Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Dokumenttyp
- Vortrag (614)
- Zeitschriftenartikel (390)
- Beitrag zu einem Tagungsband (190)
- Posterpräsentation (52)
- Forschungsbericht (9)
- Dissertation (7)
- Buchkapitel (5)
- Sonstiges (4)
- Forschungsdatensatz (4)
- Monografie (2)
Sprache
- Englisch (899)
- Deutsch (373)
- Russisch (5)
- Mehrsprachig (2)
- Spanisch (2)
Schlagworte
- Additive manufacturing (98)
- Additive Fertigung (93)
- Laser beam welding (93)
- Additive Manufacturing (83)
- Welding (70)
- Hydrogen (63)
- Eigenspannungen (55)
- Wear (48)
- Friction (42)
- Residual stress (42)
- Wasserstoff (42)
- Microstructure (40)
- Hochfester Stahl (39)
- Schweißen (39)
- Ultraschallunterstütztes Fräsen (37)
- MAG-Schweißen (36)
- Thermography (34)
- Laser powder bed fusion (32)
- Mechanical properties (32)
- Residual stresses (32)
- Laser metal deposition (24)
- TIG welding (24)
- Solidification cracking (23)
- Ultrasonic-assisted milling (23)
- LIBS (22)
- Niobium carbide (21)
- Tribology (21)
- Numerical simulation (20)
- Creep-resistant steel (19)
- In situ measurement (19)
- Legierungsmodifikation (19)
- Residual Stress (19)
- High-strength steels (18)
- Laser Powder Bed Fusion (18)
- Oberflächenintegrität (18)
- Surface integrity (18)
- Wärmeführung (18)
- Diffusion (17)
- Laser implantation (17)
- AGIL (16)
- Digitalisierung (16)
- L-PBF (16)
- Neutron diffraction (16)
- Cyclic R-curve (15)
- Duplex stainless steel (15)
- Kaltrisssicherheit (15)
- Laserstrahlschweißen (15)
- Numerical modeling (15)
- Alloy 36 (14)
- Fatigue (14)
- Process monitoring (14)
- Weld pool shape (14)
- 316L (13)
- AlSi10Mg (13)
- Fracture mechanics (13)
- High-strength steel (13)
- Open science (13)
- Steel (13)
- AM (12)
- Diffraction (12)
- Digitalisation (12)
- Heat treatment (12)
- High-entropy alloy (12)
- Hochfester Feinkornbaustahl (12)
- Hybrid laser-arc welding (12)
- Hydrogen assisted cracking (12)
- NbC (12)
- Porosity (12)
- Thermografie (12)
- TiB2 (12)
- Alloy modification (11)
- DED (11)
- High Entropy Alloy (11)
- Hochfeste Feinkornbaustähle (11)
- Inconel 718 (11)
- Laser welding (11)
- Polymers (11)
- Reparatur (11)
- Stress relief cracking (11)
- Ti-6Al-4V (11)
- Werkzeugverschleiß (11)
- Laser hybrid welding (10)
- Machining (10)
- Post weld heat treatment (10)
- Research data management (10)
- Surface texturing (10)
- Thick-walled steel (10)
- Windenergie (10)
- X-ray diffraction (10)
- AISI 316L (9)
- Deep penetration laser beam welding (9)
- Fatigue crack propagation threshold (9)
- Hardness (9)
- Hybrid laser arc welding (9)
- Infrared thermography (9)
- Laser Metal Deposition (9)
- Restraint (9)
- Stainless Steel (9)
- Submerged arc welding (9)
- AISI D2 (8)
- Element transport (8)
- Fatigue strength (8)
- Fügetechnik (8)
- Hot cracking (8)
- Implant-Test (8)
- Kaltriss (8)
- Laser-induced periodic surface structures (LIPSS) (8)
- Numerical modelling (8)
- Oxidation (8)
- Solidification (8)
- Temperature (8)
- ToF-SIMS (8)
- WAAM (8)
- Weld pool dynamics (8)
- i-TRIBOMAT (8)
- Auftragschweißen (7)
- Bruchmechanik (7)
- Carrier gas hot extraction (7)
- Characterisation (7)
- Charpy impact toughness (7)
- Chemical composition (7)
- Cryogenic temperature (7)
- Digital image correlation (7)
- Digitalization (7)
- Electromagnetic backing (7)
- Fatigue crack growth (7)
- Forschung (7)
- Friction stir welding (7)
- Harmonisation (7)
- Heat control (7)
- High power laser beam welding (7)
- Kaltrisse (7)
- LMD (7)
- Laserhybridschweißen (7)
- Magnetic field (7)
- Magnetohydrodynamics (7)
- Medium Entropy Alloys (7)
- Nickel (7)
- Open data (7)
- Pipeline (7)
- Residual Stresses (7)
- Resistance spot welding (7)
- Schwingfestigkeit (7)
- Selective laser melting (SLM) (7)
- Thermal cycles (7)
- Tool wear (7)
- Tribologie (7)
- WRC 1992 diagram (7)
- Wärmenachbehandlung (7)
- Austenitic stainless steels (6)
- Bauteilprüfung (6)
- Bulging effect (6)
- Cermet (6)
- Component assessment (6)
- Computed Tomography (6)
- Computed tomography (6)
- Critical strain (6)
- Deep penetration (6)
- Duplex (6)
- Electromagnetic forces (6)
- FEM (6)
- Fatigue crack propagation (6)
- Fracture Mechanics (6)
- Grain refinement (6)
- Heat accumulation (6)
- Hot stamping (6)
- ISO 3690 (6)
- Joining dissimilar materials (6)
- LTT (6)
- Large-scale test (6)
- Laser Powder Bed Fusion (L-PBF) (6)
- Laser-Pulver-Auftragschweißen (6)
- Laserimplantation (6)
- Lubricants (6)
- PBF-LB/M (6)
- Partial penetration (6)
- Process parameters (6)
- Prüfverfahren (6)
- Reibung (6)
- Rührreibschweißen (6)
- Selective Laser Melting (6)
- Selective Laser Melting (SLM) (6)
- Simulation (6)
- Steel and aluminium (6)
- Turbine disk (6)
- UP-Schweißen (6)
- Welding simulation (6)
- Zerspanung (6)
- 3D printing (5)
- AFM (5)
- Additive Manufacturing (AM) (5)
- Additive manufacturing (AM) (5)
- Arc welding (5)
- Artificial neural network (5)
- Austenitic stainless steel (5)
- Crack (5)
- Crack closure (5)
- Cutting tool (5)
- Direct Energy Deposition (5)
- Directed Energy Deposition (5)
- Eisenaluminid (5)
- End crater (5)
- Erstarrungsriss (5)
- GMA welding (5)
- Gefügedegradation (5)
- Gründungsstrukturen (5)
- Heißriss (5)
- Heißrisse (5)
- High entropy alloy (5)
- Hochentropie Legierung (5)
- Hochfest (5)
- Hot steam (5)
- Hybrid Laser Arc Welding (5)
- Hydrogen-assisted cracking (5)
- Interlaboratory tests (5)
- Keyhole mode welding (5)
- Kitagawa-Takahashi diagram (5)
- Künstliche Intelligenz (5)
- LIBS TIG welding (5)
- Laser energy distribution (5)
- Liquid metal embrittlement (5)
- Low Cycle Fatigue (5)
- Mechanical Engineering (5)
- Mechanics of Materials (5)
- Neutron Diffraction (5)
- Neutron imaging (5)
- Numerical Simulation (5)
- Numerical process simulation (5)
- Polymer composites (5)
- Qualitätssicherung (5)
- Repair-welding (5)
- Reparaturschweißen (5)
- Review (5)
- Round robin tests (5)
- Schadensanalyse (5)
- Sintering (5)
- Spannungsrelaxationsriss (5)
- Studie (5)
- Tensile properties (5)
- Thermal desorption analysis (5)
- Thick-plate welding (5)
- WelDX (5)
- Weldments (5)
- Widerstandspunktschweißen (5)
- X-ray and Neutron Diffraction (5)
- X38CrMoV5-3 (5)
- 3D Druck (4)
- AISI 304L (4)
- Atomic Forc Microscopy (4)
- Atomic force microscopy (4)
- Bulge effect (4)
- Cold cracking (4)
- Cold cracking safety (4)
- Constraint (4)
- Contact resonance (4)
- Cracking (4)
- Cutting tools (4)
- DED-Arc (4)
- Defects (4)
- Deuterium (4)
- Direct energy deposition (4)
- Directed energy deposition (4)
- EBSD (4)
- Elastic modulus (4)
- Electrochemical permeation (4)
- Elektromagnetische Schmelzbadbeeinflussung (4)
- Endkrater (4)
- Evaporation (4)
- Fail-safe (4)
- Forschungsdatenmanagement (4)
- Gap bridgeability (4)
- Heat conduction (4)
- High Entropy Alloys (4)
- High strength steel (4)
- High-strength structural steels (4)
- Highspeed-plasma-laser-cladding (4)
- Hochentropielegierung (4)
- Hydrogen embrittlement (4)
- IN718 (4)
- In-situ Monitoring (4)
- Inter layer time (4)
- Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung (4)
- Kaltrissprüfung (4)
- Keyhole dynamics (4)
- Laser beam melting (LBM) (4)
- Laser powder bed fusion (L-PBF) (4)
- Liquid Metal Embrittlement (4)
- MVT (4)
- Martensite (4)
- Mathematical modeling (4)
- Microstructure characterization (4)
- Mikrostruktur (4)
- Multi-principal element alloys (4)
- Niobium carbide (NbC) (4)
- Offshore (4)
- Offshore Windenergieanlagen (4)
- Oscillating magnetic field (4)
- PEEK (4)
- Pipelines (4)
- Plasma-Transferred-Arc (4)
- Plasma-transferred arc welding (4)
- Position detection (4)
- Potentiodynamic Polarization (4)
- ProMoAM (4)
- Process simulation (4)
- Properties (4)
- Quality assurance (4)
- Qualitätsinfrastruktur (4)
- Ray tracing (4)
- Research (4)
- Restlebensdauer (4)
- Rundnaht (4)
- SIMS (4)
- SLM (4)
- Scanning Kelvin Probe Force Microscopy (4)
- Schadenstolerante Bauteilauslegung (4)
- Shear modulus (4)
- Surface modification (4)
- Synchrotron (4)
- Titanium (4)
- Toughness (4)
- Tribofilm (4)
- Varestraint-Test (4)
- WIG-Schweißen (4)
- Weld metal (4)
- Wind energy (4)
- Young's modulus (4)
- Zerspankräfte (4)
- Zyklische R-Kurve (4)
- 100Cr6 (3)
- 9%Ni steel (3)
- Ageing (3)
- Aging (3)
- Alumina (3)
- Aqueous Corrosion (3)
- Artungleiche Werkstoffe (3)
- Automatisierte Fertigung (3)
- Boundary element method (3)
- Bulge formation (3)
- Bulging (3)
- Burst (3)
- CT (3)
- Chunky graphite (3)
- Circumferential weld (3)
- Cobalt (3)
- Cold Spray (3)
- Component test (3)
- Corrosion (3)
- Crack propagation (3)
- Cryogenic steel (3)
- Crystal branch development (3)
- Cyclic R-Curve (3)
- DVS (3)
- Data fusion (3)
- Data-fusion (3)
- Database (3)
- Defokussierung (3)
- Deposition welding (3)
- Dickblech (3)
- Diffusible hydrogen (3)
- Dilatometry (3)
- Dimensional accuracy (3)
- Dissimilar metal weld (3)
- Dissimilar metal weld (DMW) joint (3)
- Dissimilar metal weld overlays (3)
- Distortion (3)
- Duplex Stainless Steel (3)
- Duplex stainless steels (3)
- Edge quality (3)
- Eigenspannung (3)
- Elastomers (3)
- Electrochemical Impedance Spectroscopy (3)
- Electromagnetic Weld Pool Support (3)
- Electromagnetic weld pool support (3)
- Electron backscattered diffraction (3)
- Electron beam welding (3)
- Elektromagnetische Schmelzbadunterstützung (3)
- Endurance limit (3)
- Equivalent heat source (3)
- Experimental procedure (3)
- Fatigue life (3)
- Fatigue limit (3)
- Fe3Al (3)
- Feinkornbaustahl (3)
- Femtosecond laser (3)
- Fortschrittsbericht (3)
- Fracture (3)
- Fracture toughness (3)
- Full Penetration (3)
- Fügetechnologie (3)
- Grain size (3)
- Gutachten (3)
- Hardmetal (3)
- Heat Treatment (3)
- High-strength Steels (3)
- Hot crack (3)
- Hot-Stamping (3)
- Hybrid components (3)
- Hybrid repair (3)
- Hydrogen diffusion (3)
- ICP-MS (3)
- Implant test (3)
- In situ (3)
- In situ monitoring (3)
- In-situ monitoring (3)
- In-situ process monitoring (3)
- Keyhole collapse (3)
- Korrosionsschutz (3)
- Kupferazid (3)
- LCF (3)
- LME (3)
- LPA (3)
- LPBF (3)
- Laser (3)
- Laser Beam Welding (3)
- Laser Pulver Auftragsschweißen (3)
- Laser Welding (3)
- Laser beam melting (3)
- Laser dispersing (3)
- Leichtbau (3)
- Life Cycle Assessment (3)
- Lubricated sliding (3)
- Lubrication (3)
- MSG-Schweißen (3)
- Measurement (3)
- Mechanical mismatching (3)
- Mechanische Eigenschaften (3)
- Medium entropy alloy (3)
- Mediumentropie Legierung (3)
- Mediumentropielegierung (3)
- Melt pool dinamics (3)
- Metals and Alloys (3)
- Methane (3)
- Molten pool dynamics (3)
- Multi-physical modeling (3)
- Multi-physical modelling (3)
- Multielementlegierungen (3)
- Multispectral thermography (3)
- NDT (3)
- Neutron radiography (3)
- Ni alloy (3)
- Numerische Simulation (3)
- Online Process Monitoring (3)
- Optical Tomography (3)
- Optical flow (3)
- Optical tomography (3)
- Oscillating vapor plume (3)
- Overspeed (3)
- Periodic solidification pattern (3)
- Phase transformation (3)
- Plasma-Pulver-Auftragschweißen (3)
- Polymer materials (3)
- Presshärten (3)
- Prozesskette (3)
- Prozessmonitoring (3)
- Prozessüberwachung (3)
- Pufferschichten (3)
- Quality Assurance (3)
- Repair (3)
- Reproducibility (3)
- Residual stress analysis (3)
- Rissarrest (3)
- Schallemission (3)
- Selective laser melting (3)
- Spannungsrelaxationsrisse (3)
- Stahl und Aluminium (3)
- Structural integrity (3)
- TEKKEN (3)
- TEKKEN-Test (3)
- TES (3)
- Temperature emissivity separation (3)
- Texture (3)
- Thermisches Ausfugen (3)
- Thermo-fluid flow (3)
- Thick Materials (3)
- Transient heat transfer (3)
- Tungsten carbide (3)
- Turning (3)
- Umlaufkühler (3)
- Umweltwirkungen (3)
- Vacuum (3)
- Verschleiß (3)
- Wasserstofftechnologien (3)
- Wire arc additive manufacturing (3)
- Ökobilanzierung (3)
- Überlappbereich (3)
- (U)HMWPE (2)
- 13CrMoV9-10 (2)
- ASTM E647 (2)
- Abrasion (2)
- Achsschenkel (2)
- Adaptives Schweißen (2)
- Advanced high strength steel (2)
- Advanced high strength steels (2)
- Aerosol measurements (2)
- Al/Mg alloys (2)
- Aluminum alloys (2)
- Analytisches Modell (2)
- Applications (2)
- Archard's law (2)
- Austenite-to-martensite transformation (2)
- Automatisierte schweißtechnische Fertigung (2)
- Bauteilauslegung (2)
- Bauteilbewertung (2)
- Bead-on-plate welds (2)
- Bragg-edge imaging (2)
- Bruchmechanische Auslegung (2)
- Build direction (2)
- Build-up Orientation (2)
- CASTOR-Behälter (2)
- CFD-model (2)
- CNG (2)
- Calibration free (2)
- Capability (2)
- Carbon steel (2)
- Carbonitride (2)
- Characterization (2)
- Co-Cr-alloy (2)
- Coarse-grained heat-affected zone (2)
- Coefficient of Friction (2)
- Columnar crystal growth (2)
- Composites (2)
- Computed tomography (CT) (2)
- Condition monitoring (2)
- Copper powder particles (2)
- Crack closure effect (2)
- Crack-closure (2)
- Creep (2)
- Creep behavior (2)
- Creep resistant steel (2)
- Creep-resisting materials (2)
- Crystallographic texture (2)
- Cyclic J-integral (2)
- Cyclic R-curve analysis (2)
- DED-EB (2)
- DED-arc (2)
- DLC (2)
- Damage tolerance (2)
- Data evaluation methods (2)
- Data preparation (2)
- Datenbank (2)
- Debye-Waller-Faktor (2)
- Debye–Waller factor (2)
- Defekte (2)
- Degradation (2)
- Digital (2)
- Digital transformation (2)
- Direct Laser Metal Deposition (2)
- Directed Enery Deposition (2)
- Dual phase steel (2)
- Ductile cast iron (2)
- Duplex AISI 2205 (2)
- Duplex steels (2)
- Durability (2)
- Dynamische Beanspruchung (2)
- EBAM (2)
- Effective crack propagation data (2)
- Einspanngrad (2)
- Electrical conductivity (2)
- Electromagnetic support (2)
- Electron backscatter diffraction (2)
- Elektromagnetische Schmelzbadsicherung (2)
- Elektronenstrahlschweißen (2)
- Embedded electronics (2)
- Embrittlement (2)
- End-crater (2)
- Environmental conditions (2)
- Ermüdung (2)
- Ermüdungsrisswachstum (2)
- Europäisches Tribologie-Zentrum (2)
- Expansion joint (2)
- Experiment (2)
- Experimental design (2)
- Experimental determination (2)
- Explosion (2)
- FE-model (2)
- FGM (2)
- Fahrrad (2)
- Failure Assessment Diagram (2)
- Fatigue Crack Propagation (2)
- Fatigue Strength (2)
- Fatigue properties (2)
- Ferritic spheroidal graphite cast iron (2)
- Ferromagnetischer Stahl (2)
- Filler material distribution (2)
- Filler wire mixing (2)
- Finite element analysis (2)
- Finite element method (2)
- Finite element simulation (2)
- Flüssigmetallinduzierte Rissbildung (2)
- Force distance curve (2)
- Force-distance curves (2)
- Fractography (2)
- Fracture resistance (2)
- Fraktographie (2)
- Frequenzanalyse (2)
- Fräsen (2)
- Fuel economy (2)
- Full penetration (2)
- Fume (2)
- GMA Welding (2)
- GMAW (2)
- Gas metal arc welding (2)
- Gas tungsten arc welding (GTAW) (2)
- General Materials Science (2)
- Generative Fertigung (2)
- Gusseisen mit Kugelgraphit (2)
- HEA (2)
