Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Dokumenttyp
Sprache
- Englisch (298)
- Deutsch (2)
- Mehrsprachig (1)
Referierte Publikation
- ja (301) (entfernen)
Schlagworte
- Additive manufacturing (33)
- Laser beam welding (31)
- Microstructure (21)
- Wear (19)
- Welding (17)
- Hydrogen (15)
- Mechanical properties (15)
- Residual stresses (15)
- Friction (14)
- Residual stress (14)
- Additive Manufacturing (10)
- Laser metal deposition (10)
- Laser powder bed fusion (10)
- High-strength steels (9)
- Creep-resistant steel (7)
- Fracture mechanics (7)
- Resistance spot welding (7)
- Thermography (7)
- Ultrasonic-assisted milling (7)
- Cyclic R-curve (6)
- Neutron diffraction (6)
- Process monitoring (6)
- Selective laser melting (SLM) (6)
- Solidification cracking (6)
- Steel (6)
- Fatigue (5)
- Fatigue crack propagation threshold (5)
- Fatigue strength (5)
- GMA welding (5)
- High-strength steel (5)
- Hydrogen assisted cracking (5)
- Laser welding (5)
- Liquid metal embrittlement (5)
- Mechanical Engineering (5)
- Mechanics of Materials (5)
- Niobium carbide (5)
- Numerical modeling (5)
- AISI 316L (4)
- Artificial neural network (4)
- Crack (4)
- DED (4)
- Diffusion (4)
- Fatigue crack growth (4)
- Hybrid laser-arc welding (4)
- Infrared thermography (4)
- Laser Powder Bed Fusion (4)
- Laser powder bed fusion (L-PBF) (4)
- Numerical simulation (4)
- Polymers (4)
- Porosity (4)
- Post weld heat treatment (4)
- Process parameters (4)
- Stress relief cracking (4)
- Surface integrity (4)
- TIG welding (4)
- Ti-6Al-4V (4)
- Welding simulation (4)
- 9%Ni steel (3)
- AGIL (3)
- AISI 304L (3)
- Additive manufacturing (AM) (3)
- Alloy 36 (3)
- Crack closure (3)
- Cracking (3)
- Defects (3)
- Diffusible hydrogen (3)
- Digital image correlation (3)
- Dimensional accuracy (3)
- Electron backscattered diffraction (3)
- Electron beam welding (3)
- Fatigue crack propagation (3)
- Fracture (3)
- Hardness (3)
- Heat accumulation (3)
- Heat treatment (3)
- Hybrid laser arc welding (3)
- Inconel 718 (3)
- LMD (3)
- Laser beam melting (LBM) (3)
- Laser implantation (3)
- Magnetic field (3)
- Magnetohydrodynamics (3)
- Mechanical mismatching (3)
- Metals and Alloys (3)
- Multi-physical modelling (3)
- Restraint (3)
- Simulation (3)
- Solidification (3)
- Submerged arc welding (3)
- TiB2 (3)
- ToF-SIMS (3)
- Weldments (3)
- 3D printing (2)
- AFM (2)
- AISI D2 (2)
- Additive Fertigung (2)
- Advanced high strength steels (2)
- Alloy modification (2)
- Aluminum alloys (2)
- Archard's law (2)
- Atomic force microscopy (2)
- Carbon steel (2)
- Cermet (2)
- Chemical composition (2)
- Cold cracking (2)
- Component assessment (2)
- Composites (2)
- Computed Tomography (2)
- Computed tomography (2)
- Constraint (2)
- Critical strain (2)
- Cryogenic temperature (2)
- Crystallographic texture (2)
- Cutting tool (2)
- Deep penetration (2)
- Deuterium (2)
- Dissimilar metal weld overlays (2)
- Dual phase steel (2)
- EBSD (2)
- Element transport (2)
- Equivalent heat source (2)
- Fatigue limit (2)
- Finite element method (2)
- Finite element simulation (2)
- Fracture resistance (2)
- Friction stir welding (2)
- Full penetration (2)
- General Materials Science (2)
- Grain refinement (2)
- Grain size (2)
- Hardmetal (2)
- Heat control (2)
- Heat-affected zone (2)
- High entropy alloy (2)
- High power laser beam welding (2)
- High strength steels (2)
- High-entropy alloy (2)
- High-power laser beam welding (2)
- Hot crack (2)
- Hot cracking (2)
- Hot steam (2)
- Hydrogen embrittlement (2)
- Hydrogen-assisted cracking (2)
- IN718 (2)
- Implant test (2)
- In situ (2)
- In situ monitoring (2)
- Keyhole dynamics (2)
- Kitagawa-Takahashi diagram (2)
- LIBS (2)
- Large-scale test (2)
- Laser energy distribution (2)
- Lubricants (2)
- Machining (2)
- Martensite (2)
- Matching ferritic welding electrode (2)
- Melt pool dynamics (2)
- Metal mixing (2)
- Microstructure and texture (2)
- Microstructure characterization (2)
- Multiple cracks (2)
- NbC (2)
- Nickel (2)
- Niobium carbide (NbC) (2)
- Non-metallic inclusions (2)
- Offshore (2)
- Oxidation (2)
- Plasma-transferred arc welding (2)
- Plastic deformation (2)
- Pores (2)
- Post-weld heat treatment (2)
- Process simulation (2)
- Properties (2)
- Quality assurance (2)
- Ray tracing (2)
- Refill friction stir spot welding (2)
- Repair-welding (2)
- Residual Stress (2)
- Residual stress analysis (2)
- S-N curve (2)
- SEM (2)
- SIMS (2)
- Selective Laser Melting (2)
- Selective Laser Melting (SLM) (2)
- Selective laser melting (2)
- Short cracks (2)
- Sliding (2)
- Software (2)
- Solid lubricants (2)
- Stainless steels (2)
- Surface roughness (2)
- Surface texturing (2)
- TPU (2)
- Temperature (2)
- Temperature distribution (2)
- Thermografie (2)
- Thick-walled steel (2)
- Titanium (2)
- Toughness (2)
- Vacuum (2)
- Welded joints (2)
- Welding residual stresses (2)
- Wire arc additive manufacturing (2)
- X-ray diffraction (2)
- 100Cr6 (1)
- 100Cr6 steel (1)
- 2101 duplex stainless steel (1)
- 316L (1)
- 3D Druck (1)
- 3D Scanning (1)
- 3D-finite element modeling (1)
- AC magnetic field (1)
- ADXRD (1)
- AHSS (1)
- AISI 321 stainless steel (1)
- AM (1)
- AM 316L stainless steel (1)
- AM feature integration (1)
- ASTM (1)
- ASTM E647 (1)
- Abrasion (1)
- Abrasive wear (1)
- Absorbed energy (1)
- Accelerator magnets (1)
- Accoustic emission (1)
- Adaptive control (1)
