Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
Dokumenttyp
Sprache
- Englisch (237) (entfernen)
Schlagworte
- Laser beam welding (65)
- Additive manufacturing (18)
- Solidification cracking (18)
- Laser metal deposition (17)
- Microstructure (13)
- Numerical simulation (13)
- Mechanical properties (12)
- Resistance spot welding (10)
- Laser welding (9)
- Thick-walled steel (9)
- Hybrid laser-arc welding (8)
- Inconel 718 (8)
- Weld pool shape (8)
- Additive Manufacturing (7)
- Numerical modeling (7)
- Porosity (7)
- DED (6)
- Element transport (6)
- Hybrid laser arc welding (6)
- Laser Metal Deposition (6)
- Liquid metal embrittlement (6)
- Magnetohydrodynamics (6)
- Welding simulation (6)
- Artificial neural network (5)
- Critical strain (5)
- Electromagnetic weld pool support (5)
- High power laser beam welding (5)
- Hot cracking (5)
- Hot cracking test (5)
- Hybrid Laser Arc Welding (5)
- Laser hybrid welding (5)
- Magnetic field (5)
- Solidification (5)
- Ti-6Al-4V (5)
- Crack (4)
- Deep penetration (4)
- Deep penetration laser beam welding (4)
- Directed Energy Deposition (4)
- Directed energy deposition (4)
- Duplex stainless steel (4)
- Grain refinement (4)
- Simulation (4)
- Stainless Steel (4)
- 9%Ni steel (3)
- Advanced high strength steels (3)
- Bulging effect (3)
- Cryogenic steel (3)
- Crystal branch development (3)
- Electromagnetic Weld Pool Support (3)
- End crater (3)
- Equivalent heat source (3)
- FEA (3)
- Friction stir welding (3)
- Full Penetration (3)
- Gap bridgeability (3)
- Heat conduction (3)
- Heat treatment (3)
- L-PBF (3)
- Laser (3)
- Laser energy distribution (3)
- Laser implantation (3)
- Mechanical mismatching (3)
- Molten pool dynamics (3)
- Multi-physical modelling (3)
- Numerical modelling (3)
- Numerical process simulation (3)
- Partial penetration (3)
- Periodic solidification pattern (3)
- Process simulation (3)
- Quality assurance (3)
- Ray tracing (3)
- Refill friction stir spot welding (3)
- Selective Laser Melting (3)
- Thick Materials (3)
- Transient heat transfer (3)
- Weld pool dynamics (3)
- 316L (2)
- AC weld pool support (2)
- AHSS (2)
- Advanced high strength steel (2)
- Bulge effect (2)
- Bulge formation (2)
- Charpy impact toughness (2)
- Circumferential weld (2)
- Clad steels (2)
- Coarse-grained heat-affected zone (2)
- Data preparation (2)
- Design of experiments (2)
- Die-cast aluminum (2)
- Dimensional accuracy (2)
- Dissimilar metal weld overlays (2)
- Dual phase steel (2)
- Duplex AISI 2205 (2)
- Edge effects (2)
- Edge quality (2)
- Electromagnetic backing (2)
- Electromagnetic influence (2)
- Electromagnetic weld pool control (2)
- Electron beam welding (2)
- Energy efficiency (2)
- Finite element method (2)
- Finite element simulation (2)
- Full penetration (2)
- GMAW (2)
- Grain size (2)
- Hardness (2)
- High power welding (2)
- High-power laser beam welding (2)
- High-strength low-alloy steel (2)
- Hot crack (2)
- Hybrid components (2)
- Keyhole collapse (2)
- Keyhole mode welding (2)
- LME (2)
- Laser Powder Bed Fusion (2)
- Laser Welding (2)
- Laser beam Welding (2)
- Laser-metal-deposition (2)
- Life cycle assessment (LCA) (2)
- Lightweight concepts (2)
- Local critical strain (2)
- Matching ferritic welding electrode (2)
- Melt pool dinamics (2)
- Melt pool dynamics (2)
- Metal mixing (2)
- Moving mesh (2)
- Nickel (2)
- Nickel alloys (2)
- Optical flow (2)
- Oscillating magnetic field (2)
- Oscillating vapor plume (2)
- PBF-LB/M (2)
- Path planning (2)
- Porosity reduction (2)
- Preheating (2)
- Process chain (2)
- Process monitoring (2)
- RSW (2)
- Residual stress (2)
- SMAW (2)
- Seam geometry (2)
- Single pass welding (2)
- Submerged arc welding (2)
- Surface structuring (2)
- Temperature behavior (2)
- Testing method (2)
- Thermal cycles (2)
- Thermo-fluid flow (2)
- Transformable steels (2)
- Ultrasonic vibration (2)
- Weld pool (2)
- Welding of aluminum (2)
- Welding of thick metal plates (2)
- Welding thermal cycle (2)
- Wire arc additive manufacturing (2)
- Zinc coated steel (2)
- 3D FE-simulation (1)
- 3D-FE-Simulation (1)
- 9%Ni steel, (1)
- AC magnetic field (1)
- AC magnetic fields (1)
- AGIL (1)
- AISI D2 (1)
- AM (1)
- AM feature integration (1)
- Adaptive control (1)
- Adaptive welding beam oscillation (1)
- Advanced High-Strength Steel (AHSS) (1)
- Advanced high-strength steel (1)
- Advanced high-strength steels (1)
- Al/Mg alloys (1)
- AlMg0.7SiTiB filler wire (1)
- Aluminium (1)
- Aluminum alloy 2024-T3 (1)
- Aluminum alloys (1)
- Aluminum bronze (1)
- Analytical model (1)
- Arc sensor (1)
- Arc welding (1)
- Artificial Intelligence (1)
- Austenitic stainless steels (1)
- Austenitic welding electrode (1)
- Automated welding (1)
- Automation (1)
- Automotive application (1)
- Bead-on-plate welds (1)
- Bending test (1)
- Boundary element method (1)
- Build - up Strategy (1)
- Build direction (1)
- Build-up Orientation (1)
- Build-up strategy (1)
- Bulging (1)
- Bulging effects (1)
- CFD model (1)
- CFD-model (1)
- CTW test (1)
- CTW-Test (1)
- Calculation time (1)
- Carbon dioxide footprint (1)
- Charpy V-notch tests (1)
- Cimensional Accuracy (1)
- Circumferential welds (1)
- Cladding parameter (1)
- Clustering (1)
- Coarse grained heat affected zone (1)
- Cold Cracking Test (1)
- Columnar crystal growth (1)
- Combined laser manufacturing (1)
- Computer vision (1)
- Condition monitoring (1)
- Contact element (1)
- Conventional Ni-based austenitic welding electrode (1)
- Convolutional neural network (1)
- Cracking (1)
- Cracking susceptibility (1)
- Cracking susceptibility of AHSS (1)
- Cracks in the HAZ (1)
- Crater (1)
- Critical strain rate (1)
- Cryogenic Steel (1)
- DED-EB (1)
- DIC (1)
- DIC technique (1)
- DIP transfer (1)
- Damage prediction (1)
- Deep learning (1)
- Deformed geometry (1)
- Dendrite growth (1)
- Density measurement (1)
- Deposition rate (1)
- Deposition welding (1)
- Die-casted aluminum (1)
- Different welding position (1)
- Digital Image Correlation (1)
- Digital factory (1)
- Digitalization (1)
- Direct Energy Deposition (1)
- Direct Laser Metal Deposition (1)
- Direct energy deposition (1)
- Dissimilar joints (1)
- Dissimilar welding (1)
- Distortion (1)
- Distortion simulation (1)
- Duplex steels (1)
- EBAM (1)
- EBSD (1)
- Economic wide technology replacement (1)
- Efficient modelling (1)
- Electro-thermomechnical model (1)
- Electrode geometry (1)
- Electromagnetic (1)
- Electromagnetic Force (1)
- Electromagnetic stirring (1)
- Electromagnetic support (1)
- Electromagnetic supported degassing (1)
- Electromagnetic weld pool support system (1)
- Electromagnetic weld support system (1)
- Embedded electronics (1)
- End-crater (1)
- Energy input (1)
- Energy parameters of the arc (1)
- Environment (1)
- Environmental impact categories (1)
- Equivalent volumetric heat source (1)
- Ermüdung (1)
- Externally loaded hot cracking test (1)
- Externally loaded test (1)
- FE simulation (1)
- FE-model (1)
- FEM (1)
- FEM study (1)
- Fatigue strength (1)
- Fatigue tests (1)
- Ferritic welding electrode (1)
- Ferromagnetic steel (1)
- Ferromagnetic steels (1)
- Fiber laser (1)
- Filler material distribution (1)
- Filler wire (1)
- Filler wire mixing (1)
- Fine-grained Steel (1)
- Finite Element Method (1)
- Finite element analysis (1)
- Finite element method (FEM) (1)
- Flange width (1)
- Flow pattern (1)
- Flüssigmetallinduzierte Rissbildung (1)
- Fresnel reflection (1)
- Friction spot welding (1)
- Full penetration welding (1)
- Fusion zone (1)
- Fusion zone profile (1)
- Fusion zone size (1)
- Fusion zone, nickel alloys (1)
- GMA surfacing (1)
- GMA welding (1)
- GTAW (1)
- Galvanized steel (1)
- Gap bridging (1)
- Gaps (1)
- Gas shielded arc welding (1)
- General analytical solutions (1)
- Gleeble experiments (1)
- Gleeble testing (1)
- Grade S960QL steel (1)
- Grain structure (1)
- Greenhouse gas mitigation (1)
- Greens function method (1)
- HSLA (1)
- Hardly separable problem (1)
- Hartmann effect (1)
- Heat Input (1)
- Heat Treatment (1)
- Heat flow (1)
- Heat input (1)
- Heat source models (1)
- Heat treatments (1)
- High brightness (1)
- High power (1)
- High power laser (1)
- High power laser keyhole welding (1)
- High process speeds (1)
- High speed laser cladding (1)
- High strength steels (1)
- High-Power Welding (1)
- High-power Laserbeam Welding (1)
- High-power fibre laser (1)
- High-power laser (1)
- High-power laser beam (1)
- High-strength fine-grained steels (1)
- High-strength steel sheets (1)
- Highspeed-plasma-laser-cladding (1)
- Hochfester Stahl (1)
- Hold time (1)
- Hot Cracks (1)
- Human health G. (1)
- Hybrid Laser-Arc Welding (1)
- Hybrid Part (1)
- Hybrid welding (1)
- Hybrid-laser-arc welding (1)
- Hydrostatic and arc pressure exceed the Laplace pressure (1)
- Imaging (1)
- Impact absorbed energy (1)
- In situ strain (1)
- Inconel 625 (1)
- Inconel 939 (1)
- Industrial and Manufacturing Engineering (1)
- Initial gap (1)
- Instumented indentation test (1)
- Integrated alignment features (1)
- Intensity of Restraint (1)
- Investigated materials (1)
- Keyhole mode laser beam welding (1)
- Keyhole stability (1)
- LCA (1)
- LMD (1)
- LW (1)
- Lamé curves (1)
- Lamé curves approximation (1)
- Laser Beam Welding (1)
- Laser Metal Deposition (LMD) (1)
- Laser Metal Deposition; Laser Beam Welding; Duplex; Stainless Steel (1)
- Laser arc-hybrid welding (1)
- Laser beam welding under vacuum/reduced pressure (1)
- Laser beam weliding (1)
- Laser cladding (1)
- Laser cutting (1)
- Laser dispersing (1)
- Laser keyhole welding (1)
- Laser melting (1)
- Laser metal deposition (LMD) (1)
- Laser metal fusion (1)
- Laser powder bed fusion (1)
- Laser powder-based directed energy deposition (1)
- Laser surfacing (1)
- Laser-beam welding, (1)
- Laser-hybrid welding (1)
- Laser-plasma hybrid (1)
- Life cycle assessment (1)
- Life-cycle assessment (1)
- Lifetime (1)
- Lightweight principles (1)
- Liquation Cracking (1)
- Liquid Metal Embrittlement (1)
- Liquid Metal Embrittlement (LME) (1)
- Local fatigue spproaches (1)
- Lorentz force (1)
- Low Temperature Toughness (1)
- Low alloy steels (1)
- Low feed rates (1)
- Low heat input GMA welding (1)
- Low heat input Gma welding (1)
- MAG welding (1)
- MHD (1)
- Macro Processing (Joining, Welding) (1)
- Magnesium (1)
- Magnesium Alloy (1)
- Magnesium alloy (1)
- Magnetic bath support (1)
- Maintenance (1)
- Marangoni flow (1)
- Maritime Components (1)
- Matching ferritic filler metal (1)
- Material modeling (1)
- Material ranking (1)
- Mathematical modeling (1)
- Mechanical Properties (1)
- Mechanical properties of the joints (1)
- Mechanical property (1)
- Mechanical-technological properties (1)
- Metal forming tools (1)
- Metallic vapour plume (1)
- Microstructure Tensile strength (1)
- Misalignment of edges (1)
- Misalignment of the edges (1)
- Model calibration (1)
- Model order reduction (1)
- Molten pool behaviour (1)
- Multi - physical modeling (1)
- Multi-attribute decision method (1)
- Multi-criteria decision support (1)
- Multi-materials joining (1)
- Multi-regional inputeoutput data (1)
- Multiple reflections (1)
- Narrow gap welding (1)
- Narrow-gap welding (1)
- Natural convection (1)
- Neural network (1)
- Neural networks (1)
- Ni-based austenitic filler metal (1)
- Ni-based austenitic welding electrode (1)
- Ni-based superalloy (1)
- NiCrBSi (1)
- Nickel-based superalloy (1)
- Novel metrology (1)
- Novel optical measurement (1)
- Numerical Simulation (1)
- Numerical analysis (1)
- Numerical simulations (1)
- Numerical welding simulation (1)
- Numerical welding simulations (1)
- Offshore wind turbines (1)
- Open science (1)
- Open source (1)
- Optical measurement (1)
- Optical measurement technique (1)
- Optical measurment technique (1)
- PBF/LB-M (1)
- Partial penetration welding (1)
- Pearlitic microstructure (1)
- Penetration depth (1)
- Phase field method (1)
- Phase transformation (1)
- Pipe Welding (1)
- Pipe manufacturing (1)
- Pipe weld preparation (1)
- Pipeline (1)
- Pipeline steel X120 (1)
- Pipeline steel of grade X120 (1)
- Plasma cutting (1)
- Plasma-Transferred-Arc (1)
- Plasma-cut samples (1)
- Plasma-cutting (1)
- Plasma-transferred-arc (1)
- Plastic deformation (1)
- Plume heating (1)
- Pointwise constraints (1)
- Post-weld heat treatment (1)
- Powder Analysis (1)
- Pre-weld Preparation (1)
- Precipitation hardening aluminum alloys (1)
- Preheatin (1)
- Process diagnostics and simulation (1)
- Process innovations (1)
- Proper generalized decomposition (1)
- Pulsed laser beam welding (1)
- Rail tracks (1)
- Ray teacing (1)
- Ray-tracing (1)
- Ray-tracing methods (1)
- Recycling (1)
- Repair and overhaul (1)
- Research data management (1)
- Resistance Spot Welding (RSW) (1)
- Resource efficiency (1)
- SEP-1220-3 (1)
- SLM (1)
- SLM printed plasma torch (1)
- Secondary heat source (1)
- Selektive-laser-melting (1)
- Self-restraint hot cracking (1)
- Self-restraint test (1)
- Sensor (1)
- Ship building (1)
- Shipbuilding steel (1)
- Single-pass welding (1)
- Social life cycle assessment (SLCA) (1)
- Software (1)
- Solidification behaviour (1)
- Solidification craking (1)
- Stainless steels (1)
- Steady-state weld pool (1)
- Steel (1)
- Steel and Al (1)
- Strain fields prediction (1)
- Strain measurement (1)
- Strain rate (1)
- Strain-rate (1)
- Stress-strain behavior (1)
- Super martensitic filler material (1)
- Superalloy (1)
- Superelliptic Lamé curves (1)
- Support structures (1)
- Surface cracks (1)
- Surface texturing (1)
- Sustainability assessment (1)
- TIG welding (1)
- TRIP (1)
- TRIP - transformation induced plasticity (1)
- Tandem Gas Metal Arc Welding (1)
- Tandem gas metal arc welding (1)
- Tandem welding (1)
- Technical crack detection (1)
- Temperature distribution (1)
- Tensile performance (1)
- Tensile properties (1)
- Tensile resistance spot welding experiment (1)
- Tensile strength (1)
- Tensile tests (1)
- Texture (1)
- Thermal analysis (1)
- Thermal softening (1)
- Thermo physical simulation (1)
- Thermo-capillary convection (1)
- Thermo-fluid dynamics (1)
- Thermography (1)
- Thick materials (1)
- Thick metal plate welding (1)
- Thick plate welding (1)
- Thick plates (1)
