TY - CONF A1 - Müller, Ralf A1 - Behrens, H. A1 - Deubener, J. T1 - Impact of structure and relaxation on fatigue and micromechanical properties of oxide glasses: the role of volatiles and bonding state N2 - As subcritical crack growth (SCCG) can reduce tensile strength of glasses by many orders of magnitude, the potential for improvement of fatigue behaviour is most intriguing in developing ultra-strong glasses. An essential bottleneck is the basic understanding of the numerous interplaying pressure-, temperature- and water-affected relaxation phenomena at the crack tip and related toughening strategies. Therefore, the present project aims to advance the basic understanding of structural relaxation effects and local properties caused by increased water concentration and tensile stresses at the crack tip as they are a key for structural toughening designs to develop SCCG-free glasses and glass surfaces. Our first studies give clear evidence that glass structure and dynamics is strongly modified upon hydration of glasses. These changes are highly related to the nature of network formers but are affected as well by the counter ions (network modifier). Results of the 1st project part suggest that structural relaxation below glass transition temperature, i.e. overlapping of short-range (beta) and long-range (alpha) interactions can contribute to SCCG in water-free environments and that structurally dissolved water in the glasses can have decisive impact on this effect. In the 2nd project stage specific glasses compositions will be investigated to gain an improved understanding on the relation of sub-Tg relaxation and inert SCCG as well as to shed light to the related effects of dissolved water and its speciation. These glasses cover a broader range of different glass topologies and binding partners, whereby the coupling of alpha and beta relaxations is varied systematically by alkali-, alkaline earth ions and water species concentrations. Preparation of hydrous glasses (up to 8 wt% water) will be performed by high pressure syntheses. Structure will be resolved by NMR, Raman and IR spectroscopy while structural relaxation is accessed in the temperature and frequency domain using dynamic mechanical spectroscopy and ultrasonic damping. We will focus on measurements of inert SCCG (region III) conducting experiments in vacuum and dry gas atmospheres using indentation techniques and stressing of glass specimens in DCB geometry. Experimental data on SCCG will be provided to SPP groups, which deals with fatigue in metallic glasses and vice versa we will test theoretical predictions of ab-initio simulations of partner within SPP 1594 in order to quantify the effect of water on the crack tip. In summa topological factors controlling the subcritical crack growth with respect to water will be identified from which structural toughening designs for highly fatigue resistant-glasses can be derived. N2 - Subkritisches Risswachstum (SCCG) kann die Zugfestigkeit von Glas um viele Größenordnungen erniedrigen. Deshalb birgt die Verbesserung des Ermüdungsverhaltens ein hohes Potential für das topologische Design hochfester Gläser. Ein diesbezüglicher Engpass ist das Verständnis der zahlreichen interagierenden druck-, temperatur- und wasserbeeinflussten Relaxationsphänomene an der Rissspitze und hieraus abgeleitete Verstärkungsstrategien. Ziel des Projekts ist es daher, das grundlegende Verständnis der Effekte, die infolge erhöhter Wasserkonzentrationen und Zugspannungen an der Rissspitze entstehen, zu vertiefen, da sie als ein Schlüssel für künftige strukturelle Designprinzipien zur Entwicklung schadenstoleranter Gläser und Glasoberflächen gelten. Unsere ersten Studien zeigen, dass die Struktur und Dynamik von Gläsern nach einer Hydration stark verändert sind. Diese Modifikationen sind mit der Art der Netzwerkbildner stark verknüpft, aber auch von ihren Gegenionen (Netzwerkwandler) abhängig. Die Ergebnisse des ersten Projektabschnitts legen nahe, dass strukturelle Relaxation unterhalb der Glasübergangstemperatur, d. h. ein Überlappen von kurz-reichweitigen (beta) und lang-reichweitigen (alpha) Wechselwirkungen, zum subkritisches Risswachstum in wasserfreien Umgebungen beitragen kann und, dass strukturell gelöstes Wasser in Gläsern sich entscheidend auf diese Effekt auswirken kann. Im zweiten Projektabschnitt werden daher spezielle Glaszusammensetzungen untersucht, die zu einem besseren Verständnis der Verbindung zwischen sub-Tg Relaxation und SCCG führen aber auch den Einfluss von gelöstem Wasser und dessen Speziation näher beleuchten. Diese Gläser weisen eine großen Breite an verschiedenen Topologien und Bindungspartnern auf, wobei die Kopplung von alpha und beta Relaxation durch Veränderungen in den Gehalten von Alkali-, Erdalkalionen und der Wasserspezies systematisch variiert wird. Die Präparation hydratisierter Gläser (bis zu 8 Ma.%) erfolgt mittels Hochdrucksynthesen. Die Glasstruktur wird durch NMR, Raman und IR Spektroskopie aufgeklärt während die Strukturrelaxation anhand dynamische mechanische Spektroskopie und Ultraschalldämpfung im Temperatur- und Frequenzraum erfasst wird. Im Fokus werden Messungen des inerten subkritischen Risswachstums (Region III) stehen, die Indenter-Experimente im Vakuum und trockenen Gasatmosphären sowie Verspannen von Glasproben in DCB Geometrie beinhalten. Experimentelle SCCG Daten werden Gruppen im Schwerpunktprogramm zur Verfügung stellen, die sich mit Ermüdung in metallischen Gläsern beschäftigen und im Gegenzug werden wir theoretische Vorhersagen aus ab initio Simulationen der Partner im SPP 1594 testen, um den Einfluss von Wasser auf die mechanischen Eigenschaften an der Rissspitze und deren Einfluss auf SCCG zu quantifizieren. In summa werden topologische Faktoren bezüglich Wasser, die SCCG kontrollieren, identifiziert, um daraus Designprinzipien für hoch ermüdungsresistente Gläser abzuleiten. T2 - Kolloquium des DFG-PP 1594 CY - Jena, Germany DA - 17.9.2015 KW - Glass