5 Werkstofftechnik
Filtern
Dokumenttyp
- Vortrag (121)
- Zeitschriftenartikel (71)
- Beitrag zu einem Tagungsband (24)
- Forschungsdatensatz (21)
- Posterpräsentation (20)
- Buchkapitel (7)
- Dissertation (4)
- Forschungsbericht (4)
- Sammelband (Herausgeberschaft für den kompletten Band) (3)
- Monografie (1)
Sprache
- Englisch (227)
- Deutsch (49)
- Französisch (1)
Schlagworte
- Ontology (33)
- Creep (27)
- Microstructure (23)
- Additive manufacturing (21)
- LCF (16)
- Additive Manufacturing (14)
- Degradation (13)
- Fatigue (13)
- Ti-6Al-4V (13)
- Aluminium (11)
- Alloy 2618A (10)
- Coarsening (10)
- FAIR (10)
- 316L (9)
- Aging (9)
- EN AW-2618A (9)
- Low Cycle Fatigue (9)
- Transmission electron microscopy (9)
- Crystal plasticity (8)
- Digitalization (8)
- Nickel-base superalloys (8)
- Ontologie (8)
- Residual stress (8)
- S-phase (8)
- Semantic Web Technologies (8)
- AGIL (7)
- AISI 316L (7)
- Additive Fertigung (7)
- Aluminium alloy (7)
- Anisotropy (7)
- Kriechen (7)
- Mechanical testing (7)
- Plattform MaterialDigital (7)
- Semantic Interoperability (7)
- Thermomechanical fatigue (7)
- Zugversuch (7)
- Data Interoperability (6)
- Knowledge Representation (6)
- Mikrostruktur (6)
- P92 (6)
- TMF (6)
- Computed Tomography (5)
- Crack growth (5)
- Damage (5)
- Dark-field transmission electron microscopy (DFTEM) (5)
- Data mapping (5)
- Digitalisierung (5)
- FAIR data (5)
- FAIR data management (5)
- Fe-Al alloys (5)
- HIP (5)
- Intermetallics (5)
- Iron aluminides (5)
- Knowledge graph and ontologies (5)
- Laser powder bed fusion (5)
- PMD Core Ontology (5)
- Reference data (5)
- Shear modulus (5)
- Stress relaxation (5)
- Tensile Test (5)
- Tensile testing (5)
- Wissensrepräsentation (5)
- Young's modulus (5)
- Aluminum alloys (4)
- Brinell hardness (4)
- Creep-fatigue (4)
- Data Fusion (4)
- EBSD (4)
- Elastic modulus (4)
- Electron microscopy (4)
- Fatigue crack growth (4)
- Laser Powder Bed Fusion (4)
- Microstrucrue Design (4)
- Ni-Resist (4)
- Normung (4)
- Phase-field simulation (4)
- Plattform Material Digital (4)
- Scale-bridging (4)
- Schädigung (4)
- Superalloy (4)
- Tensile Test Ontology (4)
- Tensile test (4)
- Virtual experiments (4)
- Crack (3)
- Crack propagation (3)
- Crack tip opening displacement (3)
- Creep behavior (3)
- Creep data (3)
- Dark-field transmission electron microscopy (3)
- Diffraction (3)
- Digtial Representation (3)
- Electronic Lab Notebook (3)
- Ferritic-martensitic steels (3)
- Fractography (3)
- Hardness (3)
- Heat treatment (3)
- High temperature mechanical properties (3)
- IN 718 (3)
- Interoperability (3)
- Knowledge graph (3)
- Lebensdauer (3)
- Low cycle fatigue (3)
- Mechanical behavior (3)
- Mechanische Eigenschaften (3)
- Metadata schema (3)
- Microstructure evolution (3)
- Ontologies (3)
- PBF-LB/M/316L (3)
- PMDco (3)
- Phase-field (3)
- Precipitation (3)
- Referenzdaten (3)
- Reproducibility (3)
- Research Data Management (3)
- S-Phase (3)
- Semantic Data (3)
- Semantic Web (3)
- Single-crystals (3)
- Superalloys (3)
- Superlegierung (3)
- Syngle Crystal alloy (3)
- Tempered Martensite Ferritic Steels (3)
- Tempered martensite-ferritic steel (3)
- Tensile data (3)
- Thermo-Mechanical Fatigue (3)
- Al-Cu-Li alloys (2)
- Alterung (2)
- Aluminium Alloy (2)
- Aluminum (2)
- Aluminum alloy (2)
- CALPHAD (2)
- CT (2)
- Casting (2)
- Chemo-mechanical coupling (2)
- Computed tomography (2)
- Concrete (2)
- Continnum damage model (2)
- Copper (2)
- Copper alloys (2)
- Creep-Fatigue (2)
- Cyclic softening (2)
- Data Management (2)
- Data Structures (2)
- Data management (2)
- Dataset (2)
- Density-based Thermodynamics (2)
- Density-based model (2)
- Densty-based Thermodynamics (2)
- Diffraction Elastic Constants (2)
- Diffusion (2)
- Digital material representation (2)
- Digital representation (2)
- Digitization (2)
- Dislocation (2)
- Dislocations (2)
- Elasticity (2)
- Electron Backscatter Diffraction (2)
- Electron backscatter diffraction (2)
- Environmentally assisted cracking (2)
- FAIR Data Management (2)
- Fatigue performance (2)
- Fatigue testing (2)
- Finite element analysis (2)
- Fracture mechanics (2)
- Glass forming (2)