- HSLA (2)
- HSLA steel (2)
- Hartstoffphasen (2)
- Heat treatments (2)
- Heat-affected zone (2)
- Heissrisse (2)
- High Cycle Fatigue (2)
- High Temperature Testing (2)
- High strength steels (2)
- High-power laser (2)
- High-power laser beam (2)
- High-power laser beam welding (2)
- High-pressure (2)
- High-resolution camera (2)
- Hochleistungsschweißen (2)
- Hochtemperaturwerkstoffe (2)
- Hohlzugprobe (2)
- Holz-Stahl-Kontakte (2)
- Hot Cracks (2)
- Hybrid Part (2)
- Hybrid welding (2)
- Hydrogen Assisted Cracking (HAC) (2)
- Härteprüfung nach Vickers (2)
- Höherfeste Feinkornbaustähle (2)
- Höherfester Feinkornbaustahl (2)
- Höherfester Stahl (2)
- ISO 12108 (2)
- Image processing (2)
- In situ strain (2)
- In-situ (2)
- Ionic liquid (2)
- Iron aluminide (2)
- Irradiation (2)
- Joint sealing (2)
- Kerbschlagarbeit (2)
- Keyhole mode laser beam welding (2)
- Keyhole porosity (2)
- Korrelation (2)
- L-PBF 316L (2)
- LDX (2)
- LIMS (2)
- LIPSS (2)
- LNG (2)
- LTT Weld Filler Materials (2)
- LTT weld filler materials (2)
- Laboratory specimens (2)
- Lack-of-fusion (2)
- Large electrical high-voltage machine (2)
- Laser Metal Deposition (LMD) (2)
- Laser beam welding (LBW) (2)
- Laser energy absorption (2)
- Laser metal deposition (LMD) (2)
- Laser-Hybridschweißen (2)
- Laser-metal-deposition (2)
- Laserpulverauftragschweißen (2)
- Laserstrahlschmelzen (2)
- Leakage Rate (2)
- Lebensdauer (2)
- Lichtbogensensorik (2)
- Liquation Cracking (2)
- Localized laser dispersing (2)
- Longitudinal Wave (2)
- Low heat input GMA welding (2)
- Low transformation temperature (LTT) steel (2)
- Lubricant additives (2)
- MAG welding (2)
- MHD (2)
- MSG-Engspaltschweißen (2)
- Master Curve-Konzept (2)
- Matching ferritic welding electrode (2)
- Material defects (2)
- Material transport (2)
- Materialuntersuchung (2)
- Mechanical behavior (2)
- Melt pool dynamics (2)
- Metal (2)
- Metal mixing (2)
- Metallschutzgasschweißen (2)
- Metallsulfide (2)
- Metallurgie (2)
- Micro-shrinkages (2)
- Microbiologically influenced corrosion (2)
- Microstructure and texture (2)
- Misalignment of the edges (2)
- Model calibration (2)
- Modification of structural morphology (2)
- Molten pool (2)
- Molten pool behaviour (2)
- Moving mesh (2)
- Multiple cracks (2)
- Multiple principal element alloy (2)
- Multiple reflections (2)
- Nachwärmung (2)
- Neuronales Netz (2)
- Neutron (2)
- NiCrBSi (2)
- Nickel alloys (2)
- Non-metallic inclusions (2)
- Offshore wind (2)
- Optical measurement (2)
- Optische Tomografie (2)
- PAG (2)
- PBF-LB/M/316L (2)
- PBF/LB-M (2)
- PWHT (2)
- Particle gas emission (2)
- Path planning (2)
- Penetration depth (2)
- Performance testing (2)
- Photoresist (2)
- Pipe manufacturing (2)
- Pipeline steel X120 (2)
- Pitting (2)
- Plasma (2)
- Plasma-cutting (2)
- Plastic deformation (2)
- Plume (2)
- Pores (2)
- Post-weld heat treatment (2)
- Powder Bed Fusion (2)
- Pre-weld Preparation (2)
- Preheating (2)
- Process chain (2)
- Process parameter optimization (2)
- Pulsed laser beam welding (2)
- Quantification (2)
- RSW (2)
- Radioactive Waste (2)
- Raman spectroscopy (2)
- Ray tracing method (2)
- Ray-tracing (2)
- Recognition (2)
- Refill friction stir spot welding (2)
- Reheat cracking (2)
- Repair Welding (2)
- Repair welding (2)
- Representative specimens (2)
- Ressidual stress (2)
- Rissbildung in Stahl (2)
- Rissschließeffekte (2)
- Round robin (2)
- S-N curve (2)
- SEM (2)
- SHPB (2)
- SMAW (2)
- SWIR camera (2)
- Scanning kelvin probe force microscopy (2)
- Scattering (2)
- Schadensprävention (2)
- Schleifen (2)
- Schutzgasschweißen (2)
- Schweißeigenspannungen (2)
- Schweißeignung (2)
- Schweißnahtbewertung (2)
- Schweißverbindungen (2)
- Schweißzusatzmodifikation (2)
- Schwellenwert gegen Ermüdungsrissausbreitung (2)
- Schwer spanbar (2)
- Seal Behavior (2)
- Seam geometry (2)
- Selected Laser Melting (2)
- Selektive-laser-melting (2)
- Semi-finishing (2)
- Ship building (2)
- Short crack (2)
- Short cracks (2)
- Single pass welding (2)
- Sliding (2)
- Sliding wear (2)
- Small-scale specimens (2)
- Software (2)
- Solid lubricants (2)
- Solidification craking (2)
- Solubility (2)
- Spatter (2)
- Speed of sound (2)
- Stahl (2)
- Stainless steels (2)
- Steel 316L (2)
- Stoßdämpfer (2)
- Strain measurement (2)
- Strain rate (2)
- Stress corrosion cracking (2)
- Structural Integrity (2)
- Structure (2)
- Struktur Integrität (2)
- Superellipse (2)
- Superelliptic Lamé curves (2)
- Supermartensitic Stainless Steel (SMSS) (2)
- Surface roughness (2)
- Surface structuring (2)
- TPU (2)
- Temperature distribution (2)
- Temperature field (2)
- Tensile Properties (2)
- Tensile performance (2)
- Tensile strength (2)
- Tensile testing (2)
- Testing method (2)
- Thermal history (2)
- Thermo-capillary convection (2)
- Thermographie (2)
- Ti64 (2)
- TiAl5V4 (2)
- TiAl64V (2)
- Titan (2)
- Titanium alloy (2)
- Tool steel (2)
- Trapping (2)
- Tribologische Daten (2)
- Turbinenscheibe (2)
- Turbulence (2)
- Ultraschallunterstütztes Zerspanen (2)
- Ultrasonic Transducer (2)
- Ultrasonic assisted machining (2)
- Ultrasonic assisted milling (2)
- Ultrasonic machining (2)
- Ultrasonic vibration (2)
- Vaporization (2)
- Varestraint (2)
- Varestraint test (2)
- Varestraint testing (2)
- Verfahrensvergleich (2)
- Verschleißbeständigkeit (2)
- Vickers hardness (2)
- Viscoplasticity (2)
- WAXD (2)
- Wasserstoffdegradation (2)
- Wear resistance (2)
- Wear volume (2)
- Weld defects (2)
- Weld geometry (2)
- Weld pool (2)
- Weld pool behavior (2)
- Weld pool geometry (2)
- Weld pool shape approximation (2)
- Welded Joints (2)
- Welded joints (2)
- Welding microstructure (2)
- Welding residual stresses (2)
- Welding thermal cycle (2)
- Wire Arc Additive Manufacturing (2)
- Wire electron beam additive manufacturing (2)
- Wärmebehandlung (2)
- X-ray Diffraction (2)
- Zerspanbarkeitsanalysen (2)
- Zinc coated steel (2)
- Zink (2)
- Zirconia (2)
- Zugeigenschaften (2)
- Zwischenlagenzeit (2)
- Öffentliche Sicherheit (2)
- μCT-analysis (2)
- 100Cr6 (AISI 52100) steel (1)
- 100Cr6 steel (1)
- 100Cr6-Stahl (1)
- 2101 duplex stainless steel (1)
- 3D Scanning (1)
- 3D-finite element modeling (1)
- 9%Ni steel, (1)
- AC magnetic field (1)
- ADXRD (1)
- AFM-Kraft-Abstand-Kurven (1)
- AHSS (1)
- AISI 321 stainless steel (1)
- AM 316L stainless steel (1)
- AM feature integration (1)
- ASTM (1)
- AXRD (1)
- Abrasive wear (1)
- Absorbed energy (1)
- Abtragende Glasbearbeitung (1)
- Accelerator magnets (1)
- Accoustic emission (1)
- Acero 316L (1)
- Acero alta resistencia (1)
- Acoustic Emission (1)
- Acoustic emission (1)
- Adaptive MSG-Lichtbogenprozesse (1)
- Adaptive MSG-Lichtbogenschweißprozesse (1)
- Adaptive control (1)
- Adaptive remeshing (1)
- Adaptive welding beam oscillation (1)
- Adative arc welding processes (1)
- Additiv (1)
- Additive (1)
- Additive surface treatment (1)
- Additiver Fertigung (1)
- Additives (1)
- Adhesion (1)
- Adhesion by mechanical interlocking (1)
- Adiabatic shear bands (1)
- Adsorption (1)
- Advanced High-Strength Steel (AHSS) (1)
- Advanced high-strength steel (1)
- Advanced high-strength steels (1)
- Al-Mg-Si-Legierungen (1)
- Al/Ti dissimilar joints (1)
- AlMg0.7SiTiB filler wire (1)
- AlMgSi Legierungen (1)
- AlSi10Mg alloy (1)
- Alite (1)
- Alkyd resin-based coating (1)
- Alloy (1)
- Alloy 247 (1)
- Alloy 718 (1)
- Alloys (1)
- Alternative Kraftstoffe (1)
- Alternative fuels (1)
- Alternative test procedure (1)
- Aluminium Alloy (1)
- Aluminium oxide (1)
- Aluminium-Druckguss (1)
- Aluminium-Druckgusslegierung (1)
- Aluminum (1)
- Aluminum bronze (1)
- Analysis (1)
- Analytical calculation (1)
- Analytical model (1)
- Analytical solution (1)
- Angle dependency (1)
- Anlagen (1)
- Anlagenbau (1)
- Application properties (1)
- Arc sensor (1)
- Artefact (1)
- Artificial Intelligence (1)
- As-built LPBF IN718 alloy (1)
- As-shielded arc welding (1)
- Atomic force microscope (1)
- Aufgelöste Tragstrukturen (1)
- Aufheizrate (1)
- Auftriebskräfte (1)
- Austenit (1)
- Austenitic (1)
- Austenitic Stainless Steel (1)
- Austenitic steel (1)
- Austenitic welding electrode (1)
- Austenitischer Rostfreier Stahl (1)
- Automated manufacturing (1)
- Automated welding (1)
- Automation (1)
- Automatisierte schweißtechniche Fertigung (1)
- Automobilindustrie (1)
- Automotive application (1)
- BMDK (1)
- Backlight (1)
- Bacteria (1)
- Bainitischer Schmiedestahl (1)
- Bauteilversuch (1)
- Bayesian technique (1)
- Beam oscillation (1)
- Beam oscillations (1)
- Beanspruchungsanalyse (1)
- Bedarf (1)
- Bedeutung (1)
- Behavior (1)
- Bending test (1)
- Betriebsfestigkeit (1)
- Beugung (1)
- Bewegtes Gitter (1)
- Biaxial test (1)
- Binder (1)
- Binders (1)
- Bionik (1)
- Biopolymers (1)
- Biotische/abiotische Faktoren (1)
- Bismuth titanates (1)
- Boundary lubrication (1)
- Bragg-edge (1)
- Bragg-edge neutron 2D imaging (BENI) (1)
- Brazil nut Mesocarp (1)
- Bremsbelag (1)
- Bremsbeläge (1)
- Bridging voids (1)
- Bruch (1)
- Bruchmechanische Kennwerte (1)
- Bruchmechanische Konzepte (1)
- Build-up strategy (1)
- Bulge (1)
- Bulging effects (1)
- CCT diagrams (1)
- CFD model (1)
- Calculation time (1)
- Camera (1)
- Cantilever microprobe (1)
- Carbide (1)
- Carbon (1)
- Carbon dioxide footprint (1)
- Carrier gas hot extraction (CGHE) (1)
- Catalysis (1)
- CdSe/ZnS quantum Dots (1)
- Cellular substructure (1)
- Cellular uptake (1)
- Cemented carbide (1)
- Centerline solidification cracking (1)
- Ceramic (1)
- Ceramic matrix composites (1)
- Cermets (1)
- Chapetti’s and IBESS model (1)
- Characterization of corrosion layers (1)
- Charpy Impact Test (1)
- Charpy Transition Curve (1)
- Charpy pendulum impact test (1)
- Chemical corrosion (1)
- Chemische Zusammensetzungen (1)
- Chunky graphite degeneration (1)
- Chunky-Graphit (1)
- Cimensional Accuracy (1)
- Circumferential welds (1)
- Clad steels (1)
- Clinker substitute (1)
- Clustering (1)
- Co (1)
- Co-Cr-Legierung (1)
- Coarse grained heat affected zone (1)
- Coating (1)
- Cobalt-chromium alloy (1)
- Codes and standards (1)
- Coefficient of friction (1)
- Cold cracking and welding (1)
- Cold-welding (1)
- Complex loading (1)
- Component (1)
- Component Assessment (1)
- Component-like test (1)
- Composite (1)
- Compositionally complex alloy (1)
- Computational fluid dynamics (1)
- Computer Aided Manufacturing (1)
- Computer vision (1)
- Computertomografie (1)
- Condensed Matter Physics (1)
- Constraint faktor (1)
- Contact fatigue (1)
- Contact pressure (1)
- Contamination (1)
- Control (1)
- Conventional Ni-based austenitic welding electrode (1)
- Conversion of results (1)
- Convolutional Neural Networks (1)
- Convolutional neural network (1)
- Convolutional neural networks (CNN) (1)
- Coolant-free (1)
- Cooling rate (1)
- Coordinate measurement machine (1)
- Core-shell structures (1)
- Correlation microstructure to properties (1)
- Corrosion pits (1)
- Corrosion testing (1)
- Co–Cr-alloy (1)
- CrMoV-Stahl (1)
- Crack Tip Opening Displacement (CTOD) (1)
- Crack arrest (1)
- Crack closure mechanisms (1)
- Crack propagation resistance (1)
- Crack-tip constraint (1)
- Cracking mechanism (1)
- Crater (1)
- Crater wear (1)
- Creep resisting materials (1)
- Critical strain rate (1)
- Crown-abutment connection (1)
- Cryogenic Engineering (1)
- Cryogenic Steel (1)
- Crystal Plasticity Modelling (1)
- Crystal plasticity (1)
- Crystallographic texture control (1)
- CuSn1 (1)
- Current density (1)
- Curvas FCGR (1)
- Curve fitting (1)
- Cutting forces (1)
- Cyclic loading (1)
- Cyclic stress-strain curve (1)
- Cylindrical turning (1)
- D7755-11 (1)
- DED-L (1)
- DED-LB (1)
- DEM (1)
- DIC (1)
- DSS (1)
- Damage Tolerance (1)
- Damage prediction (1)
- Damage tolerance assessment (1)
- Damage tolerant component design (1)
- Data Integrity (1)
- Data Sciences (1)
- Data-driven quality assurance (1)
- Dataspace (1)
- Datenmanagement (1)
- Dduplex stainless steel (1)
- Debys-Waller-Factor (1)
- Deep learning (1)
- Defect detection (1)
- Defect prediction (1)
- Defekte Eigenspannung (1)
- Deformation (1)
- Deformed geometry (1)
- Dehydrogenation heat treatment (1)
- Dendrite growth (1)
- Density measurement (1)
- Dental materials (1)
- Deposition rate (1)
- Design for Additive Manufacturing (DfAM) (1)
- Design of experiments (1)
- Determinación Kth intrínseco (1)
- Diaspore (1)
- Die-cast aluminum (1)
- Die-casted aluminum (1)
- Diffraction Elastic Constants (1)
- Diffraction-elastic constants (1)
- Diffusion/diffusivity (1)
- Digital Image Correlation (1)
- Digital Image Correlation (DIC) (1)
- Digital Twin (1)
- Digital image correlation (DIC) (1)
- Digitale Bildkorrelation (DIC) (1)
- Digitale Qualitätssicherung (1)
- Digitization (1)
- Direct laser deposition (1)
- Directed Energy Depositio (1)
- Dislocation density (1)
- Dispersive XAS (1)
- Displacement (1)
- Dissimilar friction stir welding (1)
- Dissimilar joints (1)
- Dissimilar materials (1)
- Distortion simulation (1)
- Distortion upon baseplate removal (1)
- Ditigtal image correlation (1)
- Dritter Körper (1)
- Druckanschwingen (1)
- Ductile Cast Iron (1)
- Ductile iron (1)
- Duktiles Gusseisen (1)
- Duktilität (1)
- Dwell-time (1)
- Dynamic Fracture Toughness (1)
- Dynamic fracture toughness (1)
- Dynamic load (1)
- Dünnschichten (1)
- EA4T railway axle steel (1)
- EA4T steel (1)
- EDS (1)
- EDXRD (1)
- EN AW-2618A (1)
- Edge effects (1)
- Editorial Board (1)
- Effect of scanning strategies (1)
- Efficient modelling (1)
- Eigensapnnungen (1)
- Eigenspannungsmessung (1)
- Eindringprüfung (1)
- Einflussfaktoren (1)
- Einflussfaktoren auf Rissfortschrittsdaten (1)
- Einschlüsse (1)
- Elastic follow-up (1)
- Elastic-plastic fracture mechanics (1)
- Electrical connectors (1)
- Electro-plated nickel coatings (1)
- Electro-thermomechnical model (1)
- Electrochemical corrosion (1)
- Electrode geometry (1)
- Electroless Ni-P (1)
- Electromagnetic (1)
- Electromagnetic field (1)
- Electromagnetic influence (1)
- Electromagnetic stirring (1)
- Electromagnetic supported degassing (1)
- Electromagnetic weld pool support system (1)
- Electron backscatter diffraction (EBSD) (1)
- Electron beam (1)
- Electron microscopy (1)
- Elektonenstrahlschweißen (1)
- Elektromagnetische Badstütze (1)
- Elektromagnetische Porenreduktion (1)
- Elektromagnetische Schmelzbadstütze (1)
- Elektromagnetsiche Schmelzbadbeeinflussung (1)
- Elemenet transport (1)
- Element distribution (1)
- Ellipsometry (1)
- Emisssivity (1)
- Energetic reference parameter (1)
- Energieerzeugung (1)
- Energy parameters of the arc (1)
- Engine oil design (1)
- Engine oil testing (1)
- Entwicklung (1)
- Environment (1)
- Environmental effect (1)
- Environmental effects (1)
- Environmental impact categories (1)
- Equivalent stress concentration factors (1)
- Equivalent volumetric heat source (1)
- Ermüdungsfestigkeit (1)
- Ermüdungslebensdauer (1)
- Ermüdungsriss (1)
- Ermüdungsrissfortschritt (1)
- Erneuerbare Energien (1)
- Error sources analysis (1)
- Ersatzgeometrie (1)
- Erstarrungsrisse (1)
- FAIR data (1)
- FAT class (1)
- FAT class approach (1)
- FSW (1)
- Fabricación Aditiva (1)
- Fail-safe design (1)
- Fast single pulse response (1)
- Fatigue Crack Growth (1)
- Fatigue Limit (1)
- Fatigue S-N curve (1)
- Fatigue assessment (1)
- Fatigue crack initiation (1)
- Fatigue crack propagation stages (1)
- Fatigue crack propagation stagesdefects (1)
- Fatigue damage (1)
- Fatigue fracture (1)
- Fatigue lifetime prediction (1)
- Fatigue loading (1)
- Fatigue propagation threshold (1)
- Fatigue strength and life (1)
- Fatigue tests (1)
- Fatigue threshold (1)
- Feinkornbaustähle (1)
- Femtosecond (1)
- Femtosecond laser ablation (1)
- Ferngasleitung (1)
- Ferrit (1)
- Ferrite (1)
- Ferritic Alloys (1)
- Ferritic spheroidal (1)
- Ferritic steels (1)
- Ferritic welding electrode (1)
- Ferroelectricity/ferroelectric materials (1)
- Ferromagnetic steels (1)
- Fertigungstechnologie (1)
- Festigkeit (1)
- Fiber laser (1)
- Filler material (1)
- Filler metal modification (1)
- Filler wire (1)
- Fine-grained Steel (1)
- Finish milling (1)
- Finite Element Analysis (1)
- Finite Element Method (1)
- Finite element (FE) (1)
- Finite element method (FEM) (1)
- Finite-difference time-domain calculations (FDTD) (1)
- Fit4AM (1)
- Flange width (1)
- Flank (1)
- Flaw assessment procedures (1)
- Flaw detection (1)
- Flaw interaction (1)
- Flüssigmetallversprödung (1)
- Force distance curves (1)
- Formation (1)
- Formgedächtnislegierungen (1)
- Forschungsprojekt (1)
- Fracture assessment (1)
- Frequency domain (1)
- Fresnel reflection (1)
- Fretting (1)
- Fräsbearbeitung (1)
- Functionally Graded Materials (1)
- Funktionally Graded Material (1)
- Fusion Zone (1)
- Fusion welding (1)
- Fusion zone (1)
- Fusion zone profile (1)
- Fusion zone size (1)
- Fusion zone, nickel alloys (1)
- Fügequalität (1)
- Füllgradregelung (1)
- GMAwelding (1)
- GMR (1)
- GMR sensors (1)
- GTAW (1)
- Galvanized steel (1)
- Gap bridging (1)
- Gas analytic (1)
- Gas shielded arc welding (1)
- Gas storage (1)
- General analytical solutions (1)
- Gesetz von Archard (1)
- Geteilte Infrastruktur (1)
- Gleeble (1)
- Gleeble testing (1)
- Global stability criterion (1)
- Glow-discharge optical emission spectroscopy (1)
- Grade S960QL steel (1)
- Gradient-enhanced damage (1)
- Grain growth (1)
- Grain structure (1)
- Graphene oxide (1)
- Graphite cast iron (1)
- Graphite modules (1)
- Graphitentartung (1)
- Grease (1)
- Grease lubrication (1)
- Green Deal (1)
- Greens function method (1)
- Gusseisen mit Kugelgraphit GJS (1)
- H2-Abbau (1)
- H2Safety@BAM (1)
- HAZ (1)
- HCF (1)
- HT22 (1)
- Handbook (1)
- Hard metal (1)
- Hard metals (1)
- Hard tungsten (1)
- Hard turning (1)
- Hard-turning (1)
- Hardly separable problem (1)
- Hastelloy X (1)
- Haynes 282 (1)
- HeLa (1)
- Heat Input (1)
- Heat affected zone (1)
- Heat flow (1)
- Heat generation (1)
- Heat input (1)
- Heat recovery (1)
- Heat saturation function (1)
- Heat source models (1)
- Heating rate (1)
- Heißzug (1)
- High Temperature Corrosion (1)
- High brightness (1)
- High power (1)
- High process speeds (1)
- High speed laser cladding (1)
- High strength AlMgSi aluminium alloys (1)
- High strength fine grained structural steels (1)
- High temperature alloys (1)
- High temperature corrosion (1)
- High-Power Welding (1)
- High-entropy alloys (1)
- High-power fibre laser (1)
- High-pressure hydrogen environment (1)
- High-stength aluminium alloys (1)
- High-strength (1)
- High-strength filler metals (1)
- High-strength fine-grained steels (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 (1)
- Hochdruck (1)
- Hochentropiewerkstoff (1)
- Hochfeste Stähle (1)
- Hochleistungslaserstrahlschweißen (1)
- Hohlprofilknoten (1)
- Hokz-Holz-Kontakte (1)
- Hold time (1)
- Hollow specimen (1)
- Hollow tensile specimen (1)
- Holz-Holz-Kontakte (1)
- Hot Cracking (1)
- Hot cracking test (1)
- Hot tensile test (1)
- Hot working tool steel (1)
- Humidity (1)
- Hybrid Laser-Arc Welding (1)
- Hybrid part (1)
- Hybrid-laser-arc welding (1)
- Hybridschweißen (1)
- Hydraulic reactivity (1)
- Hydrogen Embrittlement (1)
- Hydrogen assisted stress corrosion cracking (1)
- Hydrogen concentration (1)
- Hydrogen degradation (1)
- Hydrogen dependent mechanical properties (1)
- Hydrogen environment (1)
- Hydrogen measurement (1)
- Hydrogen methane (1)
- Hydrogen trapping (1)
- Hydrogen-containing hot gas (1)
- Hydrophobin (1)
- Hydrostatic and arc pressure exceed the Laplace pressure (1)
- I-TRIBOMAT (1)
- I-Träger (1)
- IBESS (1)
- IBESS Approach (1)
- IBESS model for short cracks (1)
- IBESS-Prozedur (1)
- IN 718 (1)
- IN718 PBF-LB/M (1)
- IN725 (1)
- IR-Spektroskopie (1)
- IR-spectroscopy (1)
- Image registration (1)
- Impact absorbed energy (1)
- Impact damage (1)
- Imperfektion (1)
- Implant failures (1)
- Implant-supported prostheses (1)
- Implant-test (1)
- Implants (1)
- Implementierung (1)
- In situ LIBS (1)
- In situ Monitoring (1)
- In situ measurement, (1)
- In-Situ Testing (1)
- In-service (1)
- In-situ Process Monitoring (1)
- In-situ Prozessüberwachung (1)
- In-situ diffraction (1)
- In-situ thermography (1)
- In718 (1)
- Inclusion cluster (1)
- Inclusion size (1)
- Inclusions (1)
- Inconel 625 (1)
- Inconel 939 (1)
- Industrial and Manufacturing Engineering (1)
- Infractstructure (1)
- Infrared Thermography (1)
- Initial crack size (1)
- Inserts (1)
- Instumented indentation test (1)
- Integrated alignment features (1)
- Intelligent tribological material characterization (1)
- Intelligente tribologische Werkstoffcharakterisierung (1)
- Inter-layer time (1)
- Interfacial stability (1)
- Intergranular cracking (1)
- Interoperability (1)
- Interrupted milling (1)
- Intrinsic fatigue crack propagation threshold (1)
- Intrinsic fatigue propagation threshold (1)
- Iron (1)
- Iron aluminides (1)
- Iron-based alloys (1)
- J-Integral (1)
- Joining (1)
- Joining process (1)
- Joining technology (1)
- Journal (1)
- KI (1)
- Kaltriss und Schweißen (1)
- Kaltrissbildung (1)
- Kaltzähe Stähle (1)
- Karosseriebau (1)
- Keramikfeder (1)
- Kerbschlagbiegeversuch (1)
- Kerbschlagbiegeversuch, Untermaßproben, Normalproben, Skalierung von Ergebnissen (1)
- Kerbspannungskonzept (1)
- Keyhole stability (1)
- Keyhole welding (1)
- Kitagawa-Takahashi (K-T) diagram (1)
- Kl (1)
- Knotenweise Zwangsbedingungen (1)
- Kohlenstoffschichten (1)
- Kokillenguss (1)
- Komponenten (1)
- Kontamination von H2 (1)
- Korrosion (1)
- Kriechen (1)
- Kritische Last (1)
- Kryogene Temperatur (1)
- Kurz- und Langriss-Ermüdungsbruchmechanik (1)
- Kurzrissbruchmechanik (1)
- Kurzrisswachstum (1)
- Kurzzeitfestigkeit (1)
- Körperschall (1)
- Künstliche Neuronale Netze (1)
- L-PBF IN718 material (1)
- LA-ICP-SFMS (1)
- LCF region (1)
- LTT filler material (1)
- LTT filler metal (1)
- LTT-Legierung (1)
- LTT-Zusatzwerkstoff (1)
- LW (1)
- Lab-to-field up-scaling (1)
- Lab-to-field upscaling (1)
- Laboratory X-ray diffraction (1)
- Lamé curves (1)
- Lamé curves approximation (1)
- Large scale test (1)
- Laser Implantation (1)
- Laser Metal Deposition; Laser Beam Welding; Duplex; Stainless Steel (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser Powder Bed Fusion (PBF-LB/M) (1)
- Laser Powder Bed Fusion (PBF-LB/M, L-PBF) (1)
- Laser Powder Bed fusion (1)
- Laser Welding (LW) (1)
- Laser cladding (1)
- Laser cutting (1)
- Laser keyhole welding (1)
- Laser melting (1)
- Laser powder-based directed energy deposition (1)
- Laser processing (1)
- Laser surface texturing (1)
- Laser surfacing (1)
- Laser- und Lichtbogenenergie (1)
- Laser-Pulver-Auftragschweißen (LPA) (1)
- Laser-Pulver-Auftragschweißen; Laserstrahlschweißen, Duplex, Pufferschichten (1)
- Laser-based additive manufacturing (1)
- Laser-based powder bed fusion of metal (PBF-LB/M) (1)
- Laser-beam welding, (1)
- Laser-cutting (1)
- Laser-hybrid welding (1)
- Laser-induced periodic surface structures, LIPSS (1)
- Laser-induzierte periodische Oberflächenstrukturen (1)
- Laser-metal-depositon (1)
- Laser-plasma hybrid (1)
- Laserauftragschweißen (1)
- Laserdispergieren (1)
- Laserstrahl-Hybridschweißen (1)
- Laserstrahlhybridschweißen (1)
- Lattice structure (1)
- Lead-free ceramics (1)
- Leichtbauprinzipien (1)
- Life Cycle Assessment (LCA) Fusion welding (1)
- Life Cycle Assessment (LCA) Impact categories (1)
- Life Cycle Assessment (LCA) Schweißprozesse (1)
- Life Cycle Assessment (LCA) Umweltwirkungen (1)
- Life cycle assessment (1)
- Life prediction (1)
- Lifetime (1)
- Ligamentplastifizierung (1)
- Lightweight principles (1)
- Liquid Metal Embrittlement (LME) (1)
- Liquid hydrogen (1)
- Liquid phase sintering (1)
- Local Weld Geometry (1)
- Local critical strain (1)
- Local fatigue spproaches (1)
- Localized Laser Dispersing (1)
- Loch- u. Spaltkorrosion (1)
- Lorentz force (1)
- Lorentz forces (1)
- Low Temperature Toughness (1)
- Low Transformation Temperature (1)
- Low carbon steel (1)
- Low cycle fatigue (1)
- Low feed rates (1)
- Low heat input Gma welding (1)
- Low transformation temperature (1)
- Low transformation temperature filler materials (1)
- Low-Cycle-Fatigue (1)
- Low-cycle fatigue (1)
- L‐PBF (1)
- MAG (1)
- MAG Prozesssteuerung (1)
- MAG-Welding (1)
- MANUFACT (1)
- MIC (1)
- MWIR (1)
- Machinability (1)
- Machine Learning (1)
- Machine learning (1)
- Machine vision (1)
- Magnesium Alloy (1)
- Magnesium alloy (1)
- Magnetic bath support (1)
- Magnetic stray field (1)
- Magnetohydrodynamics (MHD) (1)
- Magnettechnik (1)
- Manufact (1)
- Margin design (1)
- Maritime Components (1)
- Master Curve (1)
- Master Curve Method (1)
- MatCom (1)
- Matching ferritic filler metal (1)
- Material modeling (1)
- Materialmodellierung (1)
- Materialprüfung (1)
- Materials database (1)
- Materialschaedigung (1)
- Materialschädigung (1)
- Materialuntersuchungen (1)
- Mechanical Properties (1)
- Mechanical anisotropy (1)
- Mechanical properties of the joints (1)
- Mechanical property (1)
- Mechanical-technological properties (1)
- Mechanisch technologische Kennwerte (1)
- Mecánica de Fractura (1)
- Melt pool behaviour (1)
- Melt pool defects (1)
- Melt pool depth (1)
- Melt-pool-monitoring (1)
- Melting (1)
- Messung (1)
- Metal Magnetic Memory (1)
- Metal additive manufacturing (MAM) (1)
- Metal matrix composite (1)
- Metal vapor (1)
- Metallic components (1)
- Metallic vapour plume (1)
- Metals (1)
- Methan (1)
- Micro computed tomography (1)
- Microalloyed steels (1)
- Microcracking (1)
- Microfocus X-ray computer tomography (μCT) (1)
- Micromechnical properties (1)
- Microstructure Tensile strength (1)
- Microstructure characterisation (1)
- Microtribology (1)
- Mikro-Computertomographie (1)
- Mikroorganismen (1)
- Mikrostrukturentwicklung (1)
- Mild steels (1)
- Minimum Waiting Time (1)
- Minimum waiting time (1)
- Mining head gear (1)
- Mis-match (1)
- Misalignment of edges (1)
- Mischverbindung (1)
- Misfit (1)
- Mismatch (1)
- Mittelrippendefekt (1)
- Mixing behavior (1)
- Mobility (1)
- Mock-up (1)
- Model order reduction (1)
- Modeling (1)
- Modellierung (1)
- Modelling studies (1)
- Modified Varestraint-/Transvarestraint test (1)
- Modifizierter Sprühlichtbogen (1)
- ModuH2Pipe@BAM (1)
- Molybdenum carbide (1)
- Molybdenum disulphide (1)
- Monotonic and cyclic crack driving force (1)
- Monte-Carlo simulation (1)
- Morphology control (1)
- Multi - physical modeling (1)
- Multi-materials joining (1)
- Multi-pass welding (1)
- Multi-principal element alloy (1)
- Multielement-Legierung (1)
- Multiple crack initiation (1)
- Multiple crack propagation (1)
- Multiple cracking (1)
- Multiple-principal element alloy (1)
- NIR (1)
- Nachschlagewerk (1)
- Nahtgeometrie (1)
- Nanoadditive (1)
- Nanotribology (1)
- Nanowear (1)
- Narrow gap welding (1)
- Narrow-gap welding (1)
- Natural silver wires (1)
- NbC cermets (1)
- Near-surface X-ray diffraction (1)
- Near-threshold regime (1)
- Necking (1)
- Neural networks (1)
- Neutron Imaging (1)
- Neutron and X-ray diffraction (1)
- Neutron tomography (1)
- Neutronbeugungsverfahren (1)
- Neutronenbeugung (1)
- Neutronendiffraktion (1)
- Neutronenradiographie (1)
- Neutronentomographie (1)
- New technologies (1)
- Ni-based austenitic filler metal (1)
- Ni-based austenitic welding electrode (1)
- Ni-based superalloy (1)
- NiTi-Legierungen (1)
- Nickel-based superalloy (1)
- Nickel-based superalloys (1)
- Nickel-iron-alloy (1)
- Nickelbasis-Superlegierungen (1)
- Niobcarbid (1)
- Niobcarbid (NbC) (1)
- Niobium alloying (1)
- Node-release (1)
- Non-destructive Materials (1)
- Non-destructive testing (1)
- Non-sharp defects (1)
- Normalproben (1)
- Normen (1)
- Normung (1)
- Normung Roadmap (1)
- Notch stress approach (1)
- Novel metrology (1)
- Novel optical metrology (1)
- Nuclear reactor systems (1)
- Numerical analysis (1)
- Numerical investigation (1)
- Numerical simulations (1)
- Numerical welding simulation (1)
- Numerical welding simulations (1)
- Numerische ISmulation (1)
- Oberflächenmessung (1)
- Oberflächenmodifikation (1)
- Oberflächenschädigung (1)
- Oberflächenstrukturierung (1)
- Offshore Windenergie (1)
- Offshore steel grade (1)
- Offshore steels (1)
- Offshore wind turbine (1)
- Offshore wind turbines (1)
- Online monitoring (1)
- Open Data (1)
- Open source (1)
- OpenScience (1)
- Optical Emission Spectroscopy (1)
- Optical emission spectroscopy (1)
- Optical measurement technique (1)
- Optical measurment technique (1)
- Optische Emissionsspektroskopie (1)
- Optische Emissionsspektroskopie (OES) (1)
- Oscillating ball-on-disc test (1)
- Oszillierendes Magnetfeld (1)
- Overview (1)
- Oxide-induced crack closure (1)
- PAEKs (1)
- PBF/LB (1)
- PCA (1)
- PEAK (1)
- PTFE composite (1)
- PTFE composites (1)
- Parabolic flight (1)
- Partial penetration laser hybrid welding (1)
- Partial penetration welding (1)
- Particle erosion (1)
- Particle transfer (1)
- Peak stress method (1)
- Peak stress method (PSM) (1)
- Pearlitic microstructure (1)
- Permeation (1)
- Perspektiven (1)
- Phase field method (1)
- Phase field modeling (1)
- Phasenumwandlung (1)
- Photogrammetry (1)
- Photooxidation (1)
- Physical vapor deposition (PVD) (1)
- Piezoresistive (1)
- Piezoresistive cantilever (1)
- Pipe Welding (1)
- Pipe weld preparation (1)
- Pipeline steel of grade X120 (1)
- Plane crystalization (1)
- Plasma cutting (1)
- Plasma transferred arc welding (1)
- Plasma-cut samples (1)
- Plasma-transferred-arc (1)
- Plastic material flow (1)
- Plume heating (1)
- Poly(acrylic acid) (1)
- Polyethylene (1)
- Polymer (1)
- Polymere (1)
- Polymerkomposite (1)
- Pool dimensions (1)
- Pore formation (1)
- Poren (1)
- Porenreduktion (1)
- Porosity reduction (1)
- Porosität (1)
- Post Weld Heat Treatment (PWHT) (1)
- Post processing heat treatment (1)
- Potential drop technique (1)
- Potentiodynamic measurements (1)
- Powder Analysis (1)
- Powder Bed Fusion of Metals with Laser Beams (1)
- Ppreheating temperature (1)
- Precipitation hardening aluminum alloys (1)
- Preciptiates (1)
- Predicción vida a fatiga (1)
- Preheatin (1)
- Preheating temperature (1)
- Pressure-dependent solubility (1)
- Prevention (1)
- Primär- und Sekundärspannungen (1)
- Principal Component Analysis (1)
- Principal stress (1)
- Probabilistic Assessment (1)
- Probabilistic assessment (1)
- Probengeometrie (1)
- Probetas miniatura (1)
- Process Chain Integration (1)
- Process Monitoring (1)
- Process Simulation (1)
- Process development (1)
- Processing (1)
- Product standard (1)
- Profilvermessung (1)
- Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten (1)
- Projektbegleitender Ausschuss (1)
- Proper generalized decomposition (1)
- Prostheses (1)
- Prozesse (1)
- Prozessregelung (1)
- Prozesssimulation (1)
- Prüfung (1)
- Pulse electric current sintering (1)
- Pulverbettbasiertes Laserstrahlschmelzen (1)
- QI Digital (1)
- Quality-X (1)
- Qualität (1)
- Quantitative bioimaging (1)
- R-curve analysis (1)
- Radiography (1)
- Radiological inspections (1)
- Rail tracks (1)
- Rauheit (1)
- Ray teacing (1)
- Ray-tracing methods (1)
- Reactor conditions (1)
- Reciprocating sliding (1)
- Reciprocating sliding wear (1)
- Recomendaciones procedimiento de ensayo (1)
- Recycling (1)
- Reduced Order Model (1)
- Reduced order modelling (1)
- Reference data (1)
- Reference standards (1)
- Refraction (1)
- Regelwerke (1)
- Reibungsreduktion (1)
- Relative humidity (1)
- Reliability (1)
- Repair of gas turbine blades (1)
- Representative Specimens (1)
- Representative material properties (1)
- Repräsentative Werkstoffeigenschaften (1)
- Research and Development (1)
- Residual lifetime (1)
- Residual stress in AM (1)
- Residual stress state (1)
- Resistance Spot Welding (RSW) (1)
- Restlebensdauerprognose (1)
- Retained Austenite (1)
- Ringversuch (1)
- Ripples (1)
- Riss (1)
- Rissausbreitung (1)
- Rissausbreitungsstadien (1)
- Rissbildung (1)
- Rissfortschrittsdaten (1)
- Rissschließfunktion (1)
- Rissschließphenomen (1)
- Rissspitzenbelastung (1)
- Risswachstum (1)
- Risswiderstand (1)
- Roughness (1)
- Rundnähte (1)
- Röntgenradiographie (1)
- S-N diagram (1)
- S-N probabilistic field (1)
- S-Phase (1)
- SLM printed plasma torch (1)
- SPS (1)
- SS316L alloy (1)
- SWIR (1)
- SWIR thermography (1)
- Safety (1)
- Sample random results (1)
- Scan strategies (1)
- Scan strategy influence (1)
- Schadenstolerante Bauteilauslegung, (1)
- Schadenstolerante Bauteilauslegung, Restlebensdauer, intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung (1)
- Schallemissionsanalyse (1)
- Schallemissionsanalyse (SEA) (1)
- Schallemmission (1)
- Schlichtfräsen (1)
- Schmelzbadstütze (1)
- Schmiermittel (1)
- Schmierstoffe (1)
- Schmierung (1)
- Schutzgas (1)
- Schweißdatenmanagement (1)
- Schweißeigenspannungs-Tiefen-Profile (1)
- Schweißen von kaltzähen Stählen (1)
- Schweißnahtgeometrie (1)
- Schweißprozesse (1)
- Schweißprozessparameter (1)
- Schweißsimulation (1)
- Schweißstruktursimulation (1)
- Schweißtechnik (1)
- Schweißunregelmäßigkeiten (1)
- Schweißverbindung (1)
- Scratches (1)
- Secondary heat source (1)
- Secondary stresses (1)
- Selective laser beam melting (1)
- Sensor (1)
- Sensorik (1)
- Shared infrastruture (1)
- Shielding gas (1)
- Shipbuilding steel (1)
- Short Crack Propagation (1)
- Short crack Propagation (1)
- Short crack propagation (1)
- Shrinkages (1)
- Sicherheit (1)
- Silicon nitride (1)
- SimCoLas (1)
- Single asperity (1)
- Single asperity contact (1)
- Single cell (1)
- Single-pass welding (1)
- Skalierung von Ergebnissen (1)
- Sliding friction (1)
- Slidng wear (1)
- Slip-rolling (1)
- Slow Strain Rate Testing (1)
- Small scale testing (1)
- Snergiedispersive Röntgendiffraktion (1)
- Solidification Cracking (1)
- Solidification behaviour (1)
- Spannung (1)
- Spannungs-Dehnungs-Verhalten (1)
- Spannungsrisskorrosion (1)
- Spark plasma sintering (1)
- Split Hopkinson bar (1)
- Spreading (1)
- Stabilität von Eigenspannungen (1)
- Stahllegierungen (1)
- Stainless steel (1)
- Staircase method (1)
- Standard test piece (1)
- Standardisation (1)
- Standardization (1)
- Static load (1)
- Statistical analysis (1)
- Statistical distributions (1)
- Statistics (1)
- Statistische Versuchsplanung (1)
- Steady-state weld pool (1)
- Steel and Al (1)
- Steelmaking slag (1)
- Stiffness (1)
- Stift-Scheibe-Anordnung (1)
- Stochastic sample functions (1)
- Strain fields prediction (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)
- Stretch-Zone (1)
- Structural integrity assessment procedure (1)
- Structural steel (1)
- Structure analysis (1)
- Sub-oxide (1)
- Sub-size test piece (1)
- Sulphidation (1)
- Superalloy (1)
- Superconducting magnets (1)
- Supermartensit (1)
- Supermartensitic steel (1)
- Supermatensitischer Stahl (1)
- Support configurations (1)
- Support structures (1)
- Supportless (1)
- Surface (1)
- Surface Integrity (1)
- Surface cracks (1)
- Surface preparation (1)
- Surface structures (1)
- Surface temperature (1)
- Synchrotron X-ray diffraction (1)
- Synchrotron diffraction (1)
- Synchrotron radiation (1)
- Synchrotronbeugung (1)
- Systematische Schadensanalysen, Prozeduren (1)
- T24 / 7CrMoVTiB10-10 (1)
- TEKKEN test (1)
- TEM (1)
- TIG (1)
- TIG-welding (1)
- TaC (1)
- Tantalum carbide (1)
- Technical crack detection (1)
- Technologies (1)
- Temperature behavior (1)
- Temperature dependence (1)
- Temperature dependent absorption (1)
- Temperatureinfluss (1)
- Tensile loading (1)
- Tensile resistance spot welding experiment (1)
- Test procedure (1)
- Test standard (1)
- Testing (1)
- Testing parameters (1)
- Themral cycles (1)
- Thermal analysis (1)
- Thermal conductivity device (1)
- Thermal-desorption spectroscopy (1)
- Thermal-fluid-structure coupling model (1)
- Thermo-fluid dynamics (1)
- Thermodynamic modelling (1)
- Thermograhy (1)
- Thermomechanische Eigenschaften (1)
- Thick materials (1)
- Thick plate welding (1)
- Thick plates (1)
- Thick steel plates (1)
- Thick-Walled Steel (1)
- Thick-walled (1)
- Thick-walled Structures (1)
- Thick-walled steels (1)
- Thick-walled structures (1)
- Thin steel plates (1)
- Thoughness (1)
- Three-dimensional crystallization (1)
- Threshold regime (1)
- TiC (1)
- TiN (1)
- Time over threshold (1)
- Time-of-Flight secondary ion mass spectrometry (1)
- Titanaluminid (1)
- Titandiborid (1)
- Titanium carbide (1)
- Tomography (1)
- Tool (1)
- Tool service life (1)
- Tool-workpiece interaction (1)
- Toughening mechanisms (1)
- Traglastverhalten (1)
- Transformable steels (1)
- Transient stresses (1)
- Transition temperature (1)
- Tribo-Analytik (1)
- Tribo-analytics (1)
- Tribo-film (1)
- Tribo-tests (1)
- Tribological behavior (1)
- Tribological data (1)
- Tribologische Datenbank (1)
- Tribologsches Charakterisierungsdienste (1)
- Tribometer (1)
- Tribooxidation (1)
- Triobology (1)
- Trockenreibung (1)
- Trägergasheißextraktion (1)
- Tubular X-joints (1)
- Tubular joints (1)
- Tungsten carbide (WC) (1)
- Turbine components (1)
- Two-dimensional solidification (1)
- Two-run welding technique (1)
- UHMWPE (1)
- UP Schweißen (1)
- UV radiation (1)
- UV-blocker addition (1)
- Ultra-high strength steel (1)
- Ultraschallunterstützter Fräsprozess (1)
- Ultrasonic Assisted Machining (1)
- Ultrasonic assited machining (1)
- Unterirdische Speicher (1)
- Untermaßproben (1)
- Unterpulverschweißen (1)
- V-notch impact toughness (1)
- Vakuum (1)
- Vapor recondensation (1)
- Varestraint Test (1)
- Vernetzte Produktion (1)
- Verschleiß-Map (1)
- Verschleißkoeffizient (1)
- Verschleißreduktion (1)
- Verschleißschutz (1)
- Versetzungsstrukturen (1)
- Verzug (1)
- Viskosität (1)
- Void defect formation mechanism (1)
- WAAM Ti-6Al-4V (1)
- WC (1)
- WEBAM (1)
- WIG (1)
- WIG Schweißen (1)
- WRC 92 (1)
- Waiting time (1)
- Warmfeste Stähle (1)
- Warmfester Stahl (1)
- Wasserstoffbindungsverhalten (1)
- Wasserstoffdiffusion (1)
- Wasserstoffgradient (1)
- Wasserstoffkonzentration (1)
- Wasserstofflagerung (1)
- Wasserstoffunterstützte Kaltrissbildung (1)
- Wear mechanism (1)
- Wear mechanisms (1)
- Wear particles (1)
- Wear rate (1)
- Weathering tests (1)
- Weld end crater (1)
- Weld imperfections (1)
- Weld joint (1)
- Weld metal cracking (1)
- Weld pool modeling (1)
- Weld root (1)
- Weld seam geometry (1)
- Weld toe geometry (1)
- Weldability (1)
- Welded joint (1)
- Welding Current (1)
- Welding Simulation (1)
- Welding parameter (1)
- Welding process simulation (1)
- Welding processing influences (1)
- Weldx (1)
- Werkstatt (1)
- Werkstoff (1)
- Werkstoffdatenbank (1)
- Werkstoffe (1)
- Werkzeug (1)
- Werkzeuglebensdauer (1)
- Werkzeugmodifikation (1)
- Werstoff- und geometrische Imperfektion (1)
- White light interferometry (1)
- Widerstandpunktschweißen (1)
- Wind Energy (1)
- Windkraftanlagen (1)
- Wineglass shape (1)
- Wire Electron Beam Additive Manufacturing (1)
- Wire feed laser beam welding (1)
- Wire-based additive manufacturing (1)
- Wärmbehandlung (1)
- Wärmeakkumulation (1)
- X-ray and neutron diffraction (1)
- X-ray computed tomography (1)
- X-ray computed tomography (XCT) (1)
- X-ray refraction (1)
- X153CrMoV12 (1)
- X8Ni9 (1)
- XRF (1)
- Year in Review (1)
- Zero wear (1)
- Zerspanungswerkzeug (1)
- Zinc (1)
- Zinkbeschichtung (1)
- ZnO films (1)
- ZnO nanorods Nanocrystalline (1)
- Zugversuch (1)
- Zyklische Belastung (1)
- a-C:H (1)
- abtragende Glasbearbeitung (1)
- additive manufacturing (1)
- arbidic austempered ductile iron (1)
- carrier gas hot extraction (1)
- cold cracking safety (1)
- contact resonance (1)
- contour method (1)
- deposition welding (1)
- digital image correlation (1)
- digitalisation (1)
- dual phase steel (1)
- duplex stainless steel (1)
- fatigue crack growth (1)
- high-resolution camera (1)
- high-strength steel (1)
- highspeed plasma laser cladding (1)
- hochfester Stahl (1)
- hybrid repair (1)
- i-Tribomat (1)
- infrared Thermography (1)
- keyhole dynamics (1)
- laser energy absorption (1)
- laser energy distribution (1)
- laser hybrid welding (1)
- miniature specimens; FCGR curves; intrinsic threshold (1)
- molten pool (1)
- neutron diffraction (1)
- numerical modeling (1)
- pL-droplets (1)
- position detection (1)
- powder bed fusion of metals utilizing a laser beam (1)
- relative Luftfeuchtigkeit (1)
- residual stress analysis (1)
- resistance spot welding (1)
- thermal cycles (1)
- thick plate welding (1)
- µ-gravity (1)
- µCT-analysis (1)
- Äquivalente Spannungskonzentrationsfaktoren (1)
- Äquivalente Wärmequelle (1)
- Ökonomische und ökologische Vorteile (1)
- Überblick (1)
- μCT (1)
- ГИДРОДИНАМИКА (1)
- КОНВЕКЦИЯ (1)
- ЛАЗЕРНАЯ СВАРКА (1)
- МЕТОД КОНЕЧНЫХ ЭЛЕМЕНТОВ (1)
- СВАРОЧНАЯ ВАННА (1)
- ТЕМПЕРАТУРНОЕ ПОЛЕ (1)
- ТЕПЛОПРОВОДНОСТЬ (1)
- ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ (1)
- кратер шва (1)
- кристаллизация, (1)
- плавление, (1)
- сварочная ванна (1)
- температурное поле (1)
- функция теплонасыщения (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (1281) (entfernen)
Paper des Monats
- ja (8)
Hybrid laser-arc welding of thick-walled ferromagnetic steels with electromagnetic weld pool support
(2018)
The hybrid laser-arc welding (HLAW) process provides many advantages over laser welding and arc welding alone, such as high welding speed, gap bridgeability, and deep penetration. The developments in hybrid laser-arc welding technology using modern high-power lasers allow single-pass welding of thick materials. This technology can be used for the heavy metal industries such as shipbuilding, power plant fabrication, and line-pipe manufacturing. The obvious problem for single-pass welding is the growth of the hydrostatic pressure with increasing thickness of materials leading to drop-out of molten metal. This phenomenon is aggravated at slow welding velocities because of increasing weld seam width followed by a decrease of Laplace pressure compensating the hydrostatic pressure. Therefore, weld pool support is necessary by welding of thick materials with slow welding velocities. The innovative electromagnetic weld pool support system is contactless and has been used successfully for laser beam welding of aluminum alloys and austenitic and ferromagnetic steels. The support system is based on generating Lorentz forces within the weld pool. These are produced by an oscillating magnetic field orientated perpendicular to the welding direction. The electromagnetic weld pool support facilitates a decrease in the welding speed without a sagging and drop-out of the melt thus eliminating the limitations of weldable material thickness.
The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2Gpositions.
Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx.
20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc.
Diese Arbeit zeigt erstmals die Anwendung einer elektromagnetischen Schmelzbadsicherung beim einlagigen MSG-Schweißen von dickwandigen Stählen. Die innovativen Entwicklungen im Bereich des Lichtbogenschweißverfahrens ermöglichen eine Erhöhung der Abschmelzleistung, um die Einschweißtiefe zu steigern. Somit kann die Lagenanzahl reduziert und die Produktivität gesteigert werden. Allerdings besteht insbesondere beim einlagigen Schweißen von dickwandigen Bauteilen in PA-Position ein erhöhtes Risiko für das gravitationsbedingte Austropfen der Schmelze an der Wurzel. Zur Verhinderung werden Badsicherungen eingesetzt, die mechanisch angebracht und nach dem Schweißen entfernt werden müssen, was zeit- und kostenintensiv ist.
Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadsicherung wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Sie wirkt kontaktlos, was im Gegensatz zu herkömmlichen Badsicherungen vorteilhaft ist, so dass auf eine zeit- und kostenintensive Nachbearbeitung der Schweißnahtwurzel verzichtet werden kann. Das auf extern angelegten oszillierenden Magnetfeldern beruhende Verfahren wird dabei unterhalb des zu schweißenden Bauteils positioniert. Die Magnetfeldlinien sind quer zur Schweißrichtung ausgerichtet, sodass längs zur Schweißrichtung Wirbelströme im Werkstück und eine stets nach oben gerichtete Lorentzkraft generiert werden. Mit Hilfe der elektromagnetischen Badsicherung konnten beim einlagigen MSG-Schweißen von bis zu 10 mm dicken Blechen die Tropfenbildung vermieden werden. Die innovative Technologie ermöglicht es, dickwandige Bauteile einlagig zu schweißen und reduziert die Nachbearbeitungszeiten und -kosten deutlich.
The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm.
Die technischen Entwicklungen in der Lasertechnologie in den letzten Jahrzehnten haben eine neue Generation von Hochleistungslasersystemen im Leistungsbereich bis zu 100 kW auf den Markt gebracht. Dennoch ist die industrielle Anwendung des Hochleistungslaserstrahlschweißens auf bis zu 15 mm dicke Bleche beschränkt. Mögliche Ursachen der Einschränkungen des Verfahrens sind z.B. die Sensibilität des Verfahrens auf Fertigungstoleranzen wie Spalt und Kantenversatz, die erhöhte Tropfenbildung bei höheren Blechdicken und eine inhomogene Verteilung des Zusatzwerkstoffes beim Laserhybridschweißen. In dieser Studie wird ein auf extern angelegte Magnetfelder basierte elektromagnetische Schmelzbadstütze eingesetzt, um die Grenzen des Verfahrens zu erweitern und die Herausforderungen zu minimieren. Der wesentliche Vorteil der elektromagnetischen Schmelzbadstütze ist, dass sie berührungslos arbeitet. Mit Hilfe der elektromagnetischen Schmelzbadstütze konnten bei 20 mm dicken Proben aus S355J2 die Tropfenbildung an der Wurzel vermieden werden. Zudem wurde der Einfluss der Kantenqualität auf die Schweißnahtqualität untersucht, wobei verschiedene Schneidverfahren zur Kantenvorbereitung eingesetzt wurden, wie z.B. Plasma-, Brenn- oder Laserschneiden. Es konnte gezeigt werden, dass auch bei schlechteren Kantenvorbereitung im Gegensatz zu gefrästen Bauteilen die Werkstoffe einlagig mittels Laserhybridschweißen bei einer hohen Schweißnahtqualität gefügt werden konnten. Bei plasmageschnittenen Proben wurden zudem eine Spaltüberbrückbarkeit bzw. Kantenversatz von bis zu 2 mm sicher überbrückt. Des Weiteren war es mit Hilfe der externen Magnetfelder möglich, die Durchmischung des Zusatzwerkstoffes über die gesamte Schweißnahttiefe deutlich zu homogenisieren.
The study deals with the influence of the heat input on the thermal cycles and Charpy impact toughness for hybrid laser-arc welding of 25 mm thick structural steel S355J2 using a 20-kW high-power laser in combination with an electromagnetic weld pool support. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured using a pyrometer in combination with an optical fibre in three different locations near to fusion lines corresponding to different heights of the seam. Also, Charpy impact specimens were taken from different parts of the weld joint corresponding to the different heights. The influence of the heat input was investigated for 1.8 kJ mm-1 and 3.2 kJ mm-1. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required values could be reached in dependance on applied heat input.
The study deals with the determination of the influence of an externally applied oscillating magnetic field on the melt pool dynamics in high power laser beam and hybrid laser arc welding processes. An AC magnet was positioned under the workpiece which is generating an upward directed electromagnetic force to counteract the formation of the droplets. To visualise the melt flow characteristics, several experiments were carried out using a special technique with mild steel from S355J2 with a plate thickness of up to 20 mm and a quartz glass in butt configuration. The profile of the keyhole and the melt flow were recorded with a highspeed camera from the glass side. Additionally, the influence of the magnetic field orientation to the welding direction on the filler material dilution on laser hybrid welding was studied with variating oscillation frequency. The element distribution over the whole seam thickness was measured with X-ray fluorescence (XRF). The oscillation frequency demonstrated a great influence on the melt pool dynamics and the mixing of the elements of the filler wire. The highspeed recordings showed, under the influence of the magnetic field, that the melt is affected under strong vortex at the weld root, which also avoids the formation of droplets.
One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds.
The stability of the keyhole decreases for deep penetrated high-power laser beam welding. The keyhole tends to collapse with increasing laser power and e.g. keyhole induced porosity can occur. This study deals with the observation of the keyhole during high-power laser beam welding in partial penetration mode by means of a high-speed camera. A butt configuration of 25 mm thick structural steel and transparent quartz glass was used for the experiments. An oscillating magnetic field was applied perpendicular to the welding direction on the root side of the steel plate. The keyhole was highlighted with a coaxial diode laser. It was ascertained that the stability of the keyhole and the weld penetration depth were increased by applying an oscillating magnetic field with an oscillating frequency of 1.2 kHz and a magnetic flux density of 50 mT.
It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could
be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively.
Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges.
The application of hybrid laser-arc welding (HLAW) for joining closed circumferential welds is a challenge due to the high risk of forming a defective overlap area with a shrinkage void or solidification cracks in the material thickness. A series of HLAW experiments were performed to understand the development of a faulty overlap area when closing the circumferential weld. Welding trials on flat specimens and pipe segments were supported by numerical analyses in which the thermomechanical behavior of the welds in the overlap area was investigated. Different process control strategies were tested, including variations in defocusing levels and the overlap length. The newly developed HLAW head, including laser optics with a motor-driven collimation system, made it possible to defocus the laser beam during welding without disturbing the stability of the welding process. High-level defocusing of the laser beam of more than 40 mm relative to the specimen surface with a resulting beam diameter of > 2.9 mm, and in combination with a short overlap length of 15 mm, was promising with respect to the formation of a desired cup-shaped weld profile that is resistant to solidification cracks.
Bislang kommt das Laserstrahlschweißen bzw. Laserhybridschweißen hauptsächlich bei Dickblechen mit einer Wandstärke von bis zu 15 mm zum Einsatz. Für Anwendungen über 20 mm war dieses Verfahren aufgrund einiger Herausforderungen bisher nur bedingt realisierbar. Eine von der Bundesanstalt für Materialforschung und -prüfung (BAM) entwickelte elektromagnetische Schmelzbadunterstützung ermöglicht nun ein einlagiges Schweißen von bis zu 30 mm Wandstärke.
Laserstrahlhybridschweissen von Türmen für Windkraftanlagen Ökonomische und ökologische Vorteile
(2022)
Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulverschweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm.
Diese Arbeit zeigt erstmals die Anwendung einer elektromagnetischen Schmelzbadstütze beim einlagigen MSG-Schweißen von dickwandigen Stählen. Die innovativen Entwicklungen im Bereich des Lichtbogenschweißverfahrens ermöglichen eine Erhöhung der Abschmelzleistung, um die Einschweißtiefe zu steigern. Somit kann die Lagenanzahl reduziert und die Produktivität gesteigert werden. Allerdings besteht insbesondere beim einlagigen Schweißen von dickwandigen Bauteilen in PA-Position ein erhöhtes Risiko für das gravitationsbedingte Austropfen der Schmelze an der Wurzel. Zur Verhinderung werden Badstützen eingesetzt, die mechanisch angebracht und nach dem Schweißen entfernt werden müssen, was zeit- und kostenintensiv ist.
Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadstütze wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Sie wirkt kontaktlos, was im Gegensatz zu herkömmlichen Badstützen vorteilhaft ist, so dass auf eine zeit- und kostenintensive Nachbearbeitung der Schweißnahtwurzel verzichtet werden kann. Das auf extern angelegten oszillierenden Magnetfeldern beruhende Verfahren wird dabei unterhalb des zu schweißenden Bauteils positioniert. Die Magnetfeldlinien sind quer zur Schweißrichtung ausgerichtet, sodass längs zur Schweißrichtung Wirbelströme im Werkstück und eine stets nach oben gerichtete Lorentzkraft generiert werden. Mit Hilfe der elektromagnetischen Badstütze konnten beim einlagigen MSG-Schweißen von 8 mm bis 12 mm die Tropfenbildung vermieden werden. Die innovative Technologie ermöglicht es dickwandige Bauteile einlagig zu schweißen und reduziert die Nachbearbeitungszeit deutlich.
The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm.
The study deals with the influence of the heat input on the thermal cycles and Charpy impact toughness for hybrid laser-arc welding of 25 mm thick structural steel S355J2 using a 20-kW high-power laser in combination with an electromagnetic weld pool support. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured using a pyrometer in combination with an optical fibre in three different locations near to fusion lines corresponding to different heights of the seam. Also, Charpy impact specimens were taken from different parts of the weld joint corresponding to the different heights. The influence of the heat input was investigated for 1.8 kJ mm-1 and 3.2 kJ mm-1. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required values could be reached in dependance on applied heat input.
It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20 mm thick structural steel plates which were prepared by laser and plasma-cutting. Single-pass welds were conducted in butt-joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single-pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges.
-Elektromagnetische Schmelzbadstütze wurde beim
Laserhybridschweißen von Dickblechen erfolgreich zur
Unterdrückung der Tropfenbildung eingesetzt
-Auch bei „schlechteren“ Kantenqualitäten konnten einlagige
Schweißnähte mit hoher Qualität erzielt werden
-Spaltüberbrückbarkeit bis zu 2 mm (bei plasmageschnittenen
Proben) konnte gewährleistet werden
-Homogenere Verteilung des Zusatzwerkstoffes wurde erzielt
The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2G-positions. Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx. 20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc.
High heat input leads to grain coarsening and softening in WM and HAZ; the tensile strength is reduced. Low heat input leads to inadmissible hardening in the WM; the impact strength is reduced.
The proposed t8/5-time of 3 s to 15 s could be achieved through the reduced welding velocity.
The concept of electromagnetic weld pool support system allowed single-pass welds in flat position without gravity drop-outs even for reduced welding speeds; in this way the heat input can be controlled.
The adaptation of the electromagnetic weld pool support system to laser and laser hybrid welding process can dramatically increase the potential field of application of these technologies for real industrial implementation.
High-power hybrid laser arc welding of thick materials with electromagnetic weld pool support
(2023)
In addition to the many advantages of deep penetration, increased welding speed and a low sensitivity to manufacturing tolerances such as gap and edge offset, the hybrid laser arc welding (HLAW) process is used increasingly in industrial applications such as shipbuilding or pipeline manufacturing. Nonetheless, thick-walled sheets with a wall thickness of 20 mm or more are still multi-pass welded using the arc welding process, due to increased process instability by increasing laser power. Welding at reduced speed, especially in a flat position, leads to an irregular formation of the root part such as dropping. The hydrostatic pressure exceeds the surface tension, which decreases with increasing seam width. In order to prevent gravity drop-outs, the use of a melt pool support is necessary. Usual weld pool supports such as ceramic or powder supports require time-consuming mechanical detachment. The electromagnetic weld pool support system, which is described in this study, operates without contact and based on generating Lorentz forces in the weld pool. An externally applied oscillating magnetic field induces eddy currents and generates an upward directed Lorentz force, which counteracts the hydrostatic pressure. This allows single-pass welds up to 30 mm by hybrid laser arc welding process with a 20-kW fibre laser. Moreover, it is favoured by the diminished welding speed the cooling rate which leads to an improvement of the mechanical-technological properties of the seams – the lower formation of martensite in the microstructure enables better Charpy impact toughness. The electromagnetic weld pool support extends the limitation of the laser hybrid welding process in the thick sheet area. By adapting the electromagnetic weld pool support to the laser and laser hybrid welding process, the application potential of these technologies for industrial implementation can be drastically increased.
The study deals with the influence of the heat input on the thermal cycles, the microstructure and the mechanical properties for laser-hybrid welded steels of S355J2 with thicknesses up to 30 mm using a 20-kW high-power laser with contactless electromagnetic backing. The focus is on the change of the mechanical properties over the seam thickness. Therefore, the impact toughness and tensile strength were tested in different depths. Based on the experiments, a heat input of 1.3 kJ/mm - 1.6 kJ/mm, 2 kJ/mm - 2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass welding of 20 mm, 25 mm and 30 mm with a 20-kW laser in regard to the minimum requirements of the mechanical properties, respectively. Lower heat inputs led to undesired microstructure consisting of martensite, hardening and deteriorated impact toughness, where higher heat inputs led to grain-coarsening and even loss of impact strength due to the formation of retained-austenite on the grain boundaries.
The laser hybrid welding process offers many advantages during welding oft hick-walled steels, such as the increased penetration depth and, thus, reduced number of layers, reduced heat input and decreased distortion compared to arc-based welding processes. Especially, when welding high-strength steels (HSS), the reduced heat input plays an essential role. However, a major challenge when laser hybrid welding of thick-walled steels is the limited filler wire mixing over the entire seam thickness, which can lead to changed mechanical properties over the depth. To overcome this issue, the add of oxygen into the shielding gas and its influence on the filler wire mixing and finally to the mechanical properties were investigated within this work. Therefore, 20 mm thick S690QL steels were laser hybrid welded in a single-pass. A contactless electromagnetic backing was used to avoid sagging. The admixture of oxygen was performed by a gas mixer, where the oxygen content was varied between 0 % and 7.2 %. The experiments were also accompanied by laser beam welding tests in steel/glass configuration, where the melt pool geometry as well as the melt flow characteristics were captured by a high-speed camera. It can be concluded, that adding of 2 % to 4 % oxygen into the shielding gas had a positive effect on the filler wire mixing, were up to a depth of 18 mm elements of the filler wire could be observed.
The laser hybrid welding process offers many advantages such as the high penetration depth and high welding speed, and it is characterized by its low heat input compared to the arc-based welding processes, which makes the laser hybrid welding process as a suitable alternative process when welding thick-walled steels. However, there are some challenges when using laser hybrid welding process for thick steels. Due to the uneven cooling conditions and the inhomogeneous filler wire mixing, a typical laser hybrid weld can be divided into two different zones over the depth: the arc-dominated zone on the upper part and the laser-dominated zone in the root part. This leads to different mechanical properties in a laser hybrid welded joint. Due to the high cooling rates and the lack of filler wire in the laser-dominated zone, this area is more critical regarding the mechanical properties, especially the Charpy impact toughness. A low heat input can lead to undesired microstructure consisting of martensite, hardening and deteriorated impact toughness due to the high cooling rate, where higher heat inputs can lead to grain-coarsening and even loss of impact strength. This study deals with the influence of the welding speed and resulting heat input on the cooling rates, the microstructure and the mechanical properties of single-pass laser hybrid welded steels of S355J2 with thickness up to 30 mm. The experiments were performed with a 20-kW fibre laser system and a contactless electromagnetic weld backing on up to 30 mm thick steels in butt-joint configuration in 1G welding position. The cooling time was measured in three different locations near to fusion lines corresponding to different heights of the seam using a special configuration with pyrometers, collimators, and optical fibres. The test specimens for the Charpy impact testing and tensile testing were extracted in up to three different depths. Based on the experiments, a heat input of 1.3 kJ/mm - 1.6 kJ/mm, 2 kJ/mm - 2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass laser hybrid welding of 20 mm, 25 mm and 30 mm thick structural steels in regard to the minimum requirements of the mechanical properties, respectively. The optical measurement of the cooling times in different depths could be carried out reproducibly.
Single-pass Hybrid Laser Arc Welding of Thick Materials Using Electromagnetic Weld Pool Support
(2019)
Hybrid laser-arc welding process allows single-pass welding of thick materials, provides good quality formation of joints with minimal thermal deformations and a high productivity in comparison with arc-based welding processes. Nevertheless, thick-walled steels with a thickness of 20 mm or more are still multi-pass welded using arc welding processes, due to increased process instability by increasing laser power. One limitation factor is the inadmissible formation of gravity drop-outs at the root. To prevent this, an innovative concept of electromagnetic weld pool support is used in this study. With help of such system a stable welding process can be established for 25 mm thick steel plates and beyond. Sound welds could be obtained which are tolerant to gaps and misalignment of the welded parts. The adaptation of this system to laser and hybrid laser-arc welding process can dramatically increase the potential field of application of these technologies for real industrial implementation.
The presented study deals with the performing and mechanical testing of single pass hybrid laser-arc welds (HLAW) on 25 mm thick plates made of steel grade S355J2. One of the challenges have to be solved at full penetration HLAW of thick plates is the drop formation occurring due to the disbalances of the forces acting in the keyhole and on the melt pool surface. Such irregularities mostly limit the use of high-power laser beam welding or HLAW of thick-walled constructions. To overcome this problem, an innovative concept of melt pool support based on generating Lorentz forces in the weld pool is used in this work. This method allows to perform high quality welds without sagging even for welding of 25 mm thick plates in flat position at a welding speed of 0.9 m min-1. For the obtain of full penetrated welds a laser beam power of 19 kW was needed. A high V-impact energy of up to 160 J could be achieved at the test temperature of 0 °C. Even at the most critical part in the weld root an impact energy of 60 J in average could be reached. The tensile strength of the weld reaches that of the base material. An introduce of the HLAW process with electromagnetic support of the melt pool in the industrial practice is an efficient alternative to the time- and cost-intensive arc-based multi-layer welding techniques which are established nowadays for joining of thick-walled constructions.
With global increases in clean energy demand, the natural gas is gaining in importance. Pipelines are the safest and most cost-effective way of transporting natural gas. Due to high transport volume and resulting high operation pressure, the demand for ultra-high strength steel grades such as X120 is very strong. As a result of the fact that these steels are produced by thermo-mechanical controlled processing, the welding process must be selected accordingly. Based on investigations, a high heat input such as by submerged arc welding process leads to softening in the weld metal and loss of strength whereas pure laser beam welding results in high cooling rates and deteriorate toughness of the weld metal. The objective of this research is to investigate the influence of heat input to mechanical properties of hybrid laser-arc welded pipeline steels of grade X120. Test specimens with a thickness of 20 mm could be welded without preheating in a single-pass with different welding velocities to observe the largest possible parameter window of the heat input. The achieved V-notch impact energy for hybrid laser-arc welded samples was 144±37 J at a testing temperature of -40 °C. With a tensile strength of 930±4 MPa the requirements of API 5L was achieved. To prevent gravity drop-outs at the slow welding speeds, an electromagnetic weld pool support system was used, which works contactless and is based on generating Lorentz forces. It was therefore possible to control the cooling rate in order to meet the requirements of the mechanical properties. By adapting the electromagnetic weld pool support to the laser and laser hybrid welding process, the application potential of these technologies for industrial implementation can be drastically increased.
The influence of heat input and welding speed on the microstructure and mechanical properties of single-pass hybrid laser arc welded 20mm thick plates of high-strength pipeline steel X120 were presented. The heat Input was varied in the range of 1.4 kJ mm−1 to 2.9 kJ mm−1, while the welding speed was changed between 0.5m min−1 and 1.5m min−1. A novel technique of bath support based on external oscillating electromagnetic field was used to compensate the hydrostatic pressure at low welding velocities. A major advantage of this technology is, that the welding speed and thus the cooling time t8/5 can be variated in a wide parameter window without issues regarding the weld root quality. The recommended welding thermal cycles for the pipeline steel X120 can be met by that way. All tested Charpy-V specimens meet the requirements of API 5 L regarding the impact energy. For higher heat inputs the average impact energy was 144 ± 37 J at a testing temperature of −40 °C. High heat Input above 1.6 kJ mm−1 leads to softening in the weld metal and heat-affected-zone resulting in loss of strength. The minimum tensile strength of 915 MPa could be achieved at heat inputs between 1.4 kJ mm−1 and 1.6 kJ mm−1.
The hybrid laser arc welding (HLAW) process provides many advantages such as improved gap bridgeability, deep penetration and misalignment of edges, that is why the process is used increasingly in industrial applications e.g. shipbuilding, power plant industry and line-pipe manufacturing. The obvious encountered problem for single pass welding in flat position is the gravity drop-out at low welding velocities. With the usage of an electromagnetic weld pool support system, which is based on generating Lorentz forces within the weld pool, wide seams followed by reduced welding velocities could be achieved in this study leading to the realization of a gap bridgeability up to 1 mm, misalignment of edges up to 2 mm and a single pass weld up to 28 mm thickness with a 20-kW fibre laser. These developments expand the boundaries of the HLAW process for different industrial applications. As a result, less accurate preparation of the edges would be sufficient, which saves time for manufacturing.
Hybrid laser-arc welding offers many advantages, such as deep penetration, good gap bridge-ability, and low distortion due to reduced heat input. The filler wire which is supplied to the process is used to influence the microstructure and mechanical properties of the weld seam.
A typical problem in deep penetration high-power laser beam welding with filler wire and hybrid laser-arc welding is an insufficient mixing of filler material in the weld pool, leading to a non-uniform element distribution in the seam. In this study, oscillating magnetic fields were used to form a non-conservative component of the Lorentz force in the weld pool to improve the element Distribution over the entire thickness of the material. Full penetration hybrid laser-arc welds were performed on 20-mm-thick S355J2 steel plates with a nickel-based wire for different arrangements of the oscillating magnetic field. The Energy-dispersive X-ray spectroscopy (EDS) data for the distribution of two tracing elements (Ni and Cr) were used to analyze the homogeneity of dilution of the filler wire.
With a 30° turn of the magnetic field to the welding direction, a radical improvement in the filler material distribution was demonstrated. This would lead to an improvement of the mechanical properties with the use of a suitable filler wire.
The laser hybrid welding process offers many advantages regarding deep penetration, increased welding velocity and with the help of the supplied filler wire an improved bridgeability to gap and misalignment tolerances. High power laser systems with a power of approx. 30 kW are already available on the market. Nevertheless, multi-layer technology with an arc process is still used for welding of plates from a thickness from 20 mm. A potential cause is the process instability with increasing laser power. It is inevitable that gravity drop-out due to the high hydrostatic pressure at increasing wall thickness especially at welding in flat position and with a low welding speed. The surface tension decreases with increasing root width resulting from low welding velocities. To prevent such inadmissible defects of the seam a use of weld pool support is required. Usual weld pool support systems such as ceramic or powder supports require a mechanical detachment which is time-consuming. The electromagnetic weld pool support system described in this work shows an alternative weld pool support which works contactless. It is based on generating Lorentz forces in the weld pool due to oscillating magnetic field and induced eddy currents. This innovative technology offers single pass welds up to 28 mm in flat position and reduced welding velocity with a laser power of just 19 kW. It also leads to improved mechanical-technological properties of the seams because of the slow cooling rate. With usage of an electromagnetic weld pool support the limitation of the hybrid laser arc welding process in the thick sheet metal will be extend.
The understanding of process-microstructure-property-performance (PMPP) relationships in additive manufacturing (AM) of metals is highly necessary to achieve wide-spread industrial application and replace conventionally manufactured parts, especially regarding safety-relevant applications. To achieve this understanding, reliable data and knowledge regarding material’s microstructure-property relationships (e.g. the role of defects) is needed, since it represents the base for future more targeted process optimizations and more reliable calculations of performance. However, producing reliable material data and assessing the AM material behaviour is not an easy task: big challenges are e.g. the actual lack of standard testing methods for AM materials and the occasional difficulties in finding one-to-one comparable material data for the conventional counterpart.
This work aims to contribute to end this lack of reliable material data and knowledge for the low cycle fatigue behaviour of the most used titanium alloy in aerospace applications (Ti-6Al-4V). For this purpose, two sets of test specimens were investigated. The first set was manufactured from cylindrical rods produced by an optimized DED-L process and the second was manufactured from a hot formed round bar. The test specimens were cyclically loaded until failure in the low-cycle-fatigue (LCF) regime. The tests were carried out according to ISO 12106 between 0.3 to 1.0 % axial strain amplitude from room temperature up to 400°C. The LCF behaviour is described and compared between materials and with literature values based on cyclic deformation curves and strain-based fatigue life curves. Besides, the parameters of Manson-Coffin-Basquin relationship were calculated. The microstructures (initial and after failure) and fracture surfaces were comparative characterized. Thereby, the focus lied on understanding the role of grain morphology and defects on the failure mechanisms and fatigue lifetimes. For this latter characterization, optical microscopy (OM), scanning electron microscopy (SEM) and micro computed tomography (µCT) were used.
Creep and creep damage behavior of stainless steel 316L manufactured by laser powder bed fusion
(2022)
This study presents a thorough characterization of the creep properties of austenitic stainless steel 316L produced by laser powder bed fusion (LPBF 316L) contributing to the sparse available data to date. Experimental results (mechanical tests, microscopy, X-ray computed tomography) concerning the creep deformation and damage mechanisms are presented and discussed. The tested LPBF material exhibits a low defect population, which allows for the isolation and improved understanding of the effect of other typical aspects of an LPBF microstructure on the creep behavior. As a benchmark to assess the material properties of the LPBF 316L, a conventionally manufactured variant of 316L was also tested. To characterize the creep properties, hot tensile tests and constant force creep tests at 600 °C and 650 °C are performed. The creep stress exponents of the LPBF material are smaller than that of the conventional variant. The primary and secondary creep stages and the times to rupture of the LPBF material are shorter than the hot rolled 316L. Overall the creep damage is more extensive in the LPBF material. The creep damage of the LPBF material is overall mainly intergranular. It is presumably caused and accelerated by both the appearance of precipitates at the grain boundaries and the unfavorable orientation of the grain boundaries. Neither the melt pool boundaries nor entrapped gas pores show a significant influence on the creep damage mechanism.
Characterization of Ti-6Al-4V fabricated by multilayer laser powder-based directed energy deposition
(2022)
Laser powder-based directed energy deposition (DED-L) is increasingly being used in additive manufacturing (AM). As AM technology, DED-L must consider specific challenges. It must achieve uniform volume growth over hundreds of layers and avoid heat buildup of the deposited material. Herein, Ti–6Al–4V is fabricated using an approach that addresses these challenges and is relevant in terms of transferability to DED–L applications in AM. The assessment of the obtained properties and the discussion of their relationship to the process conditions and resulting microstructure are presented. The quality of the manufacturing process is proven in terms of the reproducibility of properties between individual blanks and with respect to the building height. The characterization demonstrates that excellent mechanical properties are achieved at room temperature and at 400 °C.
Laser powder-based directed energy deposition (DED-L) is a technology that offers the possibility for 3D material deposition over hundreds of layers and has thus the potential for application in additive manufacturing (AM). However, to achieve broad industrial application as AM technology, more data and knowledge about the fabricated materials regarding the achieved properties and their relationship to the manufacturing process and the resulting microstructure is still needed. In this work, we present data regarding the low-cycle fatigue (LCF) behavior of Ti-6Al-4V. The material was fabricated using an optimized DED-L process. It features a low defect population and excellent tensile properties. To assess its LCF behavior two conventionally manufactured variants of the same alloy featuring different microstructures were additionally tested. The strain-controlled LCF tests were carried out in fully reversed mode with 0.3 % to 1.0 % axial strain amplitude from room temperature up to 400°C. The LCF behavior and failure mechanisms are described. For characterization, optical microscopy (OM), scanning electron microscopy (SEM), and micro-computed tomography (µCT) were used. The low defect population allows for a better understanding of the intrinsic material’s properties and enables a fairer comparison against the conventional variants. The fatigue lifetimes of the DED-L material are nearly independent of the test temperature. At elevated test temperatures, they are similar or higher than the lifetimes of the conventional counterparts. At room temperature, they are only surpassed by the lifetimes of one of them. The principal failure mechanism involves multiple crack initiation sites.
Eine kritische Aufgabe im Rahmen der Etablierung von Prozess-Struktur-Eigenschafts-Performance-Beziehungen bei der additiven Fertigung (AM) von Metallen ist die Ermittlung von zuverlässigen und gut dokumentierten Kennwerten zum Materialverhalten sowie das Schaffen von Wissen über die Struktur-Eigenschafts-Korrelation. Schließlich ist dies die Grundlage für die Entwicklung gezielterer Prozessoptimierungen und zuverlässigerer Lebensdauer-Vorhersagen. In diesem Zusammenhang zielt dieser Beitrag darauf ab, Daten und Erkenntnisse über das Kriechverhalten des austenitischen Edelstahls 316L zu liefern, der mittels Laser-Powder-Bed-Fusion (L-PBF) hergestellt wird. Um dieses Ziel zu erreichen, wurden Proben aus konventionellem warmgewalztem sowie AM-Material gemäß den bestehenden Normen für konventionelles Material geprüft und vor und nach dem Versagen mikrostrukturell charakterisiert. Die Probekörper wurden aus einzelnen Blöcken des AM-Materials gefertigt. Die Blöcke wurden mit einer Standard-Scan- und Aufbaustrategie hergestellt und anschließend wärmebehandelt. Das Kriechverhalten wird anhand der Kriechlebensdauer und ausgewählter Kriechkurven und Kennwerte beschrieben und vergleichend bewertet. Der Einfluss von Defekten und Mikrostruktur auf das Materialverhalten wird anhand von zerstörenden und zerstörungsfreien Auswertungen an ausgewählten Proben analysiert. Der AM-Werkstoff zeigt kürzere Kriechlebensdauern, erreicht das sekundäre Kriechstadium deutlich schneller und bei geringerer Dehnung und weist eine geringere Kriechduktilität im Vergleich zu seinem konventionellen Gegenstück auf. Das Kriechschädigungsverhalten des AM-Werkstoffs ist eher mikrostruktur- als defektgesteuert und ist durch die Bildung intergranularer Kriechrisse gekennzeichnet. Als kritische Merkmale werden die Versetzungsdichte sowie die Versprödung der Korngrenzen identifiziert. Die Mikro-Computertomographie (µCT) erweist sich als Alternative zur Metallographie, um die Kriechschädigung zu analysieren.
Creep and fracture behavior of conventionally and additively manufactured stainless steel 316L
(2020)
A critical task within the frame of establishing process-structure-property-performance relationships in additive manufacturing (AM) of metals is producing reliable and well-documented material behavior’s data and knowledge regarding the structure-property correlation, including the role of defects. After all, it represents the basis for developing more targeted process optimizations and more reliable predictions of performance in the future. Within this context, this contribution aims to close the actual gap of limited historical data and knowledge concerning the creep behavior of the widely used austenitic stainless steel 316L, manufactured by Laser-Powder-Bed-Fusion (L-PBF). To address this objective, specimens from conventional hot-rolled and AM material were tested under application-relevant conditions according to existing standards for conventional material, and microstructurally characterized before and after failure. The test specimens were machined from single blocks from the AM material. The blocks were manufactured using a standard scan and build-up strategy and were subsequently heat-treated. The creep behavior is described and comparatively assessed based on the creep lifetime and selected creep curves and characteristic values. The effect of defects and microstructure on the material’s behavior is analyzed based on destructive and non-destructive evaluations on selected specimens. The AM material shows shorter creep lives, reaches the secondary creep stage much faster and at a lower strain, and features lower creep ductility compared to its conventional counterpart. The creep damage behavior of the AM material is more microstructure than defect controlled and is characterized by the formation and accumulation of single intergranular damage along the whole volume. Critical features identified are the grain morphology and the grain-boundary as well as the dislocation’s density. Micro-computed tomography (µCT) proves to be an alternative to metallography to analyze the creep damage.
Antibiotic resistance is a growing global problem which poses a massive threat to human health. Although human activity contributes to the acceleration of the process, bacteria have a self-driven stabilisation mechanism to protect themselves from such and other external threats: biofilm formation. Nonetheless, it is the adhesion of a single bacterial cell to a surface that triggers the formation of such network of biomolecules and microorganisms, as well as its hazardous consequences. The main objective of this work was to quantify the adhesion force of a single E. coli cell on a Ti substrate via the AFM-related single-cell force spectroscopy, with both the cell and the substrate material being of high clinical relevance. A set of 25 x 25 force displacement curves was acquired with a maximum force of 3.2 nN without dwell time, yielding a topography map and an adhesion force map that showed to be correlated. A mean adhesion force of 0.85 ± 0.175 nN was measured and the presence of cell appendages on the bacterial cell wall was verified through individual force-displacement curves. Bacterial viability was assessed after the measurements via live/dead staining.
As humanity contemplates manned missions to Mars, strategies need to be developed for the design and operation of hospitable environments to safely work in space for years. The supply of spare parts for repair and replacement of lost equipment will be one key need, but in-space manufacturing remains the only option for a timely supply. With high flexibility in design and the ability to manufacture ready-to-use components directly from a computeraided model, additive manufacturing (AM) technologies appear extremely attractive. For the manufacturing of metal parts, laser-beam melting is the most widely used AM process. However, the handling of metal powders in the absence of gravity is one prerequisite for its successful application in space. A gas flow throughout the powder bed is successfully applied to compensate for missing gravitational forces in microgravity experiments. This so-called gas-flow-assisted powder deposition is based on a porous Building platform acting as a filter for the fixation of metal particles in a gas flow driven by a pressure difference maintained by a vacuum pump.
Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspruchung im Bauteil realistisch wiedergeben soll. Betrachtet wird ein halbelliptischer Riss, der bei der weiteren Ausbreitung als Umfangsriss wächst (rim peeling). Die Simulation dieser Stelle im Bauteil schließt die mechanische und thermische Beanspruchung sowie sie Dehnungsbehinderung ein. Letztere wird anhand zweier Parameter, der Spannungsmehrachsigkeit ℎ und des (allerdings modifizierten) Constraint-Parameters nach Newman, der die Spannungen über den plastisch verformten Bereich mittelt, bestimmt. Erwartungsgemäß zeigt sich, dass die höchste Dehnungsbehinderung weder an den Oberflächenpunkten, noch an den tiefsten Punkten, sondern an einer Stelle zwischen beiden auf der Rissfront auftritt. Als Versuchsgeometrie für die monotonen Tests soll eine Kreuzprobe mit wanddurchdringenden Rissen ausgehend von einer Innenbohrung dienen. Durch geeignete Wahl der Risstiefe sowie der in beiden Richtungen angreifenden Kräfte gelingt es, bauteiladäquate Zustände zu erzeugen.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present two alternative burst speed assessment methods under development based on the Failure Assessment Diagram (FAD) and a global stability criterion, respectively. In the scope of the fracture mechanics assessment, the failure modes hoop-burst and rim-peeling are investigated with semicircular surface cracks modelled at the critical regions on the turbine disk. The comparison of the predicted critical rotational speed shows good agreement between the assessment methods.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of 𝐽-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest 𝐽 -integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. In addition, probabilistic aspects are also considered in the calculations.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on productionsimilar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. In particular, the rimpeeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk, with the crack plane perpendicular to the radial direction. The crack is therefore subjected to a biaxial stress state and grows under increasing rotational speed until it triggers the rim-peeling failure. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of -integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest -integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. Probabilistic aspects are also considered in the calculations.
This presentation focuses on the basic ideas and current status of the development of an arithmetical method to predict the failure rotational speed of turbine disks. The certification specification requires that a gas turbine aero-engine must hold 5 minutes at overspeed conditions without critical failure. Therefore, instead of experimental proof from spin-tests using test-disks similar to engine components, it is considered to use simple specimen with similar test conditions compared to real overspeed scenarios. These test conditions, or stress fields are determined using arithmetical method, e.g. finite element method, with consideration of fracture mechanics under quasi-static conditions with a given rotational speed.
Failure modes like hoop burst and rim peeling are considered during determination of stress fields. Various crack-tip parameters are used to explore the similarity of stress field between simple specimen and real overspeed scenarios. Additionally, probabilistic aspects and the implementation of a global stability criterion for overspeed analysis are also considered.
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present part of a fracture mechanics-based procedure under development which aims at replacing the tests on production-similar disks with lab tests on fracture mechanics specimens. In particular, the rim-peeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk, with the crack plane perpendicular to the radial direction. The crack is therefore subjected to a biaxial stress state and grows under increasing rotational speed until it triggers the rim-peeling failure. The finite element simulation of the cracked disk considers the real thermal and mechanical loading conditions. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of J-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. This has been achieved and as expected, both the highest J-integral and constraint factor are calculated at the same location along the crack front for both disk and specimen. The results of the structural integrity assessment in the form of a Failure Assessment Diagram (FAD) show good agreement between designed specimen and disk both in terms of expected failure mode and value of the critical speed. Probabilistic aspects are also considered in the calculations.
Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspruchung im Bauteil realistisch wiedergeben soll. Dazu werden zwei Typen von bruchmechanischen Proben anwendungsnah ausgelegt und aus einer Turbinenscheibe ausgeschnitten: Der erste Typ ist eine biaxiale Probe, die die Beanspruchung und den Dehnungsbehinderungszustand am Diaphragm der Turbinenscheibe abbildet, die zweite eine bruchmechanische Probe, die die einachsige Beanspruchung und den Dehnungsbehinderungszustand am Bore der Turbinenscheibe wiedergibt.
Im Rahmen eines Schadentoleranzansatzkonzepts ist anschließend jeweils ein halbelliptischer Riss an den genannten Stellen der Turbinenscheibe zu betrachten. Mittels numerischer Berechnungen wird ein kritischer Punkt auf der Rissfront des Risses am Diaphragm bestimmt, dort wo die höchste Rissspitzenbelastung (J-Integral) auftritt. Auf der Basis der Rissspitzenbelastung, des Dehnungsbehinderungszustands und des entsprechenden Spannungsverhältnisses an diesem kritischen Punkt wird eine Kreuzprobe mit einem Durchriss konzipiert, die diese Verhältnisse im Bauteil widerspiegelt. Die Versuche werden unter der Temperatur am Diaphragm der Turbinenscheibe durchgeführt. Die J-R-Kurve und die plastische Kollapsgrenze werden bestimmt. Auch die einachsigen Versuche werden unter der Temperatur am Bore der Turbinenscheibe durchgeführt. Die Zugprobe enthält halbelliptische Oberflächenrisse. Ähnlich wie bei der Auslegung der Kreuzproben werden die Rissspitzenbelastung, der Dehnungsbehinderungszustand und das Spannungsverhältnis vergleichbar mit der Turbinenscheibe eingestellt. Die J-R-Kurve und die plastische Kollapsgrenze werden bestimmt.