- Thick-Walled Steel (1)
- Thick-plate welding (1)
- Thick-walled Structures (1)
- Ti - 6Al - 4V (1)
- TiB2 (1)
- Titanium alloy (1)
- Toughness (1)
- Transformation induced plasticity (TRIP) (1)
- Tubular X-joints (1)
- Tungsten carbide (1)
- Turbine blade (1)
- Turbine components (1)
- Turbine industry (1)
- Turbulence (1)
- Two-dimensional solidification (1)
- Two-run welding technique (1)
- V-notch impact toughness (1)
- Vacuum (1)
- Vapor recondensation (1)
- Vaporization (1)
- Variables influencing hot cracking (1)
- Viscoplasticity (1)
- Wear resistance (1)
- Weld cracks (1)
- Weld defects (1)
- Weld end crater (1)
- Weld imperfections (1)
- Weld pool behavior (1)
- Weld pool geometry (1)
- Weld pool modeling (1)
- Weld pool shape approximation (1)
- Weld pool support (1)
- Weld root (1)
- Weld specimens (1)
- Weldability (1)
- Welding (1)
- Welding Current (1)
- Welding Simulation (1)
- Welding costs (1)
- Welding jig (1)
- Welding of AlMg3 (1)
- Welding parameter (1)
- Welding process selection (1)
- Welding process simulation (1)
- Welding residual stresses (1)
- Welding under external loading (1)
- Weldx (1)
- Widerstandspunktschweißen (1)
- Wineglass shape (1)
- Wire electron beam additive manufacturing (1)
- Wire feed laser beam welding (1)
- Wire-based additive manufacturing (1)
- X8Ni9 (1)
- Zinc (1)
- Zink (1)
- cryogenic steel (1)
- deposition welding (1)
- digital image correlation (1)
- dual phase steel (1)
- hardness (1)
- highspeed plasma laser cladding (1)
- laser energy distribution (1)
- laser hybrid welding (1)
- laser welding (1)
- microstructure (1)
- resistance spot welding (1)
- sensitivity analysis (1)
- tensile strength (1)
- thermal cycles (1)
- thick plate welding (1)
- welding residual stresses (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (175)
- 9.3 Schweißtechnische Fertigungsverfahren (171)
- 9.6 Additive Fertigung metallischer Komponenten (3)
- 5 Werkstofftechnik (2)
- 5.2 Metallische Hochtemperaturwerkstoffe (2)
- 7 Bauwerkssicherheit (2)
- 7.7 Modellierung und Simulation (2)
- 5.5 Materialmodellierung (1)
- 9.0 Abteilungsleitung und andere (1)
Eingeladener Vortrag
- nein (25)
This work aims to find the thermal cycles during and after fusion welding through simulation by first calculating the resulting local temperature field in the quasi-stationary part of the process. Here complete-penetration keyhole laser beam welding with a laser power of 18 kW on a 15 mm thick slab of a low-alloyed steel at a welding speed of 2 m/min is considered. In order to physically depict the laser material interaction a multi-physics numerical model including the effects of phase transformation, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature is developed. It uses a fixed keyhole geometry with a right truncated circular cone shape to introduce the laser beam energy to the workpiece. In a subsequent study, the resulting local temperature field is then used as an equivalent heat source in order to predict the unsteady thermal cycle during and after fusion welding. The translational movement of the laser beam through the workpiece is represented by a moving mesh approach. For the simulation, stationary heat transfer and fluid dynamics are described by a system of strongly coupled partial differential equations. These are solved with the commercial finite element software COMSOL Multiphysics 5.0. The results of the numerical simulation are validated by experiments, where the weld bead shapes and the thermal cycles show good correlation.