- High Cycle Fatigue (2)
- High Temperature Testing (2)
- Joined nickel-based alloys (2)
- Kleinprobenprüfung (2)
- Knowledge Graph (2)
- Laser Powder Bed fusion (2)
- Long-term behavior (2)
- Mass transport (2)
- Material digital (2)
- Materials science (2)
- Metal seal (2)
- Micromechanical model (2)
- Microstructure-property-correlation (2)
- Multiaxial deformation (2)
- NFDI (2)
- Neutron diffraction (2)
- Nickel-base alloy (2)
- Notches (2)
- Ontologien (2)
- Ontology development (2)
- Ostwald ripening (2)
- PMD (2)
- Parametric modeling (2)
- Plastic deformation (2)
- Polymer (2)
- Probengrößeneffekt (2)
- Rapid solidification (2)
- Residual Stress (2)
- S355 steel sheet (2)
- Semantic Representation (2)
- Semantic web (2)
- Semantisches Web (2)
- Simulation (2)
- Simulation of concrete (2)
- Single-Crystal (2)
- Standard (2)
- Standardisierung (2)
- Standardization (2)
- Structural steel (2)
- Superconducting magnet (2)
- Symmetric dwell periods (2)
- TEM (2)
- Tensile Properties (2)
- Thermodynamics (2)
- Ti64 (2)
- TiAl5V4 (2)
- Titan (2)
- Titanium (2)
- Under cyclic loading (2)
- Vickers hardness (2)
- Viscoplasticity (2)
- Wall thickness (2)
- Zugeigenschaften (2)
- 316L stainless steel (1)
- 3D-finite element modeling (1)
- 9-12% Cr ferritic-martensitic steels (1)
- 9-12%Cr steel (1)
- 9–12%Cr steel (1)
- AM (1)
- Abgasturbolader Heißteile (1)
- Accelerated integration scheme (1)
- Accelerated temporal integration (1)
- Accessible (1)
- Age hardening (1)
- Ageing (1)
- Al alloys (1)
- Al-Cu alloy (1)
- Al-Cu-Li-alloy (1)
- Al-Li alloys (1)
- Al2CuMg (1)
- Allgemeine Grundlagen (1)
- Alloy 2818A (1)
- Alloy design (1)
- Alloy microstructure (1)
- Aluminiumlegierung (1)
- Aluminum Alloy Aging (1)
- Anwendungen (1)
- Atomistic simulations (1)
- Aufbau von Festkörpern (1)
- Austenite-to-martensite phase transformation (1)
- Austenitic cast iron (1)
- Austenitischer Stahl (1)
- Automatable digital approach (1)
- Automated finite element analysis (1)
- Automated image analysis (1)
- Automation (1)
- Automatische Finite Element Simulation (1)
- Beanspruchung (1)
- Bitter technique (1)
- Bruch (1)
- CKAN (1)
- CMSX4 (1)
- Calibration (1)
- Carbon steel (1)
- Centrifugal casting (1)
- Centrifugal compressor wheel (1)
- Characterisation (1)
- Characterization (1)
- Charpy test (1)
- Chemische Analyse (1)
- Coefficient of thermal expansion (1)
- Complex borides (1)
- Compositionally complex alloys (1)
- Contact mechanics (1)
- Corrosion (1)
- Craze-crack mechanism (1)
- Creep behaviour (1)
- Creep mechanisms (1)
- Creep, Creep Rupture, and Stress Rupture (1)
- Creep-fatigue interaction (1)
- Crystal Defects (1)
- Crystal Plasticity Modelling (1)
- Crystalline defects (1)
- Cyclic loading (1)
- Cyclic oxidation (1)
- DED-L (1)
- DIN (1)
- Damage Behavior (1)
- Damage behavior (1)
- Data Exchange (1)
- Data Integration (1)
- Data Mapping (1)
- Data format (1)
- Data infrastructures (1)
- Data linking (1)
- Data pipeline concept (1)
- Data storage (1)
- Data structure (1)
- Datenfusion (1)
- Datenökosystem (1)
- Defects (1)
- Defects engineering (1)
- Defects phase diagram (1)
- Defects thermodynamics (1)
- Deformation (1)
- Deformation mechanisms (1)
- Demonstrators (1)
- Die casting (1)
- Differential scanning calorimetry (DSC) (1)
- Digital Transformation (1)
- Digital image correlation (1)
- Digital representations (1)
- Digital workflow (1)
- Digital workflows (1)
- Digitalizations (1)
- Domain Ontology Development (1)
- Dwell periods (1)
- Dwell times (1)
- Dwell-Fatigue (1)
- EN AW 2618A (1)
- EN AW 2618A a (1)
- Eigenschaften (1)
- Eigenspannung (1)
- Elastic constants (1)
- Elastic energy (1)
- Elctronic Lab Notebook (1)
- Electrical resistance (1)
- Electrochemical dressing (1)
- Electropolishing (1)
- Elektronisches Laborbuch (ELN) (1)
- Elektrotechnische Grundlagen (1)
- Energiewende (1)
- Energy transition (1)
- Entwicklung (1)
- Environment (1)
- Environmental Stress Cracking (1)
- Environmental stress cracking (ESC) (1)
- Ermüdung (1)
- Expanding cavity model (1)
- FAIR Data (1)
- FAIR data. (1)
- FAIR principles (1)
- FAIR research data management (1)
- FNCT (1)