- Adaptive remeshing (1)
- Adaptive welding beam oscillation (1)
- Additive Manufacturing (AM) (1)
- Adhesion (1)
- Adhesion by mechanical interlocking (1)
- Adsorption (1)
- Advanced high strength steel (1)
- Advanced high-strength steel (1)
- Advanced high-strength steels (1)
- Aging (1)
- Al/Ti dissimilar joints (1)
- AlMg0.7SiTiB filler wire (1)
- AlSi10Mg (1)
- Alkyd resin-based coating (1)
- Alloys (1)
- Alternative test procedure (1)
- Aluminium oxide (1)
- Aluminum bronze (1)
- Analysis (1)
- Analytical calculation (1)
- Artificial Intelligence (1)
- As-built LPBF IN718 alloy (1)
- Austenite-to-martensite transformation (1)
- Austenitic (1)
- Austenitic stainless steel (1)
- Austenitic welding electrode (1)
- Automated manufacturing (1)
- Automatisierte Fertigung (1)
- Automotive application (1)
- Bayesian technique (1)
- Behavior (1)
- Bending test (1)
- Binders (1)
- Biopolymers (1)
- Bismuth titanates (1)
- Boundary element method (1)
- Boundary lubrication (1)
- Bragg-edge imaging (1)
- Bragg-edge neutron 2D imaging (BENI) (1)
- Brazil nut Mesocarp (1)
- Build-up strategy (1)
- Bulge effect (1)
- Bulge formation (1)
- Bulging effect (1)
- Bulging effects (1)
- Burst (1)
- CCT diagrams (1)
- CFD model (1)
- Carbide (1)
- Carbon (1)
- Carbon dioxide footprint (1)
- Carrier gas hot extraction (1)
- Catalysis (1)
- CdSe/ZnS quantum Dots (1)
- Cellular substructure (1)
- Cellular uptake (1)
- Ceramic (1)
- Ceramic matrix composites (1)
- Chapetti’s and IBESS model (1)
- Characterisation (1)
- Characterization (1)
- Characterization of corrosion layers (1)
- Charpy Impact Test (1)
- Charpy Transition Curve (1)
- Charpy pendulum impact test (1)
- Chunky graphite (1)
- Circumferential weld (1)
- Clad steels (1)
- Clustering (1)
- Co-Cr-alloy (1)
- Coarse grained heat affected zone (1)
- Coarse-grained heat-affected zone (1)
- Coating (1)
- Cobalt-chromium alloy (1)
- Codes and standards (1)
- Coefficient of friction (1)
- Cold cracking safety (1)
- Cold-welding (1)
- Columnar crystal growth (1)
- Component test (1)
- Component-like test (1)
- Composite (1)
- Compositionally complex alloy (1)
- Computed tomography (CT) (1)
- Computer vision (1)
- Condensed Matter Physics (1)
- Contact fatigue (1)
- Contact resonance (1)
- Conversion of results (1)
- Convolutional neural network (1)
- Convolutional neural networks (CNN) (1)
- Cooling rate (1)
- Coordinate measurement machine (1)
- Core-shell structures (1)
- Corrosion pits (1)
- Crack arrest (1)
- Crack closure mechanisms (1)
- Crater (1)
- Creep (1)
- Creep behavior (1)
- Creep resistant steel (1)
- Creep resisting materials (1)
- Creep-resisting materials (1)
- Crown-abutment connection (1)
- Crystal branch development (1)
- Crystal plasticity (1)
- Crystallographic texture control (1)
- Curve fitting (1)
- Cutting forces (1)
- Cyclic J-integral (1)
- Cyclic R-curve analysis (1)
- Cyclic loading (1)
- Cyclic stress-strain curve (1)
- D7755-11 (1)
- DED-EB (1)
- DED-arc (1)
- DIC (1)
- Damage prediction (1)
- Damage tolerance (1)
- Data evaluation methods (1)
- Data fusion (1)
- Data preparation (1)
- Data-driven quality assurance (1)
- Debye–Waller factor (1)
- Deep learning (1)
- Deep penetration laser beam welding (1)
- Defect detection (1)
- Deformation (1)
- Deformed geometry (1)
- Dendrite growth (1)
- Density measurement (1)
- Dental materials (1)
- Deposition rate (1)
- Deposition welding (1)
- Design of experiments (1)
- Diaspore (1)
- Die-cast aluminum (1)
- Die-casted aluminum (1)
- Diffraction (1)
- Diffraction-elastic constants (1)
- Diffusion/diffusivity (1)
- Digitalisierung (1)
- Digitalization (1)
- Digitization (1)
- Dilatometry (1)
- Direct Energy Deposition (1)
- Direct energy deposition (1)
- Direct laser deposition (1)
- Directed energy deposition (1)
- Dislocation density (1)
- Dispersive XAS (1)
- Displacement (1)
- Dissimilar friction stir welding (1)
- Dissimilar joints (1)
- Dissimilar materials (1)
- Dissimilar metal weld (1)
- Distortion (1)
- Distortion upon baseplate removal (1)
- Ditigtal image correlation (1)
- Ductile iron (1)
- Duplex (1)
- Duplex AISI 2205 (1)
- Duplex stainless steel (1)
- Duplex steels (1)
- Dwell-time (1)
- Dynamic load (1)
- EA4T steel (1)
- EBAM (1)
- EDS (1)
- Edge quality (1)
- Editorial Board (1)
- Effect of scanning strategies (1)
- Elastic follow-up (1)
- Elastic modulus (1)
- Elastic-plastic fracture mechanics (1)
- Elastomers (1)
- Electrical connectors (1)
- Electro-plated nickel coatings (1)
- Electro-thermomechnical model (1)
- Electrochemical permeation (1)
- Electrode geometry (1)
- Electroless Ni-P (1)
- Electromagnetic (1)
- Electromagnetic field (1)
- Electromagnetic forces (1)
- Electromagnetic influence (1)
- Electromagnetic stirring (1)
- Electromagnetic support (1)
- Electromagnetic supported degassing (1)
- Electromagnetic weld pool support (1)
- Electron backscatter diffraction (1)
- Electron backscatter diffraction (EBSD) (1)
- Electron microscopy (1)
- Ellipsometry (1)
- Embrittlement (1)
- Emisssivity (1)
- End crater (1)
- Endurance limit (1)
- Energetic reference parameter (1)
- Engine oil design (1)
- Engine oil testing (1)
- Environment (1)
- Environmental effect (1)
- Environmental effects (1)
- Environmental impact categories (1)
- Equivalent stress concentration factors (1)
- Experimental design (1)
- Experimental determination (1)
- FAIR data (1)
- FAT class (1)
- FAT class approach (1)
- Fail-safe design (1)
- Fast single pulse response (1)
- Fatigue Strength (1)
- Fatigue crack initiation (1)
- Fatigue crack propagation stages (1)
- Fatigue damage (1)
- Fatigue loading (1)
- Fatigue propagation threshold (1)
- Fatigue strength and life (1)
- Femtosecond laser (1)
- Femtosecond laser ablation (1)
- Ferritic spheroidal graphite cast iron (1)
- Ferritic steels (1)
- Ferroelectricity/ferroelectric materials (1)
- Ferromagnetic steels (1)
- Fiber laser (1)
- Filler wire mixing (1)
- Finish milling (1)
- Finite element (FE) (1)
- Finite element analysis (1)
- Finite element method (FEM) (1)
- Flange width (1)
- Flaw assessment procedures (1)
- Flaw detection (1)
- Flaw interaction (1)
- Flüssigmetallinduzierte Rissbildung (1)
- Force-distance curves (1)
- Formation (1)
- Fractography (1)
- Fracture Mechanics (1)
- Fracture assessment (1)
- Frequency domain (1)
- Fresnel reflection (1)
- Fusion zone (1)
- Fusion zone profile (1)
- Fusion zone size (1)
- Fusion zone, nickel alloys (1)
- GMAW (1)
- GMAwelding (1)
- GMR (1)
- GMR sensors (1)
- GTAW (1)
- Galvanized steel (1)
- Gap bridgeability (1)
- Gap bridging (1)
- Gas metal arc welding (1)
- Gas tungsten arc welding (GTAW) (1)
- General analytical solutions (1)
- Gleeble testing (1)
- Global stability criterion (1)
- Grade S960QL steel (1)
- Grain structure (1)
- Graphene oxide (1)
- Graphite modules (1)
- Grease (1)
- Grease lubrication (1)
- HSLA (1)
- HSLA steel (1)
- HT22 (1)
- Hard metals (1)
- Hardly separable problem (1)
- Hastelloy X (1)
- HeLa (1)
- Heat affected zone (1)
- Heat conduction (1)
- Heat flow (1)
- Heat generation (1)
- Heat input (1)
- Heat source models (1)
- High Entropy Alloy (1)
- High brightness (1)
- High power (1)
- High process speeds (1)
- High strength steel (1)
- High temperature corrosion (1)
- High-Power Welding (1)
- High-entropy alloys (1)
- High-power laser beam (1)
- High-pressure hydrogen environment (1)
- High-strength low-alloy steel (1)
- High-strength steel filler metal (1)
- High-strength steel sheets (1)
- High-strength structural steel (1)
- Highspeed-plasma-laser-cladding (1)
- Hochfester Stahl (1)
- Hohlprofilknoten (1)
- Hold time (1)
- Hot Cracks (1)
- Hot stamping (1)
- Hot tensile test (1)
- Hot-Stamping (1)
- Humidity (1)
- Hybrid Laser-Arc Welding (1)
- Hybrid repair (1)
- Hydrogen assisted stress corrosion cracking (1)
- Hydrogen dependent mechanical properties (1)
- Hydrogen diffusion (1)
- Hydrogen-containing hot gas (1)
- Hydrophobin (1)
- IBESS (1)
- IBESS Approach (1)
- IBESS model for short cracks (1)
- IN 718 (1)
- IN718 PBF-LB/M (1)
- IN725 (1)
- IR-Spektroskopie (1)
- IR-spectroscopy (1)
- ISO 12108 (1)
- Image processing (1)
- Image registration (1)
- Impact absorbed energy (1)
- Impact damage (1)
- Implant-supported prostheses (1)
- Implants (1)
- In situ strain (1)
- In-situ Process Monitoring (1)
- In-situ monitoring (1)
- In-situ process monitoring (1)
- Inclusion cluster (1)
- Inclusion size (1)
- Inclusions (1)
- Inconel 625 (1)
- Inconel 939 (1)
- Initial crack size (1)
- Instumented indentation test (1)
- Integrated alignment features (1)
- Inter layer time (1)
- Inter-layer time (1)
- Interfacial stability (1)
- Intergranular cracking (1)
- Intrinsic fatigue propagation threshold (1)
- Iron (1)
- Joining dissimilar materials (1)
- Joining technology (1)
- Journal (1)
- Kerbspannungskonzept (1)
- Keyhole collapse (1)
- Keyhole mode welding (1)
- Keyhole stability (1)
- Kitagawa-Takahashi (K-T) diagram (1)
- L-PBF (1)
- L-PBF IN718 material (1)
- LA-ICP-SFMS (1)
- LCF region (1)
- LME (1)
- LPBF (1)
- LTT Weld Filler Materials (1)
- LTT filler metal (1)
- LTT weld filler materials (1)
- Laboratory X-ray diffraction (1)
- Lack-of-fusion (1)
- Lamé curves (1)
- Lamé curves approximation (1)
- Laser Implantation (1)
- Laser Metal Deposition (1)
- Laser Powder Bed Fusion (L-PBF) (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser Powder Bed Fusion (PBF-LB/M, L-PBF) (1)
- Laser Pulver Auftragsschweißen (1)
- Laser beam melting (1)
- Laser beam welding (LBW) (1)
- Laser cutting (1)
- Laser dispersing (1)
- Laser energy absorption (1)
- Laser hybrid welding (1)
- Laser keyhole welding (1)
- Laser melting (1)
- Laser powder-based directed energy deposition (1)
- Laser surfacing (1)
- Laser-Pulver-Auftragschweißen (1)
- Laser-based additive manufacturing (1)
- Laser-induced periodic surface structures (LIPSS) (1)
- Lead-free ceramics (1)
- Life cycle assessment (1)
- Life prediction (1)
- Lifetime (1)
- Liquid Metal Embrittlement (1)
- Liquid phase sintering (1)
- Local Weld Geometry (1)
- Localized laser dispersing (1)
- Lorentz force (1)
- Lorentz forces (1)
- Low carbon steel (1)
- Low feed rates (1)
- Low heat input GMA welding (1)
- Low heat input Gma welding (1)
- Low transformation temperature (1)
- Low transformation temperature (LTT) steel (1)
- Low transformation temperature filler materials (1)
- Low-cycle fatigue (1)
- Lubricant additives (1)
- L‐PBF (1)
- MAG welding (1)
- MHD (1)
- MVT (1)
- MWIR (1)
- Machine learning (1)
- Machine vision (1)
- Magnesium Alloy (1)
- Magnesium alloy (1)
- Magnetic stray field (1)
- Magnetohydrodynamics (MHD) (1)
- Margin design (1)
- Matching ferritic filler metal (1)
- Material defects (1)
- Material modeling (1)
- Mathematical modeling (1)