Recent studies have confirmed the widening of the weld pool interface, known as a bulge effect, during deep penetration high power laser beam welding. The link between such geometric particularities of the weld pool shape and the hot cracking phenomena is significant. The present work seeks to extend the level of understanding by investigating their relationship. A coupled multiphysics, multiscale numerical framework is developed, comprising a series of subsequent analyses. The study examines the influences of the bulge on the three most dominant effects causing hot cracking, namely the thermal cycles, the mechanical loading, and the local microstructure. The bulge in the weld pool shape forms approximately in the middle of the plate, thus correlating with the location of hot cracking. It increases the hot cracking susceptibility by enhancing the three dominant effects. The numerical results are backed up by experimental data.
A three-dimensional multi-physics numerical model was developed for the calculation of an appropriate equivalent volumetric heat source and the prediction of the transient thermal cycle during and after fusion welding. Thus the modelling process was separated into two studies. First, the stationary process simulation of full-penetration keyhole laser beam welding of a 15 mm low-alloyed steel thick plate in flat position at a welding speed of 2 m/min and a laser power of 18 kW was performed. A fixed keyhole with a right circular cone shape was used to consider the energy absorbed by the workpiece and to calibrate the model. In the calculation of the weld pool geometry and the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature were taken into account. The obtained local temperature field was then used in a subsequent study as an equivalent heat source for the computation of the transient thermal field during the laser welding process and the cooling stage of the part. The system of partial differential equations, describing the stationary heat transfer and the fluid dynamics, were strongly coupled and solved with the commercial finite element software COMSOL Multiphysics 5.0. The energy input in the transient heat transfer simulation was realised by prescription of the nodes temperature. The prescribed nodes reproduced the calculated local temperature field defining the equivalent volumetric heat source. Their translational motion through the part was modelled by a moving mesh approach. An additional remeshing condition and helper lines were used to avoid highly distorted elements. The positions of the elements of the polygonal mesh were calculated with the Laplace’s smoothing approach. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and transient temperature distributions was found.
Transient Process Simulation of Heat Transfer in Laser Beam Welding with an Equivalent Heat Source
(2017)
This paper presents a multiphysics modelling framework developed for the prediction of the three-dimensional transient temperature field of the laser welding process. The numerical model consists of two studies. In the first study, a steady-state CFD process simulation of full-penetration keyhole laser beam welding was performed. Considering the effects of, thermo-capillary and natural convection, latent heat of fusion and temperature-dependent material properties up to evaporation temperature the local weld pool geometry and temperature field were obtained. These results were used in the second subsequent study as an equivalent volumetric heat source by the prediction of the transient thermal cycle during and after fusion welding. Here the energy input and the movement of the heat source were realized by a novel technique, making use of pointwise constraints and a moving mesh provided with helper lines and additional remeshing condition. The numerically calculated results were compared to experimentally observed weld pool shapes and time-temperature curves showing a very good agreement.
A mathematical model for physical processes in fusion welding has been developed. It is based on the equivalent heat source concept and consists of two parts: thermo-hydrodynamics of the weld pool and heat conduction in the weldment outside the pool. In thermo-hydrodynamic problem, temperature – dependent material properties, keyhole shape, thermo-capillary and natural convection, phase transformations and other physical phenomena are taken into consideration.
Solution of the thermo-hydrodynamic problem by the finite element method is demonstrated with keyhole laser beam welding of a 15 mm thick steel plate. