5 Werkstofftechnik
Filtern
Erscheinungsjahr
- 2018 (228) (entfernen)
Dokumenttyp
- Vortrag (88)
- Zeitschriftenartikel (73)
- Posterpräsentation (31)
- Beitrag zu einem Tagungsband (29)
- Buchkapitel (3)
- Beitrag zu einem Sammelband (1)
- Dissertation (1)
- Sonstiges (1)
- Forschungsbericht (1)
Sprache
- Englisch (188)
- Deutsch (39)
- Französisch (1)
Schlagworte
- Additive manufacturing (12)
- Creep (11)
- Additive Manufacturing (10)
- Degradation (10)
- Glass (9)
- Aluminium (8)
- Coarsening (8)
- Residual stress (8)
- Alloy 2618A (7)
- Fatigue (7)
- CCUS (6)
- Corrosion (6)
- Crack growth (6)
- High temperature corrosion (6)
- S-phase (6)
- Vickers (6)
- Carbon steels (5)
- DCB (5)
- LCF (5)
- Martensitic steel (5)
- Microstructure (5)
- Mikroplastik (5)
- Neutron diffraction (5)
- Superaustenite steel (5)
- Supercritical/dense phase CO2 (5)
- Transmission electron microscopy (5)
- Water speciation (5)
- CCS (4)
- Concrete (4)
- Damage (4)
- Dark-field transmission electron microscopy (DFTEM) (4)
- Droplet corrosion (4)
- EBSD (4)
- Hydrogen (4)
- Microplastics (4)
- Nanoparticles (4)
- Selective laser melting (4)
- Soda-lime silicate glass (4)
- TED-GC-MS (4)
- 3D-Printing (3)
- Calcination (3)
- Ceramic (3)
- Coating (3)
- Crack (3)
- Crystallization (3)
- Dark-field transmission electron microscopy (3)
- Data Fusion (3)
- Electron microscopy (3)
- Ferritic-martensitic steels (3)
- IN718 (3)
- Inconel 686 (3)
- Infrarotspektroskopie (3)
- Laser ablation in liquid (3)
- Luftultraschall (3)
- PE-HD (3)
- Powder (3)
- Pulveraktivkohle (3)
- Residual Stresses (3)
- Rotor blade (3)
- SLM (3)
- Schädigung (3)
- Selective Laser Melting (3)
- Sintering (3)
- Sulfidation (3)
- Thermoelectrics (3)
- Thermogravimetrie (3)
- Titanium oxide (3)
- ToF-SIMS (3)
- VSSA (3)
- Wasser (3)
- Wind turbine blades (3)
- 3D printing (2)
- AISI 304L (2)
- Adiabatic calorimeter (2)
- Aging (2)
- Air-coupled ultrasonic testing (2)
- Airborne ultrasonic testing (2)
- Alumina (2)
- Aluminum (2)
- Analysis (2)
- Anisotropy (2)
- Austenitic stainless steel (2)
- Bacteria (2)
- Belebtschlamm (2)
- Carbon capture (2)
- Carbon dioxide (2)
- Composite (2)
- Composites (2)
- Continnum damage model (2)
- Crystal plasticity (2)
- Destabilization (2)
- Deuterium (2)
- Diffraction contrast (2)
- Diffusion (2)
- Diffusion coefficient (2)
- Dislocation (2)
- Environmental stress cracking (ESC) (2)
- Fatigue of sandwich shell structures (2)
- Ferroelectret (2)
- Ferroelektret (2)
- Foaming (2)
- Fraktographie (2)
- Glas (2)
- Glass composition (2)
- High-temperature corrosion (2)
- Hochtemperatur (2)
- Impurities (2)
- Injection (2)
- Kriechen (2)
- Lebensdauer (2)
- Long-term behavior (2)
- Metal seal (2)
- Microstructure evolution (2)
- Multilayer (2)
- Ni-Resist (2)
- Non-destructive testing (2)
- Oxidation (2)
- Particle morphology (2)
- Phase change material (2)
- Plastic deformation (2)
- Polymer (2)
- Porcelain (2)
- Precipitation (2)
- Pressure-assisted sintering (2)
- Reaction-sintering (2)
- Relaxation (2)
- Residual stresses (2)
- Ressidual stress (2)
- Risswachstum (2)
- Rotorblattschalen (2)
- S-Phase (2)
- Safety assessment (2)
- Salt eutectics (2)
- Sandwich (2)
- Scale-bridging (2)
- Scanning transmission electron microscopy (STEM) (2)
- Simulation of concrete (2)
- Sinter additive (2)
- Spray drying (2)
- Steel (2)
- Superalloy (2)
- Superalloy single crystals (2)
- TEM (2)
- TMF (2)
- Temperature (2)
- Thermal energy storage (2)
- Thermoanalyse (2)
- Thermoelectric oxide (2)
- Thermographie (2)