KW - Fatigue PY - 2015 AN - OPUS4-38334 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Müller, Ralf A1 - Behrens, H. A1 - Deubener, J. A1 - Reinsch, Stefan A1 - Bauer, Ute A1 - Rößler, C. T1 - Impact of structure and relaxation on fatigue and micro-mechanical properties of oxide glasses: the role of volatiles and bonding state N2 - As subcritical crack growth (SCCG) can reduce tensile strength of glasses by many orders of magni-tude, the potential for improvement of fatigue behaviour is most intriguing in developing ultra-strong glasses. An essential bottleneck is the basic understanding of the numerous interplaying pressure-, temperature- and water-affected relaxation phenomena at the crack tip and related toughening strat-egies. Therefore, the present project aims to advance the basic understanding of structural relaxa-tion effects and local properties caused by increased water concentration and tensile stresses at the crack tip as they are a key for structural toughening designs to develop SCCG-free glasses and glass surfaces. Our first studies give clear evidence that glass structure and dynamics is strongly modified upon hy-dration of glasses. These changes are highly related to the nature of network formers but are affect-ed as well by the counter ions (network modifier). Results of the 1st project part suggest that struc-tural relaxation below glass transition temperature, i.e. overlapping of short-range (beta) and long-range (alpha) interactions can contribute to SCCG in water-free environments and that structurally dissolved water in the glasses can have decisive impact on this effect. In the 2nd project stage specific glasses compositions will be investigated to gain an improved un-derstanding on the relation of sub-Tg relaxation and inert SCCG as well as to shed light to the relat-ed effects of dissolved water and its speciation. These glasses cover a broader range of different glass topologies and binding partners, whereby the coupling of alpha and beta relaxations is varied systematically by alkali-, alkaline earth ions and water species concentrations. Preparation of hy-drous glasses (up to 8 wt% water) will be performed by high pressure syntheses. Structure will be resolved by NMR, Raman and IR spectroscopy while structural relaxation is accessed in the temper-ature and frequency domain using dynamic mechanical spectroscopy and ultrasonic damping. We will focus on measurements of inert SCCG (region III) conducting experiments in vacuum and dry gas atmospheres using indentation techniques and stressing of glass specimens in DCB geometry. Experimental data on SCCG will be provided to SPP groups, which deals with fatigue in metallic glasses and vice versa we will test theoretical predictions of ab-initio simulations of partner within SPP 1594 in order to quantify the effect of water on the crack tip. In summa topological factors con-trolling the subcritical crack growth with respect to water will be identified from which structural toughening designs for highly fatigue resistant-glasses can be derived. T2 - Kolloquium des DFG-PP 1593 Ultrastrong Glasses CY - Jena, Germany DA - 17.9.2015 KW - Glass KW - Fatigue PY - 2015 AN - OPUS4-38335 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weise, Frank A1 - Meng, Birgit A1 - Voland, K. A1 - Pirskawetz, Stephan T1 - Influence of simultaneous cyclic loading and external alkali supply on the alkali-silica reaction in concrete pavements N2 - In recent years the German highway network has seen an increase in the occurrence of damage in concrete road surfaces which can be attributed to the alkali-silica reaction (ASR). In view of the often drastic reduction in life expectancy experienced by concrete pavements due to ASR, research activity in this field has notably increased. Until now the main research focus has been, alongside preventative measures in concrete technology, the development of performance-oriented testing procedures for ASR prevention. This included more specifically the accelerated simulation of climatic effects and external alkali supply on concrete pavements. The effects of pre-damage from the additionally interacting cyclic traffic loading had previously not been taken into consideration. Since 2011, a five-partner research group from the German Research Foundation has been pursuing research on the effects of simultaneous cyclic loading and external alkali supply on the destructive ASR in concrete pavements. The depiction of the myriad degradation and transport processes necessary for an understanding of these effects requires a close interaction between experiments and their multi-scale modelling. This contribution aims to focus on the aforementioned experiments by means of innovative testing techniques. The research is founded on a series of cyclic fatigue tests performed on large-format beams, both with and without previous application of a NaCl solution, with simultaneous tracking of crack development. Thereafter, smaller test specimens were extracted from the pre-damaged beams for further experiments. These included the spatial visualization and quantification of fatigue-induced cracks with X-ray 3D-computed tomography. Additionally, the effects of fatigue-induced cracks on moisture and alkali transport were investigated using 3D-CT and Laser-Induced Breakdown Spectroscopy (LIBS). Subsequent storage of the small-format test specimens, with and without cyclic pre-damage, in an ASR-conducive environment was then able to shed light on the influence of fatigue-induced pre-damage on the ASR. T2 - 15th International Conference on Alkali-Aggregate Reaction (ICAAR 2016) CY - Sao Paulo, Brazil DA - 03.07.2016 KW - Concrete pavements KW - Alkali-silica-reaction KW - Fatigue KW - Damage monitoring PY - 2016 AN - OPUS4-36950 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc A1 - Petryna, Y. A1 - Rogge, Andreas ED - Saouma, V. ED - Bolander, J. ED - Landis, E. T1 - Experimental investigation of damage evolution in concrete under high-cycle fatigue T2 - The 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures N2 - The current knowledge about fatigue behavior of concrete is still incomplete. This concerns especially the progress of fatigue which precedes the fatigue failure. Therefore, the process of fatigue itself under cyclic compressive loading was investigated in a systematic and comprehensive way. The aim of this investigation was to obtain a deeper insight and to provide a better understanding of the damage process occurring within the material during fatigue loading. Concrete cylinders were tested with a number of cycles to failure between 106 and 107. To investigate macroscopic and microscopic changes in the material, various methods of non-destructive and destructive testing were used. One main result was, in contrast to other authors, that the investigated changes in macroscopic material behavior could not be explained only by a development of micro-cracks. The results indicated rather, that the related changes in the fatigue behavior are mainly a result of viscous processes in the hardened cement paste, similar to the processes of creep. Based on the experimental results a description of the possible processes was derived which take place in the material structure during fatigue loading and also leads to the observed macroscopic changes in the material behavior. In this context, the results have shown that in case of isotropic material behavior a stiffness reduction related to a scalar value could not capture the damage effect on the stress-strain-relationship caused by fatigue. T2 - The 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures CY - Berkeley, CA, USA DA - 29.5.2016 KW - Fatigue KW - Concrete KW - High-cycle KW - Damage evolution PY - 2016 DO - https://doi.org/10.21012/FC9.302 SP - 1 EP - 9 AN - OPUS4-38242 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Trappe, Volker A1 - Hickmann, Stefan A1 - Müller, Alexander T1 - Infinite life of CFRP evaluated non-destructively with X-ray-refraction topography in-situ mechanical loading N2 - Carbon Fibre Reinforced Plastics (CFRP) are more and more used in modern civil aircrafts. These days the whole fuselage is made of this material (B787; A350). Due to strict certification standards the normal in-service loading gives a low stress level compared to the static and even the fatigue strength of the material. Hence CFRP are assumed to have an infinite life. To evaluate this assumption, fatigue tests on CFRP-specimens were performed up to 108 load cycles and the first inter-fibre failure was evaluated non-destructively by accompanying X-ray-refraction topography. A tensile testing machine was integrated in a small angle X-ray scattering (SAXS) setup. X-ray refraction topography was performed while the CFRP-samples were tensile loaded. This non-destructive technique enables the detection of micro-cracking and inter-fibre failure especially for CFRP. For Glass Fibre Reinforced Plastic (GFRP) X-ray refraction and in-situ loading has already been successfully used. The increase of inner surfaces due to inter fibre failure was measured as a function of the stress state. Fatigue tests were performed at and below the limit of inter-fibre failure strength. State of the art is to assume the failure of the samples under cyclic loading as the fatigue life. Accompanying non-destructive X-ray refraction measurements reflects the damage state and enables to trace its evolution even if the total failure of the specimens does not occur. This investigation technique is of high interest to give the engineer a design value of infinite life which is practically often reached due to knock down factors of certification standards. Finally the infinite life was found for cyclic fatigue loaded CFRP-samples even under high inter fibre transverse and shear loading investigated up to 108 load cycles. T2 - 19th World Conference on Non-Destructive Testing CY - Munich, Germany DA - 13.06.2016 KW - CFRP KW - NDT KW - Fatigue KW - Damage evolution PY - 2016 AN - OPUS4-37567 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc A1 - Petryna, Y. A1 - Rogge, Andreas T1 - Experimental investigation of damage evolution in concrete under high-cycle fatigue N2 - The current knowledge about fatigue behavior of concrete is still incomplete. This concerns especially the progress of fatigue which precedes the fatigue failure. Therefore, the process of fatigue itself under cyclic compressive loading was investigated in a systematic and comprehensive way. The aim of this investigation was to obtain a deeper insight and to provide a better understanding of the damage process occurring within the material during fatigue loading. Concrete cylinders were tested with a number of cycles to failure between 1E6 and 1E7. To investigate macroscopic and microscopic changes in the material, various methods of non-destructive and destructive testing were used. One main result was, in contrast to other authors, that the investigated changes in macroscopic material behavior could not be explained only by a development of micro-cracks. The results indicated rather, that the related changes in the fatigue behavior are mainly a result of viscous processes in the hardened cement paste, similar to the processes of creep. Based on the experimental results a description of the possible processes was derived which take place in the material structure during fatigue loading and also leads to the observed macroscopic changes in the material behavior. In this context, the results have shown that in case of isotropic material behavior a stiffness reduction related to a scalar value could not capture the damage effect on the stress-strain-relationship caused by fatigue. T2 - The 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures CY - Berkeley, CA, USA DA - 29.05.2016 KW - Fatigue KW - Concrete KW - High-Cycle KW - Damage Evolution PY - 2016 AN - OPUS4-38723 