5 Werkstofftechnik
Filtern
Erscheinungsjahr
- 2018 (88) (entfernen)
Dokumenttyp
- Vortrag (88) (entfernen)
Referierte Publikation
- nein (88)
Schlagworte
- 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)
- Gasgehalt (1)
- Geopolymers (1)
- Glas (1)
- Glass composition (1)
- 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)
Calciumcobaltit und Calciummanganat gehören zu den vielversprechendsten thermoelektrischen Oxiden im Temperaturbereich zwischen 600 °C und 800 °C an Luft. Mittels thermoelektrischer Generatoren kann ein Temperaturgradient direkt in elektrische Leistung umgewandelt werden. Für die kostengünstige Pulverherstellung von Funktionsmaterialien wird im industriellen Maßstab meist die Festphasenreaktion (bzw. Kalzinierung) verwendet. Da es sich dabei um einen Hochtemperaturprozess handelt, ist diese Kalzinierung sehr energieintensiv. In der Literatur werden sehr unterschiedliche Prozessbedingungen zur Pulversynthese thermoelektrischer Oxide genutzt. Soweit dem Autor bekannt, ist keine systematische Untersuchung des Einflusses der Pulversynthesebedingungen auf die thermoelektrischen Eigenschaften publiziert.
Deshalb wurde eine systematische Untersuchung des Einflusses der Pulversynthesebedingungen (Temperatur, Haltezeit, Partikelgröße, Wiederholungen) auf die thermoelektrischen Eigenschaften von Calciumcobaltit und Calciummanganat durchgeführt.
Es konnte gezeigt werden, dass sich ein höherer Energieeintrag während der Kalzinierung negativ auf die thermoelektrischen Eigenschaften auswirkt.
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.
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.
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.
The first documentation of fuel biodeterioration dates back to the late 19th century. However, extensive studies concerning the microbial fuel contamination started in 1980’s. Polymeric fuel storage tanks containing diesel and biodiesel provide environmental conditions for microbial growth. Several studies demonstrated that bacteria, which were found in contaminated fuel systems, can use fuels as macronutrient; but such bacteria can also cause microbiologically influenced corrosion and fouling.
The aim of this study is to investigate the initial attachment behavior of bacteria, isolated from a diesel contamination, on neat and photooxidized high-density polyethylene (PE-HD). Two common PE-HD’s, less- and biodiesel-stabilized, were radiated to UV light representing a tank exposed to sunlight. The effect of photooxidiation on PE-HD’s surface were characterized chemically by Fourier-transform infrared spectroscopy (FTIR). The attached bacteria Pseudomonas aeruginosa and Bacillus subtilis on the polymer surface were evaluated by fluorescence microscopy and colony-forming unit tests (CFU).
PE-HD as a polymeric fuel storage tank material: Photooxidation, fuel sorption and long-term storage
(2018)
High-density polyethylene (PE-HD) is a commodity thermoplastic polymer which is typically used for packing of dangerous goods. Its good resistance against photooxidation, fuels, chemicals and other environmental factors in addition to low production costs makes PE-HD attractive for fuel storage applications. Typical engine fuels stored in polymer tanks are petrol, diesel and biodiesel that receives increasing attention as proper alternative to fossil fuels. One of the major problems with biodiesel is its susceptibility to oxidize due to its chemical composition of unsaturated fatty acids which also can cause polymer degradation.
The aim of this study is to investigate the influence of different environmental factors, UV radiation and commonly stored fuels, on the mechanical, physical and chemical properties of two types of PE-HD polymers (stabilized and non-stabilized). The influence on the mechanical properties was tested by Charpy and tensile tests, chemical and physical properties were evaluated by Fourier-transform infrared spectroscopy (FTIR) and by dynamical mechanical analysis (DMA) tests. Samples were characterized after varying exposure time of UV radiation and after fully and partially immersion in biodiesel. In addition, similar experiments were conducted using diesel for comparison.
The creep behavior of single-crystals of the nickel-base superalloy CMSX-4 was investigated at 1288°C, which is the temperature of the hot isostatic pressing (HIP) treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where no Gamma’-strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic, e.g. the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-section area psi of [001] crystals reached nearly 100%, while for a [111] crystal psi=62%. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals didn’t not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. From the shape of deformed specimens and TEM investigations it was concluded that the main strain contribution resulted from <011> {111} octahedral slip.
Efficient energy provision using fuel cells requires effective hydrogen storage capacities. Glass is a material of low intrinsic hydrogen permeability and is therefore a promising material for hydrogen storage containers or diffusion barriers. Pioneer work on oxidic glasses seems to indicate a correlation between glass composition and hydrogen permeation, which was mainly derived from the behavior of silica glass. In this study, we focus on the relationship between topologic (free volume; network polymerization) and thermodynamic (configurational entropy) glass parameters. Experiments were performed well below the glass transition temperature, which excludes significant structural relaxation and chemical dissolution of hydrogen. The compositional dependence of seven glasses on the SiO2-NaAlO2 join pointed out that in fully polymerized glasses the H2 permeability cannot be solely derived from the total free volume of the glass structure. Hence, evidence is provided that the size distribution of free volume contributes to hydrogen diffusion and solubility. Additionally, results indicate that hydrogen permeability of the glasses is affected by the configurational heat capacity ΔCp at Tg.