- Measurement (1)
- Mechanical anisotropy (1)
- Mechanical property (1)
- Mechanical-technological properties (1)
- Medium Entropy Alloys (1)
- Medium entropy alloy (1)
- Melt pool defects (1)
- Metal (1)
- Metal Magnetic Memory (1)
- Metal additive manufacturing (MAM) (1)
- Metallic vapour plume (1)
- Micro-shrinkages (1)
- Microalloyed steels (1)
- Microbiologically influenced corrosion (1)
- Microcracking (1)
- Microfocus X-ray computer tomography (μCT) (1)
- Microstructure Tensile strength (1)
- Microtribology (1)
- Mild steels (1)
- Minimum Waiting Time (1)
- Mining head gear (1)
- Mis-match (1)
- Misfit (1)
- Model calibration (1)
- Model order reduction (1)
- Modeling (1)
- Modelling studies (1)
- Modification of structural morphology (1)
- Molten pool (1)
- Molten pool dynamics (1)
- Molybdenum disulphide (1)
- Monotonic and cyclic crack driving force (1)
- Morphology control (1)
- Multi-materials joining (1)
- Multi-pass welding (1)
- Multi-physical modeling (1)
- Multi-principal element alloy (1)
- Multi-principal element alloys (1)
- Multiple crack initiation (1)
- Multiple crack propagation (1)
- Multiple cracking (1)
- Multiple principal element alloy (1)
- Multispectral thermography (1)
- NIR (1)
- Nanoadditive (1)
- Nanotribology (1)
- Narrow gap welding (1)
- Natural silver wires (1)
- Near-surface X-ray diffraction (1)
- Near-threshold regime (1)
- Neural networks (1)
- Neutron Diffraction (1)
- Neutron and X-ray diffraction (1)
- Neutron imaging (1)
- Neutron radiography (1)
- Ni alloy (1)
- Ni-based austenitic filler metal (1)
- Ni-based austenitic welding electrode (1)
- Ni-based superalloy (1)
- NiCrBSi (1)
- Nickel alloys (1)
- Nickel-based superalloys (1)
- Niobium alloying (1)
- Non-destructive Materials (1)
- Non-sharp defects (1)
- Notch stress approach (1)
- Nuclear reactor systems (1)
- Numerical analysis (1)
- Numerical investigation (1)
- Numerical process simulation (1)
- Numerical simulations (1)
- Numerical welding simulation (1)
- Numerical welding simulations (1)
- Offshore steel grade (1)
- Offshore steels (1)
- Online Process Monitoring (1)
- Online monitoring (1)
- Open science (1)
- Open source (1)
- Optical Tomography (1)
- Optical measurement (1)
- Optical measurment technique (1)
- Optical tomography (1)
- Oscillating magnetic field (1)
- Oscillating vapor plume (1)
- Oxide-induced crack closure (1)
- PAEKs (1)
- PBF-LB/M/316L (1)
- PEAK (1)
- Parabolic flight (1)
- Partial penetration (1)
- Partial penetration welding (1)
- Path planning (1)
- Peak stress method (1)
- Peak stress method (PSM) (1)
- Periodic solidification pattern (1)
- Phase field method (1)
- Phase transformation (1)
- Photogrammetry (1)
- Photooxidation (1)
- Physical vapor deposition (PVD) (1)
- Pipe Welding (1)
- Pipe weld preparation (1)
- Pipeline steel of grade X120 (1)
- Plasma cutting (1)
- Plastic material flow (1)
- Plume heating (1)
- Poly(acrylic acid) (1)
- Polyethylene (1)
- Pool dimensions (1)
- Porosity reduction (1)
- Position detection (1)
- Post Weld Heat Treatment (PWHT) (1)
- Potential drop technique (1)
- Potentiodynamic measurements (1)
- Precipitation hardening aluminum alloys (1)
- Preheating (1)
- Pressure-dependent solubility (1)
- Prevention (1)
- Principal stress (1)
- Probabilistic assessment (1)
- Process development (1)
- Product standard (1)
- Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten (1)
- Proper generalized decomposition (1)
- Prostheses (1)
- Quantitative bioimaging (1)
- R-curve analysis (1)
- RSW (1)
- Raman spectroscopy (1)
- Ray teacing (1)
- Ray-tracing methods (1)
- Reactor conditions (1)
- Reciprocating sliding (1)
- Reciprocating sliding wear (1)
- Reference data (1)
- Reference standards (1)
- Relative humidity (1)
- Reliability (1)
- Repair welding (1)
- Representative specimens (1)
- Reproducibility (1)
- Research data management (1)
- Residual Stresses (1)
- Residual stress in AM (1)
- Residual stress state (1)
- Retained Austenite (1)
- Review (1)
- Roughness (1)
- S-N probabilistic field (1)
- S-Phase (1)
- SLM (1)
- SMAW (1)
- SS316L alloy (1)
- SWIR (1)
- SWIR camera (1)
- SWIR thermography (1)
- Safety (1)
- Sample random results (1)
- Scan strategies (1)
- Scan strategy influence (1)
- Scattering (1)
- Schweißnahtgeometrie (1)
- Scratches (1)
- Seam geometry (1)
- Secondary heat source (1)
- Secondary stresses (1)
- Sensor (1)
- Shear modulus (1)
- Ship building (1)
- Shipbuilding steel (1)
- Short crack propagation (1)
- Shrinkages (1)
- Single asperity (1)
- Single cell (1)
- Sintering (1)
- Sliding wear (1)
- Small-scale specimens (1)
- Solubility (1)
- Spark plasma sintering (1)
- Spreading (1)
- Stainless Steel (1)
- Staircase method (1)
- Standard test piece (1)
- Standardisation (1)
- Static load (1)
- Statistical distributions (1)
- Statistics (1)
- Steady-state weld pool (1)
- Steel and Al (1)
- Steel and aluminium (1)
- Stiffness (1)
- Stochastic sample functions (1)
- Strain fields prediction (1)
- Strain rate (1)
- Strain rates (1)
- Strain-free lattice references (1)
- Strain-free lattice spacing (1)
- Strain-rate (1)
- Strength mismatch (1)
- Stress Relief Cracking (SRC) (1)
- Stress balance (1)
- Stress balance condition (1)
- Stress-strain behavior (1)
- Structural integrity assessment procedure (1)
- Structure analysis (1)
- Sub-oxide (1)
- Sub-size test piece (1)
- Sulphidation (1)
- Superalloy (1)
- Superconducting magnets (1)
- Support configurations (1)
- Surface (1)
- Surface cracks (1)
- Surface preparation (1)
- Surface structuring (1)
- Surface temperature (1)
- Synchrotron X-ray diffraction (1)
- Synchrotron diffraction (1)
- Synchrotron radiation (1)
- TEKKEN (1)
- TES (1)
- TIG (1)
- TIG-welding (1)
- Temperature dependence (1)
- Temperature emissivity separation (1)
- Tensile loading (1)
- Tensile properties (1)
- Tensile resistance spot welding experiment (1)
- Tensile strength (1)
- Tensile testing (1)
- Test standard (1)
- Testing method (1)
- Testing parameters (1)
- Texture (1)
- Thermal analysis (1)
- Thermal conductivity device (1)
- Thermal cycles (1)
- Thermal desorption analysis (1)
- Thermal history (1)
- Thermal-desorption spectroscopy (1)
- Thermal-fluid-structure coupling model (1)
- Thermo-fluid dynamics (1)
- Thermo-fluid flow (1)
- Thermodynamic modelling (1)
- Thick materials (1)
- Thick-Walled Steel (1)
- Thick-walled (1)
- TiC (1)
- TiN (1)
- Titanium alloy (1)
- Tool (1)
- Tool service life (1)
- Tool wear (1)
- Tool-workpiece interaction (1)
- Toughening mechanisms (1)
- Transformable steels (1)
- Transient heat transfer (1)
- Transition temperature (1)
- Trapping (1)
- Tribo-film (1)
- Tribofilm (1)
- Tribology (1)
- Tribooxidation (1)
- Tubular joints (1)
- Tungsten carbide (1)
- Turbine components (1)
- Turbine disk (1)
- Turning (1)
- Two-dimensional solidification (1)
- Two-run welding technique (1)
- UHMWPE (1)
- UV radiation (1)
- UV-blocker addition (1)
- Ultra-high strength steel (1)
- Ultrasonic assited machining (1)
- Vapor recondensation (1)
- Varestraint test (1)
- Varestraint testing (1)
- Viscoplasticity (1)
- Void defect formation mechanism (1)
- WAAM (1)
- WAAM Ti-6Al-4V (1)
- Wear mechanism (1)
- Wear mechanisms (1)
- Wear resistance (1)
- Weathering tests (1)
- Weld end crater (1)
- Weld geometry (1)
- Weld metal (1)
- Weld metal cracking (1)
- Weld pool (1)
- Weld pool behavior (1)
- Weld pool dynamics (1)
- Weld pool shape (1)
- Weld root (1)
- Weld seam geometry (1)
- Weld toe geometry (1)
- Welded Joints (1)
- Welded joint (1)
- Welding parameter (1)
- Welding process simulation (1)
- Weldx (1)
- Widerstandspunktschweißen (1)
- Wind Energy (1)
- Wind energy (1)
- Wineglass shape (1)
- Wire electron beam additive manufacturing (1)
- Wire feed laser beam welding (1)
- Wire-based additive manufacturing (1)
- X-ray Diffraction (1)
- X-ray and Neutron Diffraction (1)
- X-ray and neutron diffraction (1)
- X-ray computed tomography (1)
- X-ray computed tomography (XCT) (1)
- X-ray refraction (1)
- X38CrMoV5-3 (1)
- XRF (1)
- Year in Review (1)
- Young's modulus (1)
- Zinc (1)
- Zinc coated steel (1)
- Zink (1)
- Zirconia (1)
- ZnO films (1)
- ZnO nanorods Nanocrystalline (1)
- arbidic austempered ductile iron (1)
- contour method (1)
- digital image correlation (1)
- dual phase steel (1)
- infrared Thermography (1)
- neutron diffraction (1)
- pL-droplets (1)
- residual stress analysis (1)
- resistance spot welding (1)
- µ-gravity (1)
- Äquivalente Spannungskonzentrationsfaktoren (1)
- μCT-analysis (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (301) (entfernen)
Paper des Monats
- ja (7)
AbstractPowder Bed Fusion with Laser Beam of Metals (PBF-LB/M) has gained more industrial relevance and already demonstrated applications at a small series scale. However, its widespread adoption in various use cases faces challenges due to the absence of interfaces to established Manufacturing Execution Systems (MES) that support customers in the predominantly data-driven quality assurance. Current state-of-the-art PBF-LB/M machines utilize communication architectures, such as OPC Unified Architecture (OPC UA), Message Queuing Telemetry Transport (MQTT) and Representational State Transfer Application Programming Interface (REST API). In the context of the Reference Architecture Model Industry 4.0 (RAMI 4.0) and the Internet of Things (IoT), the assets, particularly the physical PBF-LB/M machines, already have an integration layer implemented to communicate data such as process states or sensor values. Missing is an MES component acting as a communication and information layer. To address this gap, the proposed Extract Transform Load (ETL) pipeline aims to extract relevant data from the fabrication of each build cycle down to the level of scan vectors and additionally to register process signals. The suggested data schema for archiving each build cycle adheres to all terms defined by ISO/TC 261—Additive Manufacturing (AM). In relation to the measurement frequency, all data are reorganized into entities, such as the AM machine, build cycle, part, layer, and scan vector. These scan vectors are stored in a runtime-independent format, including all metadata, to be valid and traceable. The resulting machine log represents a comprehensive documentation of each build cycle, enabling data-driven quality assurance at process level.
In this contribution, we present a physically motivated heat source model for the numerical modeling of laser beam welding processes. Since the calibration of existing heat source models, such as the conic or Goldak model, is difficult, the representation of the heat source using so-called Lamé curves has been established, relying on prior Computational Fluid Dynamics (CFD) simulations.
