TY - CONF A1 - Klingelhöffer, Hellmuth T1 - Thermo-mechanical fatigue life of nimonic 90 nickel base superalloy T2 - Euromat 2007 CY - Nuremberg, Germany DA - 2007-09-10 PY - 2007 AN - OPUS4-15956 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Klingelhöffer, Hellmuth T1 - Microstructural degredation of CMSX-4 unter creep conditions T2 - Euromat 2007 CY - Nuremberg, Germany DA - 2007-09-10 PY - 2007 AN - OPUS4-15992 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Bettge, Dirk A1 - Fedelich, Bernard A1 - Klingelhöffer, Hellmuth T1 - Modelling the orientation and direction dependence of the critical resolved shear stress of nickel-base superalloy single crystals PY - 2000 SN - 1359-6454 SN - 1873-2453 VL - 48 SP - 689 EP - 700 PB - Elsevier Science CY - Kidlington AN - OPUS4-2366 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Klingelhöffer, Hellmuth T1 - Cyclic stress strain behaviour T2 - HTMT-Seminar with concern to "Generation and application of materials property data" CY - Warrington, England DA - 2004-12-06 PY - 2004 AN - OPUS4-4830 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fedelich, Bernard A1 - Epishin, A. A1 - Link, T. A1 - Klingelhöffer, Hellmuth A1 - Künecke, Georgia A1 - Portella, Pedro Dolabella T1 - Experimental characterization and mechanical modeling of creep induced rafting in superalloys N2 - A constitutive model has been developed for the high temperature mechanical behavior of single crystal superalloys, including rafting and its consequences. The flow stress depends on the γ channel width via the Orowan stress. An evolution equation for channel widening during high temperature straining has been derived and calibrated with measurements. Therein, rafting is assumed to be driven by the relaxation of internal stresses. The model is able to represent the mechanical softening at high stresses consecutive to rafting. The model has been applied to simulate rafting during uniaxial creep in several crystal orientations, in notched specimens as well as in cyclically loaded specimens. KW - Single crystal KW - Superalloys KW - Rafting KW - Creep KW - Viscoplasticity KW - Constitutive law PY - 2012 DO - https://doi.org/10.1016/j.commatsci.2012.05.071 SN - 0927-0256 VL - 64 SP - 2 EP - 6 PB - Elsevier CY - Amsterdam AN - OPUS4-26401 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epishin, Alexander A1 - Link, T. A1 - Klingelhöffer, Hellmuth A1 - Fedelich, Bernard A1 - Portella, Pedro Dolabella T1 - Creep damage of single-crystal nickel base superalloys: mechanisms and effect on low cycle fatigue N2 - The main mechanisms of creep damage of single-crystal nickel-base superalloys are the loss of the interface coherency, coarsening of the γ / γ'-microstructure, precipitation of topologically closed packed phases and growth of porosity. This degradation deteriorates the mechanical properties such as yield stress, creep lifetime and especially low-cycle fatigue life, which can be reduced nearly by a factor of 10. The degradation kinetics during creep was characterised quantitatively on the superalloy CMSX-4. A new non-destructive testing technique was applied to cover a wide test parameter range with few specimens in a relatively short time: repeated load annealing of wedge shaped specimens. KW - Creep damage KW - Nickel-base superalloys KW - Low-cycle fatigue KW - Rafting KW - Porosity KW - Prior exposure PY - 2010 DO - https://doi.org/10.3184/096034009X12603595726283 SN - 0960-3409 VL - 27 IS - 1 SP - 53 EP - 59 PB - Science Reviews CY - St. Albans, Herts. [u.a.] AN - OPUS4-23912 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epishin, A. A1 - Link, T. A1 - Klingelhöffer, Hellmuth A1 - Fedelich, Bernard A1 - Brückner, Udo A1 - Portella, Pedro Dolabella T1 - New technique for characterization of microstructural degradation under creep: Application to the nickel-base superalloy CMSX-4 N2 - A new experimental technique (repeated load annealing of flat wedge shaped specimens) was proposed for characterization of microstructural degradation under creep conditions. This technique was applied to investigate the microstructural degradation of the nickel-base superalloy CMSX-4 in a wide range of temperatures