- Fatigue crack propagation (1)
- Fatigue damage (1)
- Ferritic–martensitic steel (1)
- Finite elmenet simulation (1)
- Finite-Elemente-Methode (1)
- Fourier series (1)
- Full notch creep test (FNCT) (1)
- Full-Notch Creep Test (1)
- Full-notch creep test (1)
- Fullerite (1)
- GMR (1)
- GMR sensors (1)
- Gefügeuntersuchung (1)
- Gefügte Nickelbasislegierungen (1)
- General Chemistry (1)
- General Computer Science (1)
- General Engineering (1)
- General Materials Science (1)
- Glas (1)
- Gleichgewicht (1)
- Grade S960QL steel (1)
- Gradient-enhanced fatigue model (1)
- Grain Boundary Phase Diagram (1)
- Grain Boundary Segregation (1)
- Grain Boundary Spinodal (1)
- Grain boundaries (1)
- Grain boundary (1)
- Grain boundary phase diagram (1)
- Grain boundary thermodynamics (1)
- Graphic design (1)
- Grundlagen des Maschinenbaus (1)
- HCF (1)
- Hardness test (1)
- Heat Treatment (1)
- Hertzian cracks (1)
- High cycle fatigue (1)
- High entropy alloy (1)
- High entropy alloys (1)
- High-Entropy Alloys (1)
- High-entropy alloys (1)
- High-strength steel (1)
- High-temperature corrosion (1)
- Hochentropie-Legierung (1)
- Hochtemperatur (1)
- Hochtemperaturermüdung (1)
- Honing (1)
- Honing Stone (1)
- Hot isostatic pressing (HIP) (1)
- IN718 (1)
- In-Situ Testing (1)
- In-situ Process Monitoring (1)
- In-situ SEM micro shear deformation (1)
- In-situ diffraction (1)
- Inconel 718 (1)
- Incremental lifetime models (1)
- Indentation (1)
- Industrial and Manufacturing Engineering (1)
- Informationstechnische Grundlagen (1)
- Interfacial Spinodal (1)
- Interfacial anisotropy (1)
- Interfacial free energy (1)
- Intermetallische FeAl-Legierungen (1)
- Interoperable (1)
- Inverse ostwald ripening (1)
- Investment casting (1)
- Irregular topography (1)
- Isostatic hot pressing (HIP) (1)
- Kennwertermittlung (1)
- Keramik (1)
- Knowledge Graphs (1)
- Knowledge graphs (1)
- Knowledge representation (1)
- Korrosion (1)
- Kreislaufwirtschaft (1)
- Kriechermüdung (1)
- Kristallsystem (1)
- Kupfer (1)
- L-PBF 316L (1)
- LMD (1)
- Laser Poeder Bed Fusion (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser Scanning Microscopy (1)
- Laser beam melting (LBM) (1)
- Laser powder-based directed energy deposition (1)
- Laser scanning microscopy (LSM) (1)
- Laser-Pulverbettschmelzen (1)
- Layering misalignment (1)
- Lebensdauervorhersage (1)
- Legierung mit komplexer Zusammensetzung (1)
- Life cycle (1)
- Lifetime prediction (1)
- Linked open data (1)
- Long-term aging (1)
- Low Cycle Fatigue (LCF) (1)
- Low carbon steel (1)
- Low strain (1)
- Low-Cycle Fatigue (LCF) (1)
- Low-Cycle-Fatigue (1)
- Low-cycle fatigue (1)
- Low-cycle fatigue. (1)
- Low-cycle-fatigue behaviour (1)
- Lötverbindung (1)
- Machine learning (1)
- Magnetic domain distribution (1)
- Magnetic domains (1)
- Magnetic stray field (1)
- Magnetic stray fields (1)
- Magnetische Domänen (1)
- Magnetoelastic effect (1)
- Magnetoelastischer Effekt (1)
- Magnetomechanical effect (1)
- Martensitic transformation (1)
- Mat-o-lab (1)
- Material Life Cycle (1)
- Material degradation (1)
- Material modeling (1)
- MaterialDigital (1)
- Materialcharakterisierung (1)
- Materialentwicklung (1)
- Materialkreislauf (1)
- Materialprüfung (1)
- Materials Chemistry (1)
- Materials Science (1)
- Materials Testing (1)
- Materials and Processes Data Reusability (1)
- Materials informatics (1)
- Materials science and engineering (1)
- Materials testing (1)
- Mathematisch-naturwissenschaftliche Grundlagen (1)
- Mechanical Engineering (1)
- Mechanical Properties (1)
- Mechanical anisotropy (1)
- Mechanics of Materials (1)
- Mechanisches Verhalten (1)
- Mechanistic Modelling (1)
- Mehrachsige Verformung (1)
- Mehrskalenmodell (1)
- Metal Magnetic Memory (1)
- Metal magnetic memory (1)
- Metall (1)
- Metals and Alloys (1)
- Micro computed tomography (1)
- Microstructural evolution (1)
- Microstructure analysis (1)
- Microstructure characterisation (1)
- Microstructure modification (1)
- Mid-Level Ontology for MSE (1)
- Mikro-Computertomographie (1)
- Mikrostrukturentwicklung (1)
- Mikrostrukturuntersuchung (1)
- Miniature specimens (1)
- Misfitting precipitate (1)
- Missing acknowledgment (1)
