Wissenschaftliche Artikel der BAM
Filtern
Dokumenttyp
Schlagworte
- Laser beam welding (25)
- Additive manufacturing (23)
- Welding (14)
- Microstructure (11)
- Additive Manufacturing (10)
- Hydrogen (10)
- Mechanical properties (10)
- Laser powder bed fusion (9)
- Residual stress (9)
- Residual stresses (9)
- Solidification cracking (8)
- Friction (7)
- Tribology (7)
- Ultrasonic-assisted milling (7)
- Wear (7)
- Creep-resistant steel (6)
- Laser metal deposition (6)
- Process monitoring (6)
- Thermography (6)
- Fatigue (5)
- Resistance spot welding (5)
- Surface integrity (5)
- TIG welding (5)
- AFM (4)
- AISI 316L (4)
- Diffusible hydrogen (4)
- Hardness (4)
- Heat accumulation (4)
- High-strength steel (4)
- Hybrid laser arc welding (4)
- Hybrid laser-arc welding (4)
- L-PBF (4)
- Laser Powder Bed Fusion (4)
- Neutron diffraction (4)
- Numerical modeling (4)
- Selective laser melting (SLM) (4)
- Stress relief cracking (4)
- Thick-walled steel (4)
- AGIL (3)
- Alloy 36 (3)
- Artificial neural network (3)
- Atomic force microscopy (3)
- DED (3)
- Deep penetration (3)
- Fatigue crack propagation threshold (3)
- Fatigue tests (3)
- Heat treatment (3)
- High entropy alloy (3)
- Hydrogen embrittlement (3)
- In situ measurement (3)
- In situ monitoring (3)
- Inconel 718 (3)
- Infrared thermography (3)
- LIBS (3)
- Laser powder bed fusion (L-PBF) (3)
- Mechanical Engineering (3)
- Numerical modelling (3)
- Polymers (3)
- Post weld heat treatment (3)
- Quality assurance (3)
- Steel (3)
- Submerged arc welding (3)
- Ti-6Al-4V (3)
- Tubular X-joints (3)
- Varestraint test (3)
- Weld pool shape (3)
- 316L (2)
- AISI 304L (2)
- Additive manufacturing (AM) (2)
- Alloy modification (2)
- Austenite-to-martensite transformation (2)
- Bragg-edge imaging (2)
- Bulge effect (2)
- Chemical composition (2)
- Computed Tomography (2)
- Computed tomography (2)
- Contact resonance (2)
- Crack (2)
- Cracking (2)
- Critical strain (2)
- Crystallographic texture (2)
- Cyclic R-curve (2)
- Data preparation (2)
- Debye–Waller factor (2)
- Deuterium (2)
- Diffusion (2)
- Directed Energy Deposition (2)
- Distortion (2)
- EBSD (2)
- Electron backscattered diffraction (2)
- Finite element simulation (2)
- Force-distance curves (2)
- Fracture (2)
- Full penetration (2)
- GMA welding (2)
- Gap bridgeability (2)
- Gas metal arc welding (2)
- Gas tungsten arc welding (GTAW) (2)
- Grain refinement (2)
- Hardmetal (2)
- Heat control (2)
- High strength steels (2)
- High-entropy alloy (2)
- High-power laser beam welding (2)
- High-strength structural steel (2)
- Hot cracking (2)
- Hot stamping (2)
- Hydrogen Embrittlement (2)
- Hydrogen assisted cracking (2)
- Hydrogen-assisted cracking (2)
- Implant test (2)
- Inter layer time (2)
- LPBF (2)
- Laser beam melting (LBM) (2)
- Laser energy distribution (2)
- Laser hybrid welding (2)
- Laser-metal-deposition (2)
- Liquid metal embrittlement (2)
- Low transformation temperature (LTT) steel (2)
- Lubricants (2)
- Machining (2)
- Mechanics of Materials (2)
- Medium entropy alloy (2)
- Metals and Alloys (2)
- Microstructure characterization (2)
- Neutron imaging (2)
- Neutron radiography (2)
- Niobium carbide (2)
- Niobium carbide (NbC) (2)
- Numerical process simulation (2)
- Numerical simulation (2)
- Offshore (2)
- Optical flow (2)
- Pipeline steel (2)
- Plasma-transferred arc welding (2)
- Porosity (2)
- Post-weld heat treatment (2)
- Preheating (2)
- Ray tracing (2)
- Refill friction stir spot welding (2)
- Representative specimens (2)
- Residual Stress (2)
- Residual stress analysis (2)
- SSRT (2)
- Selective Laser Melting (2)
- Selective Laser Melting (SLM) (2)
- Simulation (2)
- Single pass welding (2)
- Software (2)
- Surface modification (2)
- Technical crack detection (2)
- Tensile properties (2)
- Texture (2)
- Thermal history (2)
