. With extensions by Manfred Staat.}, year = {2006}, abstract = {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}, subject = {Technische Mechanik}, language = {en} } @inproceedings{Staat2006, author = {Staat, Manfred}, title = {Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability. - {\"U}berarb. Ausg.}, year = {2006}, abstract = {In: Technical feasibility and reliability of passive safety systems for nuclear power plants. Proceedings of an Advisory Group Meeting held in J{\"u}lich, 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.}, subject = {Bruchmechanik}, language = {en} } @article{Staat2001, author = {Staat, Manfred}, title = {Cyclic plastic deformation tests to verify FEM-based shakedown analyses}, year = {2001}, abstract = {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.}, subject = {Materialerm{\"u}dung}, language = {en} } @article{Staat2005, author = {Staat, Manfred}, title = {Local and global collapse pressure of longitudinally flawed pipes and cylindrical vessels}, year = {2005}, abstract = {Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. FEM suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to FEM limit analyses for all crack dimensions.}, subject = {Finite-Elemente-Methode}, language = {en} } @article{Staat2005, author = {Staat, Manfred}, title = {Direct finite element route for design-by-analysis of pressure components}, year = {2005}, abstract = {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.}, subject = {Einspielen }, language = {en} }