Mit den Versuchsergebnissen werden die kritischen Lasten für verschiedene Versagensmechanismen (instabiles Risswachstum, plastischer Kollaps) der bruchmechanischen Proben ermittelt, die der kritischen Überdrehzahl der Turbinenscheibe entsprechen.
Turbinenscheiben sind thermisch und mechanisch hochbeanspruchte, sicherheitsrelevante Komponenten in Gasturbinen. Ihre Integrität wird in Bauteiltests unter Überdrehzahlbedingungen nachgewiesen. Kontext des Aufsatzes ist die Erarbeitung einer zusätzlichen Bewertungsebene auf der Grundlage von Versuchen unter monotoner Beanspruchung, die die Beanspruchung im Bauteil realistisch wiedergeben soll. Betrachtet wird ein halbelliptischer Riss, der bei der weiteren Ausbreitung als Umfangsriss wächst (rim peeling). Die Simulation dieser Stelle im Bauteil schließt die mechanische und thermische Beanspruchung sowie sie Dehnungsbehinderung ein. Letztere wird anhand zweier Parameter, der Spannungsmehrachsigkeit ℎ und des (allerdings modifizierten) Constraint-Parameters nach Newman, der die Spannungen über den plastisch verformten Bereich mittelt, bestimmt. Erwartungsgemäß zeigt sich, dass die höchste Dehnungsbehinderung weder an den Oberflächenpunkten, noch an den tiefsten Punkten, sondern an einer Stelle zwischen beiden auf der Rissfront auftritt. Als Versuchsgeometrie für die monotonen Tests soll eine Kreuzprobe mit wanddurchdringenden Rissen ausgehend von einer Innenbohrung dienen. Durch geeignete Wahl der Risstiefe sowie der in beiden Richtungen angreifenden Kräfte gelingt es, bauteiladäquate Zustände zu erzeugen.
Friction stir welding (FSW) has the capacity to join the Al/Ti dissimilar structures with superior mechanical properties. The microstructures and mechanical characteristics of Al/Ti dissimilar FSW joints are determined by the heat and mass transfer during the welding process. However, a quantitative study of the Al/Ti dissimilar FSW process is lacking. Therefore, using the computational fluid dynamics (CFD) and volume of fluid (VOF) approach, a multi-phase model was constructed for quantitatively analyzing the heat and mass transfer behaviour in dissimilar FSW of TC4 titanium alloy and AA2024-T4 aluminium alloy. The mixed material was treated as a functionally graded material (FGM) to compute the thermophysical characteristics at the weld nugget zone (WNZ). Due to the vast disparity in the thermophysical characteristics of aluminum and titanium alloy, the temperature field in Al/Ti dissimilar FSW was severely asymmetric. The temperature of titanium alloy on the advancing side (AS) was higher than that of aluminium alloy on the retreating side (RS) at the same distance from the tool centre line near the tool shoulder, but it was lower than that of aluminium alloy on the RS without the influence of the shoulder. Due to the high flow stress of titanium alloy, plastic material flow mostly occurred on the RS of aluminium alloy in the Al/Ti dissimilar FSW, with its percentage exceeding 80%. This model was validated by experiment results.
Three high-strength Nb-,.Ti- and Ti+ V-bearing S690QL steels were welded to investigate and compare the effects of microalloy addition on heat-affected zone (HAZ) toughness. Charpy V notch impact tests from three microalloyed welds under different cooling rates have been performed. Fractographic examination shows that several factors, including large-sized grain, upper bainite or hard second phase, interact to determine brittle fracture and impaired toughness in Nb-bearing weld with high heat input. In contrast to this reduced toughness, Ti-bearing welds exhibits satisfied toughness regardless of at fast or slow cooling. This is attributed to its limited austenite grain and refines favorable intragranular acicular ferrite structure. Moreover, in the case of such refined structure as matrix, TiN particles are found to be irrelevant to the facture process. The crystallographic results also confirm that high-angle boundaries between fine ferrites plates provide effective barriers for crack propagation and contribute to improved toughness.
Common fracture mechanics based fatigue considerations are usually limited to the residual lifetime determination of so-called long cracks. The extension of this concept to the total lifetime, as in the S-N curve approach, requires an adequate description of short crack propagation which cannot be based on the Delta K concept, and it must consider the crack closure phenomenon as well as its gradual build-up at the short crack stage. Further, it has to provide a meaningful definition of initial crack dimensions and a solution for the multiple crack problem at stress levels higher than the fatigue limit as it is specific for some configurations such as weldments. This paper aims at a discussion of all these points and offers possible solutions which are illustrated by examples taken from the German IBESS project on fracture mechanics based determination of the fatigue strength of weldments, the results of which will be discussed in more detail in this Special issue.
A discussion is provided on demands that must be met in order to apply fracture mechanics to the determination of overall fatigue lifetime and strength, i.e., S-N curves and fatigue limits. These comprise the determination of the cyclic crack driving force for all stages of fatigue crack propagation, in particular for the short crack stage where the crack driving force has to be determined for elastic-plastic deformation and the gradual build-up of the crack closure phenomenon. Special emphasis is put on a fatigue damage relevant specification of the initial crack size. Different approaches in the literature are discussed. Another important aspect is the adequate treatment of multiple crack propagation. Finally, the discussion is illustrated by an example of a butt weld made of a medium strength steel.
The cyclic J-integral (∆J-integral) is a crack tip parameter of elastic-plastic fracture mechanics which can be used as governing parameter for the description of fatigue crack growth (FCG) in metallic structures. In this contribution, it is applied for modelling FCG in weldments. The ∆J-integral is determined by means of analytical approximation formulas as well as numerical methods. An analytical solution, which takes into account effects of the local ligament plasticity, was derived. This solution is based on well established methods such as R6, BS7910 and SINTAP which were modified for cyclic loading. It incorporates methods for the description of short crack closure behaviour as well as the well known analytical (long) crack closure function of Newman. A specific code was written to evaluate the ∆J-integral numerically in the course of finite element based crack growth simulations. The code was first validated for an infinite plate with centre crack by applying elastic and elastic-plastic material behaviour. Next, the ∆J-integral was calculated for cracks in various butt and cruciform welded joints. The results were compared with the results of the derived analytical approximation formula. A good accordance was achieved between the results.
The paper provides an application of the IBESS approach to the investigation of the influence of various parameters of the global and local weld geometry as well as material defects on the fatigue strength of weldments. For this purpose, the global weld parameters, such as the weld toe radius, the flank angle, the excess weld metal, local secondary notches (in the present study as a measure of surface imperfections) and inclusions sizes have been determined as statistical distributions for different joint types and geometries and two steels of different strengths. The results are in line with literature data and reveal the potential of the theoretical approach to predict the correct trends. The combination with an advanced weld quality system has been demonstrated to be possible.
This book provides a comprehensive and thorough guide to those readers who are lost in the often-confusing context of weld fatigue. It presents straightforward information on the fracture mechanics and material background of weld fatigue, starting with fatigue crack initiation and short cracks, before moving on to long cracks, crack closure, crack growth and threshold, residual stress, stress concentration, the stress intensity factor, J-integral, multiple cracks, weld geometries and defects, microstructural parameters including HAZ, and cyclic stress-strain behavior. The book treats all of these essential and mutually interacting parameters using a unique form of analysis.
The so-called cyclic R curve, i.e. the crack size dependence of the fatigue crack propagation threshold in the physically short crack regime, is a key parameter for bringing together fatigue strength and fracture mechanics concepts. Its adequate determination is of paramount importance. However, notwithstanding this relevance, no test guideline is available by now and only very few institutions have spent research effort on cyclic R curves so far. The aim of the present paper is to give an overview on the state-of-the-art. Besides an introduction into the basic principles, the discussion will concentrate on the experimental determination on the one hand and questions of its application on the other hand.
This third part of the review on defects as root cause of fatigue failure addresses cavities (pores, micro-shrinkages, unmelted regions), defective microstructures and microcracks as material defects and defects due to local damage during manufacturing, service and maintenance such as dents, scratches and localized corrosion. In addition, damage due to contact fatigue and the effect of surface roughness are discussed in the context of fatigue failure. Also addressed is the competition between different kinds of defects in controlling the initiation and early growth of fatigue cracks.
According to the definition of the ASM handbook [1,3], a defect is "an imperfection. that can be shown to cause failure by a quantitative analysis and that would not have occurred in the absence of the imperfection". The topic of the present three-part review is a discussion of defects which can cause failure in cyclically loaded structures. The features discussed comprise material defects such as non-metallic inclusions, pores or micro-shrinkages, etc. and geometric defects such as surface roughness and secondary notches which have their origin in manufacturing, and defects such as surface damage due to scratches, impact events or contact fatigue as well as corrosion pits which arise in service. In this first part, the discussion is prefaced by an introduction to basic aspects which are essential for a deeper understanding of the characteristics and mechanisms how the defects influence fatigue crack initiation and propagation. These include the life cycle of a fatigue crack from initiation up to fracture, crack arrest, multiple crack initiation and coalescence, and the material and geometrical properties affecting these.
Defects as a root cause of fatigue failure of metallic components. II: Non-metallic inclusions
(2019)
This second part of the review on defects as root cause of fatigue failure comprises the origin, the nature and the effects of non-metallic inclusions. Topics addressed are the different kinds of inclusions formed during the manufacturing process, various types of mis-match causing local stresses and, as a consequence, fatigue crack initiation, and effects of characteristics such as size, morphology, localization, spatial distribution and orientation of the defects on the fatigue behavior. Methods for inclusion counting and sizing are discussed along with statistical aspects necessary to be considered when evaluating structural components.
Using the case study of a fail-safe design criterion for a steering knuckle of a commercial vehicle, the effect of stiffness/constraint on the crack driving force in the component is discussed. The problem arises when assessment procedures such as R6, BS 7910 or SINTAP/FITNET are applied in conjunction with substitute geometries for determining the model parameters K-factor and limit load (or a substitute for the latter), as it is common practice. In the example, the conservatism was so pronounced that this procedure was in fact unusable. A way out could be the finite element-based determination of the model parameters and their use in the analytical framework. This procedure is useful and effective if the finite element-based calculations are used in parameter sensitivity analyses.
Any fracture mechanics based determination of the fatigue strength of weldments requires different input information such as the local weld geometry and material data of the areas the crack is passing through during its propagation. The latter is so far not a trivial task as the fatigue crack is usually initiated at the weld toe at the transition from the weld metal to the heat affected zone and it subsequently propagates through the different microstructures of the latter to eventually grow into the base material and to cause final fracture. This paper describes how the material input information has gained particularly for heat affected zone material by thermo-mechanically simulated material specimens for two steels of quite different static strength. The data comprise the cyclic stress-strain curve, the crack closure effect-corrected crack growth characteristics, long crack fatigue crack propagation thresholds, the dependency of the parameter on the crack length and monotonic fracture resistance. The substantial experimental effort was necessary for the validation exercises of the IBESS approach, however, within the scope of practical application more easily applicable estimating methods are required. For that purpose the paper provides a number of appropriate proposals in line with its check against the reference data from the elaborate analyses.
The safe fatigue design of metallic components fabricated by additive manufacturing (AM) is still a largely unsolved problem. This is primarily due to (a) a significant inhomogeneity of the material properties across the component; (b) defects such as porosity and lack of fusion as well as pronounced surface roughness of the asuilt components; and (c) residual stresses, which are very often present in the as‐built parts and need to be removed by post‐fabrication treatments. Such morphological and microstructural features are very different than in conventionally manufactured parts and play a much bigger role in determining the fatigue life. The above problems require specific solutions with respect to the identification of the critical (failure) sites in AM fabricated components. Moreover, the generation of representative test specimens characterized by similar temperature cycles needs to be guaranteed if one wants to reproducibly identify the critical sites and establish fatigue assessment methods taking into account the effect of defects on crack initiation and early propagation. The latter requires fracture mechanics‐based approaches which, unlike common methodologies, cover the specific characteristics of so‐called short fatigue cracks. This paper provides a discussion of all these aspects with special focus on components manufactured by laser powder bed fusion (L‐PBF). It shows how to adapt existing solutions, identifies fields where there are still gaps, and discusses proposals for potential improvement of the damage tolerance design of L‐PBF components
If a component is cyclically loaded, its load carrying capacity is considerably lower than in the monotonic loading case. This general observation applies in particular to L-PBF parts. The causes of this are mainly material defects such as pores and unwelded regions (Chapter 8) and a pronounced surface roughness in the as-built condition (Chapter 9). In addition, effects due to the anisotropy of the microstructure (Chapter 6) and a complex residual stress pattern (Chapter 7) play an important role. A consequence is that common strategies of fatigue assessment cannot be transferred to L-PBF applications without modifications. Due to the inhomogeneity of the material, the determination of representative material properties and the transfer to the component is a problem, and this is also the case with regard to the consideration of defects, surface roughness and residual stresses. The chapter gives a brief introduction to these problem areas.
Die sichere Auslegung von Bauteilen kommt an der Anwendung bruchmechanischer Methoden heute nicht mehr vorbei. Das vorliegende Buch bietet eine Einführung in diese Methoden mit besonderen Schwerpunkten auf dem aktuellen Stand der bruchmechanischen Kennwertermittlung und den Methoden der analytischen bruchmechanischen Bauteilbewertung. Es beschreibt die Mechanismen von Risswachstum und Bruch, die grundlegenden Konzepte der Bruchmechanik, die analytische Ermittlung der Rissspitzenbelastung in Bauteilen sowie die Anwendung der Bruchmechanik in unterschiedlichen Kontexten. Der Schwerpunkt liegt dabei auf der praktischen Anwendung u. a. anhand von Demonstrationsbeispielen, die im Detail nachvollzogen werden können.
Analytical flaw assessment
(2018)
The paper provides a review on analytical flaw assessment methods with the focus on fracture under monotonic loading and fatigue crack propagation. The first topic comprises linear elastic as well as elastic-plastic fracture mechanics approaches. It essentially follows their historical development. Topics which are separately discussed are reference/Limit loads, the treatment of secondary stresses, strength mismatch, constraint, unstable crack propagation (monotonic R-curve analyses) and statistical aspects. With respect to fatigue crack propagation the analytical treatment of crack closure and constraint and the Determination of the cyclic elastic-plastic crack driving force is discussed. Finally, cyclic Rcurve analyses are briefly addressed.
The paper provides an overview on material defects which may serve as fatigue crack initiation sites and can cause final fatigue failure of a component. These comprise nonmetallic inclusions in Steel and aluminum alloys, cavities such as pores, micro-shrinkages and un-welded regions in cast, sinter and additively manufactured alloys, graphite nodules, shrinkages and other items in modular cast iron, regions of defective microstructure, microcracks and secondary notches such as undercuts and surface roughness. Besides their origin, the effect and mechanisms on fatigue crack initiation and propagation are discussed.
The considerations are proceeded and accompanied by a Brief discussion of some Basic aspects such as the stages of crack propagation along their length scale, the overcoming of crack arrest and the question when a secondary notch can be treated as a crack.
Welding residual stresses have an impact on the performance of welded structures, on their fracture resistance, their resistance against fatigue crack propagation and, most important, their fatigue strength and fatigue lifetime. The present paper provides an overview on the issue mainly from the point of view of the application of fracture mechanics to the determination of the fatigue strength as the topic of this Special issue. Besides own experimental and theoretical data a comprehensive discussion is provided in that context which includes the definition and interaction of short- and long-range (or reaction) residual stresses, the effect of cyclic mechanical loading and its treatment in fracture and fatigue analyses.
This article is an outcome of a workshop on Fatigue of Additive Manufactured Metallic Components jointly organized by the Federal Institute for Materials Research and Testing (BAM) Berlin, Germany and the National Institute of Standards and Technology (NIST) Boulder, CO, U.S.A. The aim of the workshop was a comprehensive discussion of the specific aspects of additively manufactured (AM) components in regard to failure under cyclic loading. Undoubtedly, a better understanding and the further development of approaches for damage tolerant component design of AM parts are among the most significant challenges currently facing the use of these new technologies.
This article presents a thorough overview of the workshop discussions. It aims to provide a review of the parameters affecting the damage tolerance of AM parts with special emphasis on the process parameters intrinsic to the AM technologies, the resulting defects and residual stresses. Based on these aspects, concepts for damage tolerant component design for AM are reviewed and critically discussed.
Der Vortrag behandelt in grundsätzlicher weise die Anwendung bruchmechanischer Methoden auf die rechnerische Ermittlung der Wöhlerkurve. Dabei werden die Besonderheiten des Kurzrisswachstums (Notwendigkeit der elastisch-plastischen Beschreibung der zyklischen Rissspitzenbelastung, gradueller Aufbau des Rissschlißphänomens) ebenso diskutiert wie das Problem des Mehrfachrissewachstums und Rissarrest. Die Ausführungen werden an einem Beispiel illustriert.
The two-part paper series provides an overview on the state-of-the-art in the application of engineering fracture mechanics to weldments limited to butt and fillet welds with crack initiation at weld toes. In the present second part, one focus is on welding residual stresses, their characteristics and stability under cyclic loading and their effect on structural integrity. Subsequently, features will be addressed which are essential for applying fracture mechanics to overall fatigue life and fatigue strength considerations of weldments. These comprise fatigue life relevant initial crack sizes and multiple crack initiation and Propagation due to various stress peaks along the weld toe. A concept is briefly introduced which covers all these aspects.
The presentation provides a discussion and damage tolerant assessment of metallic AM components. In the focus are problems of the determination of representative material data, the effect of material defects and residual stresses. Starting with the actual state-of-the-art in the field, options and possibilities of a damage tolerant design for AM are discussed.
Foreword
(2018)
The subject of this Special Issue is the fracture mechanics-based determination of the fatigue strength of weldments. Except for one, all papers were written in closer or wider relation to a methodology developed within the framework of the German Project cluster IBESS. Some of them provide background or supplementary information needed in that context but which is also relevant in a wider frame of research activities. The acronym IBESS stands for the topic of this Special Issue (in German: „Integrale Methode zu Bruchmechanischen Ermittlung der Schwingfestigkeit von Schweißverbindungen). Eight partners were involved. The cluster was cooperatively founded by the German Research Foundation (Deutsche Forschungsgemeinschaft) and by the German AiF Network (Arbeitsgemeinschaft industrieller Forschungsvereinigungen) for industrial research.
Der Vortrag thematisiert die Behandlung von Schweißeigenspannungen bei der Auslegung geschweißter Bauteile. Ausgehend von Fragen der Klassifizierung unterschiedlicher Typen von Eigenspannungen wird auf Fragen der Behandlung von Primär- und Sekundärspannungen, der Ermittlung und Aussagefähigkeit von Eigenspannungs-Tiefen-Profilen und der Stabilität der Eigenspannungen bei zyklischer Beanspruchung eingegangen. Neben der Auslegung auf Bruch wird die Beschreibung der Ermüdungsrissausbreitung bei Vorhandensein von Eigenspannungen diskutiert, wobei neben der klassischen Langrissbruchmechanik auch Besonderheiten der Kurzrissbruchmechanik angesprochen werden.
Ein Defekt ist „eine Imperfektion …, für die in einer quantitativen Analyse gezeigt werden kann, dass sie Versagen verursacht hat, welches ohne die Imperfektion nicht aufgetreten wäre“. Defekte in diesem Sinn können einerseits Werkstoffimperfektionen wie nichtmetallische Einschlüsse, Poren und Porennester, Nichtdurchschweißungen oder Bereiche defekter Mikrostruktur, andererseits unbeabsichtige geometrische Imperfektionen wie Kratzer, Eindrücke, Korrosionsgrübchen, Einbrandkerben, zu große Oberflächenrauheit u.a. sein. Sie können in der Fertigung, im Betrieb oder auch bei der Wartung entstehen. Nicht jede Imperfektion ist ein Defekt im oben genannten Sinn. Entscheidend ist zumeist nicht, dass an ihr ein oder mehrere Risse initiiert werden, sondern dass wenigstens ein Riss wachstumsfähig bleibt und so innerhalb der projektierten Lebensdauer zum Bruch oder anderweitigem Versagen führt. Aufgrund des begrenzten Umfangs bleibt die vorliegen-de Übersicht beschränkt.
Unter der zyklischen R-Kurve versteht man die Abhängigkeit des Schwellenwertes gegen Ermüdungsrissausbreitung von der Risstiefe im Kurzrissbereich. Bei Spannungsverhältnissen R = omin/omax < ca. 0,7 erhöht sich der Schwellenwert AKltl ausgehend von einer intrinsischen, werkstoffspezifischen Untergrenze mit zunehmender Risstiefe, bis er einen risslängenunabhängigen Wert erreicht.
Ursache ist der graduelle Aufbau unterschiedlicher Rissschließeffekte. Die besondere Bedeutung des Kurzrisswachtums allgemein und der zyklischen R-Kurve speziell besteht darin, dass sie ein physikalisches Bindeglied zwischen der konventionellen Schwingfestigkeit (Wöhlerkurve) und der Bruchmechanik repräsentieren. Der Beitrag befasst sich sowohl mit der experimentellen Ermittlung der zyklischen R-Kurve als auch mit ihrer Anwendung auf Rissarrest im Zusammenhang mit Schwingfestigkeitsbetrachtungen.
Die experimentelle Ermittlung der zyklischen R-Kurve erfordert einen experimentellen Aufwand, der deutlich über den der Langrissbruchmechanik hinausgeht. Insbesondere im Anfangsbereich ist eine sehr genaue Messung der Risstiefe erforderlich, was eine Verbesserung etwa der konventionellen Potentialmethode erforderlich macht. Von wesentlicher Bedeutung ist auch, dass der Ausgangsriss vor
Beginn des eigentlichen Versuchs keine Rissschließeffekte gesehen haben darf. Realisiert wird das durch eine vorgeschaltete Phase von sog. „Compression Pre-cracking“, d.h. durch Anschwingen komplett im Druckbereich.
Die Präsentation diskutiert Besonderheiten von Schweißnähten bei der Bestimmung der Zähigkeit bei monotoner Belastung, bei der Ermittlung des zyklischen Rissfortschritts und bei der Ermittlung der Gesamtlebensdauer/Schwingfestigkeit mittels moderner bruchmechanischer Methoden. Besonderes Augenmerk liegt auf der Inhomogenität des Werkstoffs in den einzelnen Nahtbereichen, die sich statistisch (stochastische Verteilung von Gefügeschwachstellen) und systematisch (Effekte von Festigkeits-Mismatch) auswirkt. Als weiterer Faktor kommen Schweißeigenspannungen hinzu, bei denen für die bruchmechanische Analyse eine Fallunterscheidung in primäre und sekundäre Eigenspannungen vorgenommen werden muss. Diskstiert werden die Konsequenzen für die Zähigkeitsermittlung und die Bauteilbewertung.
The Topic of the presentationis a discussion on defects which can cause failure in cyclically loaded metallic components. Although also touching Features such as material defects such as pores or micro-shrinkages, etc. and geometric defects such as surface roughness and secondary notches (which are not considered in the design process) which origin in manufacturing, and others the presentation concentrates on non-metallic inclusions. It is prefaced by an introduction to the life cycle of a fatigue crack from initiation up to fracture. Special emphasis is put on the fact that only cracks which are not arrested during one of their distinct Propagation stages can grow to a critical size.
Overview of ongoing research and future prospects on polyethylene neutron shielding materials at bam
(2023)
The extension of the interim storage period of radioactive waste before disposal will cause additional challenges for the nuclear waste management in Germany, so that an extensive knowledge of the long-term performance of casks, including their components and inventories, will be required for future extended storage licenses.
Ultra-high and high molecular weight polyethylenes ((U)HMW-PE) are used for neutron shielding purposes in casks for storage and transport of spent fuel and high-level waste due to their extremely high hydrogen content. During their service life of several decades as cask components, the PE materials are exposed to neutron and gamma radiation from the radioactive inventory of the casks, mechanical assembling stresses and temperature. All these combined effects affect the material properties of such components which in turn may be crucial for some possible accident scenarios.
At the Bundesanstalt für Materialforschung und -prüfung (BAM), the effects of high temperature exposure in combination with subsequent or previous irradiation were investigated with a comprehensive aging program including thermal aging at 125 °C for different aging periods up to 5 years and irradiation with doses ranging from 50 to 600 kGy.
This contribution provides an overview of the ongoing research related to the structural changes of (U)HMW-PE induced by gamma irradiation and high temperature exposure and focuses on current research perspectives at BAM with regard to the prediction of the dynamic behavior of the material during extended interim storage in case of an accident scenario. First results of the coupled effect of temperature, radiation and mechanical loading will be presented. The effect of microstructural changes induced by gamma irradiation and high temperature on the mechanical behavior of (U)HMW-PE will be assessed.
Overview of ongoing research and future prospects on polyethylene neutron shielding materials at BAM
(2023)
The extension of the interim storage period of radioactive waste before disposal will cause additional challenges for the nuclear waste management in Germany, so that an extensive knowledge of the long-term performance of casks, including their components and inventories, will be required for future extended storage licenses.
Ultra-high and high molecular weight polyethylenes ((U)HMW-PE) are used for neutron shielding purposes in casks for storage and transport of spent fuel and high-level waste due to their extremely high hydrogen content. During their service life of several decades as cask components, the PE materials are exposed to neutron and gamma radiation from the radioactive inventory of the casks, mechanical assembling stresses and temperature. All these combined effects affect the material properties of such components which in turn may be crucial for some possible accident scenarios.
At the Bundesanstalt für Materialforschung und -prüfung (BAM), the effects of high temperature exposure in combination with subsequent or previous irradiation were investigated with a comprehensive aging program including thermal aging at 125 °C for different aging periods up to 5 years and irradiation with doses ranging from 50 to 600 kGy.
This contribution provides an overview of the ongoing research related to the structural changes of (U)HMW-PE induced by gamma irradiation and high temperature exposure and focuses on current research perspectives at BAM with regard to the prediction of the dynamic behavior of the material during extended interim storage in case of an accident scenario. First results of the coupled effect of temperature, radiation and mechanical loading will be presented. The effect of microstructural changes induced by gamma irradiation and high temperature on the mechanical behavior of (U)HMW-PE will be assessed.
Laser powder bed fusion (LPBF) of Ni-based superalloys shows great potential for high temperature applications, for example, as a burner repair application for gas turbines where the thin-walled structure is important. It motivates this work to investigate the evolution of microstructure and the anisotropic mechanical behavior when plate-like specimens are built with a thickness from 4 mm down to 1 mm. By performing texture analysis using neutron diffraction, a clear transition in fiber texture from <011> to <001> is indicated when the specimen becomes thinner. The residual stress shows no thickness dependence, and at the subsurface the residual stress reaches the same level as the yield strength. Due to the rough as-built surface, a roughness compensation method for mechanical properties of thin-walled structures is outlined and demonstrated. Tensile tests from room temperature up to 700 ◦C have been carried out. Anisotropic mechanical behavior is found at all temperatures, which is strongly related to the anisotropic texture evolution. Stronger texture evolution and grain rotations are discovered when the tensile loading is applied along the building direction. The mechanical behavior has been compared to a wrought material, where the high dislocation density and the subgrain structure of the LPBF material result in a higher yield strength. Combining the statistical texture analysis by neutron diffraction with mechanical testing, EBSD grain orientation mapping and the investigation of dislocation structures using transmission electron microscopy, this work illustrates the significance of texture for the thin-wall effect and anisotropic mechanical behavior of LPBF materials.
The subsurface residual stress in laser powder bed fused 316L structures was analyzed using X-ray diffraction (XRD) and layer removal. The influence of varying structure thicknesses was investigated. In this study the importance of combining surface roughness measurements with XRD was shown. Moreover, a clear relation between the structure thickness and the subsurface residual stress profiles was observed.
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.
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 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 the experimental and numerical method. 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 the 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 molten pool shape. The probability of keyhole collapse at the bottom increases significantly to 72% due to the oscillating laser power induced by the laser beam attenuation. The internal interplay between the metal vapor plume, molten pool shape, and the keyhole collapse are obtained. The developed model has been validated by the experiments, which shows a good agreement.
The contactless magnetohydrodynamic technology has been considered as a potential and promising method to improve the weld qualities of deep penetration laser beam welding. In this paper, numerical investigations are conducted to study the influence of the auxiliary oscillating magnetic field on the porosity suppression in laser beam welding of 5754 aluminum alloy. To obtain a deeper insight into the suppression mechanism, a three-dimensional transient multi-physical model is developed to calculate the heat transfer, fluid flow, keyhole dynamic, and magnetohydrodynamics. A ray tracing algorithm is employed to calculate the laser energy distribution on the keyhole wall. A time-averaged downward Lorentz force is produced by an oscillating magnetic field. This force acts in the molten pool, leading to a dominant downward flow motion in the longitudinal section, which blocks the bubble migration from the keyhole tip to the rear part of the molten pool. Therefore, the possibility for the bubbles to be captured by the solidification front is reduced. The electromagnetic expulsive force provides an additional upward escaping speed for the bubbles of 1 m/s ~ 5 m/s in the lower and middle region of the molten pool. The simulation results are in a good agreement with experimental measurements. Based on the results obtained in this study, a better understanding of the underlying physics in laser beam welding enhanced by an auxiliary oscillating magnetic field can be provided and thus the welding process can be further optimized reducing the porosity formation.
The contactless magnetohydrodynamic technology has been considered as a potential and promising method to improve the weld qualities of deep penetration laser beam welding. In this paper, numerical investigations are conducted to study the influence of the auxiliary oscillating magnetic field on the porosity suppression in laser beam welding of 5754 aluminum alloy. To obtain a deeper insight into the suppression mechanism, a three-dimensional transient multi-physical model is developed to calculate the heat transfer, fluid flow, keyhole dynamic, and magnetohydrodynamics. A ray tracing algorithm is employed to calculate the laser energy distribution on the keyhole wall. A time-averaged downward Lorentz force is produced by an oscillating magnetic field. This force acts in the molten pool, leading to a dominant downward flow motion in the longitudinal section, which blocks the bubble migration from the keyhole tip to the rear part of the molten pool. Therefore, the possibility for the bubbles to be captured by the solidification front is reduced. The electromagnetic expulsive force provides an additional upward escaping speed for the bubbles of 1 m/s ~ 5 m/s in the lower and middle region of the molten pool. The simulation results are in a good agreement with experimental measurements. Based on the results obtained in this study, a better understanding of the underlying physics in laser beam welding enhanced by an auxiliary oscillating magnetic field can be provided and thus the welding process can be further optimized reducing the porosity formation.
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.
Magnetohydrodynamic technology is increasingly recognized as a promising approach for enhancing the quality of deep penetration laser beam welding. This study employs experimental and numerical methods to investigate the effects of an auxiliary oscillating magnetic field on reducing porosity in the laser beam welding of 5754 aluminum alloy. The experimental results clearly demonstrate a significant reduction in the porosity ratio, thereby validating the efficacy of applying MHD technology in mitigating porosity during the laser beam welding process. In addition, a transient 3D multi-physical model has been developed, integrating the magnetohydrodynamic and metal vapor plume, to gain a more comprehensive understanding of the porosity suppression mechanism. The introduction of an oscillating magnetic field generates a time-averaged downward Lorentz force. This Lorentz force, in turn, induces an electromagnetic expulsive force, which effectively increases the upward escape velocity of bubbles in the molten pool. Furthermore, the molten pool shape is significantly enlarged, which further facilitate the escape of bubbles. The simulation results agree well with the experimental results.
Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase of the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are analyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain size after welding verifies the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains that have been solidified and formed previously from further growth and generates some small cellular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement.
Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase in the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are analyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain
size after welding verify the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains, that have been solidified and formed previously, from further growth and generates some small cellular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement.
Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase in the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are ana lyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain size after welding verify the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains, that have been solidified and formed previously, from further growth and generates some small cel lular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement.
Electromagnetic stirring is known to promote material flow, reduce porosity, uniform elements distribution, and refine grain in laser beam welding (LBW), which enhances the applicability of LBW in various industries. In this study, a phase-field model of dendrite growth in AA5754 Al alloy electromagnetic stirring laser beam welding was established. The model considered the thermal electromagnetic Lorentz force resulting from the interaction between the electric field generated by the Seebeck effect and the magnetic field, as well as the temperature gradient and solidification rate of the solidification interface obtained from the computational fluid dynamics electromagnetic stirring LBW model. The variation rules of dendrite growth with different magnetic parameters and effects are analyzed. Comprehensively, the magnetic field promotes the solidification rate, thus promoting interfacial instability and a large magnetic flux density leads to a faster interface instability. The solidification rate as well as the temperature gradient affect the growth rate, and the accelerated growth caused by the so lidification rate with a high frequency and a large magnetic flux density effectively inhibits the slow growth caused by the temperature gradient. The thermal electromagnetic Lorentz force is the main factor for the branch increment at low frequencies, while both thermal electromagnetic Lorentz force and temperature gradient in crease the number of branches at high frequencies. The calculated average branch numbers considering various factors in the stable stage under different magnetic parameters were consistent with the results of the scanning electron microscope tests.
Numerical analysis of ultrasonic vibration enhanced friction stir welding of dissimilar Al/Mg alloys
(2023)
The ultrasonic vibration enhanced friction stir welding (UVeFSW) process has unique advantages in joining dissimilar Al/Mg alloys. While there are complex coupling mechanisms of multi-fields in the process, it is of great significance to model this process, to reveal the influence mechanism of ultrasonic vibration on the formation of Al/Mg joints.
In this study, the acoustic-plastic constitutive equation was established by considering the influence of both ultrasonic softening and residual hardening on the flow stress at different temperatures and strain rates. And the ultrasonic induced friction reduction (UiFR) effect on friction coefficient in different relative directions at the FSW tool-workpiece interface was quantitatively calculated and analyzed.
The Al/Mg UVeFSW process model was developed through introducing the above acoustic effects into the model of Al/Mg friction stir welding (FSW). The ultrasonic energy is stronger on the aluminum alloy side. In the stirred zone, there is the pattern distribution of ultrasonic sound pressure and energy. The heat generation at the tool-workpiece contact interface and viscous dissipation were reduced after applying ultrasonic vibra-tion. Due to the UiFR effect, the projection of friction coefficient and heat flux distributions at the tool-workpiece interface present a "deformed" butterfly shape. The calculated results show that ultrasonic vibra-tion enhanced the material flow and promoted the mixing of dissimilar materials.
Numerical analysis of ultrasonic vibration enhanced friction stir welding of dissimilar Al/Mg alloys
(2022)
The ultrasonic vibration enhanced friction stir welding (UVeFSW) process has unique advantages in joining dissimilar Al/Mg alloys. While there are complex coupling mechanisms of multi-fields in the process, it is of great significance to model this process, to reveal the influence mechanism of ultrasonic vibration on the formation of Al/Mg joints.
In this study, the acoustic-plastic constitutive equation was established by considering the influence of both ultrasonic softening and residual hardening on the flow stress at different temperatures and strain rates. And the ultrasonic induced friction reduction (UiFR) effect on friction coefficient in different relative directions at the FSW tool-workpiece interface was quantitatively calculated and analyzed.
The Al/Mg UVeFSW process model was developed through introducing the above acoustic effects into the model of Al/Mg friction stir welding (FSW). The ultrasonic energy is stronger on the aluminum alloy side. In the stirred zone, there is the pattern distribution of ultrasonic sound pressure and energy. The heat generation at the tool-workpiece contact interface and viscous dissipation were reduced after applying ultrasonic vi-bration. Due to the UiFR effect, the projection of friction coefficient and heat flux distributions at the tool-workpiece interface present a "deformed" butterfly shape. The calculated results show that ultrasonic vibration enhanced the material flow and promoted the mixing of dissimilar materials.
Self-mated magnesia stabilized zirconia (Mg-PSZ) ceramic sliding couples have been investigated at 100 N load (P0max= 1324 MPa) in oscillating sliding conditions in different humidity conditions in air and in hot steam. Temperatures have been varied up to 400 °C and pressures up to 6 bars. The results show that the wear behavior of MgO-ZrO2 under high Hertzian contact pressures is strongly dependent on temperature and is similar for both dry oscillating and oscillating in hot steam. However, although the evolution in wear rates on temperature is similar and the wear rates of MgO-ZrO2 plunged above 300 °C in hot steam and air by nearly three orders of magnitude, SEM micrographs revealed in hot steam at 400 °C smooth wear tracks. In contrast, hot steam enhanced the tribochemistry of self-mated alumina couples and reduced wear rates. Hot steam decreased the coefficients of friction of MgO-ZrO2 with increasing temperature, but not the wear rates.
Niobium carbide is a ceramic material which can be used with excellent results to replace tungsten carbide with cobalt binder. Furthermore, it might be manufactured by classic ceramic technologies and even colloidal processing. To achieve high toughness and strength, it is necessary to have a perfect mix of hard phase and binder, which is mainly achieved by ball milling. Mechanical and physical properties as well as results on different tribological and application-oriented machining tests are presented. The results have been compared with results obtained with NbC grades with Co and Fe3Al binders as well as with pure binderless hot-pressed NbC and SPS sintered Nb2O5.