- Thermogravimetry (2)
- Thermomechanics (2)
- UV-irradiation (2)
- Under cyclic loading (2)
- Virtual experiments (2)
- Viscoplasticity (2)
- Wandler (2)
- Wind turbine (2)
- X-ray laminography (2)
- XANES (2)
- 316L (1)
- 3D glass structure model (1)
- 3D-finite element modeling (1)
- 3D-printing (1)
- 9-12% Cr ferritic-martensitic steels (1)
- Abwasser (1)
- Accelerated integration scheme (1)
- Accelerated temporal integration (1)
- Active thermography (1)
- Additive Fertigung (1)
- Advanced wastewater treatment (1)
- Age hardening (1)
- Ageing (1)
- Aggressive environement (1)
- Aggressive environment (1)
- Aggressive gases (1)
- Al-Cu-Li-alloy (1)
- Al-Li alloys (1)
- Alloy 2818A (1)
- Alloys (1)
- Alterung (1)
- Alumina coatings (1)
- Aluminium alloys (1)
- Aluminiumlegierung (1)
- Aluminum alloy (1)
- Aluminum alloys (1)
- Amorphization (1)
- Amorphous silica (1)
- Analyse (1)
- Analytik (1)
- Analytische Zentrifuge (1)
- Annealing (1)
- Aquifer (1)
- Artefact (1)
- Atomic packing factor (1)
- Austenitic steel (1)
- BCS (1)
- BTEX (1)
- Betriebsfestigkeit (1)
- Biaxial strength (1)
- Bilanzierung (1)
- Bimodal distribution (1)
- Binder jetting (1)
- Bio Ceramic (1)
- Bio Ceramics (1)
- Bioactive glass (1)
- Biodiesel (1)
- Biogeochemistry (1)
- Bioresorbable (1)
- Bitter technique (1)
- Boden (1)
- Bone regeneration (1)
- Borosilicate glass (1)
- Bravais lattice (1)
- Brittle / ductile fracture behavior (1)
- Brown-rot fungi (1)
- CCUS, supercritical/dense phase CO2, carbon steels, martensitic steel, superaustenite steel, droplet corrosion (1)
- CFK (1)
- CMSX4 (1)
- CO2 corrosion (1)
- Calcium Cobaltite (1)
- Calcium cobaltite (1)
- Calciumcobaltit (1)
- Calciummanganat (1)
- Carbon steels (1)
- Carbon fibre-reinforced-plastics (1)
- Carbon steel (1)
- Carbon storage (1)
- Ccs (1)
- Cement (1)
- Centrifugal compressor wheel (1)
- Ceramic springs (1)
- Ceramics (1)
- Chemometrics (1)
- Chemometrie (1)
- Chromatography (1)
- Co2-Storage (1)
- Cobald based alloy (1)
- Complex loading (1)
- Composite structures (1)
- Coniophora puteana (1)
- Coordinate measurement machine (1)
- Corrosion Fatigue (1)
- CrN/NbN (1)
- Crack Propagation (1)
- Crack healing (1)
- Crack propagation (1)
- Crack propagation analysis (1)
- Creep mechanisms (1)
- Creep, Creep Rupture, and Stress Rupture (1)
- Creep-fatigue (1)
- Critical energy release rate (1)
- Crystal Orientation (1)
- Crystallographic texture (1)
- Cupriavidus metallidurans (1)
- Cycle jump (1)
- Cyclic loading (1)
- Cyclic oxidation (1)
- Cyclic softening (1)
- Damage evolution (1)
- Datenfusion (1)
- Deformation (1)
- Dentine (1)
- Dielectric strength (1)
- Diesel (1)
- Diffraction (1)
- Digital image correlation (1)
- Dislocations (1)
- Dissolved water (1)
- Distributed fibre optic sensors (1)
- Dynamic recrystallization (1)
- EDXRD (1)
- EFTEM (1)
- Early stages (1)
- Efficiency (1)
- Electric conductivity (1)
- Electrical resistance (1)
- Electron back-scattered diffraction (1)
- Enamel (1)
- End of life (1)
- Environmentally assisted cracking (1)
- Epoxidharz (1)
- Epoxy resin (1)
- Ermüdung (1)
- Expanding cavity model (1)
- FCH JU (1)
- FIB Tomography (1)
- Failure rate (1)
- Faserverstärkte Kunstoffe (1)
- Fatigue crack propagation (1)
- Fatigue damage (1)
- Fatigue fracture (1)
- Fatigue of sandwich structures (1)
- Femtosecond laser (1)
- Fertigungstechnologie (1)
- Fiber-matrix interface (1)
- Filters (1)
- Finland (1)
- Flow Coefficient (1)
- Fluoride nanoparticles (1)
- Fluorolytic sol−gel (1)
- Formerkennung (1)
- Fourier series (1)
- Fourier transform infrared spectroscopy (1)
- Fracture mechanics (1)
- Friction (1)
- Friction stir processing (1)
- Full Notch Creep Test (FNCT) (1)
- Full notch creep test (FNCT) (1)
- Fungi (1)
- GC-MS (1)
- GFK (1)
- GMR (1)
- GMR sensors (1)
- Gasabgabe (1)
- Gasgehalt (1)
- Geometrical factors (1)
- Geopolymers (1)
- Geothermal (1)
- Glass capillaries (1)
- Glass crystallization stress (1)
- Glass fiber reinforced polymers (1)
- Glass transition (1)
- Glass-ceramics definition (1)
- Gold (1)
- Grade S960QL steel (1)
- Gradient-enhanced fatigue model (1)
- Grain Boundary Corrosion (1)
- Grain boundaries (1)
- Granules (1)
- Graphite (1)
- Heat treatment (1)
- High - temperature corrosion (1)
- High Cycle Fatigue (1)
- High Temperature Corrosion (1)
- High interstitial austenitic steel (1)
- High temperature (1)
- Hipims (1)
- Horizon 2020 (1)
- Hot Press (1)
- Hot isostatic pressing (HIP) (1)
- Hydrogen permeability (1)
- Hydrogen permeation (1)
- Hydrogen storage (1)
- Imaging techniques (1)
- Impact wear (1)
- Implant failures (1)
- In situ (1)
- In situ diffraction (1)
- In-situ (1)
- In-situ SEM micro shear deformation (1)
- In718 (1)
- Inconel 625 (1)
- Inconel 686 coating (1)
- Indentation (1)
- Indentation hardness (1)
- Initial attachment (1)
- Interdiffusion (1)
- Interface (1)
- Interfacial shear strength (1)
- Internal Sulfidation (1)
- Internal friction (1)
- Inverse ostwald ripening (1)
- Isostatic hot pressing (HIP) (1)
- Kalzinierung (1)
- Kennwertermittlung (1)
- Keramikfeder (1)
- Kikuchi pattern (1)
- Kunststoffe (1)
- Laboratory X-ray diffraction (1)
- Laminographie (1)
- Laser (1)
- Laser Cladding (1)
- Laser cladding (1)
- Laser curing (1)
- Laser scanning microscopy (LSM) (1)
- Lattice parameters (1)
- Lebensdauervorhersage (1)
- Lifetime prediction (1)
- Light curing (1)
- Lightweight materials (1)
- Limestone Filler (1)
- Log-normal distribution (1)
- Long-term calculation (1)
- Long-term storage (1)
- Low Cycle Fatigue (LCF) (1)
- Low carbon steel (1)
- Low cycle fatigue (1)
- Magnetic domain distribution (1)
- Magnetic stray field (1)
- Magnetic stray fields (1)
- Magnetomechanical effect (1)
- Manufacturing (1)
- Mars (1)
- Martensite (1)
- Martensitic steel (1)
- Martensitic transformation (1)
- Mass transport (1)
- Master curve (1)
- Masterschädigungslinie (1)
- Material characterization (1)
- Material defects (1)
- Material modeling (1)
- Material oxidation (1)
- Mechanical and thermal testing (1)
- Mechanisches Verhalten (1)
- Metal Magnetic Memory (1)
- Metal magnetic memory (1)
- Metallic components (1)
- Metformin (1)
- Micro-shrinkages (1)
- Micromechanical model (1)
- Microsegregation (1)
- Microstructur (1)
- Microstructural evolution (1)
- Microstructure and texture (1)
- Microwave technology (1)
- Mikrostruktur (1)
- Misorientation (1)
- Mobility (1)
- Model alloy (1)
- Modeling (1)
- Molecular dynamics (1)
- Multiaxial deformation (1)
- Multiaxial stress state (1)
- Multilayer technology (1)
- NGS (1)
- Nahinfrarotspektroskopie (1)
- Nano particle (1)
- Nano screening (1)
- Nano-powder characterization (1)
- Nano-scratch test (1)
- Nanomaterial screening (1)
- Nanoparticle structure (1)
- Nanoscale multilayers (1)
- Natural silver wires (1)
- Near Infrared Spectroscopy (1)
- NiTi (1)
- Nickel based coatings (1)
- Nickel-base superalloy (1)
- Nickel-base superalloys (1)
- Notch (1)
- Number density (1)
- Optical backscatter reflectometry (1)
- Optical centrifugation (1)
- Optical fibre (1)
- Orientation (1)
- Orientation refinement (1)
- Oxide coatings (1)
- Oxide scale (1)
- Oxyfuel (1)
- P92 steels (1)
- PLS-DA (1)
- PV modules (1)
- Particle Size Distribution (1)
- Particle size (1)
- Partikelgrößenverteilung (1)
- Passive components and circuits (1)
- Permeability (1)
- Phase field simulation (1)
- Phase-field (1)
- Phase-field simulation (1)
- Photocatalysis (1)
- Photocleavable organosilanes (1)
- Photopolymer composites (1)
- Phototrophs (1)
- Photovoltaic modules (1)
- Phytolith (1)
- Pipeline (1)
- Polyaniline (1)
- Polymer matrix composites (1)
- Polymeric Materials (1)
- Polymerwissenschaften (1)
- Polypropylene (1)
- Polystyrene (1)
- Porosity (1)
- Powdered activated carbon (1)
- Power factor (1)
- Preceramic polymer (1)
- Precipitates (1)
- ProMoAM (1)
- Production scatter (1)
- Prozessmonitoring (1)
- Pull-out composite materials (1)
- Rafting (1)
- Raman spectroscopy (1)
- Real-time qPCR (1)
- Reference Material (1)
- Relaxation tests (1)
- Relaxationsphänomene (1)
- Resistance stress (1)
- Rheology (1)
- Rhodonia placenta (1)
- Risse (1)
- Rissform (1)
- Rotorblatt (1)
- Roughness (1)
- Röntgenrefraktion (1)
- SEM (1)
- SEM wood characterization (1)
- SIMS (1)
- Sand blasting (1)
- Scanning acoustic microscopy (SAM) (1)
- Scanning electron microscopy (1)
- Schalenprüfstand (1)
- Schwingbrüche (1)
- Segregation (1)
- Self-Assembly (1)
- Sewage treatment plant (1)
- Shape memory alloys (1)
- Shear load (1)
- Shear testing (1)
- SiO2 (1)
- Silicate Glasses (1)
- Silicatglas (1)
- Silicon Carbide (1)
- Single crystal superalloys (1)
- Single fiber pull-out test (1)
- Single-crystal (1)
- Single-crystals (1)
- Sintermechanismen (1)
- Sinterung (1)
- Sliding simulation (1)
- Slow crack growth (SCG) (1)
- Slurry optimization (1)
- Soil (1)
- Soil sample (1)
- Solar panels (1)
- Solid-State-Synthesis (1)
- Solid-state-synthesis (1)
- Sorption (1)
- Spannungs-Dehnungs-Verhalten (1)
- Steam oxidation resistance (1)
- Steel P92 (1)
- Stereoscopy (1)
- Strain difference (1)
- Stress-strain-behavior (1)
- Structural health monitoring (SHM) (1)
- Structural steel (1)
- Structured heating (1)
- Struktur (1)
- Subsurface defects (1)
- Sulphidation (1)
- Superaustenite steel (1)
- Superconducting magnet (1)
- Supercritical/dense phase CO 2 (1)
- Support configurations (1)
- Support vector machines (1)
- Surface Nucleation (1)
- Surface modification (1)
- Surface nucleation (1)
- Swept wavelength interferometry (SWI) (1)
- Synchrotron X-ray diffraction (1)
- T1 precipitate (1)
- TAHYA (1)
- TED (1)
- TIG-welding (1)
- Technische Keramik (1)
- Texturation (1)
- Thermal degradation (1)
- Thermal expansion (1)
- Thermische Analyse (1)
- Thermo-mechanical fatigue (1)
- Thermo-mechanical loading (1)
- Thermoanalysis (1)
- Thermoanalytical Methods (1)
- Thermoelectric generator (1)
- Thermoelectric oxides (1)
- Thermoelektrika (1)
- Thermomechanical Fatigue (TMF) (1)
- Thermomechanische Eigenschaften (1)
- Thickening (1)
- Thin tribofilm (1)
- Titanium (1)
- Tooth wear (1)
- Topography (1)
- Transducers (1)
- Transmittance (1)
- Tricalcium Phosphate (1)
- Ultrasound (1)
- VCSEL (1)
- Vacancies (1)
- Very high cycle fatigue (1)
- Vickers indentation (1)
- Visualization (1)
- Volume Fraction (1)
- Volume fraction (1)
- Waste water (1)
- Water (1)
- Water droplet erosion resistance (1)
- Windkraft (1)
- Withstand voltage tests (1)
- Wood protection (1)
- X-ray computed tomography (CT) (1)
- X-ray refractography (1)
- XRD (1)
- Young`s modulus (1)
- ZfP (1)
- Zyklische Belastung (1)
- laser cladding (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (228) (entfernen)