and stress levels. The results obtained allowed to describe analytically the kinetics of rafting, which is important to predict the reduction of fatigue lifetime and yield stress. KW - Microstructural degradation KW - Nickel-base superalloys KW - Rafting PY - 2009 DO - https://doi.org/10.1016/j.msea.2008.04.135 SN - 0921-5093 SN - 1873-4936 VL - 510-511 SP - 262 EP - 265 PB - Elsevier CY - Amsterdam AN - OPUS4-19354 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Sievert, Rainer A1 - Fedelich, Bernard A1 - Günther, Burkhard A1 - Klingelhöffer, Hellmuth ED - Borsutzki, M. T1 - Zur Vorgehensweise bei der Bestimmung der Materialparameterwerte von inelastischen Verformungs- und Lebensdauer-Modellen für die Simulation des Materialverhaltens bei Hochtemperaturbeanspruchung N2 - Für viskoplastische Stoffgesetze wird das prinzipielle Verfahren der Identifikation von Materialmodell-Parametern für das Spannungs-Verformungs- und Versagens-Verhalten metallischer Werkstoffe am Beispiel von Hochtemperatur-Ermüdung aufgezeigt. Dies betrifft zum Einen die Verwendung geeigneter und auch möglichst weniger Experimente zur Hervorbringung der zu beschreibenden Phänomene des Werkstoffverhaltens und deren gezielte Auswertung sowie zum Anderen die physikalisch kontrollierte Führung einer numerischen Optimierung zur Ermittlung vertrauenswürdiger Materialparameterwerte. Diese Vorgehensweise wurde erfolgreich auf Warmarbeitsstähle sowie poly- und einkristalline Superlegierungen angewendet. T2 - Fortschritte der Kennwertermittlung für Forschung und Praxis CY - Bad Neuenahr, Deutschland DA - 2006-12-07 KW - Viskoplastische Materialmodelle KW - Lebensdauer-Regeln KW - Materialidentifikation PY - 2006 SN - 3-514-00734-9 SP - 121 EP - 126 PB - Stahleisen CY - Düsseldorf AN - OPUS4-14410 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Klingelhöffer, Hellmuth T1 - Creep damage mechanisms of single-crystal Nickel-base superalloys T2 - 2nd ECCC Creep Conference CY - Zurich, Switzerland DA - 2009-04-21 PY - 2009 AN - OPUS4-19477 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Epishin, Alexander A1 - Link, T. A1 - Klingelhöffer, Hellmuth A1 - Fedelich, Bernard A1 - Portella, Pedro Dolabella ED - S.R. Holdsworth, ED - I.A. Shibli, T1 - Creep damage mechanisms of single-crystal Nickel base superalloys T2 - 2nd ECCC Creep Conference CY - Zurich, Switzerland DA - 2009-04-21 KW - Creep damage KW - Nickel-base superalloys PY - 2009 SN - 978-1-60595-005-1 SP - 692 EP - 701 PB - DEStech Publications, Inc. AN - OPUS4-19448 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brookes, Stephen-Peter A1 - Kühn, Hans-Joachim A1 - Skrotzki, Birgit A1 - Klingelhöffer, Hellmuth A1 - Sievert, Rainer A1 - Pfetzing, J. A1 - Peter, D. A1 - Eggeler, G. T1 - Axial-torsional thermomechanical fatigue of a near-gamma TiAl-alloy N2 - The uniaxial, torsional and axial-torsional thermomechanical fatigue (TMF) behavior of the near-γ TiAl-alloy TNB-V5 was investigated. TMF tests were performed at 400-800 °C with mechanical strain amplitudes ranging from 0.15% to 0.7%. The tests were conducted thermomechanically in-phase (IP) and out-of-phase (OP). For the same lifetimes, uniaxial IP tests required the highest strain amplitudes, while OP test conditions were most damaging and needed the lowest strain amplitudes. The Mises equivalent mechanical strain amplitudes of pure torsional tests were found in between uniaxial in-phase and out-of-phase tests for the same lifetimes. The non-proportional multiaxial out-of-phase test showed a lower lifetime at the same equivalent mechanical strain amplitude compared to the other types of tests. The microstructure has been characterized applying electron microscopy and microstructural parameters such as fraction of twinned grains, grain size, lamellar distance and dislocation density have been quantified. KW - Gamma titanium aluminide KW - TNB-V5 KW - Thermomechanical fatigue (TMF) KW - Axial-torsional loading KW - Microstructure PY - 2010 DO - https://doi.org/10.1016/j.msea.2010.03.073 SN - 0921-5093 SN - 1873-4936 VL - 527 IS - 16-17 SP - 3829 EP - 3839 PB - Elsevier CY - Amsterdam AN - OPUS4-21289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -