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[en] For the assessment of cracks in First Wall structures built from EUROFER 97 of future fusion reactors the fatigue crack behaviour in EUROFER 97 was investigated at room temperature (RT), 300, 500 and 550 C. For this purpose fatigue crack growth tests were performed using CT specimens with two R-ratios, R=0.1 and R=0.5, respectively. Hence, fatigue crack threshold, fatigue crack growth behaviour in the near-threshold range and their dependences on temperature and R-ratio were determined and described using an analytical formula. The fatigue crack threshold showed a monotonic dependence on temperature which is for insignificantly small. The fatigue crack growth behaviour exhibited for a nonmonotonic dependence on temperature which is explained by the decrease of yield stress and the increase of creep damage when increasing the temperature
[de]
Zur Beurteilung von Rissen in aus EUROFER 97 gefertigten Strukturen der Ersten Wand zukuenftiger Fusionsreaktoren wurde das Ermuedungsrissverhalten in EUROFER 97 bei Raumtemperatur (RT), 300, 500 und 550 C untersucht. Hierfuer wurden bei jeder Temperatur Ermuedungsrissexperimente an CT-Proben mit zwei unterschiedlichen R-Verhaeltnissen, und durchgefuehrt. Daraus wurden der Ermuedungsrisswiderstand und das Ermuedungsrissverhalten im risswiderstandsnahen Bereich sowie ihre Abhaengigkeiten von der Temperatur und dem R-Verhaeltnis ermittelt und mit analytischen Formeln beschrieben. Der Ermuedungsrisswiderstand zeigte eine monotone Abhaengigkeit von der Temperatur, die bei geringfuegig ist. Das Ermuedungsrissverhalten hingegen wies bei eine nicht-monotone Abhaengigkeit von der Temperatur auf, die auf die Abnahme der Fliessspannung und die Zunahme der Kriechschaedigung mit steigender Temperatur zurueckgefuehrt wirdSource
May 2005; 19 p; ISSN 0947-8620; 
; Available from TIB Hannover: ZA 5141(7119)
; Available from TIB Hannover: ZA 5141(7119)
[en] Structural materials of fusion reactors are subjected to complex creep-fatigue loading and high irradiation doses. Correct modelling of their deterioration is a precondition of a sufficiently reliable lifetime prediction procedure. In the continuum mechanics approach selected for lifetime prediction of RAFM steels under creep-fatigue conditions the ISRM (Inelastic Strain Rate Modified) damage model is coupled with a modified viscoplastic deformation model taking into account the complex nonsaturating cyclic softening of RAFM steels. The resulting coupled model is a powerful prediction tool, which can be applied to arbitrary creep-fatigue loading provided that the material, temperature and possibly irradiation dose dependent parameters of the model have been determined. Therefore a fitting procedure has been developed for the parameters identification on the base of deformation and lifetime data from standard low cycle fatigue (LCF) tests without and with hold time as well as creep tests. The coupled deformation-damage model has been meanwhile applied to F82H mod and EUROFER 97 in the reference (unirradiated) state under isothermal cyclic loading at 450, 550 and 650 C. The comparisons between model and experiment show that the observed lifetimes in the LCF-tests could be fairly well calculated even for the tests with hold time, which were not considered for the identification of the damage model parameters. However before releasing the model further verifications have to be done by applying the model to isothermal two-steps LCF-tests (low-to-high and high-to-low), to thermo-mechanical LCF-tests, to isothermal multiaxial LCF-tests as well as to a suitable benchmark component test. To take into account the influence of irradiation applications of the model are in long term foreseen to several irradiated states with sufficient data base
Source
Wissenschaftliche Berichte; May 2004; 32 p; ISSN 0947-8620; ; Available from TIB Hannover: ZA5141(6931)
; Available from TIB Hannover: ZA5141(6931)
[en] This report summarizes Fracture Mechanical (FM) experiments carried out under the contract of the European Fusion Development Agreement (EFDA), subtask TW5-TTMS-005-D04 for supporting the modeling work on size effects in ductile and ductile to brittle transition region performed within a task TW5-TTMS-005-D3. Quasi-static three-point-bend (3PB) experiments have been performed on the European reference RAFM steel EUROFER 97 and on a martensitic steel MANET II. The crack resistance curves have been constructed from the original fracture mechanical data in the ductile and ductile to brittle transition regions. Additionally, in the ductile region, where complexity of the three dimensional fracture surfaces prevented an explicit quantitative assessment of the crack extension, the validity of the failure assessment diagram (R6) has been verified for RAFM steel EUROFER 97. (orig.)