- Model (1)
- Modeling (1)
- Modell (1)
- Molecular dynamics (1)
- NFDI-MatWerk (1)
- NIST (1)
- Nanocrystalline alloys (1)
- Nanoindentation (1)
- NiTi (1)
- Nickel alloys (1)
- Nickel-base superalloy (1)
- Nimonic 75 (1)
- Non-destructive Materials (1)
- Non-destructive testing (1)
- Notch (1)
- Number density (1)
- Numerische Simulation (1)
- Ordering (1)
- Orowan Mechanism (1)
- Overaging (1)
- P92 steels (1)
- PE-HD (1)
- Phase Diagram (1)
- Phase field crystal (1)
- Phase field method (1)
- Phase field model (1)
- Phase field simulation (1)
- Phase stability (1)
- Phase-field model (1)
- Plasticity (1)
- Platform Material Digital (1)
- Platform Material Digital (PMD) (1)
- Platform MaterialDigital (1)
- Platform MaterialDigital (PMD) (1)
- Plattform Material Digital (PMD) (1)
- Polyethylene (1)
- Pore (1)
- Pores (1)
- Porosity (1)
- Positron annihilation spectroscopy (1)
- Power plant (1)
- Precipitate shape (1)
- Precipitates (1)
- Precipitation Analysis (1)
- Precipitation hardening (1)
- Process development (1)
- Quantitative Precipitation Analysis (1)
- Quantitative image analysis (1)
- Radii distribution (1)
- Rafting (1)
- Reference Data (1)
- Reference Dataset (1)
- Reference material BCR-425 (1)
- Referenzmaterial (1)
- Referenzorganismus (1)
- Referenzverfahren (1)
- Reheating (1)
- Relaxation fatigue (1)
- Relaxation tests (1)
- Resonance testing (1)
- Reusability (1)
- Reusable data (1)
- Rissausbreitung (1)
- Risse (1)
- Rissform (1)
- Rissfortschritt (1)
- Rissverlauf (1)
- SEN-Probe (1)
- Safety (1)
- Schadenskunde (1)
- Selective laser melting (1)
- Selective laser melting (SLM) (1)
- Semantic Data Integration (1)
- Semantic Interioerability (1)
- Semantic Web technologies (1)
- Semantic data integration (1)
- Semantic interoperability (1)
- Semantic structuring (1)
- Semantische Daten (1)
- Shape memory alloy (1)
- Shape memory alloys (1)
- Shear testing (1)
- Simulationsgestützte Gießkonzepte (1)
- Single crystal superalloys (1)
- Single-crystal (1)
- Slow crack growth (SCG) (1)
- Solidification (1)
- Spinodal Decomposition (1)
- Spinodal decomposition (1)
- Standardisation (1)
- Strain difference (1)
- Strain energy (1)
- Strength (1)
- Stress-strain behavior (1)
- Stress-strain-behavior (1)
- Structured Data (1)
- Struktur (1)
- Superalloy single crystals (1)
- T1 precipitate (1)
- TIG-welding (1)
- TMF experiments (1)
- Temperature dependence (1)
- Tempered martensite ferritic steels (1)
- Tensile properties (1)
- Tensile strength (1)
- Tensile stress relaxation (1)
- Tensile stress relaxation testing (1)
- Tensile tests (1)
- Texture (1)
- Thermal Cycling (1)
- Thermal expansion (1)
- Thermo-mechanical fatigue (1)
- Thermographie (1)
- Thermomechanical Fatigue (TMF) (1)
- Thermomechanische Ermüdung (1)
- Thermophysikalische Eigenschaften (1)
- Thesaurus (1)
- Thickening (1)
- Tools (1)
- Topography (1)
- Transmission electron microscopy (TEM) (1)
- Tribologie (1)
- Ungleichgewicht (1)
- Unlegierter Baustahl (1)
- Vacancies (1)
- Verbundwerkstoff (1)
- Vernetzung (1)
- Vickers Hardness (1)
- Virtueller Materialdatenraum (1)
- Viskoplastisch (1)
- Visual ontology development (1)
- Vocabulary providers (1)
- Volume fraction (1)
- Werkstoffauswahl (1)
- Werkstoffkennwerte (1)
- Werkstoffmechanische Prüfung (1)
- Werkstoffprüfung (1)
- Workshop (1)
- X-ray computed tomography (CT) (1)
- Young`s modulus (1)
- Young´s modulus (1)
- Zerstörungsfreie Prüfung (1)
- Zugversuchsontologie (1)
- coarsening (1)
- hardness (1)
- microstructural changes (1)
- γ″ phase (1)
- θ′ phase (1)
- θ′-(Al2Cu) precipitate phase (1)
Organisationseinheit der BAM
- 5.2 Metallische Hochtemperaturwerkstoffe (277) (entfernen)
Paper des Monats
- ja (1)
The influence of prestraining on the aging response of an Al-Cu-Li alloy is investigated by preparation of different strain states (3 %, 4 %, 6 %) of the initial aging state. The Brinell hardness of the subsequently aged samples (up to 60 h aging time) was measured and it was found that the increasing dislocation concentration in the 3 different initial states leads to faster hardness increases and slightly higher maximum hardness.
