5 Werkstofftechnik
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- Additive Manufacturing (7)
- Glass (6)
- Additive manufacturing (5)
- Alloy 2618A (4)
- Aluminium (4)
- CCUS (4)
- Coarsening (4)
- Crack growth (4)
- Creep (4)
- DCB (4)
- Fatigue (4)
- Vickers (4)
- Water speciation (4)
- Carbon steels (3)
- Corrosion (3)
- Degradation (3)
- Droplet corrosion (3)
- Martensitic steel (3)
- Mikroplastik (3)
- Powder (3)
- S-phase (3)
- Superaustenite steel (3)
- Supercritical/dense phase CO2 (3)
- Transmission electron microscopy (3)
- Wasser (3)
- Alumina (2)
- Ceramic (2)
- Concrete (2)
- Dark-field transmission electron microscopy (2)
- Ferritic-martensitic steels (2)
- Foaming (2)
- Fraktographie (2)
- Hochtemperatur (2)
- LCF (2)
- Microplastics (2)
- Neutron diffraction (2)
- PE-HD (2)
- Residual Stresses (2)
- Ressidual stress (2)
- Rotor blade (2)
- Sandwich (2)
- Selective Laser Melting (2)
- Sinter additive (2)
- Sintering (2)
- Soda-lime silicate glass (2)
- TED-GC-MS (2)
- Thermoelectrics (2)
- UV-irradiation (2)
- Wind turbine blades (2)
- XANES (2)
- 3D glass structure model (1)
- 3D printing (1)
- 3D-printing (1)
- 9-12% Cr ferritic-martensitic steels (1)
- Accelerated integration scheme (1)
- Active thermography (1)
- Age hardening (1)
- Aggressive gases (1)
- Air-coupled ultrasonic testing (1)
- Airborne ultrasonic testing (1)
- Al-Li alloys (1)
- Aluminum (1)
- Analyse (1)
- Analysis (1)
- Analytik (1)
- Analytische Zentrifuge (1)
- Anisotropy (1)
- Betriebsfestigkeit (1)
- Biodiesel (1)
- CCS (1)
- Calcination (1)
- Calciumcobaltit (1)
- Calciummanganat (1)
- Carbon steels (1)
- Carbon capture (1)
- Carbon dioxide (1)
- Ceramic springs (1)
- Ceramics (1)
- Chromatography (1)
- Complex loading (1)
- Composite (1)
- Composites (1)
- Continnum damage model (1)
- Crack (1)
- Creep-fatigue (1)
- Crystal Orientation (1)
- Crystal plasticity (1)
- Crystallization (1)
- Cycle jump (1)
- Cyclic oxidation (1)
- Cyclic softening (1)
- Damage (1)
- Dark-field transmission electron microscopy (DFTEM) (1)
- Data Fusion (1)
- Destabilization (1)
- Dielectric strength (1)
- Diesel (1)
- Diffraction (1)
- Diffraction contrast (1)
- Diffusion (1)
- Diffusion coefficient (1)
- Dislocation (1)
- Dissolved water (1)
- EBSD (1)
- EDXRD (1)
- Electron microscopy (1)
- FCH JU (1)
- Faserverstärkte Kunstoffe (1)
- Fatigue damage (1)
- Fatigue fracture (1)
- Fatigue of sandwich shell structures (1)
- Fatigue of sandwich structures (1)
- Ferroelectret (1)
- Ferroelektret (1)
- Fertigungstechnologie (1)
- Formerkennung (1)
- GC-MS (1)
- Gasabgabe (1)
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- Geopolymers (1)
- Glas (1)
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- Glass fiber reinforced polymers (1)
- Grain boundaries (1)
- Granules (1)
- High Temperature Corrosion (1)
- High temperature corrosion (1)
- High-temperature corrosion (1)
- Horizon 2020 (1)
- Hot Press (1)
- Hydrogen permeation (1)
- Implant failures (1)
- Impurities (1)
- In situ (1)
- In-situ (1)
- Inconel 686 coating (1)
- Initial attachment (1)
- Injection (1)
- Inverse ostwald ripening (1)
- Kalzinierung (1)
- Kennwertermittlung (1)
- Keramikfeder (1)
- Kriechen (1)
- Kunststoffe (1)
- Laser (1)
- Laser cladding (1)
- Laser curing (1)
- Lebensdauer (1)
- Lightweight materials (1)
- Long-term storage (1)
- Low cycle fatigue (1)
- Luftultraschall (1)
- Manufacturing (1)
- Martensitic steel (1)
- Material defects (1)
- Mechanical and thermal testing (1)
- Mechanisches Verhalten (1)
- Metallic components (1)
- Micro-shrinkages (1)
- Micromechanical model (1)
- Microstructural evolution (1)
- Microstructure (1)
- Multiaxial stress state (1)
- Multilayer (1)
- Multilayer technology (1)
- Nano particle (1)
- Nano screening (1)
- Ni-Resist (1)
- Nickel-base superalloy (1)
- Nickel-base superalloys (1)
- Non-destructive testing (1)
- P92 steels (1)
- Particle size (1)
- Partikelgrößenverteilung (1)
- Phase field simulation (1)
- Phase-field simulation (1)
- Polymerwissenschaften (1)
- Porcelain (1)
- Precipitates (1)
- Precipitation (1)
- Pressure-assisted sintering (1)
- Rafting (1)
- Relaxation (1)
- Relaxationsphänomene (1)
- Residual stresses (1)
- Risswachstum (1)
- Rotorblattschalen (1)
- SLM (1)
- Safety assessment (1)
- Scale-bridging (1)
- Scanning transmission electron microscopy (STEM) (1)
- Schwingbrüche (1)
- Schädigung (1)
- Silicate Glasses (1)
- Silicatglas (1)
- Silicon Carbide (1)
- Simulation of concrete (1)
- Single-crystals (1)
- Sinterung (1)
- Spannungs-Dehnungs-Verhalten (1)
- Spray drying (1)
- Structured heating (1)
- Struktur (1)
- Subsurface defects (1)
- Sulfidation (1)
- Superalloy single crystals (1)
- Superaustenite steel (1)
- Supercritical/dense phase CO 2 (1)
- Surface Nucleation (1)
- TAHYA (1)
- TED (1)
- TMF (1)
- Temperature (1)
- Texturation (1)
- Thermal degradation (1)
- Thermische Analyse (1)
- Thermo-mechanical fatigue (1)
- Thermoanalytical Methods (1)
- Thermoelectric generator (1)
- Thermoelectric oxide (1)
- Thermoelektrika (1)
- Thermographie (1)
- Thermogravimetry (1)
- Thermomechanics (1)
- Thermomechanische Eigenschaften (1)
- Ultrasound (1)
- Under cyclic loading (1)
- VCSEL (1)
- VSSA (1)
- Virtual experiments (1)
- Viscoplasticity (1)
- Wandler (1)
- Waste water (1)
- Wind turbine (1)
- Withstand voltage tests (1)
- X-ray laminography (1)
- Zyklische Belastung (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (88) (entfernen)
Eingeladener Vortrag
- nein (88)
We investigated the effect of water vapor in the initial stages of SO2 corrosion of an Fe-9Cr-0.5Mn model alloy at 650 °C. Two separate experiments were run, one with 99.5%-Ar + 0.5%-SO2 and one with 69.5%-Ar + 0.5%-SO2 with 30%-H2O atmosphere. During the experiment the scale growth was observed in-situ, using energy dispersive X-ray diffraction (EDXRD). Our results confirm an increased speed of oxygen transport into the material, with the addition of water, while the transport of sulfur appears to be less affected.