[de]
In diesem Bericht werden die bruchmechanischen Untersuchungen zusammengefasst, welche zur Unterstuetzung von Modellierungsarbeiten von Groesseneffekten in duktilen und sproedduktilen Uebergangsbereichen (Subtask TW5-TTMS-005-D03) im Rahmen des Europaeischen Abkommens zur Entwicklung der Fusionsforschung (EFDA), Subtask TW5-TTMS-005-D04 durchgefuehrt wurden. Es wurden quasi-statische Drei-Punkt-Biegeversuche (3PB) an dem Europaeischen RAFM Referenzstahl EUROFER 97 und an dem martensitischen Stahl MANET II durchgefuehrt. Die Risswiderstandskurven wurden durch die Auswertung von bruchmechanischen Versuchen in duktilen und sproed-duktilen Uebergangsbereichen erstellt. Im duktilen Bereich, wo die Komplexitaet der drei dimensionalen Bruchflaechen eine explizite quantitative Auswertung des Risswachstums verhinderte, wurde zusaetzlich die Gueltigkeit der Auslegungskurve (R6) an dem RAFM Stahl EUROFER 97 ueberprueftSource
Aug 2006; 24 p; ISSN 0947-8620; ; Available from TIB Hannover: ZA 5141(7252)
; Available from TIB Hannover: ZA 5141(7252)
[en] In the first line, the aim of the activity represented in this work is an application of two advanced material models to a simulation of the test blanket module (TBM) undergoing cyclic thermal and mechanical loadings. The first model is thereby the ABAQUS standard combined non-linear isotropic-kinematic hardening model whereas the second is a viscoplastic material model considering material damage and being newly implemented as an ABAQUS user material (UMAT). Material parameters for both models are adjusted using results of isothermal tensile and cyclic experiments performed at Forschungszentrum Karlsruhe GmbH (FZK) on EUROFER 97. As is generally known, EUROFER 97 is an important blanket material for the future fusion reactor and belongs to reduced activation ferriticmartensitic steels (RAFM), which soften under cyclic loading in contrast to austenitic steels exhibiting cyclic hardening. Moreover, the work is focused on the application of some existing design rules considered for austenitic steels and further evaluation of the rules by comparison of their predictions with results of cyclic simulations using the advanced material models mentioned above. Thereby, some important allowable stress limits are calculated under consideration of the cyclic softening of RAFM. Finally, new considerations concerning a mock-up experiment allowing to verify the advanced material models used in the present work and to assess a capability of the actual TBM design are represented here. (orig.)
[de]
Die in dieser Arbeit praesentierte Aktivitaet ist ausgerichtet auf die Anwendung von zwei recht komplizierten Materialmodellen an die Simulation vom Testblanketmodul unter der Einwirkung von thermischen und mechanischen Lasten. Das erste Modell ist dabei ein standardmaessiges kombiniertes nichtlineares isotropisch-kinematisches Verfestigungsmodell aus der ABAQUS-Bibliothek, waehrend das Andere ein gekoppeltes viskoplastisches Deformation/Schaedigungsmodell ist, das als ein anwenderdefiniertesMaterial (UMAT) in ABAQUS implementiert wurde. Die Materialparameter fuer beide Modelle wurden aufgrund von Experimentaldaten aus den isothermischen zyklischen Zugversuchen angefittet, die bei verschiedenen Temperaturen am Forschungszentrum Karlsruhe GmbH (FZK) an EUROFER 97 durchgefuehrt wurden. Es ist allgemein bekannt, dass der Stahl EUROFER 97 ein wichtiges Material fuer die erste Wand der zukuenftigen Fusionsreaktoren konzipiert wurde. Dieses Material gehoert zu den so genannten niedrigaktivierenden ferritisch-martensitischen Staehlen (RAFM), die im Gegensatz zu den austenitischen Staehlen eine zyklische Entfestigung aufweisen. Weiterhin ist diese Arbeit schwerpunktmaessig auf den Einsatz von einigen existierenden Designregeln fokussiert, die urspruenglich fuer austenitische Staehle formuliert wurden. Die ausgewaehlten Regeln sollen dabei evaluiert werden, indem ihre Aussagen mit den Ergebnissen der zyklischen Simulation unter Verwendung der o.g. Materialmodelle verglichen werden. Nebenbei sind auch einige wichtige zulaessige Spannungsintensitaeten unter Beruecksichtigung der zyklischen Entfestigung von RAFM hergeleitet worden. Ein Mock-Up-Experiment soll fuer die Zwecke der Verifizierung der verwendeten Materialmodelle sowie der Bewertung der Tauglichkeit der vorgeschlagenen TBM-Designs dienen. Neue Ueberlegungen bezueglich eines solchen Mock-Up-Experiments sind auch in dieser Arbeit dargestelltSource
Aug 2006; 66 p; ISSN 0947-8620; ; Available from TIB Hannover: ZA 5141(7241); 17 refs.
; Available from TIB Hannover: ZA 5141(7241); 17 refs.
[en] High temperature creep-fatigue design rules already established in the ASME and RCC-MR codes have been reviewed, analysed and reformulated for the assessment of components built from EUROFER 97. For the verification of the rules isothermal two-steps fatigue, thermo- mechanical fatigue and isothermal multiaxial fatigue tests have been performed and evaluated. It has been found that the conventional design rules are not straightforward applicable for EUROFER 97. They can not cover the strong lifetime reduction observed under thermo-mechanical and multiaxial cyclic loadings which has been mainly attributed to the different cyclic softening behaviour under these loading modes in comparison to isothermal uniaxial loading. Hence, the rules have been modified by deriving new fatigue design curves taking into account cyclic softening effects. Thereby, a damage model recently developed to describe the deterioration of EUROFER 97 under creep fatigue loading has been used. Even the improved rules have been sufficiently conservative when considering the verification tests performed further verifications are recommended. (orig.)
Source
Aug 2007; 37 p; ISSN 0947-8620; ; Available from TIB Hannover: ZA 5141(7309)
; Available from TIB Hannover: ZA 5141(7309)
[en] Highlights: • Fracture toughness tests of two different tungsten plates with two orientation in the brittle and semi brittle regime. • Fracture surface analysis by scanning electron microscope (SEM). • Crack path analysis by light microscope. -- Abstract: Polycrystalline tungsten is a promising candidate for future fusion applications as plasma facing material due to its good thermophysical properties at high temperatures. Fracture mechanical properties of sintered and rolled, commercially available polycrystalline tungsten are characterized taking into account the strong anisotropy due to different grain shape and orientation with respect to the rolling direction. The fracture mechanics investigations are accompanied by fractographic analyses of two tungsten plate grades with varying cold working ratios of two different manufacturers (PLANSEE SE, Austria and A.L.M.T Corp., Japan). In this respect three point bending tests (3-PB) with sub sized fracture mechanical specimens in different orientations of the anisotropic microstructure are performed at three temperatures, ranging from 25 °C to 400 °C at a deflection rate of 2 µm s − 1. In addition, crack initiation and crack growth mechanisms depending on texture and cold working ratio are investigated by means of scanning electron microscopy (SEM).
Journal
Nuclear Materials and Energy; ISSN 2352-1791; ; v. 21; vp
; v. 21; vp
[en] This paper presents a method for the numerical inductance calculation of a passive electromagnetic inductive device using cores made of a nonlinear magnetic material. The material model used for this purpose describes the nonlinear magnetic behavior by a set of differential equations. The coupled implicit system of Maxwell equations and material model equations is solved by a simplified algorithm which shall be explained while applied to a new design of a microinductor, the so called I-inductor
Journal
[en] The paper presents a new kind of numerical model describing nonlinear magnetic behaviour. The model is formulated as a set of differential equations taking into account history dependence phenomena like the magnetisation hysteresis as well as saturation effects. The capability of the model is demonstrated carrying out comparisons between measurements and calculations
Journal
Journal of Magnetism and Magnetic Materials; ISSN 0304-8853; ; CODEN JMMMDC; v. 212(1-2); p. 267-272
; CODEN JMMMDC; v. 212(1-2); p. 267-272
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