Lamé curves, which describe the melting isotherm, are used in a subsequent finite-element (FE) simulation to define a moving Dirichlet boundary condition, which prescribes a constant temperature in the melt pool. As an alternative to this approach, we developed a physically motivated heat source model, which prescribes the heat input as a body load directly. The new model also relies on prior CFD simulations to identify the melting isotherm. We demonstrate numerical results of the new heat source model on boundary-value problems from the field of laser beam welding and compare it with the prior CFD simulation and the results of the Lamé curve model and experimental data.
Stresses in repair welding of high-strength steels—part 2: heat control and stress optimization
(2024)
In welding of high-strength steels, e.g. for foundations and erection structures of wind energy plants, unacceptable defects can occasionally be found in the weld area, which should be removed by thermal gouging and subsequent re-welding. High shrinkage restraint of repair welds may lead to crack formation and component failure, predominantly in interaction with degraded microstructures and mechanical properties due to repair cycles. This study aims for elaboration of recommendations for repair concepts appropriate to the stresses and materials involved to avoid cold cracking, damage and expensive reworking. In part 1 [1] of this study, systematic investigations of influences of shrinkage restraint on residual stresses and cold cracking risk during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures were focussed. In this part 2, the microstructure, particularly hardness, and residual stresses due to gouging and influences of heat control parameters in repair welding are analysed. A clear reduction in residual stress after gouging can be observed, especially for the specimens with restrained transverse shrinkage. Gouging to a depth of approx. 2/3 of the seam height does not lead to a complete relaxation of the observed reaction forces. Particularly for the higher strength steel S960QL, there are pronounced areas influenced by the gouging process in which a degradation of the microstructure and properties should be assumed. Overall, the repair welds show a significant increase in the width of the weld and HAZ compared to the original weld, especially in the case of S960QL/G89. The repair welds show higher welding-induced stresses than the original welds, especially in the areas of the HAZ and the base metal close to the weld seam. This behaviour can be attributed overall to increased restraint conditions due to the remaining root weld or shorter gouge grooves. In good agreement with earlier investigations, the residual stresses transverse to the weld can be significantly reduced by upwardly limited working or interpass temperatures, and the reaction stresses resulting from high restraint conditions can be effectively counteracted. The influence of the heat input on the stress formation is low compared to the interpass temperature for both test materials.
This study investigates the room‐ and high‐temperature (650 °C) tensile and low‐cycle‐fatigue behavior of Inconel 718 produced by laser powder bed fusion (PBF‐LB/M) with a four‐step heat treatment and compares the results to the conventional wrought material. The microstructure after heat treatment is characterized on different length scales. Compared to the wrought variant, the elastic and yield properties are comparable at both test temperatures while tensile strength, ductility, and strain hardening capacity are lower. The fatigue life of the PBF‐LB/M variant at room temperature is slightly lower than that of the wrought material, while at 650 °C, it is vice versa. The cyclic stress response for both material variants is characterized by cyclic softening, which is more pronounced at the higher test temperature. High strain amplitudes (≥0.7%) at room temperature and especially a high testing temperature result in the formation of multiple secondary cracks at the transitions of regions comprising predominantly elongated grain morphology and columns of stacked grains with ripple patterns in the PBF‐LB/M material. This observation and pronounced crack branching and deflection indicate that the cracks are controlled by sharp micromechanical gradients and local crystallite clusters.
The development of hydrogen technologies entails high safety requirements in distribution and dispensing infrastructure. Therefore, it is necessary to pursue research on material compatibility in hydrogen, especially for critical parts with tribological issues.
The focus of this study is to evaluate the influence of hydrogen on a wider range of commercially available polymer materials. Thereby, the friction and wear behavior of different grades of TPE, POM, PA66, PA12, PPA, PEEK, PPS, PTFE, PAI, PI and PBI were investigated against a rotating steel disk (AISI 304). Filled and unfilled polymers from different suppliers were evaluated at room temperature in air, vacuum and hydrogen gas (H2) as well as in liquid hydrogen at - 253°C (LH2).
The sliding behavior of the polymer materials is discussed by means of surface analyses, whereby special attention is paid to the formation of a transfer film.
According to the results at ambient temperature, the effect of hydrogen environment on the tribological behavior of neat polymers may be related to lack of moisture, but also to saturated hydrocarbons in gaseous hydrogen. In liquid hydrogen, the best tribological performances were achieved with neat PA polymers as well as PPS and PI composites.
Effect of high-pressure hydrogen environment on the physical and mechanical properties of elastomers
(2024)
This study presents the influence of high-pressure hydrogen environment on the physical and mechanical properties of two types of cross-linked hydrogenated acrylonitrile butadiene rubbers. Based on the CSA/ANSI standard, static exposures in hydrogen experiments were performed up to 100 MPa at 120 °C. Characterization before and after exposure was conducted by means of density and hardness measurements, dynamic mechanical analysis (DMA), tensile tests, compression set, FT-IR and AFM analyses to assess effects after decompression. While the effect of high-pressure exposure is significant immediately after exposure, most of the physical and mechanical properties recover after 48 hours. FT-IR, AFM, SEM and compression set results indicate, however, permanent effects.
A fundamental study of physical mechanisms of wineglass-shaped fusion zone profile in laser melting
(2024)
The fusion zone geometry in laser melting processes e.g., laser welding and laser-based additive manufacturing, of metallic materials has commonly a wineglass-shaped profile which is critical to the grain orientation and stress distribution. Hereby, we adopt for the first time a decoupling work through a combination of multi-physics modelling and experiments to reveal the fundamental mechanisms of this special morphology. Two physicsbased easy-to-use metal vapour models are proposed to consider the vapour’s momentum and thermal effects separately. It is found that the direct laser energy absorption and Marangoni shear stress which are widely hypothesised to dominate the wineglass-shape formation show only a minor influence. The additional heating from the metallic vapour plume rather than its momentum impact contributes predominantly to the enlarging of the molten pool top region, resulting directly in the formation of the wineglass-shaped fusion zone. The generality of the plume heating effect is also validated in two types of materials (steel and Al) in a wide range of parameters.
Despite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibility and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in the form of a beadon-plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is developed, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control, and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the temperature.
The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data.