Um den sicheren Betrieb von Windkraftanlagen zu gewährleisten, werden Rotorblätter nach der Fertigung und nach Reparatur mit verschiedenen zerstörungsfreien Verfahren auf Schaden untersucht. Bei der Fertigung von Blattschalen, die in einer Sandwich-Schalenbauweise gefertigt werden, entstehen Imperfektionen, die unter Belastung zu großen Rissen führen können. Zur Prüfung von Blattschalen wird unter anderem Ultraschallprüfung in Kontakttechnik eingesetzt. Um den Wartungsaufwand von Ultraschallanlagen zu reduzieren und um manche Kompositstrukturen vor Koppelmittel zu schützen, wird die Anwendung von Luftultraschall erforscht. Insbesondere große Fortschritte gibt es im Bereich der Entwicklung neuer Wandler.
In diesem Beitrag berichten wir über die Luftultraschallprüfung von Schalen für Rotorblätter. Es wurden typische Sandwichschalenstrukturen hergestellt und mit einem eigenentwickelten Schalenprüfstand unter simulierter Betriebsbeanspruchung belastet. Die in den Schalenprüfkörpern entstandenen Schäden wurden außerhalb des Prüfstandes mit Luftultraschall in Durchschallung untersucht. Es wurden fokussierende Wandler auf Basis von Ferroelektreten entwickelt und für diese Prüfungen eingesetzt. Mit zusätzlicher elektrischer Vorspannung konnte die Empfindlichkeit der Empfänger deutlich erhöht werden. Die nach dem Lastwechsel entstandenen Schäden in den Rotorblattschalen waren eindeutig zu detektieren.
Entwickelt wurde eine mehrstufige Fertigungstechnologie (Schruppen, Schlichten, Trennschnitt) zur Herstellung keramischer Federn aus gesinterten Hohlzylindern. Durch Optimierung von Maschinenparametern, Schleifscheiben sowie Werkstück- und Werkzeugaufnahmen ist es gelungen, Federn aus Hochleistungskeramik (Aluminiumoxid und Zirkonoxid) mit hoher Kanten- und Oberflächenqualität reproduzierbar herzustellen. Eine hohe Variabilität bezüglich Außen- und Innendurchmesser, Steigung, Windungsquerschnitt und Abstand zwischen den Windungen ermöglicht es, die Federkonstante über drei Größenordnungen zu variieren.
Untersucht wurden Federstabilität und Spannungs-Dehnungs-Verhalten unter konstanter und zyklischer Druckbelastung sowie die thermomechanische Stabilität der Keramikfedern. Aluminiumoxid-Federn können bis etwa 800°C, Zirkonoxid-Federn bis etwa 600°C ohne bleibende geometrische Verformung eingesetzt werden.
Unter konstanter Spannung zeigen Federn aus Y-stabilisiertem TZP (Zirkonoxid)-Werkstoffen, von anderen Keramikwerkstoffen abweichend, bei Raumtemperatur eine zeitabhängige, elastische, Verformung (Superelastizität), die nach Entlastung über einen Zeitraum von mehreren Stunden reversibel verläuft. Als Ursache wird eine spannungsinduzierte reversible Phasenumwandlung zwischen austenitischer (tetragonales ZrO2) und martensitischer (monoklines ZrO2) Phase postuliert.
Diskutiert wird das Anwendungspotenzial der entwickelten Federn für kapazitive keramische Federsensoren für Gravimeter und Wägetechnik.
Carbon Capture and Storage (CCS) is identified as an excellent technology to reach the target of CO2 reduction. However, the safety issue and cost effectiveness hinder the future of CCS. For the reliability and safety issues of injection wells the corrosion resistance of the materials used needs to be determined.
In this study, representative low cost materials including carbon steel 1.8977 and low alloyed steel 1.7225 were embedded in cement to mimic the realistic casing-cement interface. Electrochemical studies were carried out using these metal-cement specimens in comparison with those made of metal only in CO2 saturated synthetic aquifer fluid, at 333 K, to reveal the effect of cement on the steel performance. The results showed the protective effect of cement on the performance of pipeline metals during polarisation process. However, the corrosion current density was high in all cases, with and without cement, indicating that the corrosion resistance of these materials is low. This conclusion was supported by the surface analysis of the polarized specimens, which revealed both homogenous and pitting corrosions. Furthermore, to reveal the possible protective performance of FeCO3, the pipeline steels were pre-carbonated and then tested in the same condition as freshly polished specimens.
Most additive manufacturing processes which produce dense ceramics are nowadays limited in size because of inevitable post-processing steps like for example binder removal in stereolithography. The additive manufacturing of voluminous ceramic parts is realized by powder bed based processes which, however, generate parts with residual porosity. Via infiltration these parts can be processed to dense parts like for example SiC but this is not possible for all ceramics like for example Si3N4. There is a lack of methods for the additive manufacturing of dense voluminous parts for most ceramics.
We have developed a new additive manufacturing technology, the Laser Induced Slip casting (LIS), based on the layerwise deposition of slurries and their local drying by laser radiation. Laser Induced Slip casting generates ceramic green bodies which can be sintered to dense ceramic components like traditional formed ceramic powder compacts. We will introduce the LIS technology, green bodies and sintered parts will be shown and their microstructure and mechanical properties will be discussed.
Most additive manufacturing processes which produce dense ceramics are nowadays limited in size because of inevitable post-processing steps like for example binder removal in stereolithography. The additive manufacturing of voluminous ceramic parts is realized by powder bed based processes which, however, generate parts with residual porosity. Via infiltration these parts can be processed to dense parts like for example SiC but this is not possible for all ceramics like for example Si3N4. There is a lack of methods for the additive manufacturing of dense voluminous parts for most ceramics.
We have developed a new additive manufacturing technology, the Laser Induced Slip casting (LIS), based on the layerwise deposition of slurries and their local drying by laser radiation. Laser Induced Slip casting generates ceramic green bodies which can be sintered to dense ceramic components like traditional formed ceramic powder compacts. We will introduce the LIS technology, green bodies and sintered parts will be shown and their microstructure and mechanical properties will be discussed.
Having been introduced almost two decades ago, Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing.
The residual stress distribution in IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron (bulk) and laboratory X-ray (surface) diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-build condition (on a build plate) and after removal from the build plate.
The absolute values of all stress components decreased after removal from the build plate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component depending on the thermal gradient in the respective direction.
Having been introduced almost two decades ago, Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing.
The residual stress distribution in IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron (bulk) and laboratory X-ray (surface) diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-build condition (on a build plate) and after removal from the build plate.
The absolute values of all stress components decreased after removal from the build plate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component depending on the thermal gradient in the respective direction.
Lock-in- and flash thermography are standard methods in active thermography. They are widely used in industrial inspection tasks e.g. for the detection of delaminations, cracks or pores. The requirements for the light sources of these two methods are substantially different. While lock-in thermography requires sources that can be easily and above all fast modulated, the use of flash thermography requires sources that release a very high optical energy in the very short time.
By introducing high-power vertical cavity surface emitting lasers (VCSELs) arrays to the field of thermography a source is now available that covers these two areas. VCSEL arrays combine the fast temporal behavior of a diode laser with the high optical irradiance and the wide illumination range of flash lamps or LEDs and can thus potentially replace all conventional light sources of thermography.
However, the main advantage of this laser technology lies in the independent control of individual array areas. It is therefore possible to heat not only in terms of time, but also in terms of space. This new degree of freedom allows the development of new NDT methods. We demonstrate this approach using a test problem that can only be solved to a limited extent in active thermography, namely the detection of very thin, hidden defects in metallic materials that are aligned vertically to the surface. For this purpose, we generate destructively interfering thermal wave fields, which make it possible to detect defects within the range of the thermal wave field high sensitivity. This is done without pre-treatment of the surface and without using a reference area to depths beyond the usual thermographic rule of thumb.
High-performance composites, including glass-fiber reinforced plastic (GFRP) materials, are favored as a construction material for wind turbine rotor blades due to their high specific strength and stiffness properties. During the manufacturing process, however, imperfections are often introduced, then further propagated due to harsh environmental conditions and a variety of loads. This leads to failure significantly before their projected 20-year lifespan. As replacement of entire blades can be a costly potential outcome, localized repair of the damaged region to restore structural integrity and thus lengthen its lifespan has become an important issue in recent years. Rotor blades are often repaired using a common technique for composite laminates: adhesively bonded structural repair patches. These methods involve replacing the lost load path with a new material that is joined to the parent structure, and include scarf or plug repairs. However, there currently do not exist any standardized repair procedures for wind turbine rotor blades, as comparisons of blade properties repaired with the existing methods have not been studied in depth. Namely, there is a lack of understanding about the effects of various repair methods on the fatigue life of the shells of rotor blades. This study therefore aims to begin to fill this knowledge gap by testing the influence of different repair patches on the blades’ mechanical properties. Manufactured with the vacuum-assisted resin infusion process, the test specimens are produced as a curved structure with GFRP sandwiching a polyvinyl chloride foam core to best represent a portion of a rotor blade shell. Scarf repairs are then introduced with varying layup techniques, and material properties are examined with cyclical fatigue tests. Crack growth and development is monitored during fatigue testing by various non-destructive testing methods, including passive thermography with an infrared camera system, and a 3D deformation analysis system with ARAMIS. Large deformation fields and detection of in- and out-of-plane deformations is thus possible in-situ. The mechanical behavior and development of defects in the various repaired specimens is compared to each other as well as to reference test specimens with no repair patches. In-situ test data is combined with further non-destructive testing methods, including laminography, and active thermography, to develop a robust understanding of the effects of repair concepts.
The influence of heat treatment and creep loading on the microstructure of an Al-Cu-Li alloy was investigated. Especially the formation of different precipitates (T1 and Theta') were characterized and the microstructural changes under different ageing conditions (with and without external strain) were investigated to determine the effect od stress on the ageing process.
The durability of concrete structures and its performance over the lifetime is strongly influenced by many interacting phenomena such as e.g. mechanical degradation due to fatigue loading, loss of prestress, degradation due to chemical reactions or creep and shrinkage. Failure due to cyclic loading is generally not instantaneous, but characterized by a steady damage accumulation.
Many constitutive models for concrete are currently available, which are applicable for specific loading regimes, different time scales and different resolution scales. A key limitation is that the models often do not address issues related to fatigue on a structural level. Very few models can be found in the literature that reproduce deterioration of concrete under repeated loading-unloading cycles.
The objective of this paper is the presentation of numerical methods for the simulation of concrete under fatigue loading using a temporal multiscale method.
First, a continuum damage model for concrete is developed with a focus on fatigue under compressive stresses. This includes the possibility to model stress redistributions and capture size effects. In contrast to cycle based approaches, where damage is accumulated based on the number of full stress cycles, a strain based approach is developed that can capture cyclic degradation under variable loading cycles including different amplitudes and loading frequencies. Second, a multiscale approach in time is presented to enable structural computations of fatigue failure with a reduced computational effort. The damage rate within the short time scale corresponding to a single cycle is computed based on a Fourier based approach. This evolution equation is then solved on the long time scale using different time integration schemes.
Die Festigkeit von Gläsern wird durch die Oberflächenqualität beeinflusst. Kommt es neben dem Auftreten von Defekten zusätzlich zum Risswachstum ausgehend hiervon, wird die Festigkeit minimiert. Das Wachstum hängt dabei maßgeblich von der Luftfeuchtigkeit ab. Dieses Ermüdungsverhalten von Gläsern besser zu verstehen und dabei die Mechanismen und den Einfluss von im Volumen eingebauten Wasser auf das unterkritische Risswachstum zu untersuchen, ist Ziel der Arbeiten. Als Teilprojekt im Rahmen des DFG Schwerpunktprogramms SPP 1594 „Ultrastrong glasses“ soll der Einfluss des im Volumen eingebauten Wassers auf die Rissspitze untersucht werden. Zusammen mit der Leibniz Universität Hannover und der TU Clausthal werden hierfür hochwasserhaltige Gläser (bis zu 8 Gew%) bei 8 kbar über die Flüssigphase synthetisiert, die makroskopisch den hohen Wasseranteil nachstellen. Die Charakterisierung erfolgt hinsichtlich des Wassereinbaus, der mechanischen Eigenschaften und des Risswachstums. Die Arbeiten in Berlin beziehen sich hierbei auf die Messungen des unterkritischen Risswachstums in Luft und Vakuum, sowie Verlustwinkelmessungen.
Erste Ergebnisse zeigen Unterschiede im korrosionsbeeinflussten (langsames) und inerten (schnelles und im Vakuum stattfindendes) Risswachstumsverhalten der untersuchten Gläsern. Die Rissgeschwindigkeit beim Übergang vom korrosionsbeeinflussten zum inerten Risswachstum ist hin¬gegen für alle Gläser ähnlich und folglich ein kinetisch durch den äußeren Wassertransport an die Rissspitze bestimmter Prozess. Der Widerstand gegen Risswachstum steigt mit Tg und zusätzlich kann anhand der Verlustwinkelmessungen ein Zusammenhang zwischen der Netzwerk- und der β-Relaxation ermittelt werden. Je höher der Wassergehalt im Glas ist, desto niedriger wird Tg und einfacher das Risswachstum, welches sich durch längere Risse kennzeichnet. Besonders stark tritt dieser Effekt bei einem Überschuss an molekularem Wasser auf.
Der Vortrag gibt eine Einführung in die Methode der Vakuumheißextraktion und beschreibt die Anwendungsmöglichkeiten der an der BAMN betriebenen Anlage.
Dissolved water decisively influences numerous thermally activated relaxation phenomena in glasses like stress relaxation, sub-critical crack growth, internal friction, viscosity, sintering, and crystallization. Thermoanalytical methods can essentially help for better understanding of these phenomena. The lecture introduces the Vacuum Hot Extraction method (VHE) and illustrates its possibilities for measuring water content, degassing and mobility. As another thermoanalytical method, the Dynamic Mechanical Themoanalysis (DMA), allowing to study the effect of dissolved water on the internal friction in glasses, is introduced.
Cyclic fatigue behavior of glass fiber reinforced epoxy resin at ambient and elevated temperatures
(2018)
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.
Wasser in Silicatglas
(2018)
Glass powders are promising candidates for manufacturing a broad diversity of sintered materials like sintered glass-ceramics, glass matrix composites or glass bonded ceramics with tailored mechanical, thermal, electrical and optical properties and complex shape. Its wide and precise adjustability makes this class of materials a key component for advanced technologies. Processing of glass or composite powders often allow even more flexibility in materials design. At the same time, however, processing can have substantial effects on the glass powder surface and sinterability. Thus, mechanical damage and surface contamination can strongly enhance surface crystallization, which may retard or even fully prevent densification. Whereas sintering and concurrent crystallization have been widely studied, partially as cooperative effort of the TC7 of the ICG, and although glass powder sintering is predominantly applied for glasses of low crystallization tendency, sintering is also limited by gas bubble formation or foaming. The latter phenomenon is much less understood and can occur even for slow crystallizing glass powders. The lecture illustrates possible consequences of glass powder processing on glass sintering, crystallization and foaming.