Eingeladener Vortrag
- nein (88)
Today, more than 12% of the primary energy is lost in the form of waste heat. Thermoelectric generators (TEGs) can convert waste heat directly into electrical power by utilizing the Seebeck effect. The performance of such a generator is defined by a dimensionless figure of merit ZT of the thermoelectric pairs and the resistance R of the metallic contacts between these pairs. The figure of merit of thermoelectric oxides is considerably smaller compared to semiconductors. Still, thermoelectric oxides like calcium cobaltite (Ca3Co4O9) are attractive for applications at elevated temperatures in air. In contrast to the established π-type architecture of common TEGs, tape casting and multilayer technology may be applied for cost-effective manufacturing of oxide TEGs. Promising demonstrations of multilayer TEGs have been published in the last years. Still, the development of reliable and scalable manufacturing processes and proper material combinations is necessary. The aim of our project is to evaluate the feasibility of low temperature co-fired ceramics (LTCC) technology for a practical manufacturing of oxide multilayer TEGs of Ca3Co4O9 (p-type) and calcium manganate (CaMnO3, n-type). Ca3Co4O9 exhibits an undesired phase decomposition at 926 °C. Because of that, the application of sintering strategies and interconnect concepts well known from LTCC technology is a promising approach. We present results of pressure-assisted sintering of Ca3Co4O9 multilayer at 900 °C and axial pressures of up to 7.5 MPa. Ca3Co4O9 was produced by solid state reaction of CaCO3 and cobalt(II,III)oxide at 900 °C. Green tapes were prepared by a doctor-blade process, manually stacked and laminated by uniaxial thermocompression. Sintering was conducted in a LTCC sintering press between SiC setter plates. The thickness shrinkage was recorded by an in-situ technique. After sintering under 7.5 MPa, the microstructure of the single phase material shows a high density of 95 % and an advantageous alignment of the platelet grains. This results in good electrical conductivity and a comparatively high ZT of 0.018 at room temperature. However, the lowering of CaMnO3 sintering temperature from above 1200 °C to below 920 °C remains a challenge. To select a proper metal paste for interconnections of an oxide TEG, several pastes have been investigated regarding contact resistance of internal and external (soldered) connections in a preliminary study. Commercial pastes containing Ag, Au, Au/Pt, Ag/Pd, and Ag/Pd/Bi were manually applied and post-fired on sintered test bars of Ca3Co4O9 and CaMnO3 at 900 °C for 2 h. All tested pastes formed mechanically stable metallization after firing. For resistance measurement, 4-wire method and a custom-made probe head were used. The contacts on Ca3Co4O9 exhibit significantly (2-sample t-test, α = 5%) higher resistance compared to contacts on CaMnO3. Pure silver paste exhibits the lowest resistance for internal contacts on both materials, lower than 5 mΩ on CaMnO3. Ag/Pd/Bi paste resulted in conspicuously high variance of resistance. EDX analyses clarified an enrichment of Bi in the thermoelectric material near the interface and thereby the formation of an oxide layer with probably high electrical resistance. The thickness of that layer varies with the thickness of metallization. In conclusion, the use of Bi containing pastes is not advisable. Pure Ag paste shows the best results regarding resistance and solderability.