Multiple principal element alloys encompass the well-known high entropy alloys (HEA). The alloy system represents a new class of materials consisting of at least three alloying elements, each containing 5 to 35 at.%. Thus, this alloying concept differs fundamentally from conventional materials such as steel or nickel alloys. For this purpose, the alloying elements are specifically selected, the microstructures are adjusted in a single-phase and, in some cases, multi-phase manner. In particular, conflicting goals, such as the trade-off between strength and ductility in conventional steels, are overcome. However, in the last 20 years, the focus has been on material synthesis. With the increase in available material quantities, the focus is now on processing issues such as joining and welding processes. The weldability of HEAs has received very little attention so far. The experience with dissimilar metal welds is completely lacking but is essential for the application of these materials in combination with conventional materials. The present study presents comprehensive experimental results on the weldability of an equimolar CoCrFeMnNi-HEA in cold-rolled and heat-treated condition, which was joined by tungsten inert gas welding to an austenitic steel AISI 304. The mechanical properties of the dissimilar metal welds were characterized by cross-weld tensile samples, whereas the local deformation in the weld of the different welding zones was measured by digital image correlation. In accordance with the respective initial HEA condition (cold-rolled vs. heat-treated), the local strain behavior was divergent and influenced the global mechanical properties of both DMW types. Nonetheless, the experiments provided proof in principle of the weldability for dissimilar joints of the CoCrFeMnNi-HEA welded to conventional materials like austenitic stainless steels ensuring a corresponding capability for mechanical loading. This allows further considerations on the application of these innovative materials.
AbstractThe sustainable and resource-efficient production of wind energy plants requires the use of modern high-strength fine-grain structural steels. This applies to both foundation and erection structures, like mobile or ship cranes. During the assembly of steel structures, unacceptable defects can occasionally be found in the weld area. In most cases, the economical solution would be local thermal gouging of the affected areas and re-welding. Due to the high shrinkage restraint of the joint groove in the overall structure, the superposition of global and local welding-induced stresses may lead to crack formation and component failure, particularly in interaction with the degradation of the microstructure and mechanical properties of high-strength steels during the repair process. However, manufacturers hardly have any information about these issues and there is a lack of recommendations and guidelines to take these safety-relevant aspects into account in adequate repair concepts. The aim of this research is to derive recommendations for repair concepts appropriate to the stresses and materials involved providing a basis for standards and guidelines to avoid cold cracking, damage and expensive reworking especially for high-strength steels. Part 1 of this study involves systematic investigations of influences of shrinkage restraint during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures. The quantification of the shrinkage restraint of repair weld joints was achieved by means of experimental and numerical restraint intensity analysis. In welding experiments with self-restrained slot specimens, restraint intensity and introduction of hydrogen via the welding arc using anti spatter spray were varied systematically to analyse the effect on welding result, residual stresses and cold cracking. It could be shown that increasing restraint intensities result in significantly higher transverse residual stress levels. In the case of hydrogen introduction S500MLO showed no cold cracking independent of the restraint conditions. However, S960QL was found to be considerably cold cracking sensitive if hydrogen is introduced. With increasing restraint intensity length and number of cold cracks increases significantly. Part 2 [1] of this study is focussed on microstructure and residual stresses due to gouging and stress optimization via adequate heat control parameters in repair welding.
Numerical and experimental assessment of liquid metal embrittlement in externally loaded spot welds
(2024)
Zinc-based surface coatings are widely applied with high-strength steels in automotive industry. Some of these base materials show an increased brittle cracking risk during loading. It is necessary to examine electrogalvanized and uncoated samples of a high strength steel susceptible to liquid metal embrittlement during spot welding with applied external load. Therefore, a newly developed tensile test method with a simultaneously applied spot weld is conducted. A fully coupled 3D electrical, thermal, metallurgical and mechanical finite element model depicting the resistant spot welding process combined with the tensile test conducted is mandatory to correct geometric influences of the sample geometry and provides insights into the sample’s time dependent local loading. With increasing external loads, the morphology of the brittle cracks formed is affected more than the crack depth. The validated finite element model applies newly developed damage indicators to predict and explain the liquid metal embrittlement cracking onset and development as well as even ductile failure.
High-strength steels offer potential for weight optimization due to reduced wall thicknesses in modern constructions. Additive manufacturing processes such as Wire Arc Additive Manufacturing (WAAM) enable the resource-efficient production of structures. In the case of defects occurring in weld seams orWAAM components due to unstable process conditions, the economical solution is local gouging or machining and repair welding. It is important to understand the effects of machining steps on the multiaxial stress state in conjunction with the design-related shrinkage restraints. Research into how welding and slot milling of welds andWAAM structures affects residual stresses is still lacking. For this reason, component-related investigations with high-strength steels with yield strengths ≥790 MPa are carried out in our research. In-situ digital image correlation (DIC) and ex-situ X-ray diffraction (XRD) were used to analyze the stresses and strains induced on specimens during and after milling. The systematic analyses revealed a significant interaction of the stiffness and microstructure of the specimens with the initial residual stresses induced by welding. Subsequent repair welds can result in significantly higher residual stresses.
The new multi-element alloying concept of systems with defined entropy (HEA — high-entropy alloy or MEA — medium-entropy alloy) is increasing in material research interest. Improved properties or combinations of properties are shown by several systems. Thus, the resulting microstructures and production of HEA/MEA as well as properties have been primarily investigated so far. Furthermore, processing is a key issue to transfer HEA/MEA systems to real components. Since welding is the most important joining process for metals, it is crucial to investigate the influence of welding to guarantee component integrity. Since most HEA are made of expensive alloying elements such as Co or Ni, they will not be used entirely as structural materials. Thus, it can be advantageous to weld conventional alloys such as austenitic stainless steels with the HEA and MEA to produce components that are both application-oriented and economically viable. Therefore, in this paper, first results of dissimilar metal welding, by tungsten inert gas (TIG) and friction stir welding (FSW), of a CoCrFeMnNi HEA as well as a CoCrNi MEA with a conventional AISI 304 austenitic stainless steel are presented. The focus is on the microstructure formation due to the two welding processes. The results of TIG welding show a dendritic microstructure, whereas in FSW both materials are stirred but still coexist.
Offshore wind turbines continuously increase in size and weight and demand adequate offshore foundations concepts like monopiles, tripods, or jackets. These components are typically constructed using submerged arc welding (SAW) with high-strength thick steel plates like the S420ML. During welding, the occurrence of delayed hydrogen-assisted cracking (HAC) must be anticipated. HAC is a critical combination of the local hydrogen concentration within a susceptible microstructure under certain mechanical load, i.e., the occurring (welding) residual stresses. The welding sequence of the thick-walled plates complicates the residual stress distribution due to the necessary repeated thermal cycling, i.e., welding seam/layer deposition to fill the joint. For that purpose, SAW with two-wire-technique was used to weld a specially designed and prototype-like mock-up of a real component with a thickness of 50 mm, filled with over 20 passes and a seam length of 1000 mm. Additional welded stiffeners simulated the effect of a high restraint, to achieve critical HAC conditions. The necessity of a minimum waiting time (MWT) before the NDT can be conducted (to exclude HAC) was critically verified by the application of ultrasonic testing of the welded joint at different time-steps of the NDT of up to 48 h after the completion welding. The residual stresses were determined by a robot XRD goniometer. Tensile residual stresses up to the yield limit are found both in the weld metal and in the heat-affected zone. Numerical modeling allowed the qualitative estimation of the hydrogen diffusion in the weld. No noticeable HAC occurrence was identified and confirms the high cracking resistance of the investigated material. Finally, the applicability of the MWT concept should be critically discussed.
State-of-the-art laser powder bed fusion (PBF-LB/M) machines allow pre-heating of the substrate plate to reduce stress and improve part quality. However, two major issues have been shown in the past: First, with increasing build height the apparent pre-heat temperature at the surface can deviate drastically from the nominal pre-heat temperature in the substrate plate. Second, even within a single layer the local surface pre-heat temperature can show large gradients due to thermal bottlenecks in the part geometry underneath the top surface. Both lead to unwanted changes in microstructure or defects in the final parts. In this study, a first attempt is taken to show the feasibility of pre-heating the top surface with the onboard laser beam to overcome the mentioned issues. A single layer of a group of three parts built from IN718 to a height of 33.5 mm is pre-heated in a commercially available PBF-LB/M machine to an average steady state surface temperature of 200 °C using the onboard laser beam. The parts are continuously heated, omitting powder deposition and melting step. Temperatures are measured by thermocouples underneath the surface. The experiments are supported by a thermal finite element (FE) model that predicts the temperature field in the parts. When heating the parts uniformly with the laser beam, differences in surface temperatures as large as 170 K are observed. To overcome this inhomogeneity, the heat flux supplied by the laser beam is modulated. An optimized, spatial heat flow distribution is provided by the thermal FE model and translated into a scan pattern that reproduces the optimized heat distribution on the PBF-LB/M machine by locally modulating hatch distance and scan velocity. This successfully reduces the differences in surface temperature to 20 K. Thermographic imaging shows that a homogeneous surface temperature can be achieved despite the localized heat input by the beam. The potential for industrial application of the optimized laser-heating technique is discussed.
The effect of the oscillating metal vapor plume on the keyhole and molten pool behavior during the laser beam welding of AlMg3 aluminum alloys is investigated by experimental and numerical methods. The real-time height of the metal vapor plume is measured by high-speed camera observation. The obtained experimental results are used to evaluate the additional heating source and laser beam attenuation caused by the scattering and absorption based on the Beer–Lambert theory. Furthermore, the dynamic behavior of the metal vapor plume is incorporated into a 3D transient heat transfer and fluid flow model, coupled with the ray tracing method, for the laser beam welding of the AlMg3 alloy. It is found that additional heating resulting from the scattered and absorbed laser beam energy by the metal vapor plume significantly expands the shape of the molten pool on the top region. Moreover, the oscillating metal vapor plume caused the fluctuation of the high-temperature region in the molten pool. The probability of keyhole collapse at the bottom increases 17% due to the oscillating laser power induced by the laser beam attenuation. The internal interplay between the metal vapor plume, molten pool shape, and keyhole collapse is obtained. The developed model has been validated by experiments, which shows a good agreement.
The spatial laser energy absorption inside the keyhole is decisive for the dynamic molten pool behaviors and the resultant weld properties in high-power laser beam welding (LBW). In this paper, a numerical simulation of the LBW process, considering the 3D transient heat transfer, fluid flow, and keyhole dynamics, is implemented, in which the free surface is tracked by the volume-of-fluid algorithm. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by an advanced ray-tracing method based on a localized level-set strategy and a temperature-dependent absorption coefficient. The laser energy absorption is analyzed from a time-averaged point of view for a better statistical representation. It is found for the first time that a significant drop in the time-averaged laser energy absorption occurs at the focus position of the laser beam and that the rest of the keyhole region has relatively homogeneous absorbed energy. This unique absorption pattern may lead to a certain keyhole instability and have a strong correlation with the detrimental bulging and narrowing phenomena in the molten pool. The influence of different focus positions of the laser beam on the keyhole dynamics and molten pool profile is also analyzed. The obtained numerical results are compared with experimental measurements to ensure the validity of the proposed model.
Liquid metal embrittlement (LME) cracking is a phenomenon observed during resistance spot welding (RSW) of zinccoated advanced highstrength steels (AHSS) in automotive manufacturing. In this study, severe cracks are observed at the edge of the sheet under reduced flange widths. These cracks, traversing the AHSS sheet, culminate at the edge with a width of approximately 1.2 mm.
Through combined numerical and experimental investigations, and material testing, these cracks are identified and validated as a new type of LME crack. The mechanism behind this crack formation is attributed to unique geometric conditions that, when compared to center welding, amplify radial material flow by ninefold to 0.87 mm. The resultant tangential tensile stresses approximate 760 MPa, which exceed the yield strength of the examined advanced highstrength steel (AHSS) under heightened temperature conditions, and when combined with liquid zinc, promote the formation of this new type of LME crack.
Effect of Tensile Loading and Temperature on the Hydrogen Solubility of Steels at High Gas Pressure
(2023)
The hydrogen solubility in ferritic and martensitic steels is affected by hydrostatic stress, pressure, and temperature. In general, compressive stresses decrease but tensile stresses increase the hydrogen solubility. This important aspect must be considered when qualifying materials for high‐pressure hydrogen applications (e.g., for pipelines or tanks) by using autoclave systems. In this work, a pressure equivalent for compensating the effect of compressive stresses on the hydrogen solubility inside of closed autoclaves is proposed to achieve solubilities that are equivalent to those in pipelines and tanks subjected to tensile stresses. Moreover, it is shown that the temperature effect becomes critical at low temperatures (e.g., under cryogenic conditions for storing liquid hydrogen). Trapping of hydrogen in the microstructure can increase the hydrogen solubility with decreasing temperature, having a solubility minimum at about room temperature. To demonstrate this effect, the generalized law of the hydrogen solubility is parameterized for different steels using measured contents of gaseous hydrogen. The constant parameter sets are verified and critically discussed with respect to the high‐pressure hydrogen experiments.