- ToF-SIMS (2)
- Tool wear (2)
- Tribologie (2)
- WAAM (2)
- Weld pool dynamics (2)
- Wire arc additive manufacturing (2)
- X-ray diffraction (2)
- i-TRIBOMAT (2)
- 100Cr6 (AISI 52100) steel (1)
- 2101 duplex stainless steel (1)
- 3D Scanning (1)
- 3D printing (1)
- 9% Ni Steel (1)
- 9%Ni steel (1)
- AC magnetic field (1)
- AHSS (1)
- AM feature integration (1)
- ASTM E647 (1)
- Abdichtbauwerk (1)
- Accoustic emission (1)
- Additive Manufacturing (AM) (1)
- Additives (1)
- Advanced high strength steels (1)
- Advanced high-strength steel (1)
- Aging (1)
- AlMg0.7SiTiB filler wire (1)
- AlSi10Mg (1)
- AlSi10Mg alloy (1)
- Alite (1)
- Alkyd resin-based coating (1)
- Aluminum alloys (1)
- Aluminum bronze (1)
- Analytical calculation (1)
- Applications (1)
- Artificial Intelligence (1)
- Artificial intelligence (1)
- As-built LPBF IN718 alloy (1)
- Atomic force microscope (1)
- Austenitic stainless steels (1)
- Automated arc welding (1)
- Automated manufacturing (1)
- Automotive (1)
- Backlight (1)
- Bainitischer Schmiedestahl (1)
- Bauteilauslegung (1)
- Bayesian technique (1)
- Bead-on-plate welds (1)
- Beam oscillation (1)
- Bending test (1)
- Betriebsfestigkeit (1)
- Binders (1)
- Bismuth titanates (1)
- Bohrlochsonde (1)
- Bruchmechanik (1)
- Bulge formation (1)
- Bulging (1)
- Bulging effects (1)
- CFD model (1)
- Cantilever microprobe (1)
- Carbide (1)
- Carbon (1)
- Carbon dioxide footprint (1)
- Carbon steel (1)
- Catalysis (1)
- Cellular substructure (1)
- Cermet (1)
- Characterisation (1)
- Characterization (1)
- Characterization of corrosion layers (1)
- Charakterisierung (1)
- Charpy impact toughness (1)
- Chunky graphite (1)
- Cimensional Accuracy (1)
- Circumferential weld (1)
- Clinker substitute (1)
- Clustering (1)
- Co-Cr-alloy (1)
- Cobalt-chromium alloy (1)
- Cold cracking (1)
- Cold cracking safety (1)
- Columnar crystal growth (1)
- Component test (1)
- Component-like test (1)
- Composites (1)
- Computed tomography (CT) (1)
- Computer vision (1)
- Condensed Matter Physics (1)
- Condition monitoring (1)
- Convolutional neural network (1)
- Convolutional neural networks (CNN) (1)
- Core-shell structures (1)
- Corrosion (1)
- Crack closure effect (1)
- Crack-tip constraint (1)
- Creep (1)
- Creep behavior (1)
- Creep-resisting materials (1)
- Critical strain rate (1)
- Cryogenic steel (1)
- Cryogenic temperature (1)
- Crystal branch development (1)
- Crystal plasticity (1)
- Cutting forces (1)
- Cutting tool (1)
- Cyclic loading (1)
- Cylindrical turning (1)
- DED-EB (1)
- DED-arc (1)
- Damage prediction (1)
- Damage tolerance (1)
- Data evaluation methods (1)
- Data fusion (1)
- Data-driven quality assurance (1)
- Debye-Waller-Faktor (1)
- Deep learning (1)
- Deep penetration laser beam welding (1)
- Defect detection (1)
- Defects (1)
- Dental materials (1)
- Dichtungen (1)
- Diffraction (1)
- Diffraction-elastic constants (1)
- Diffusion/diffusivity (1)
- Digital Image Correlation (1)
- Digital image correlation (1)
- Digitalisation (1)
- Digitalization (1)
- Direct laser deposition (1)
- Directed energy deposition (1)
- Dislocation density (1)
- Dispersive XAS (1)
- Displacement (1)
- Dissimilar joints (1)
- Dissimilar materials (1)
- Dissimilar metal weld (1)
- Distortion upon baseplate removal (1)
- Ditigtal image correlation (1)
- Dual phase steel (1)
- Duplex AISI 2205 (1)
- Duplex stainless steel (1)
- Duplex stainless steels (1)
- Duplex steels (1)
- Dwell-time (1)
- EBAM (1)
- Edge quality (1)
- Effect of scanning strategies (1)
- Elastic modulus (1)
- Elastomers (1)
- Electrochemical permeation (1)
- Electromagnetic backing (1)
- Electromagnetic field (1)
- Electromagnetic forces (1)
- Electromagnetic stirring (1)
- Electromagnetic weld pool support (1)
- Electromagnetic weld pool support system (1)
- Electron backscatter diffraction (1)