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc A1 - Petryna, Y. A1 - Rogge, Andreas A1 - Baeßler, Matthias ED - Beushausen, Hans T1 - Experimental investigation of fatigue process in concrete under high-cycle loading T2 - Performance-based approaches for concrete structures N2 - Fatigue is of relevance not only for metals but also for concrete. The current knowledge about fatigue behaviour of concrete is, however, incomplete. This concerns especially the progress of fatigue which precedes the fatigue failure. Some macroscopic effects of this process are well known but the governing material changes behind them are still less studied. The focus of the present contribution lay on a systematic and comprehensive investigation of the fatigue process under cyclic compressive loading. The aim was to obtain a deeper insight and to provide a better understanding of the damage process in the material. Cylindrical specimens were tested with a number of cycles to failure between 106 and 107. Various methods of non-destructive and destructive testing were used to investigate macroscopic and microscopic changes in the material. One main result was that the changes in the macroscopic material behaviour could not be explained only by the development of micro cracks. The results indicated that the related changes in the fatigue behaviour originate rather from viscous processes in the cement stone, similar to the process of creep. A sound description of the possible processes was derived from the obtained experimental results which concerns material structure during fatigue loading. It has been shown that in case of isotropic material behaviour a stiffness reduction related to a scalar value could not capture the damage effect on the stress-strain relationship caused by fatigue. T2 - fib symposium 2016 CY - Cape Town, South Africa DA - 21.11.2016 KW - High-cycle KW - Fatigue KW - Concrete KW - Damage evolution PY - 2016 SN - 978-2-88394-121-2 VL - 2016 SP - 1 EP - 10 PB - University of Cape Town CY - Cape Town AN - OPUS4-38720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc A1 - Petryna, Y. A1 - Rogge, Andreas A1 - Baeßler, Matthias T1 - Experimental investigation of fatigue process in concrete under high-cycle loading N2 - Fatigue is of relevance not only for metals but also for concrete. The current knowledge about fatigue behaviour of concrete is, however, incomplete. This concerns especially the progress of fatigue which precedes the fatigue failure. Some macroscopic effects of this process are well known but the governing material changes behind them are still less studied. The focus of the present contribution lay on a systematic and comprehensive investigation of the fatigue process under cyclic compressive loading. The aim was to obtain a deeper insight and to provide a better understanding of the damage process in the material. Cylindrical specimens were tested with a number of cycles to failure between 106 and 107. Various methods of non-destructive and destructive testing were used to investigate macroscopic and microscopic changes in the material. One main result was that the changes in the macroscopic material behaviour could not be explained only by the development of micro cracks. The results indicated that the related changes in the fatigue behaviour originate rather from viscous processes in the cement stone, similar to the process of creep. A sound description of the possible processes was derived from the obtained experimental results which concerns material structure during fatigue loading. It has been shown that in case of isotropic material behaviour a stiffness reduction related to a scalar value could not capture the damage effect on the stress-strain relationship caused by fatigue. T2 - fib symposium 2016 CY - Cape Town, South Africa DA - 21.11.2016 KW - High-cycle KW - Fatigue KW - Concrete KW - Damage evolution PY - 2016 AN - OPUS4-38721 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Trappe, Volker A1 - Müller, Alexander A1 - Hickmann, Stefan T1 - Infinite life of CFRP evaluated non-destructively with X-ray-refraction topography in-situ mechanical loading T2 - WCNDT-Proceedings 2016 N2 - Carbon Fibre Reinforced Plastics (CFRP) are more and more used in modern civil aircrafts. These days the whole fuselage is made of this material (B787; A350). Due to strict certification standards the normal in-service loading gives a low stress level compared to the static and even the fatigue strength of the material. Hence CFRP are assumed to have an infinite life. To evaluate this assumption, fatigue tests on CFRP-specimens were performed up to 108 load cycles and the first inter-fibre failure was evaluated non-destructively by accompanying Xray-refraction topography. A tensile testing machine was integrated in a small angle X-ray scattering (SAXS) setup. X-ray refraction topography was performed while the CFRP samples were tensile loaded. This non-destructive technique enables the detection of micro-cracking and inter-fibre failure especially for CFRP. For Glass Fibre Reinforced Plastic (GFRP) X-ray refraction and in-situ loading has already been successfully used. The increase of inner surfaces due to inter fibre failure was measured as a function of the stress state. Fatigue tests were performed at and below the limit of inter-fibre failure strength. State of the art is to assume the failure of the samples under cyclic loading as the fatigue life. Accompanying non-destructive X-ray refraction measurements reflects the damage state and enables to trace its evolution even if the total failure of the specimens does not occur. This investigation technique is of high interest to give the engineer a design value of infinite life which is practically often reached due to knock down factors of certification standards. Finally the infinite life was found for cyclic fatigue loaded CFRP-samples even under high inter fibre transverse and shear loading investigated up to 108 load cycles. T2 - 19th