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 properties and complex shape. Powder processing, however, can substantially affect sinterability, e.g. by promoting surface crystallization. On the other hand, densification can be hindered by gas bubble formation for slow crystallizing glass powders. Against this background, we studied sintering and foaming of silicate glass powders with different crystallization tendency for wet milling and dry milling in air, Ar, N2, and CO2 by means of heating microscopy, DTA, Vacuum Hot Extraction (VHE), SEM, IR spectroscopy, XPS, and ToF-SIMS. In any case, foaming activity increased significantly with progressive milling. For moderately milled glass powders, subsequent storage in air could also promote foaming. Contrarily, foaming could be substantially reduced by milling in water and 10 wt% HCl. Although all powder compacts were uniaxially pressed and sintered in air, foaming was significantly affected by different milling atmosphere and was found most pronounced for milling in CO2 atmosphere. Conformingly, VHE studies revealed that foaming is mainly driven by carbonaceous species, even for powders milled in other gases. Current results of this study thus indicate that foaming is caused by carbonaceous species trapped on the glass powder surface.
Der Vortrag zeigt zwei Möglichkeiten zur Verbesserung der VSSA-Screening-Methode zur Identifizierung von Nanopulvern auf. Bisher ist das Verfahren nur für monodisperse Partikel mit idealer Kugelform valide. Die Verteilungsbreite der Partikelgröße soll durch die Nutzung des Modells einer logarithmischen Normalverteilung implementiert werden. Die Abweichung der gemessenen Partikel von einer idealen Kugel in Sphärizität, Rundheit und Rauigkeit sind über einen Morphologiefaktor MF zu berücksichtigen. An einem konkreten Beispiel werden Auswirkungen der Implementierungen rechnerisch dargestellt und mit dem bisherigen Verfahren verglichen.
Hochleistungsverbundwerkstoffe, bzw. Glasfaser-Kunststoff-Verbunde (GFK), haben sich als Leichtbauwerkstoffe für Leichtflugzeuge und Rotorblätter von Windkraftanlagen etabliert. Die hohe spezifische Festigkeit und Steifigkeit qualifizieren sie besonders für diese Anwendung. Während der Fertigung werden Imperfektionen häufig in die Blattschalen eingebracht. Durch Witterungseinflüsse kommt es zum Schadensfortschritt. Infolgedessen treten Schäden in der Blattschale, die den sicheren Betrieb gefährden können, weit vor der projektierten Lebensdauer von 20 Jahren auf. Da der Austausch von ganzen Blättern sehr kostintensiv ist, ist eine lokale Reparatur des geschädigten Bereichs zur Wiederherstellung der strukturellen Integrität, viel preisgünstiger. Die Reparatur von Rotorblättern ist in den letzten Jahren zu einem wichtigen Thema geworden. Derzeit werden verschiedenste Reparaturkonzepte angewendet. Eine einheitliche Reparaturvorgabe gibt es bisher nicht. Die Auswirkungen der angewendeten Reparaturkonzepte auf die Betriebsfestigkeit der Reparaturstelle sind weitestgehend unbekannt und sollen deshalb in diesem Projekt untersucht werden. Gekrümmte Voll-Laminat sowie Sandwich Prüfkörper werden mit dem Vacuum-Assisted-Resin-Infusion-Prozess (VARI) produziert. Um einen Teil einer Rotorblattschale darzustellen, sind sie als GFK aufgebaut, beziehungsweise die Sandwich Strukturen mit einem Polyvinylchlorid-Schaumkern (PVC) Kern, wie im Original. Schalenreparaturen in verschiedenen Layup-Techniken und Geometrie werden eingebracht und die Materialeigenschaften mit zyklischen Ermüdungstests untersucht. Im Projekt werden ideal im Labor erzeugte Reparaturstellen mit in der Praxis angewendeten Ausführungstechniken eines Industriepartners experimentell verglichen. Für die in-situ Detektion der Schadensentwicklung während des Ermüdungsversuches kommt ein kombiniertes Felddehnungs- und Thermografie-Kamerasystem zum Einsatz. Das mechanische Verhalten und die Schadensentwicklung in den verschiedenen reparierten Prüfkörper wird miteinander sowie mit den Referenzproben ohne Reparaturstellen verglichen. Zudem wird in numerischen Modellen für die verschiedenen Reparaturtechniken eine Spannungsanalyse durchgeführt um hinsichtlich der Betriebsbeanspruchung eine Bewertung angeben zu können.
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.