- Electron beam welding (1)
- Electron microscopy (1)
- Element transport (1)
- Embedded electronics (1)
- Emisssivity (1)
- End crater (1)
- Endurance limit (1)
- Energy Engineering and Power Technology (1)
- Environmental conditions (1)
- Environmental impact categories (1)
- Error sources analysis (1)
- Evaporation (1)
- Experimental determination (1)
- Experimental procedure (1)
- FAIR data (1)
- FAT class (1)
- FEM (1)
- Fatigue Strength (1)
- Fatigue damage (1)
- Fatigue life (1)
- Fatigue limit (1)
- Fatigue properties (1)
- Femtosecond laser (1)
- Femtosecond laser processing (1)
- Ferritic spheroidal graphite cast iron (1)
- Ferroelectricity/ferroelectric materials (1)
- Filler material distribution (1)
- Filler wire (1)
- Filler wire mixing (1)
- Finish milling (1)
- Finite Element Method (1)
- Finite element (FE) (1)
- Finite element analysis (1)
- Finite element method (1)
- Finite element method (FEM) (1)
- Flange width (1)
- Flaw detection (1)
- Flüssigmetallinduzierte Rissbildung (1)
- Formation (1)
- Fractography (1)
- Fracture Mechanics (1)
- Frequency domain (1)
- Frequenzanalyse (1)
- Friction stir welding (1)
- Fuel Technology (1)
- Fusion zone size (1)
- Galvanized steel (1)
- General analytical solutions (1)
- Geteilte Infrastruktur (1)
- Green Deal (1)
- HAZ-softening (1)
- HCF (1)
- HSLA steel (1)
- Hard metals (1)
- Hardly separable problem (1)
- Harmonisation (1)
- Hastelloy X (1)
- Heat Treatment (1)
- Heat source models (1)
- Heat-affected zone (1)
- High power laser beam welding (1)
- High process speeds (1)
- High strength steel (1)
- High-entropy alloys (1)
- High-pressure hydrogen environment (1)
- High-strength filler metals (1)
- High-strength steel filler metal (1)
- High-strength steels (1)
- Hochfester Stahl (1)
- Hollow Specimen Technique (1)
- Hollow specimen (1)
- Hollow specimen technique (1)
- Hot Cracks (1)
- Hot cracking test (1)
- Hot tensile test (1)
- Hot working tool steel (1)
- Hybrid Laser arc Welding (1)
- Hybrid repair (1)
- Hydraulic reactivity (1)
- Hydrogen Transfer Film (1)
- Hydrogen diffusion (1)
- Hydrogen measurement (1)
- IBESS (1)
- IBESS Approach (1)
- IN 718 (1)
- IN725 (1)
- ISO 12108 (1)
- Image processing (1)
- Image registration (1)
- Impact Absorbed Energy (1)
- Implants (1)
- In situ (1)
- In-situ process monitoring (1)
- In-situ tensile test (1)
- Inconel 625 (1)
- Industrial and Manufacturing Engineering (1)
- Instumented indentation test (1)
- Integrated alignment features (1)
- Intelligent tribological material characterization (1)
- Intelligente tribologische Werkstoffcharakterisierung (1)
- Inter-layer time (1)
- Interoperability (1)
- Iron aluminide (1)
- Joining dissimilar materials (1)
- Joining technology (1)
- Kernel average misorientation (1)
- Keyhole collapse (1)
- Keyhole dynamics (1)
- Kitagawa-Takahashi diagram (1)
- L-PBF IN718 material (1)
- LCF (1)
- LIBS TIG welding (1)
- LMD (1)
- LTT Weld Filler Materials (1)
- LTT filler metal (1)
- LTT weld filler materials (1)
- Lab-to-field up-scaling (1)
- Lab-to-field upscaling (1)
- Lack-of-fusion (1)
- Lamé curves (1)
- Large-scale test (1)
- Laser Metal Deposition (LMD) (1)
- Laser Powder Bed Fusion (L-PBF) (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser Powder Bed Fusion (PBF-LB/M, L-PBF) (1)
- Laser Welding (1)
- Laser beam melting (1)
- Laser cutting (1)
- Laser energy absorption (1)
- Laser implantation (1)
- Laser metal deposition (LMD) (1)
- Laser powder-based directed energy deposition (1)
- Laser welding (1)
- Laser-based additive manufacturing (1)
- Laser-induced oxide layer (1)
- Laser-induced periodic surface strctures (LIPSS) (1)
- Laser-induced periodic surface structures (LIPSS) (1)
- Laser-plasma hybrid (1)
- Lead-free ceramics (1)
- Life cycle assessment (1)
- Lifetime (1)
- Liquid Metal Embrittlement (1)
- Liquid phase sintering (1)
- Local Weld Geometry (1)
- Local critical strain (1)
- Local fatigue approaches (1)
- Local fatigue spproaches (1)
- Localized laser dispersing (1)
- Lorentz force (1)
- Lorentz forces (1)
- Low-cycle fatigue (1)
- L‐PBF (1)
- MVT (1)
- MWIR (1)
- Machine learning (1)
- Machine vision (1)
- Magnesium Alloy (1)
- Magnesium alloy (1)
- Magnetic bath support (1)
- Magnetic field (1)
- Martensite (1)
- Matching ferritic filler metal (1)
- Materials database (1)
- Mechanical anisotropy (1)
- Mechanical mismatching (1)
- Mechanical property (1)
- Melt pool depth (1)
- Melt pool dynamics (1)
- Metal (1)
- Metal mixing (1)
- Microalloying influences (1)
- Microbiologically influenced corrosion (1)
- Microcracking (1)
- Microfocus X-ray computer tomography (μCT) (1)
- Mild steels (1)
- Minimum Waiting Time (1)
- Mining head gear (1)
- Misalignment of edges (1)
- Model calibration (1)
- Model order reduction (1)
- Modellierung (1)
- Modelling studies (1)
- Modification of structural morphology (1)
- Molten pool (1)
- Multi-materials joining (1)
- Multi-physical modelling (1)
- Multi-principal element alloy (1)
- Multi-principal element alloys (1)
- Multiple principal element alloy (1)
- Multiple reflections (1)
- NIR (1)
- Nanotribology (1)
- Nanowear (1)
- Natural silver wires (1)
- Near-surface X-ray diffraction (1)
- Neutron Diffraction (1)
- Neutron and X-ray diffraction (1)
- Ni alloy (1)
- Ni-based austenitic filler metal (1)
- Nickel (1)
- Notch stress approach (1)
- Novel metrology (1)
- Numerical Simulation (1)
- Numerical investigation (1)
- Numerical welding simulations (1)
- Offshore steel grade (1)
- Online Process Monitoring (1)
- Online monitoring (1)
- Open science (1)
- Open source (1)
- Optical Tomography (1)
- Optical tomography (1)
- Oscillating ball-on-disc test (1)
- Oscillating magnetic field (1)
- Oscillating vapor plume (1)
- Oxidation (1)
- PBF-LB/M (1)
- PBF-LB/M/316L (1)
- Parabolic flight (1)
- Partial penetration (1)
- Particle transfer (1)
- Path planning (1)
- Peak stress method (1)
- Peak stress method (PSM) (1)
- Penetration depth (1)
- Periodic solidification pattern (1)
- Piezoresistive (1)
- Piezoresistive cantilever (1)
- Pipe weld preparation (1)
- Plasma cutting (1)
- Plasma-cut samples (1)
- Plasma-transferred-arc (1)
- Plastic deformation (1)
- Polymer (1)
- Polymere (1)
- Polyurethan (1)
- Position detection (1)
- Post Weld Heat Treatment (PWHT) (1)
- Potential drop technique (1)
- Potentiodynamic measurements (1)
- Ppreheating temperature (1)
- Precipitation hardening aluminum alloys (1)
- Pressure-dependent solubility (1)
- Prevention (1)
- Probabilistic assessment (1)
- Process chain (1)
- Process simulation (1)
- Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten (1)
- Proper generalized decomposition (1)
- Properties (1)
- Prostheses (1)
- Pulsed laser beam welding (1)
- Quality monitoring (1)
- Ray teacing (1)
- Ray-tracing methods (1)
- Reactor conditions (1)
- Reference data (1)
- Reference standards (1)
- Refraction (1)
- Renewable Energy, Sustainability and the Environment (1)
- Repair welding (1)
- Repair-welding (1)
- Research data management (1)
- Residual Stresses (1)
- Residual stress in AM (1)
- Residual stress state (1)
- Ripples (1)
- Rissbildung in Stahl (1)
- Roughness (1)
- S-N curve (1)
- S-Phase (1)
- SEM (1)
- SIMS (1)
- SLM printed plasma torch (1)
- SWIR (1)
- SWIR thermography (1)
- Sample random results (1)
- Scan strategy influence (1)
- Scanning kelvin probe force microscopy (1)
- Scattering (1)
- Schallemission (1)
- Seam geometry (1)
- Selective laser beam melting (1)
- Selektive-laser-melting (1)
- Shared infrastruture (1)
- Shear modulus (1)
- Ship building (1)
- Shipbuilding steel (1)
- Sicherheit (1)
- Single asperity (1)
- Single asperity contact (1)
- Single-pass welding (1)
- Sliding wear (1)
- Small-scale specimens (1)
- Solidification (1)
- Solubility (1)
- Spark plasma sintering (1)
- Stainless Steel (1)
- Stainless steel (1)
- Stainless steels (1)
- Staircase method (1)
- Statistical analysis (1)
- Steel and aluminium (1)
- Steelmaking slag (1)
- Stochastic sample functions (1)
- Strain fields prediction (1)
- Strain measurement (1)
- Strain-free lattice references (1)
- Strain-free lattice spacing (1)
- Stress Relief Cracking (SRC) (1)
- Stress balance (1)
- Stress balance condition (1)
- Structural stress approach (1)
- Structure analysis (1)
- Sub-oxide (1)
- Supermartensitic steel (1)
- Surface Integrity (1)
- Surface preparation (1)
- Surface processing (1)
- Surface structures (1)
- Synchrotron radiation (1)
- TEKKEN (1)
- Temperature (1)
- Temperature dependence (1)
- Tensile Strength (1)
- Tensile loading (1)
- Tensile resistance spot welding experiment (1)
- Tensile strength (1)
- Tensile testing (1)
- Thermal analysis (1)
- Thermal cycles (1)
- Thermodynamic modelling (1)
- Thermodynamic simulation (1)
- Thick materials (1)
- Thick plate welding (1)
- Thick-plate welding (1)
- Thick-walled (1)
- Titanium (1)
- Trapping (1)
- Tribo-Analytik (1)
- Tribo-analytics (1)
- Tungsten carbide (WC) (1)
- Two-dimensional solidification (1)
- Two-run welding technique (1)
- UV-blocker addition (1)
- Ultraschall-Echoverfahren (1)
- Ultraschall-Messtechnik (1)
- Ultrasonic Assisted Machining (1)
- Ultrasonic machining (1)
- Upscaling (1)
- V-notch impact toughness (1)
- Vaporization (1)
- Varestraint testing (1)
- Verschlussbauwerk (1)
- WRC 1992 diagram (1)
- Wear particles (1)
- Weathering tests (1)
- Weld metal cracking (1)
- Weld pool (1)
- Weldability (1)
- Welded Joints (1)
- Welded joint (1)
- Welded joints (1)
- Welding Simulation (1)
- Welding simulation (1)
- Welding thermal cycle (1)
- Weldx (1)
- Werkstoffdatenbank (1)
- White light interferometry (1)
- Widerstandspunktschweißen (1)
- Wind energy (1)
- Wire electron beam additive manufacturing (1)
- Wire feed laser beam welding (1)
- Wire-based additive manufacturing (1)
- X-ray Diffraction (1)
- X-ray and Neutron Diffraction (1)
- X-ray and neutron diffraction (1)
- X-ray computed tomography (XCT) (1)
- X-ray refraction (1)
- Young's modulus (1)
- Zero wear (1)
- Zerstörungsfreie Prüfung (1)
- Zink (1)
- contact resonance (1)
- infrared Thermography (1)
- µ-gravity (1)
- µCT (1)
- µCT-analysis (1)
- μCT-analysis (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (215) (entfernen)
Paper des Monats
- ja (9)
One of the main factors affecting the use of lasers in the industry for welding thick structures is the process accompanying solidification cracks. These cracks mostly occurring along the welding direction in the welding center, and strongly affect the safety of the welded components. In the present study, to obtain a better understanding of the relation between the weld pool geometry, the stress distribution and the solidification cracking, a three-dimensional computational fluid dynamic (CFD) model was combined with a thermo-mechanical model. The CFD model was employed to analyze the flow of the molten metal in the weld pool during the laser beam welding process. The weld pool geometry estimated from the CFD model was used as a heat source in the thermal model to calculate the temperature field and the stress development and distributions. The CFD results showed a bulging region in the middle depth of the weld and two narrowing areas separating the bulging region from the top and bottom surface. The thermo-mechanical simulations showed a concentration of tension stresses, transversally and vertically, directly after the solidification during cooling in the region of the solidification cracking.