Helical springs with a rectangular cross-section have been machined from sintered and grinded hollow cylinders with high geometrical precision and good reproducibility. Such springs made from tetragonal zirconia polycrystal (TZP) ceramic show excellent edge quality because of high fracture toughness and bending strength of the starting material. Hence, springs with desired geometric dimension and tailored spring constant can be manufactured for highly demanding applications at high temperatures and in harsh environments.
Prior to any practical use, application limits of springs under mechanical and thermal load have to be analyzed. Therefore, different displacement experiments were carried out on the helical TZP springs.
- Dynamic displacement tests at various temperatures from -15°C to +60°C using a piezo actor to load/unload springs with frequencies between 1 and 40 Hz: Springs remained undamaged and the spring constants were not altered, even after more than one million cycles of compression loading.
- Long-time displacement measurements under static tensile loading at room temperature with a high-precision interferometer test facility: Significant spring elongation under constant strain was surprisingly proved over a period of many hours already at room temperature.
- Creeping experiments for 48 h under static compression load at different temperatures up to 1000 °C: After cooling down and load removing no permanent length reduction of springs was observed for test temperatures up to 700 °C. However, reshaping of TZP springs by plastic deformation is possible at higher temperatures and opens up additional possibilities for spring design and manufacturing.
The present work provides a comparative study on the interface and adhesion properties of surface modified single glass fibers embedded in an acrylate matrix. To facilitate a covalent bonding at the fibermatrix interface, the fibers are functionalized with selected organosilanes that comprise either passive (unsaturated C¼C bonds of methacrylate moieties) or photoactive functionalities (photocleavable bis(acyl)phosphane oxide groups). Immobilization of the functional silanes is carried out by a classic silanization reaction involving a condensation reaction across the surface hydroxyl groups of the inorganic glass fibers. The change of the physico-chemical properties of the fibers due to desizing and subsequent surface modification is monitored by X-ray photoelectron spectroscopy and zeta potential measurements. In addition, scanning electron microscopy is used to follow the changes in surface morphology. After the modification step, the desized and modified single fibers are embedded in a photocurable acrylate resin formulation. By performing single fiber pull-out tests, maximum pull-out force, friction strength and apparent interfacial shear strength are determined as a function of the coupled silanes. The results reveal that the attached organosilanes lead to a significant increase in adhesion strength, whilst the performance of the photo-cleavable organosilane is superior to the passive methacryl-functional derivative.
In diesem Forschungsvorhaben wurde ein Verfahren entwickelt, um die Genauigkeit der Lebensdauerbewertung für Abgasturbolader (ATL)-Verdichterräder aus der ausscheidungs-härtbaren Aluminiumlegierung EN AW-2618A zu verbessern. Dies umfasst insbesondere die Berücksichtigung der Werkstoffalterung, mit der beim Einsatz dieser Bauteile unter entsprechender Betriebsbeanspruchung (Temperatur, Zeit, Spannung) gerechnet werden muss. Zunächst wurde eine solide experimentelle Datenbasis für den untersuchten Werkstoff geschaffen. Dies umfasste sowohl eine mechanische als auch eine mikrostrukturelle Charakterisierung des Ausgangszustands (T61) sowie von ausgelagerten Zuständen bis zu 25.000 h bei betriebsrelevanten Temperaturen (160 °C, 180 °C, 190 °C). Bei den Untersuchungen zur Mikrostruktur wurde der Fokus auf die Entwicklung der Radien der stäbchen-förmigen aushärtenden Phase gelegt, die während der Alterung vergröbern. Der Zusammenhang zwischen Auslagerungstemperatur, -zeit und ggfs. mechanischer Belastung wurde erstmals in diesem Umfang quantifiziert und entsprechende Gesetzmäßigkeiten zur Beschreibung der Vergröberung ermittelt. Vergleichend dazu wurde der Einfluss der Alterung auf die Härte, die Festigkeit, das Kriechverhalten und die Ermüdungslebensdauer (LCF, TMF) bestimmt, so dass eine Korrelation zur Mikrostruktur vorliegt.
