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3. Creep, fatigue and creep-fatigue behaviour of martensitic/bainitic steels and nickel-based alloys and their welded joints at the temperature range 500°C–750°C.

Author

Osorio, Daniel, Gotti, Arianna, Kauffmann, Florian, Klenk, Andreas, and Weihe, Stefan

Subjects
MATERIAL fatigue, WELDED joints, BAINITIC steel, STRAINS & stresses (Mechanics), ALLOY fatigue
Abstract

The aim of the paper is to investigate experimentally the fatigue and creep-fatigue material behaviour of improved materials and welded joints for the application in flexible future power plants. These materials promise a reduction in manufacturing costs as well as an increase in flexibility by providing enhanced creep strength thorugh a wall thickness reduction. At the temperature range between 500°C −550°C, the investigation focusses on the creep and low-cycle fatigue behaviour of dissimilar welded joints from conventional materials (bainitic and martensitic materials T24 and T92) to nickel-based alloys (A617B and HR6W) fabricated as tubes. At the temperature range between 700°C and 750°C, it focusses on the creep, low-cycle fatigue and creep-fatigue behaviour of similar and dissimilar welded joints from nickel-based alloys (A740H, A617B and A263) fabricated as tubes and as pipes. Metallographic investigations after testing provide support for understanding the influence of temperature, strain amplitude and dwell time on the microstructure change and the fatigue strength. [ABSTRACT FROM AUTHOR]

Published
2024
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8. On the Applicability of Knowledge Based NAT-Traversal for Home Networks

Author

Müller, Andreas, Klenk, Andreas, Carle, Georg, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Das, Amitabha, editor, Pung, Hung Keng, editor, Lee, Francis Bu Sung, editor, and Wong, Lawrence Wai Choong, editor

Published
2008
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9. Automated Trust Negotiation in Autonomic Environments

Author

Klenk, Andreas, Petri, Frank, Radier, Benoit, Salaun, Mikael, Carle, Georg, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Katz, Randy H., editor

Published
2007
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10. Advanced Detection of Selfish or Malicious Nodes in Ad Hoc Networks

Author

Kargl, Frank, Klenk, Andreas, Schlott, Stefan, Weber, Michael, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Castelluccia, Claude, editor, Hartenstein, Hannes, editor, Paar, Christof, editor, and Westhoff, Dirk, editor

Published
2005
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22. Experimental and Numerical Investigations on the Relaxation Behavior of Power Plant Flange Connections Under Steady State and Transient Conditions

Author

Kettler, Kevin, Klenk, Andreas, and Weihe, Stefan

Abstract

An essential part of today's power plants are flanges, for example, as connection between turbine housings and pipes. They allow for revisions, inspections, and maintenance measures. Ongoing changes toward higher amounts of renewable energy sources leading to higher demands in flexibility to counterbalance weather-related fluctuations. This flexibility leads to changing load types with more frequent warm and hot starts, causing uncertainties for the design and the determination of maintenance intervals of bolted flange connections. In this context, results of a recently finished research project and ongoing numerical investigations are presented. Tests were conducted on a model of an IP turbine flange under near-to-service loads, such as internal pressure and temperature, using a test rig allowing heating on the flange's inner surface. Concerning different influences on the stress relaxation behavior, results are shown for tests with martensitic and nickel-based bolted joints. The total test time of 5000 h for each bolted joint consist of 2000 h under steady-state conditions and 3000 h under transient conditions. Comparisons of the results with the martensitic and nickel-based bolted joint show an opposite creep strain distribution in the bolt and flange. In addition, a significant influence of the already existing creep deformation from previous load periods can be observed. Comparative simulations with a modified Graham–Walles creep model are carried out. The results confirm the differences in creep behavior with both bolted joints and reproduce the observed influence of the previous creep deformation.

Published
2024
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31. Long term stress relaxation modelling

Author

Holmström, Stefan, Auerkari, Pertti, Friedmann, Valerie, Klenk, Andreas, Leibing, Benjamin, Buhl, P., Spindler, Mike, and Riva, Andrea

Subjects
modelling, stress relaxation
Abstract

Data assessments, materials modelling and development as well as recommendations for model selection have been a main objective of the ECCC Working Group 1. This paper describes the latest inter-comparison round robin on relaxation modelling. Most models found in the public domain are limited in either strain range or temperature. Here the bolting steel 1Cr-0.5Mo-0.25V steel tested by NIMS, Japan is assessed by a number of assessors striving to define models capable of predicting the relaxation in the full data range, i.e. in both strain (0.1-0.25% total strain) and temperature (450-550°C). The assessors use methods of their own preference giving all model parameters to enable interpolation/extrapolation and calculation of prediction errors within the range of data. The methods include forward creep with different creep strain models as base, classical relaxation models, parametric (Time-Temperature-Parameter curve families) solutions and entirely new modelling approaches. The main target is the general overall model for prediction of relaxed stress up to 3 000 h hold time. However, the model robustness is tested by fitting to a drastically culled data set consisting of only the short term data with durations of 0.1 to 10h. The predictive performance of the models optimised for the short term data are compared with the long term data as well as the long term models. Conclusions and recommendations are given on model interpolation performance, extrapolation ability and model complexity.

Published
2014

35. Sensors for Detection of Misbehaving Nodes in MANETs

Author

Klenk, Andreas, Kragl, Frank, Schlott, Stefan, and Weber, Michael

Subjects
MANETs, Intrusion Detection
Abstract

The fact that security is a critical problem when implementing mobile ad hoc networks (MANETs) is widely acknowledged. One of the different kinds of misbehavior a node may exhibit is selfishness. A selfish node wants to preserve its resources while using the services of others and consuming their resources. One way of preventing selfishness in a MANET is a detection and exclusion mechanism. In this paper, we focus on the detection and present different kinds of sensors that will find selfish nodes. First we present simulations that show the negative effects which selfish nodes cause in MANET. In the related work section we will analyze the detection mechanisms proposed by others. Our new detection mechanisms that we describe in this paper are called activity-based overhearing, iterative probing, and unambiguous probing. Simulation-based analysis of these mechanisms show that they are highly effective and can reliably detect a multitude of selfish behaviors., Lecture Notes in Informatics;P-46

Published
2004

38. Bilateral and Multilateral Negotiation for Agreement Discovery and Formation

Author

Schill, Alexander (Prof. Dr. Dr.), Carle, Georg (Prof. Dr.), Klenk, Andreas, Schill, Alexander (Prof. Dr. Dr.), Carle, Georg (Prof. Dr.), and Klenk, Andreas

Abstract

Negotiation is one of the most important tools for the coordination of collaborations and for conducting trade. Policy intersection protocols are efficient in identifying mutually compatible parameters, if the negotiating parties know the possible parameter space beforehand. It is no tool to discover new and unforeseen agreements. Iterative requirements-driven agreement negotiation with the novel VersaNeg protocol overcomes these limitations. It allows each party to state what it can offer and what it wants in turn. An iterative exchange of requirements and offers leads to a rooted tree structure of alternative agreement options. The agreement negotiation protocol becomes a tool to discover new agreement options and to form comprehensive agreements. VersaNeg works equally well for bilateral and multilateral negotiations. In multilateral negotiations, the involved parties can discover and define collaborations on the fly., Die Aushandlung von Übereinkünften ist eines der wichtigsten Werkzeuge um die Zusammenarbeit verschiedener Parteien zu koordinieren und um Handel zu treiben. Policy Intersection Protokolle sind effizient um für alle Parteien akzeptable Parameter zu finden, aber nur sofern die möglichen Parameter im Vorhinein bekannt sind. Das neue VersaNeg Protokoll überwindet mit seiner iterativen anforderungsgetriebenen Aushandlung diese Beschränkungen. Jede Partei drückt aus was sie anbieten kann und was sie als Gegenleistung erwartet. Durch einen iterativen Austausch von Anforderungen und Angeboten entsteht eine Baumstruktur mit alternativen Übereinkünften. Damit werden durch das Protokoll neue Übereinkünfte entdeckt und in einem Dokument festgehalten, welches die vollständige Übereinkunft definiert. VersaNeg unterstützt multilaterale Verhandlungen und erlaubt es den Parteien spontane Kollaborationen zu bilden.

Published
2012

39. Bilateral and Multilateral Negotiation for Agreement Discovery and Formation

Author

Carle, Georg (Prof. Dr.), Carle, Georg (Prof. Dr.);Schill, Alexander (Prof. Dr. Dr.), Klenk, Andreas, Carle, Georg (Prof. Dr.), Carle, Georg (Prof. Dr.);Schill, Alexander (Prof. Dr. Dr.), and Klenk, Andreas

Abstract

Negotiation is one of the most important tools for the coordination of collaborations and for conducting trade. Policy intersection protocols are efficient in identifying mutually compatible parameters, if the negotiating parties know the possible parameter space beforehand. It is no tool to discover new and unforeseen agreements. Iterative requirements-driven agreement negotiation with the novel VersaNeg protocol overcomes these limitations. It allows each party to state what it can offer and what it wants in turn. An iterative exchange of requirements and offers leads to a rooted tree structure of alternative agreement options. The agreement negotiation protocol becomes a tool to discover new agreement options and to form comprehensive agreements. VersaNeg works equally well for bilateral and multilateral negotiations. In multilateral negotiations, the involved parties can discover and define collaborations on the fly., Die Aushandlung von Übereinkünften ist eines der wichtigsten Werkzeuge um die Zusammenarbeit verschiedener Parteien zu koordinieren und um Handel zu treiben. Policy Intersection Protokolle sind effizient um für alle Parteien akzeptable Parameter zu finden, aber nur sofern die möglichen Parameter im Vorhinein bekannt sind. Das neue VersaNeg Protokoll überwindet mit seiner iterativen anforderungsgetriebenen Aushandlung diese Beschränkungen. Jede Partei drückt aus was sie anbieten kann und was sie als Gegenleistung erwartet. Durch einen iterativen Austausch von Anforderungen und Angeboten entsteht eine Baumstruktur mit alternativen Übereinkünften. Damit werden durch das Protokoll neue Übereinkünfte entdeckt und in einem Dokument festgehalten, welches die vollständige Übereinkunft definiert. VersaNeg unterstützt multilaterale Verhandlungen und erlaubt es den Parteien spontane Kollaborationen zu bilden.

Published
2012

40. Materials for Advanced Ultra-Supercritical Fossil-Fuel Power Plants: Materials Properties, Microstructure, and Component Behavior.

Author

Speicher, Magdalena, Hueggenberg, Daniel, Klenk, Andreas, Zickler, Stefan, and Metzger, Klaus

Subjects
FOSSIL fuel power plants, FOSSIL fuels, NICKEL alloys
Abstract

Piping and components made of nickel alloys under plant specific loading conditions were tested to ensure the feasibility of high-efficiency ultra-supercritical coal-fired power plants by using the test loop HWT II system ( Hochtemperatur- Werkstoff- Teststrecke) installed in the fossil power plant GKM in Mannheim, Germany. The performance of the materials and the applicability of advanced numerical simulations for the lifetime assessment of components were performed. The results of materials investigations on Alloy 617 mod., Alloy 263, and their welded joints as well as numerical simulations for selected components under static and cyclic loading are presented. [ABSTRACT FROM AUTHOR]

Published
2016
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