Investigations on weldability often deal with hot cracking as one of the most prevalent failure mechanisms during weld fabrication. The modified varestraint transvarestraint hot cracking test (MVT) is well known to assess the hot cracking susceptibility of materials. The shortcoming of this approach is that the information is only from the very near surface region which inhibits access to the characteristic of the hot crack network in the bulk. Here, we report about an alternative approach to monitor the entire 3D hot crack network after welding by means of microfocus X-ray computer tomography (µCT). However, to provide sufficient high spatial resolution small samples must be sectioned from the MVT-welded joint. The sampling is accompanied by local relaxation of the residual stress distributions that are induced by welding, which can have an impact on the crack volumes prior to the sampling. The studies were carried out to investigate the hot cracking susceptibility of low transformation temperature filler materials (LTT). As high compression residual stresses up to -600 MPa in the area of the crack networks were determined by means of the contour method, stress relaxation caused by sectioning for µCT sample extraction can affect the detectability of the cracks later on. X-ray diffraction studies revealed surface residual stress relaxations up to about 400 MPa due to cutting. To investigate this effect, the specimens with hot cracks were subjected to a load test with known stress states. The results clearly show that local stress relaxations will have a strong impact on the volume images reconstructed from tomography analysis. This effect must be considered during hot crack assessment on basis of µCT data.
Due to rapid, localized heating and cooling, distortions accumulate in additive manufactured laser metal deposition (LMD) components, leading to a loss of dimensional accuracy or even cracking. Numerical welding simulations allow the prediction of these deviations and their optimization before conducting experiments. To assess the viability of the simulation tool for the use in a predictive manner, comprehensive systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to Cluster these products in new assembly oriented product families for the optimization.
The performance and safety of welded high-strength low-alloyed steel (HSLA) components are substantially affected by the stresses occurring during and after welding fabrication, especially if welding shrinkage and distortion are severely restrained. The surrounding structure of the whole component affects loads in the far-field superimposing with welding stresses in the near-field of the weld. In this study a unique testing facility was used to restrain shrinkage and bending while analyse multiaxial far-field loads (max. 2 MN) during assembly of thick-walled component. A novel approach for the assessment of the in-situ-measured far-field data in combination with the actual weld geometry was elaborated. For the first time, analyses of the global bending moments of restrained welds based on the neutral axis of the actual weld load bearing section were achieved. Hence, far-field measurements offered the possibility to determine critical near-field stresses of the weld crosssections for the entire joining process. This work presents the approach for far-to-near field in-situ determination of stresses in detail for the 2-MN-testing system based on an extensive experimental work on HSLA steel welds, which demonstrates sources and consequences of these high local welding stresses. Thus, it was clarified, why the first weld beads are crucial regarding welding stresses and cold cracking, which is well known, but has never been measured so far. Accompanying analyses using X-ray diffraction (XRD) after welding show effects on local residual stress distributions. These analyses indicated viable prospects for stress reduction during assembly of thick-walled HSLA steel components.
Laser-Metal-Deposition (LMD) and Plasma-Transferred-Arc (PTA) are well known Technologies which can be used for cladding purposes. The prime objective in combining LMD and PTA as a Hybrid Metal Deposition-Technology (HMD) is to achieve high Deposition rates at low thermal Impact. Possible applications are coatings for wear protection or repair welding for components made of steel. The two energy sources (laser and Plasma arc) build a Joint process Zone and are configurated to constitute a stable process at laser powers between 0.4-1 kW (defocused) and Plasma currents between 75-200 A. Stainless steel 316L serves as filler material. For this HMD process, a Plasma Cu-nozzle is designed and produced by powder bed based Selective Laser Melting. The potential of the HMD Technology is investigated and discussed considering existing process. This paper demonstrates how the interaction of the two energy sources effects the following application-relevant properties: Deposition rate, powder Efficiency and energy Input.
A transient simulation including the impact of the laser energy, the melting of the metal and the development of the weld pool was conducted to observe the evolution of the vapor capillary and the solidification of the melt in pulsed laser beam welding of AISI 304 steel. The phase field method was implemented to investigate the evolution and behavior of the liquid-gas interface during welding and to describe the condensed and vapor phases. The effects of phase transition, recoil pressure, thermo-capillary and natural convection, vaporization and temperature dependent material properties were taken into account. A Gaussian-like heat source under consideration of the Fresnel absorption model was used to model the energy input of the laser beam. The heat source model was extended by a newly developed empirical approach of describing multiple beam reflections in the keyhole. To validate this new model, the numerical results were compared to experimental data and good agreement regarding the size and shape of the weld pool was observed.
The geometry of the melt pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. In this study, a butt configuration of 15 mm thick structural steel and transparent quartz glass was used to observe the weld pool geometry by means of high-speed camera and an infrared camera recording. The observations show that the dimensions of the weld pool vary depending on the depth. The areas close to the weld pool surface take a teardrop-shape. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a 3D transient thermal-fluid numerical simulation was performed to obtain the weld pool shape and to understand the formation mechanism of the observed bulging effect. The model takes into account the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. The numerical results showed good accordance and were furthermore used to improve the understanding of the experimentally observed bulging effect.
Additive Manufacturing (AM) through the Selective Laser Melting (SLM) route offers ample scope for producing geometrically complex parts compared to the conventional subtractive manufacturing strategies. Nevertheless, the residual stresses which develop during the fabrication can limit application of the SLM components by reducing the load bearing capacity and by inducing unwanted distortion, depending on the boundary conditions specified during manufacturing. The present study aims at characterizing the residual stress states in the SLM parts using different diffraction methods. The material used is the nickel based superalloy Inconel 718. Microstructure as well as the surface and bulk residual stresses were characterized. For the residual stress analysis, X-ray, synchrotron and neutron diffraction methods were used. The measurements were performed at BAM, at the EDDI beamline of -BESSY II synchrotronand the E3 line -BER II neutron reactor- of the Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. The results reveal significant differences in the residual stress states for the different characterization techniques employed, which indicates the dependence of the residual state on the penetration depth in the sample. For the surface residual stresses, longitudinal and transverse stress components from X-ray and synchrotron agree well and the obtained values were around the yield strength of the material. Furthermore, synchrotron mapping disclosed gradients along the width and length of the sample for the longitudinal and transverse stress components. On the other hand, lower residual stresses were found in the bulk of the material measured using neutron diffraction. The longitudinal component was tensile and decreased towards the boundary of the sample. In contrast, the normal component was nearly constant and compressive in nature. The transversal component was almost negligible. The results indicate that a stress re-distribution takes place during the deposition of the consecutive layers. Further investigations are planned to study the phenomenon in detail.
Submerged arc welded (SAW) components of creep-resistant low-alloyed Cr-Mo-V steels are used for thick-walled heavy petrochemical reactors (wall-thickness up to 475 mm) as well as employed in construction of modern high-efficient fossil fired power plants. These large components are accompanied by significant restraints during welding fabrication, especially at positions of different thicknesses like welding of nozzles. As a result, residual stresses occur, playing a domi-nant role concerning so-called stress relief cracking (SRC) typically during post weld heat treat-ment (PWHT). Besides specific metallurgical factors (like secondary hardening due to re-precipitation), high tensile residual stresses are a considerable influence factor on SRC. For the assessment of SRC susceptibility of certain materials mostly mechanical tests are applied which are isolated from the welding process. Conclusions regarding the influence of mechanical factors are rare so far. The present research follows an approach to reproduce loads, which occur during welding of real thick-walled components scaled to laboratory conditions by using tests designed on different measures. A large-scale slit specimen giving a high restraint in 3 dimensions by high stiffness was compared to a medium-scale multi-pass welding U-profile specimen showing a high degree of restraint in longitudinal direction and a small-scale TIG-re-melted specimen. The small-scale specimens were additionally subjected to mechanical bending to induce loads that are found during fabrication on the real-scale in heavy components. Results show for all three cases compa-rable high tensile residual stresses up to yield strength with high gradients in the weld metal and the heat affected zone. Those high tensile stresses can be significant for cracking during further PWHT.
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.
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.
A simplified model for numerical simulation of laser metal deposition process with beam oscillation
(2018)
A model of laser metal deposition with beam oscillation has been developed. The proposed model consists of two coupled sub-models calculating the heat transfer in the deposited part and the free surface of the molten pool, respectively. The heat transfer simulation of the deposited part solves a three-dimensional quasi-stationary heat conduction problem. The free surface of the molten pool are determined by solving the Laplace-Young equation. The developed model enables the layer-by-layer prediction of the shape of the deposited part and the resulting temperature field. It is shown that for an oscillation amplitude equal to the beam radius the peak value of the heat flux decreases by about 53% and 73% in the case of lateral oscillation and circular oscillation, respectively. Lateral oscillating laser beam results in a higher penetration depth due to the higher thermal efficiency. The amplitude of the laser beam oscillation effects the shape of the deposited wall and the deposition rate. A good correlation between the numerically calculated and experimentally observed results is obtained.
This paper represents the results for proposed optical flow method based on the Lucas-Kanade (LK) algorithm applied to two different problems. The following observations can be made:
- The estimated strain and displacement for conducted tensile test are generally very close to those measured with conventional DIC-technique.
- The LK technique allows measurement of strain or displacement without special selection of a region of interest.
Using a novel optical measurement technique together with the optical flow algorithm, a twodimensional deformation analysis during welding was conducted. This technique is the first to provide a measurement of the full strain field locally in the immediate vicinity of the solidification front. Additionally, the described procedure of the optical measurement allows the real material-dependent values of critical strain characterizing the transition to hot cracking during laser welding processes to be determined.
The paper deals with the integration of a light emitting diode (LED) into an additive manufactured metal component. Selective laser melting (SLM) and laser metal deposition (LMD) are used. The material used is the chrome-nickel steel 316L. The basic component is manufactured by means of SLM and consists of a solid body and an area with grid structure. The solid body includes a duct in the shape of a groove with a recess for the positioning of the power cable. The LED is embedded in the grid structure via an inlet from the solid body. In further processing, the groove is filled with LMD. Two strategies with different parameter combinations were investigated. It shows that a high energy input near the power cable leads to its destruction. By using multiple parameter combinations during the manufacturing process, this destruction can be prevented. There was a comparison of both strategies with regard to the necessary number of tracks and duration of welding time.
Due to the increasing global demand for pure silver, native wire silver aggregates in very high purities are gaining more industrial attention. Up to the present, no substantial metallurgical Investigation of natural wire silver exists in the accessible literature. To convey urgently needed cross-disciplinary fundamental knowledge for geoscientists and metallurgical engineers, twenty natural wire silver specimens from eight different ore deposits have been investigated in detail for the first time by EBSD (Electron Back Scattering Diffraction), supported by light microscopy and micro-probe analyses. The improved understanding of the natural silver wire microstructure provides additional Information regarding the growth of natural silver aggregates in comparison to undesired artificial growth on electronic devices. Clear evidence is provided that natural silver curls and hairs exhibit a polycrystalline face-centered cubic microstructure associated with significant twinning. Although the investigated natural wire silver samples have relatively high purity (Ag > 99.7 wt.-%), they contain a variety of trace elements such as, S, Cu, Mn, Ni, Zn, Co and Bi, As and Sb. Additionally, Vickers micro-hardness measurements are provided for the first time which revealed that natural silver wires and curls are softer than it might be expected from conversion of the general Mohs hardness of 2.7.
Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.
To increase the competitiveness of jacket substructures compared to monopiles a changeover from an individual towards a serial jacket production based on automated manufactured tubular joints combined with standardized pipes has to be achieved. Therefore, this paper addresses fatigue tests of automatically welded tubular X-joints focusing on the location of the technical fatigue crack. The detected location of the technical crack is compared to numerical investigations predicting the most fatigue prone notch considering the structural stress approach as well as the notch stress approach. Besides, the welding process of the automated manufactured tubular X-joints is presented.
Among the various welding technologies, resistance spot welding (RSW) and laser beam welding (LBW) play a significant role as joining methods for the automobile industry. The application of RSW and LBW for the automotive body alters the microstructure in the welded areas. It is necessary to identify the mechanical properties of the welded material to be able to make a reliable statement about the material behavior and the strength of welded components. This study develops a method by which to determine the mechanical properties for the weldment of RSW and LBW for two dual phase (DP) steels, DP600 and DP1000, which are commonly used for the automotive bodies. The mechanical properties of the resistance spot weldment were obtained by performing tensile tests on the notched tensile specimen to cause an elongation of the notched and welded area in order to investigate its properties. In order to determine the mechanical properties of the laser beam weldment, indentation tests were performed on the welded material to calculate its force-penetration depth-curve. Inverse numerical simulation was used to simulate the indentation tests to determine and verify the parameters of a nonlinear isotropic material model for the weldment of LBW. Furthermore, using this method, the parameters for the material model of RSW were verified. The material parameters and microstructure of the weldment of RSW and LBW are compared and discussed. The results show that the novel method introduced in this work is a valid approach to determine the mechanical properties of welded high-strength steel structures. In addition, it can be seen that LBW and RSW lead to a reduction in ductility and an increase in the amount of yield and tensile strength of both DP600 and DP1000.