Single crystal superalloys usually contain pores of sizes 5-10 micro-m after casting and heat treatment. These pores can be reduced under compression by combined creep and diffusion in a subsequent treatment called Hot Isostatic Pressing (HIP). The paper presents a methodology to simulate pore shrinkage under HIP conditions in two dimensions (2D).
At the scale of the pores, which is also the scale of the sub-grains (<50 micro-m) the dislocation sources cannot be assumed to be homogeneously distributed. Thus, the applicability of classical crystal plasticity is questionable. In this case, the transport of dislocations under an applied stress from the location where they are nucleated must be explicitly modelled. This is done by solving the transport equations for the dislocation densities and the elasticity equations in 2D. The dislocations are assumed to be nucleated at Low Angle Boundaries. They glide or climb through the sub-grains with a stress dependent velocity.
The transport equations are solved by the Flux-Corrected Transport method, which belongs to the predictor-corrector class of algorithms. In the first step, an artificial diffusion is introduced, which suppresses spurious oscillations of the solution. In a second step, the solution is corrected in such a way that no additional extremes appear and that the extremes do not grow. The algorithm is validated by simulating the transport of simple distributions with a constant velocity field.
With the dislocation velocities and the computed dislocation densities, the inelastic shear rate at the slip system level is computed by integrating the Orowan equation. In the 2D-setting, three slip systems are considered. The contributions of these slip systems are summed up to obtain the total inelastic strain rate. Dislocation glide and climb and the coupling of climb with vacancies diffusion are considered.
The resolution of the equilibrium equations from the inelastic strains turned out to be prone to numerical instabilities. As an alternative, the stresses are directly computed from the distribution of geometrically necessary dislocations following the method presented in. The resulting boundary value problem is solved by the Least-Square Finite Element method.
Examples of simulations are presented for a representative region under creep tension and for a pore shrinking under external pressure.
Der Aufbau der Werkstoffe wird durch Merkmale wie Bindungsart, atomare Strukturen, Kristallstrukturen einschließlich ihrer Gitterbaufehler, Körner und Phasen bestimmt. Die Mikrostruktur (Gefüge) stellt den Verbund der Kristalle, Phasen und Gitterbaufehler auf mikroskopischer und nanoskopischer Skala dar. Die Grundlagen der Phasenumwandlungen werden behandelt und die Bedeutung von Diffusionsprozessen erläutert. Werkstoffe sind bedeutend für Kultur, Wirtschaft, Technik und Umwelt. Ihre Herstellung benötigt Ressourcen und Energie. Recycling ist eine Möglichkeit zur Erhöhung der Ressourcenproduktivität.
Die Metal Magnetic Memory (MMM) Methode ist ein standardisiertes, zerstörungsfreies Prüfverfahren, das für die Detektion von lokal geschädigten Materialbereichen in ferromagnetischen Bauteilen oder Proben verwendet wird. Es basiert auf der Annahme lokaler magnetoelastischer Wechselwirkungen an Spannungskonzentrationsstellen, die schwache magnetische Streufelder an den geschädigten Prüfkörperoberflächen hervorrufen. Die MMM-Methode überträgt dabei die für einachsige und elastische Verformungen entwickelten magnetoelastischen Modellvorstellungen ohne weitere Anpassungen in den Schädigungskontext, der jedoch mehrachsige Beanspruchungen und elastisch-plastische Deformationsprozesse erwarten lässt. Das Ziel der Arbeit ist es daher, die gängigen MMM-Hypothesen zur Signalentstehung fach- und skalenübergreifend und unter stärkerer Berücksichtigung mechanischer und mikrostruktureller Aspekte zu überprüfen.
Zu diesem Zweck wurden zum einen gekerbte Flachzugproben aus einem unlegierten Baustahl inhomogen elastisch-plastisch verformt und die entstehenden magnetischen Streufelder an deren Oberflächen mit einem Drei-Achsen-GMR-Magnetometer detektiert. Die so ermittelten Magnetfeld-verteilungen wurden für unterschiedliche Verformungszustände ortsaufgelöst und richtungsabhängig mit gemessenen Dehnungsverteilungen (digitale Bildkorrelation) und mit simulierten Lastspannungs-verteilungen korreliert. Die eingeschnürten Probenbereiche wurden zusätzlich topographisch mittels Streifenlichtprojektion und Weißlichtinterferenzmikroskopie vermessen, um den Magnetisierungs-prozess ebenfalls vor dem Hintergrund geometrischer Effekte diskutieren zu können.
Um systematische, verformungsinduzierte Veränderungen der magnetischen Mikrostruktur (magnetischer Domänen) im polykristallinen, quasi-isotropen Material nachzuweisen, wurde zum anderen ein in dieser Arbeit entwickelter statistischer Ansatz der Domänenanalyse angewandt. Hierfür wurde das Material zunächst durch Härteeindrücke mehrachsig elastisch-plastisch verformt, und die verformten Probenbereiche wurden anschließend mit Hilfe der Bitterstreifentechnik hauptsächlich bei niedriger Vergrößerung lichtmikroskopisch untersucht. Die beobachteten makroskopischen Domänen-kontraste wurden über ein analytisches, kontaktmechanisches (ECM-) Modell und über Makro-Eigen-spannungsmessungen (energiedispersive Synchrotron-Beugungsuntersuchungen) charakteristischen Verformungszonen unter den Härteeindrücken zugeordnet.
Die Ergebnisse dieser Untersuchungen belegen, dass die Entstehung der Streufelder – entgegen bisheriger Annahmen – nicht allein auf mechanische Spannungs- und Verformungsgradienten im Material zurückzuführen, sondern auch topographisch bedingt ist. Die Vernachlässigung überlagerter geometrischer Effekte kann zu sicherheitsrelevanten Fehlinterpretationen der magnetischen Signale führen. Einachsige magnetoelastische Modellvorstellungen sollten zudem nicht ohne Anpassungen auf komplexe Beanspruchungen übertragen werden, da u. a. sowohl mechanische Größen (wie Spannungen oder Dehnungen) als auch mikrostrukturelle Parameter (wie z. B. Versetzungsdichten) bei komplexen Belastungen als ortsabhängige Variablen behandelt werden müssen. Die in dieser Arbeit beobachteten Domänenkontraste lassen sich zweifelsfrei charakteristischen Verformungszonen zuordnen, mikro-strukturell jedoch nicht allein mit anzunehmenden Gradienten der Versetzungsdichte erklären. Statt-dessen entstehen beispielsweise lokale Verformungstexturen, die zusätzliche magnetische Anisotropien bewirken könnten. Da bisher weder die makroskopischen noch die mikrostrukturellen Ursachen der Streufeldentstehung hinreichend verstanden sind, scheint die MMM-Methode für die quantitative Bewertung des Schädigungszustands derzeit ungeeignet.
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. The model is designed to represent failure under static loading as a particular case of fatigue failure after a single loading cycle. As a consequence, most of the material parameters can be deduced from statictests. Only a limit set of additional constitutive parameters is required to accurately describe the evolution under fatigue loading. Another advantage of the proposed model is the possibility to directly incorporate other multi-physics effects such as creep and shrinkage or thermal loading on the constitutive level. 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 implicit and explicit time integration schemes. Their performance and some limitations for specific loading regimes is discussed.
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. The model is designed to represent failure under static loading as a particular case of fatigue failure after a single loading cycle. As a consequence, most of the material parameters can be deduced from statictests. Only a limit set of additional constitutive parameters is required to accurately describe the evolution under fatigue loading. Another advantage of the proposed model is the possibility to directly incorporate other multi-physics effects such as creep and shrinkage or thermal loading on the constitutive level. 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 implicit and explicit time integration schemes. Their performance and some limitations for specific loading regimes is discussed.
Computational methods for lifetime prediction of metallic components under high-temperature fatigue
(2019)
The issue of service life prediction of hot metallic components subjected to cyclic loadings is addressed. Two classes of lifetime models are considered, namely, the incremental lifetime rules and the parametric models governed by the fracture mechanics concept. Examples of application to an austenitic cast iron are presented. In addition, computational techniques to accelerate the time integration of the incremental models throughout the fatigue loading history are discussed. They efficiently solve problems where a stabilized response of a component is not observed, for example due to the plastic strain which is no longer completely reversed and accumulates throughout the fatigue history. The performance of such an accelerated Integration technique is demonstrated for a finite element simulation of a viscoplastic solid under repeating loading–unloading cycles.