Die Ergebnisse der Kriechversuche wurden zur Kalibrierung eines modifizierten Sinus-hyperbolicus-Kriechmodells verwendet. Ein zeit- und temperaturabhängiges Verformungsmodell nach Chaboche, welches die wesentlichen Phänomene der Hochtemperaturverformung und der Wechselplastizität beschreibt, wurde erweitert und berücksichtigt nun die Werkstoffalterung, indem die Festigkeit nicht nur als Funktion der Temperatur, sondern auch des Alterungszustands (d. h. des mittleren Radius der Ausscheidungen) dargestellt wird. Für die Erweiterung des Modells zur Bewertung der Ermüdungslebensdauer wurde analog verfahren. Die berechnete Lebensdauer der im Verlauf des Vorhabens durchgeführten LCF- und TMF-Versuche stimmt gut mit den experimentellen Ergebnissen überein. Lediglich ein LCF-Versuch mit einer Haltezeit von 900 s im Zug weicht deutlich vom Mittelwert ab und zeigt die Grenzen des zeitunabhängigen Schädigungsmodells auf. Versuche mit kürzeren Haltezeiten bis zu 60 s liegen im Streuband, ebenso die verschiedenen Alterungszustände. Eine Schädigungsakkumulation unter Berücksichtigung der fortschreitenden Alterung über der Lebensdauer wurde entwickelt und implementiert. Neben der Berücksichtigung der Alterung in der Verformungs- und Lebensdaueranalyse besteht auch die Möglichkeit, komplexe Belastungszyklen in einem Postprozessing zu bewerten, indem Rainflow-Klassierungen typischer komplexer Belastungszyklen vorgenommen werden.
Die Methodik und die Modelle wurden in die Finite-Elemente-Programme Abaqus und Ansys implementiert und stehen für die rechnerische Bewertung von Bauteilen zur Verfügung.
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.
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.
The increasing pollution of terrestrial and aquatic ecosystems with plastic debris leads to the accumulation of microscopic plastic particles of still unknown amount. To monitor the degree of contamination analytical methods are urgently needed, which help to quantify microplastics (MP). Currently, time-costly purified materials enriched on filters are investigated both by micro-infrared spectroscopy and/or micro-Raman. Although yielding precise results, these techniques are time consuming, and are restricted to the analysis of a small part of the sample in the order of few micrograms. To overcome these problems, here we tested a macroscopic dimensioned NIR process-spectroscopic method in combination with chemometrics. For calibration, artificial MP/soil mixtures containing defined ratios of polyethylene, polyethylene terephthalate, polypropylene, and polystyrene with diameters < 125 µm were prepared and measured by a process FT-NIR spectrometer equipped with a fiber optic reflection probe. The resulting spectra were processed by chemometric models including support vector machine regression (SVR), and partial least squares discriminant analysis (PLS-DA). Validation of models by MP mixtures, MP-free soils and real-world samples, e.g. and fermenter residue, suggest a reliable detection and a possible classification of MP at levels above 0.5 to 1.0 mass% depending on the polymer. The benefit of the combined NIRS chemometric approach lies in the rapid assessment whether soil contains MP, without any chemical pre-treatment. The method can be used with larger sample volumes and even allows for an online prediction and thus meets the demand of a high-throughput method.
3D structural investigations are described by X-ray laminography studies of sandwich shell segments, made of a PVC foam core, covered by non-crimp fabric glass fibre composite lay-ups processed by vacuum assisted resin infusion of epoxy. The specific scope of this study is to image transversal flaws within the foam core (joints) and of single ply overlaps. Test flaws were purposely implemented in order to simulate typical failure under cyclic load. In a dedicated test rig for shell structures, the flaw evolution/propagation is monitored by thermography and optical 3D inspection of deformation. Due to the unfavourable preconditions for classical computed tomography as of large aspect ratio, the samples were investigated by coplanar translational laminography. Its limited range of observation angles of ± 45°, results in anisotropic artefacts about the normal to the sample surface, but the typical flaws are well visualized in the as-prepared state, in a state of early damage, and in the repaired state.
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 the bulk of IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron 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.