TY - CHAP A1 - Tran, Thanh Ngoc A1 - Staat, Manfred A1 - Kreißig, R. T1 - Calculation of load carrying capacity of shell structures with elasto-plastic material by direct methods N2 - 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. KW - Finite-Elemente-Methode Y1 - 2007 ER - TY - CHAP A1 - Fredebeul-Krein, Markus T1 - 10 years of liberalised telecom markets in Germany: Assessing the degree of competition on the markets for voice telephony N2 - Market data for the German telecom market shows that Deutsche Telekom as the former incumbent is constantly loosing shares on all arkets for voice telephony: the market for local calls, the market for long-distance calls and the market for international calls. At the same time prices decline steadily with the latest trend being that operators offer voice services free of charge, the costs of which are covered by a monthly subscription charge. Against this background the paper examines the state of policy and regulatory reform in the telecommunications sector in Germany almost 10 years after the liberalisation of the fixed telecommunications market. Thereby the focus is on the analysis of the competitive conditions that have been established on the German market for voice telephony services. If these retail markets are competitive, there might be a need to remove remaining regulatory provisions. In the new environment of converging markets the future challenge of regulating fixed telecom markets might be to ensure that access to the network and/or services of a potentially dominant provider in a relevant market will satisfy requirements for openness and non-discrimination. KW - Telekommunikationsmarkt KW - Telekommunikationsmarkt Y1 - 2007 N1 - paper presented at 18th European Regional ITS Conference of the International Telecommunications Society, September 2-4, 2007 Istanbul, Turkey ER - TY - CHAP A1 - Tran, Thanh Ngoc A1 - Staat, Manfred A1 - Kreißig, R. T1 - Finite element shakedown and limit reliability analysis of thin shells N2 - A procedure for the evaluation of the failure probability of elastic-plastic thin shell structures is presented. The procedure involves a deterministic limit and shakedown analysis for each probabilistic iteration which is based on the kinematical approach and the use the exact Ilyushin yield surface. Based on a direct definition of the limit state function, the non-linear problems may be efficiently solved by using the First and Second Order Reliabiblity Methods (Form/SORM). This direct approach reduces considerably the necessary knowledge of uncertain technological input data, computing costs and the numerical error. In: Computational plasticity / ed. by Eugenio Onate. Dordrecht: Springer 2007. VII, 265 S. (Computational Methods in Applied Sciences ; 7) (COMPLAS IX. Part 1 . International Center for Numerical Methods in Engineering (CIMNE)). ISBN 978-1-402-06576-7 S. 186-189 KW - Finite-Elemente-Methode KW - Limit analysis KW - shakedown analysis KW - Exact Ilyushin yield surface KW - Random variable KW - First Order Reliabiblity Method Y1 - 2007 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 - 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 - 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 - TY - JOUR A1 - Kühn, Raoul-Roman A1 - Haugner, Werner A1 - Staat, Manfred A1 - Sponagel, Stefan T1 - A Two Phase Mixture Model based on Bone Observation N2 - 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. KW - Knochen KW - Knochenbildung KW - Knochenchirugie KW - Strukturanalyse KW - Schwammknochen KW - Knochendichte KW - Wolffsches Gesetz KW - bone structure KW - bone density KW - Wolff's Law KW - cancellous bone Y1 - 2004 ER - TY - JOUR A1 - Baroud, G. A1 - Wu, J.Z. A1 - Bohner, M A1 - Sponagel, Stefan A1 - Steffen, T. T1 - How to determine the permeability for cement infiltration into osteoporotic cancellous bone JF - Medical Engineering & Physics. 25 (2003), H. 4 N2 - 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. KW - Osteoporose KW - Permeabilität KW - Viskose Strömung KW - Viskosität KW - Vertebroplastie KW - Cement infiltration KW - Vertebroplasty KW - Osteoporosis KW - Permeability KW - Experiment KW - Analysis KW - Viscous flow Y1 - 2003 SN - 1350-4533 SP - 283 EP - 288 ER - TY - CHAP A1 - Brüssermann, Klaus A1 - Deuster, M. T1 - Temperature measurement to optimise the burning process N2 - One of the most important parameters in a burning chamber - in power stations, in waste to energy plants - is the temperature. This temperature is in the range of 700-1500 °C - one of the most advanced measuring methods being the acoustic pyrometry with the possibility of producing temperature mapping in one level of the burning chamber - comparable to computer tomography. The results of these measurements discussed in the presentation can be used - to fulfil the legal requirements in the FRG or in the EU - to equalise the temperature in one level of the burning chamber to optimise the steam production (better efficiency of the plant) and to minimise the production of temperature controlled flue gas components (NO, CO a. o.) - to control the SNCR-process if used. KW - Pyrometrie KW - Temperaturmessung KW - temperature measurement KW - acoustic pyrometry KW - steam production KW - flue gas components Y1 - 2005 ER - TY - CHAP A1 - Gebhardt, Andreas T1 - Technology Diffusion through a Multi-Level Technology Transfer Infrastructure. Contribution to the 1st. All Africa Technology Diffusion Conference Boksburg, South Africa June 12th - 14th 2006 N2 - Table of contents 1. Introduction 2. Multi-level Technology Transfer Infrastructure 2.1 Level 1: University Education – Encourage the Idea of becoming an Entrepreneur 2.2 Level 2: Post Graduate Education – Improve your skills and focus it on a product family. 2.3 Level 3: Birth of a Company – Focus your skills on a product and a market segment. 2.4 Level 4: Ready to stand alone – Set up your own business 2.5 Level 5: Grow to be Strong – Develop your business 2.6 Level 6: Competitive and independent – Stay innovative. 3. Samples 3.1 Sample 1: Laser Processing and Consulting Centre, LBBZ 3.2 Sample 2: Prototyping Centre, CP 4. Funding - Waste money or even lost Money? 5. Conclusion KW - Technologietransfer KW - technology transfer KW - technology diffusion Y1 - 2006 ER - TY - JOUR A1 - Gebhardt, Andreas T1 - Generative Manufacturing of Ceramic Parts "Vision Rapid Prototyping" N2 - Table of Contents Introduction 1. Generative Manufacturing Processes 2. Classification of Generative Manufacturing Processes 3. Application of Generative Processes on the Fabrication of Ceramic Parts 3.1 Extrusion 3.2 3D-Printing 3.3 Sintering – Laser Sintering 3.4 Layer-Laminate Processes 3.5 Stereolithography (sometimes written: Stereo Lithography) 4. Layer Milling 5. Conclusion - Vision KW - Rapid prototyping KW - Rapid Technologie KW - Rapid Prototyping Y1 - 2006 ER - TY - GEN A1 - Staat, Manfred T1 - Engineering Mechanics. Lecture Notes. 2nd edition, translation of the 3rd corrected and extended German edition of "Technische Mechanik" N2 - English translation of the corrected lectures notes of Sebastian Krämer. Contents 0 Introduction to Mechanics 1 Statics of Rigid Bodies 2 Elastostatics (Strength of Materials) 3 Kinematics 4 Kinetics Literature KW - Technische Mechanik KW - Mechanics KW - Statics KW - Elastostatics KW - Kinematics KW - Kinetics Y1 - 2006 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 - RPRT A1 - Weßling, Matthias T1 - How to deal with foreign cultures: an cross-cultural training-approach based on the didactical methodology of 'experiential learning' following Kolb & Fry N2 - Many companies still conduct the worldwide management of people as if neither the external economic nor the internal structure of the firm had changed. The costs of cross-cultural failure, for individuals and their companies, are enormous: personal and family costs; financial, professional and emotional costs; costs to one’s career prospects, to one’s self-esteem, to one’s marriage and family. This scenario describes sufficiently the reason for learning “the art of crossing cultures” (Craig Storti). To this end, this research paper describes an innovative approach of cross-cultural training, following the didactical ideas of Kolb and Fry, the so-called 'experiential learning'. N2 - Viele international agierende Unternehmen verfahren mit dem weltweiten Personalmanagement so, als wenn sich weder der ökonomische Kontext noch die internen Strukturen der Firmen geändert hätten. Die Kosten von interkulturellen Mißverständnissen und Fehlschlägen sind enorm - sowohl für alle beteiligten Personen, als auch für die betroffenen Unternehmen: hier geht es um berufliche, emotionale, soziale Kosten bis hin zu Beeinträchtigungen der Selbstwertschätzung oder auch der ehelichen Paarbeziehungen. Dieses Szenario beschreibt die Notwendigkeit, sich intensive auseinanderzusetzen mit dem, was Craig Storti "the art of crossing cultures" nennt. Vor diesem Hintergrund beschreibt das vorliegende Forschungspapier einen innovativen Ansatz für ein interkulturelles Managementtraining auf der methodischen Basis der didaktischen Idee des 'experiential learning' nach Kolb und Fry. KW - Interkulturelles Lernen KW - Kulturvergleich KW - Interkulturelles Management KW - Erfahrungsorientiertes Lernen KW - Völkerpsychologie KW - Interkulturelles Training KW - Managementtraining KW - Erfahrungslernen KW - Interkulturelles Lernen KW - Kulturvergleichende Psychologie KW - Cross-Cultural Training KW - Intercultural Awareness KW - Experiential Learning KW - Managementtraining KW - Cross-Cultural Psychology Y1 - 2009 ER - TY - CHAP A1 - Staat, Manfred T1 - Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability. - Überarb. Ausg. N2 - 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. KW - Bruchmechanik KW - probabilistic fracture mechanics KW - PFM Y1 - 2006 ER - TY - JOUR A1 - Kämper, Klaus-Peter A1 - Picard, Antoni A1 - Brill, Manfred A1 - Cassel, Detlev A1 - Jentsch, Andreas A1 - Merten, Sabine A1 - Rollwa, Markus T1 - The Virtual Clean Room - a new tool in teaching MST process technologies N2 - The Virtual Clean Room - a new tool in teaching MST process technologies University education in high-technology fields like MST is not complete without intensive laboratory sessions. Students cannot fully grasp the complexity and the special problems related to the manufacturing of microsystems without a thorough hands-on experience in a MST clean room. KW - Virtuelle Maschine KW - VM KW - Mikrosystemtechnik KW - MST KW - virtual clean room Y1 - 2003 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 - Local and global collapse pressure of longitudinally flawed pipes and cylindrical vessels N2 - 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. KW - Finite-Elemente-Methode KW - Grenzwertberechnung KW - Axialbelastung KW - FEM KW - Grenzwertberechnung KW - Axialbelastung KW - Traglastanalyse KW - Limit analysis KW - Global and local collapse KW - Axially cracked pipe KW - Pressure loaded crack-face Y1 - 2005 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 - 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 -