Despite of the significant advances in additive manufacturing (AM) process optimization there is still a lack of experimental results and understanding regarding the mechanical behavior and its relationship with the microstructural features of AM-parts, especially in loading conditions typical for safety-relevant applications. Within the scope of the presented ongoing investigations, a basic microstructural characterization, tensile tests at room and elevated temperature (400°C) as well as a characterization of the fatigue behavior of additively manufactured Ti-6Al-4V in the low cycle fatigue regime are carried out in the as-built state. After failure, different techniques are used to describe the failure mechanisms of the specimens. The AM-Specimens are provided by the Fraunhofer institute for production systems and design technology and investigated at the BAM following the philosophy of the TF-Project AGIL.
Virtual-lab-based determination of a macroscopic yield function for additively manufactured parts
(2019)
This work aims for a yield function description of additively manufactured parts of S316L steel at the continuum-mechanical macro-scale by means of so-called virtual experiments using a crystal plasticity (CP) model at meso-scale. Additively manufactured parts require the consideration of the specific process-related microstructure, which prevents this material to be macroscopically treated as isotropic, because of crystallographic as well as topological textures. From virtual experiments, yield loci under various loading conditions are simulated. The scale bridging from meso- to macro-scale is realised by the identification of the simulated yield loci as a modified anisotropic Barlat-type yield model representation.
Lifetime aspects including fatigue failure of concrete structures were traditionally only of minor importance. Because of the growing interest in maxing out the capacities of concrete, its fatigue failure under compression has become an issue. A variety of interacting phenomena such as e.g. loss of prestress, degradation due to chemical reactions or creep and shrinkage influence the fatigue resistance. Failure due to cyclic loads is generally not instantaneous, but characterized by a steady damage accumulation. Therefore, a reliable numerical model to predict the performance of concrete over its lifetime is required, which accurately captures order effects and full three-dimensional stress states.
Many constitutive models for concrete are currently available, which are applicable for specific loading regimes, different time scales and different resolution scales.
However, a key limitation of those models is that they generally 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. This is due to the computational effort necessary to explicitly resolve every cycle which exceeds the currently available computational resources. The limitation can only be overcome by the application of multiscale methods in time.
The objective of the paper is the development of numerical methods for the simulation of concrete under fatigue loading using temporal multiscale methods.
First, a continuum damage model for concrete is developed with a focus on fatigue under compressive stresses [1]. 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. The model is designed to represent failure under static loading as a particular case of fatigue failure after a single loading cycle. As a consequence, most of the material parameters can be deduced from static tests. Only a limit set of additional constitutive parameters is required to accurately describe the evolution under fatigue loading. Another advantage of the proposed model is the possibility to directly incorporate other multi-physics effects such as creep and shrinkage or thermal loading on the constitutive level.
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 [2]. This evolution equation is then solved on the long time scale using different implicit and explicit time integration schemes. Their performance and some limitations for specific loading regimes is discussed.
Finally, the developed methods will be validated and compared to experimental data.
[1] Vitaliy Kindrachuk, Marc Thiele, Jörg F. Unger. Constitutive modeling of creep-fatigue interaction for normal strength concrete under compression, International Journal of Fatigue, 78:81-94, 2015
[2] Vitaliy Kindrachuk, Jörg F. Unger. A Fourier transformation-based temporal integration scheme for viscoplastic solids subjected to fatigue deterioration, International Journal of Fatigue, 100:215-228, 2017
Lifetime aspects including fatigue failure of concrete structures were traditionally only of minor importance. Because of the growing interest in maxing out the capacities of concrete, its fatigue failure under compression has become an issue. A variety of interacting phenomena such as e.g. loss of prestress, degradation due to chemical reactions or creep and shrinkage influence the fatigue resistance. Failure due to cyclic loads is generally not instantaneous, but characterized by a steady damage accumulation. Therefore, a reliable numerical model to predict the performance of concrete over its lifetime is required, which accurately captures order effects and full three-dimensional stress states.
Many constitutive models for concrete are currently available, which are applicable for specific loading regimes, different time scales and different resolution scales.
However, a key limitation of those models is that they generally 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. This is due to the computational effort necessary to explicitly resolve every cycle which exceeds the currently available computational resources. The limitation can only be overcome by the application of multiscale methods in time.
The objective of the paper is the development of numerical methods for the simulation of concrete under fatigue loading using temporal multiscale methods.
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. The model is designed to represent failure under static loading as a particular case of fatigue failure after a single loading cycle. As a consequence, most of the material parameters can be deduced from static tests. Only a limit set of additional constitutive parameters is required to accurately describe the evolution under fatigue loading. Another advantage of the proposed model is the possibility to directly incorporate other multi-physics effects such as creep and shrinkage or thermal loading on the constitutive level.
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 implicit and explicit time integration schemes. Their performance and some limitations for specific loading regimes is discussed.
Finally, the developed methods will be validated and compared to experimental data.
The coefficient of thermal expansion (CTE) and the thermomechanical properties of the polymers used in superconducting magnets need to be known in order to predict their stress state under the different magnet assembly and operating conditions.
We have measured Young’s moduli of typically used polymers during in situ heat cycles with the dynamic resonancemethod. The dynamic test results are compared with Young’s moduli determined from quasi-static stress–strain measurements at room temperature, 77 K and 4.2 K. A moderate elastic anisotropy is found for the fiber reinforced polymers. CTEs are compared based on dilation experiments. TheCTEs of the fiber reinforced polymers studied are similar to those of copper or steel. In contrast, the pure resins exhibit relatively larger CTEs.