World Conference on Non-Destructive Testing CY - Munich, Germany DA - 13.06.2016 KW - CFRP KW - NDT KW - Fatigue KW - Damage evolution PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-375015 UR - https://www.ndt.net/?id=19360 SN - 978-3-940283-78-8 VL - 2016 SP - 1 EP - 9 PB - DGZFP CY - Berlin AN - OPUS4-37501 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Thiele, Marc T1 - Experimentelle Untersuchung und Analyse der Schädigungsevolution in Beton unter hochzyklischen Ermüdungsbeanspruchungen N2 - Im Mittelpunkt der vorliegenden Arbeit steht das Ermüdungsverhalten von Beton unter hochzyklischen Druckschwellbeanspruchungen. Der aktuelle Wissensstand bezüglich des Ermüdungsverhaltens ist nach wie vor sehr lückenhaft. Ganz besonders trifft das auf den eigentlichen Ermüdungsprozess zu, der dem abschließenden Ermüdungsversagen vorausgeht. Dem Defizit im Wissen um das Ermüdungsverhalten steht allerdings eine zunehmende Bedeutung der Thematik in der Baupraxis gegenüber. Daher wurde im Rahmen dieser Arbeit eine systematische Untersuchung des Ermüdungsprozesses vorgenommen. Damit wird ein Beitrag geleistet, um einen tieferen Einblick und ein besseres Verständnis für den Schädigungsprozess und die damit verbundenen Vorgänge innerhalb des Betons zu gewinnen. Die experimentellen Untersuchungen bestehen im Wesentlichen aus einstufigen Dauerschwingversuchen im Druckschwellbereich an zylindrischen Probekörpern aus Normalbeton. Verwendet wurden zwei verschiedene Ermüdungslastniveaus, die Bruchlastzyklen zwischen 10⁶ und 10⁷ sowie zwischen 10³ und 10⁴ erzeugten. Die Untersuchung des Ermüdungsvorgangs erfolgte durch den Einsatz verschiedener ZfP- und ZP-Methoden, wie der Dehnungsmessung, der Messung flächiger Oberflächenverformungen, der Ultraschallmessung, der Schallemissionsmessung, der Lichtmikroskopie und des Rasterelektonenmikroskops. Zur Bewertung einiger Einflussgrößen im Zusammenhang mit dem Ermüdungsverhalten fanden zudem ergänzende Versuche zum Kriecheinfluss sowie zum Einfluss der Probengröße statt. Es konnte festgestellt werden, dass es sich bei dem Ermüdungsvorgang um eine von Beginn an einsetzende Schädigungsevolution innerhalb des Betons handelt. Diese beeinflusst die verschiedenen Materialeigenschaften des Betons in vielfältiger und sehr unterschiedlicher Weise. Die wesentlichste Feststellung in diesem Zusammenhang ist, dass die ermüdungsbedingte Materialschädigung zu einer Veränderung der gesamten Spannungs-Dehnungs-Beziehung führt, die sich ebenfalls in einem fortlaufenden Evolutionsprozess äußert. Aus den Untersuchungen konnten als entscheidende Ursache für die beobachteten Veränderungen im makroskopischen Materialverhalten Veränderungen in der Mikrorissstruktur nicht festgestellt werden. Vielmehr weisen die Ergebnisse der Untersuchungen darauf hin, dass die ermüdungsbedingten Veränderungen speziell in den Phasen I und II vorrangig das Resultat von viskosen Prozessen innerhalb des Zementsteins sind. Darüber hinaus geht aus den Versuchen hervor, dass auch das Kriechen zu relativ ähnlichen, aber weniger stark ausgeprägten Veränderungen im Material führt. Ein Einfluss der Probengröße auf das resultierende Verhalten konnte sowohl im statischen als auch im zyklischen Fall beobachtet werden. Aus den gewonnenen experimentellen Erkenntnissen wird eine Beschreibung der Vorgänge abgeleitet, die während des Ermüdungsprozesses im Materialgefüge ablaufen und zu den beobachteten makroskopischen Veränderungen führen. In diesem Zusammenhang hat sich herausgestellt, dass eine Erfassung der ermüdungsbedingten Schädigung anhand einer skalaren Größe über die Steifigkeit der tatsächlichen Veränderung der Spannungs-Dehnungs-Beziehung nicht gerecht wird. Eine Betrachtung im Hinblick auf einen zuverlässigen Schädigungsindikator im Zusammenhang mit den gemessenen Größen liefert zudem einen Überblick über die Eignung verschiedener Größen zur Erfassung des Ermüdungsschädigungsgrades im Beton. Abschließend wird ein Ansatz vorgestellt, der die beobachteten Entwicklungen entscheidender Größen im Ermüdungsvorgang abzubilden vermag. N2 - The main objective of this thesis is the fatigue behavior of concrete under high-cycle compressive loadings. Current knowledge about fatigue behavior of concrete is still incomplete. This concerns especially the process of fatigue which is preceding the fatigue failure. The leak of knowledge about fatigue behavior is opposed to the steady growing importance of this topic within the practice in civil engineering. Therefore, within this thesis a systematic and comprehensive investigation of the process of fatigue itself was done. This contributes to the better understanding of the progression of damage and the corresponding processes within the material. The experimental investigation consisted mainly of experiments with constant amplitude loadings in compression with cylindrical specimen made of normal strength concrete. Two differed load levels were used which resulted in numbers of cycles to failure of 10⁶ and 10⁷ as well as 10³ and 10⁴. The experiments were done in combination with different types of nondestructive and destructive testing methods like strain measuring, deformation of surface, ultrasonic signals, acoustic emissions, optical microscopy and also scattering electron microscopy. To access some parameters of influence in relation to the fatigue behavior additional creep tests and also several tests with different scales of specimen were done. The fatigue process of concrete is determined as an evolution of damage that starts from the beginning of the loading process. This evolution has manifold and different influences on the different material properties of concrete. In this relation a major finding was that fatigue related damage leads to a transformation of the complete stress-strain-relationship. This relationship is also subjected to an evolution process. Due to the authors observations it could not be determined that the investigated changes in macroscopic