Die warmfeste austenitische Gusseisenlegierung EN-GJSA-XNiSiCr35-5-2 (häufig auch als Ni-Resist D-5S bezeichnet) wurde hinsichtlich ihres mechanischen Verhal-tens bei hoher Temperatur charakterisiert. Dazu wurden (isotherme) niederzyklische (LCF-) und (nicht-isotherme) thermomechanische Ermüdungsversuche (TMF) zwischen Raumtemperatur und 900 °C durchgeführt. Diese Ergebnisse dienten (zu-sammen mit weiteren Versuchsdaten) der Kalibrierung werkstoffmechanischer Modelle. Bei den höchsten Prüftemperaturen wurde Schädigung in Form von Kriechen beobachtet und metallographisch dokumentiert.
Metalle
(2019)
Dieses Standardwerk bietet eine Darstellung der Struktur und Eigenschaften der Metalle und ihrer Anwendungen als Werkstoffe. Im ersten, wissenschaftlichen Teil werden der atomare und mikroskopische Aufbau, die thermodynamischen und die grundlegenden physikalischen und mechanischen Eigenschaften der Metalle beschrieben sowie die Grundlagen der thermisch aktivierten Reaktionen und der Phasenumwandlungen. Die wichtigsten experimentellen Untersuchungsmethoden werden erläutert, wobei die mikroskopischen und Beugungsverfahren einen Schwerpunkt bilden.
Im zweiten, technischen Teil werden die Werkstoffgruppen der Metalle und ihre anwendungsbezogenen Eigenschaften behandelt. Dabei wird auf die zugrunde liegenden Legierungen und die Verfahren zur gezielten Einstellung ihrer Eigenschaften eingegangen. Schwerpunkte bei der Darstellung der Werkstoffe sind die Stähle, die teilchengehärteten Legierungen, die Magnetwerkstoffe und die pulvermetallurgisch hergestellten Werkstoffe. Außerdem werden die Oberflächeneigenschaften und die Verfahren zur Oberflächenbehandlung dargestellt.
Due to their excellent creep resistance and good oxidation resistance, 9–12% Cr ferritic–martensitic stainless steels are widely used as high temperature construction materials in power plants. However, the mutual combination of different loadings (e.g., creep and fatigue), due to a “flexible” operation of power plants, may seriously reduce the lifetimes of the respective components. In the present study, low cycle fatigue (LCF) and relaxation fatigue (RF) tests performed on grade P92 helped to understand the behavior of ferritic–martensitic steels under a combined loading. The softening and lifetime behavior strongly depend on the temperature and total strain range. Especially at small strain amplitudes, the lifetime is seriously reduced when adding a hold time which indicates the importance of considering technically relevant small strains.
Modelling of environmentally assisted material degradation in the crack phase-field framework
(2019)
The simulation of crack propagation was conducted with a diffusive crack model in a variational framework. Moreover, the physically sound introduction of mass transport and coupling mechanisms due to environmentally assisted effects could be realised in this framework. The objective consists of the application of the phase-field Approach towards the simulation of environmentally assisted material degradation with the advantage of a non-required predefined crack path and a mesh-independent non-local formulation that facilitates the damage evolution with respect to material softening. The sharp crack is regularised by the introduction of a phase-field order parameter leading to a diffusive crack formulation.
Besides the equations originating from the linear momentum balance an additional evolution equation for the crack phase-field is introduced. Furthermore, mass transport is simulated by a Diffusion equation. The description delivered by the variational phase-field framework is able to simulate crack propagation according to published numerical test cases.
Additionally, the calculation of stress intensity factors is possible as well as crack resistance curves that describe stable crack propagation.
The age hardening response of a high-purity Al–4Cu–1Li–0.25Mn alloy (wt. %) during isothermal aging without and with an applied external load was investigated. Plate shaped nanometer size T1 (Al2CuLi) and θ′ (Al2Cu) hardening phases were formed. The precipitates were analyzed with respect to the development of their structure, size, number density, volume fraction and associated transformation strains by conducting transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies in combination with geometrical Phase analysis (GPA). Special attention was paid to the thickening of T1 phase. Two elementary types of single-layer T1 precipitate, one with a Li-rich (Type 1) and another with an Al-rich (Defect Type 1) central layer, were identified. The results show that the Defect Type 1 structure can act as a precursor for the Type 1 structure. The thickening of T1 precipitates occurs by alternative stacking of These two elementary structures. The thickening mechanism was analyzed based on the magnitude of strain associated with the precipitation transformation normal to its habit plane. Long-term aging and aging under load resulted in thicker and structurally defected T1 precipitates. Several types of defected precipitates were characterized and discussed. For θ′ precipitates, a ledge mechanism of
thickening was observed. Compared to the normal aging, an external load applied to the peak aged state leads to small variations in the average sizes and volume fractions of the precipitates.