material behavior are caused by a development of micro cracks within the material structure. The results of the investigation indicated that rather the fatigue related changes in material behavior are mainly a result of viscous processes in cement stone especially in phase I and II of the fatigue process. Furthermore, it was observed that creep in concrete leads to similar but lesser changes in material behavior of concrete. Beside this, tests with different scales of specimens have shown an appreciable effect of size on the resulting material behavior under static and cyclic loadings respectively. From these experimental findings a detailed description was derived about the processes which take place within the material structure during the fatigue loading and also leads to the observed macroscopic changes in material behavior. In this context, the tests have shown that relating to stiffness reduction a scalar value could not capture the damage effect on the stress-strain-relationship caused by fatigue. A following consideration gives an overview about applicability of the different measured parameters for the detection of the degree of fatigue damage with regard to a reliable damage indicator. Finally an approach is presented which is able to describe the investigated developments of significant values within the observed fatigue process. T3 - BAM Dissertationsreihe - 140 KW - Ermüdung KW - Beton KW - Hochzyklisch KW - Schädigungsevolution KW - Fatigue KW - Concrete KW - High-cycle KW - Damage evolution PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-354487 VL - 140 SP - 1 EP - 286 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-35448 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krütt, Enno T1 - Degradation of pavement concrete under cyclic loading and the effect on moisture transport N2 - In Germany the damages on concrete motorways have increased during the past 15 years. This led often to a reduction of service life from 30 to 10 years. In spite of comprehensive research the reasons for these damages have not been clarified yet. But it is known that in this context the ASR plays a decisive role. Against this background ASR performance tests have been developed. However, these tests do not take into account the effects of mechanical loading due to cyclic traffic and climatic impact. Therefore in Germany the ASR research group 1498 was founded. The research group consists of three experimentally- and two multi-scale modelling oriented subprojects, which are working closely together. Selected findings of BAM’s experimental subproject SP4 are content of this contribution. The aim was to investigate the impact of a cyclic mechanical pre-damage on moisture transport. The pre-damaging was carried out on large-format beams using a cyclic four point bending test with a total number of 5 million load cycles. Thereby the damage process was monitored by using different NDT-techniques. After the mechanical pre-damaging, smallsized specimens were taken from loaded as well as unloaded areas of the large format beams. Absorption tests were carried out on these specimens using water and NaCl solution. Thereby moisture distribution was measured with Nuclear Magnetic Resonance (NMR) and Time Domain Reflectometry (TDR). Additionally, moisture suction was quantified integrally by means of gravimetric measurements. The analysis of the first test data shows that the mechanical loading influences the moisture transport. T2 - PhD-Symposium: Alkali-Silica Reaction in concrete structures - cyclic loading, fluid transport and modelling CY - Bochum, Germany DA - 05.10.2016 KW - Building Materials KW - AKR KW - Fatigue PY - 2016 AN - OPUS4-40166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kindrachuk, Vitaliy A1 - Unger, Jörg F. T1 - A Multi-scale temporal integration scheme for viscoplatic solids subjected to fatigue deterioration N2 - Using a continuum mechanics framework for lifetime prediction requires numerical integration of evolving damage until the onset of failure. The primary challenge for the simulation of structural fatigue failure is caused by the enormous computational costs due to cycle by cycle temporal integration throughout the whole loading history, which is in the order of 10^3 - 10^7 cycles. As a consequence, most approaches circumvent this problem and use an empirical method such as Wöhler curves. They are well suited for approximation of the lifetime, but they are not capable to capture a realistic degradation of the material with a redistribution of the stresses. The main objective of the paper is to provide a technique for the long time response of a finite element (FE) model while reducing computational costs. A multi-scale temporal integration scheme is proposed, which adapts the conventional FE method for realistic modeling of deterioration in a structure subjected to cyclic loading. For a particular case of two-scale temporal homogenization, the displacement field is assumed to satisfy scale separation: a short time scale arises from the oscillatory loading and a long time scale is due to the slow response relating to yielding and damage evolution. The original boundary value Problem (BVP) is approximated by the time-Independent BVPs on the short time scale. Alternation of the displacement field on the long time scale is correlated with the damage evolution by means of the adaptive cycle jump method. The significant acceleration of FE simulations is demonstrated for a constitutive damage model where the progressive damage accumulation under fatigue loading is driven by viscoplastic deformation. T2 - ECCOMAS 2016 CY - Crete, Greece DA - June 5th KW - Fatigue PY - 2016 AN - OPUS4-38654 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kraus, David A1 - Trappe, Volker T1 - Impact of thermal loads on the damage onset of fiber reinforced plastics T2 - ICCM21 - 21th International conference on composite materials (Proceedings) N2 - In this study, quasi-static material tests on unidirectional and multi-angle glass fiber reinforced epoxy laminates at ambient temperatures from -213 K to 353 K (-60 °C to +80 °C) are performed. In addition, neat resin is investigated under tension and compression loads at different temperatures. The coefficient of thermal expansion is determined for neat resin and unidirectional reinforced specimens. The dependence of the resin’s thermomechanical properties on the ambient temperature is shown. The point of damage onset at which first cracks appear within the matrix under quasi-static loading is investigated by means of optical grey scale analysis. The correlation between damage onset and effective matrix stress at different ambient temperatures is identified. An approach for the calculation of thermomechanical loads and the prediction of the damage onset by means of inverse calculations is presented. The impact of the strain blocking effect of the matrix is considered as well as residual thermal stresses due to curing and resin shrinkage. T2 - ICCM21 - 21th International conference on composite materials CY - Xi'an, China DA - 20.08.2017 KW - Fatigue KW - Composite KW - Thermomechanics KW - Fiber reinforced plastics KW - Damage onset PY - 2017 SP - 1 EP - 12 AN - OPUS4-42075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kraus, David A1 - Trappe, Volker T1 - Impact of thermal loads on the damage onset of fiber reinforced plastics N2 - In this study, quasi-static material tests on unidirectional and multi-angle glass fiber reinforced epoxy laminates at ambient temperatures from -213 K to 353 K (-60 °C to +80 °C) are performed. In addition, neat resin is investigated under tension and compression loads at different temperatures. The coefficient of thermal expansion is determined for neat resin and unidirectional reinforced specimens. The dependence of the resin’s thermomechanical properties on the ambient temperature is shown. The point of damage onset at which first cracks appear within the matrix under quasi-static loading is investigated by means of optical grey scale analysis. The correlation between damage onset and effective matrix stress at different ambient temperatures is identified. An approach for the calculation of thermomechanical loads and the prediction of the damage onset by means of inverse calculations is presented. The impact of the strain blocking effect of the matrix is considered as well as residual thermal stresses due to curing and resin shrinkage. T2 - International Conference of Composite Materials 21, ICCM21 CY - Xi'an, China DA - 20.08.2017 KW - Fatigue KW - Composite KW - Thermomechanics KW - Fiber reinforced plastics PY - 2017 AN - OPUS4-42074 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Boller, Ch. A1 - Mueller, Bernd R. A1 - Heckel, Thomas A1 - Starke, P. A1 - Gohlke, Daniel A1 - Venkat, R. S. A1 - Bruno, Giovanni T1 - Nonlinearities based inverse approach for the characterisation of the damage evaluation process in very high cycle fatigued CFRP specimens T2 - Proceedings of the VHCF7 Conference N2 - This paper focuses on the aspect on how damage evolution processes in composite materials and structures including matrix fracture, delamination, fibre-matrix debonding, and fibre fracture can be detected by taking advantage of the material’s inherit mechanical properties. These properties can be described on the basis of non-linear mechanical phenomena measurable as an inert frequency response signal. The approach is proposed as a means for residual life structural assessment specifically in the context of VHCF. T2 - The Seventh International Conference on Very High Cycle Fatigue - VHCF7 CY - Dresden, Germany DA - 03.07.2017 KW - Composite materials KW - Damage KW - Non-destructive testing KW - Fatigue KW - Structural simulation KW - Non-linear vibration PY - 2017 VL - 2017 SP - 1 EP - 8 PB - DVM AN - OPUS4-41102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfennig, Anja A1 - Kranzmann, Axel T1 - Potential of martensitic stainless steel X5CrNiCuNb 16-4 as pipe steel in corrosive CCS environment JF - IJSSD International Journal of Environmental Science and Development N2 - Pipe steels suitable for carbon capture and storage technology (CCS) require resistance against the corrosive environment of a potential CCS-site (heat, pressure, salinity of the aquifer, CO2-partial pressure). X5CrNiCuNb16-4 has been proven to be sufficient resistant in corrosive environments, but shows rather unusual corrosion behaviour in CCS environment. Therefore differently heat treated coupons of 1.4542 were kept at T=60 °C and ambient pressure as well as p=100 bar for 700 h - 8000 h in an a) water saturated supercritical CO2 and b) CO2-saturated synthetic aquifer environment similar to on-shore CCS-sites in the Northern German Basin. Additionally fatigue tests were performed via push-pull tests with a series of 30 specimens was tested at stress amplitudes between 150 MPa and 500 MPa (sinusoidal dynamic test loads, R=-1; resonant frequency ~ 30 Hz). Best corrosion resistance in the liquid phase is achieved via normalizing prior to exposure and hardening+tempering at 670 °C leads to lowest corrosion rates in the supercritical phase. With no regard to atmosphere discontinuously ellipsoidal surface corrosion regions appear after exposure of 4000 h and more. The endurance limit of X5CrNiCuNb16-4 measured in air is reduced by more than 50% when exposed to CCS environment (maximum number of cycles (10 x 106) at a stress amplitude of 150 MPa) The scatter range TN = 1:34 is disproportionately large contributing to an overall unusual corrosion behaviour. KW - Corrosion KW - CCS KW - Carbon storage KW - Aquifer KW - Heat treatment KW - Fatigue KW - Endurance limit PY - 2017 DO - https://doi.org/10.18178/ijesd.2017.8.7.998 SN - 2010-0264 VL - 8 IS - 7 SP - 466 EP - 473 AN - OPUS4-41863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rehmer, Birgit A1 - Skrotzki, Birgit A1 - Glaubitz, Steffen T1 - Influence of casting skin on fatigue lifetime of ferritic ductile cast iron JF - Materials Testing N2 - The fatigue behaviour of cast iron is usually investigated on machined specimens. Components of cast iron, however, have a casting skin; therefore the investigation of the influence of the casting skin on the lifetime is of interest. To study this influence isothermal fatigue tests were carried out on heat-resisting spheroidal graphite cast iron EN GJS SiMo 4.05 in 4–point-bending set-up at 400 °C. Specimens with and without casting skin were investigated comparatively. The number of cycles to failure was significantly lower for specimens with casting skin. Metallographic investigations underline the reduction of lifetime caused by casting skin. KW - Cast iron KW - Casting skin KW - Fatigue KW - Lifetime PY - 2017 SN - 0025-5300 VL - 59 IS - 1 SP - 5 EP - 10 PB - Carl Hanser Verlag CY - München AN - OPUS4-38929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Jörg F. A1 - Kindrachuk, Vitaliy T1 - A Fourier transformation-based temporal integration scheme for viscoplastic solids subjected to fatigue deterioration JF - International Journal of Fatigue N2 - Using continuum damage mechanics (CDM) for lifetime prediction requires numerical integration of evolving damage until the onset of failure. The primary challenge for the simulation of structural fatigue failure is caused by the enormous computational costs due to cycle-by-cycle temporal integration throughout the whole loading history, which is in the order of 103–107 cycles. As a consequence, most approaches circumvent this problem and use empirical methods such as Wöhler curves. They are well suited for approximating the lifetime, but they are not capable to capture a realistic degradation of the material including redistribution of stresses. The main objective of the paper is to provide a technique for finite element (FE) simulations of structures under fatigue loading while reducing computational costs. A Fourier transformation-based temporal integration (FTTI) scheme is proposed, which adapts the conventional FE method for modeling the viscoplastic deterioration in a structure subjected to cyclic loading. The response fields are represented by a Fourier series which assumes a temporal scale separation: a microchronological (short time) scale arises from the oscillatory loading and a macrochronological (long time) scale is due to the slow material relaxation resulting from yielding and damage evolution. The original dynamic boundary value problem (BVP) is approximated by the stationary BVP on the microchronological scale. Alternation of the displacement field on the macrochronological scale is correlated with evolution of the history variables by means of a high order adaptive cycle jump method. Performance and significant acceleration of the FE simulations is demonstrated at different loading scenarios for a constitutive damage model where the progressive damage accumulation is driven by viscoplastic yielding. KW - Fatigue KW - Accelerated time integration KW - Continuum damage mechanics KW - Fourier series PY - 2017 DO - https://doi.org/10.1016/j.ijfatigue.2017.03.015 SN - 0142-1123 SN - 1879-3452 VL - 100 IS - 1 SP - 215 EP - 228 PB - Elsevier Ltd. AN - OPUS4-39616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kraus, David A1 - Trappe, Volker T1 - Cyclic fatigue behavior of glass fiber reinforced epoxy resin at ambient and elevated temperatures T2 - ECCM18 - 18th European conference on composite materials (proceedings) N2 - The fatigue behavior of ±45° glass fiber reinforced epoxy resin under cyclic mechanical and constant thermal loading is investigated in this study. Tests at three different temperature levels in the range 296 K to 343 K have been performed in order to create S-N curves for each temperature level. The specimen damage is measured in-situ using optical grayscale analysis. The characteristic damage state (CDS) is evaluated for each specimen. It is shown that the point of CDS is suitable as a failure criterion to compare the resulting S-N curves. With micromechanical formulations, the temperature-dependent matrix effort is calculated for each stress-temperature level. In terms of matrix effort, the longest fatigue life is reached at high temperatures, while, in terms of stress, the lowest fatigue life is reached at the highest temperatures. T2 - ECCM18 - 18th European conference on composite materials CY - Athens, Greece DA - 24.06.2018 KW - Composite KW - Fatigue KW - Thermomechanics KW - Residual stresses KW - Temperature PY - 2018 SP - 1 EP - 7 PB - European society for composite materials AN - OPUS4-45338 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kraus, David A1 - Trappe, Volker T1 - Cyclic fatigue behavior of glass fiber reinforced epoxy resin at ambient and elevated temperatures N2 - The fatigue behavior of ±45° glass fiber reinforced epoxy resin under cyclic mechanical and constant thermal loading is investigated in this study. Tests at three different temperature levels in the range 296 K to 343 K have been performed in order to create S-N curves for each temperature level. The specimen damage is measured in-situ using optical grayscale analysis. The characteristic damage state (CDS) is evaluated for each specimen. It is shown that the point of CDS is suitable as a failure criterion to compare the resulting S-N curves. With micromechanical formulations, the temperature-dependent matrix effort is calculated for each stress-temperature level. In terms of matrix effort, the longest fatigue life is reached at high temperatures, while, in terms of stress, the lowest fatigue life is reached at the highest temperatures. T2 - ECCM18 - 18th European conference on composite materials CY - Athens, Greece DA - 24.06.2018 KW - Composite KW - Fatigue KW - Thermomechanics KW - Residual stresses KW - Temperature PY - 2018 AN - OPUS4-45346 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -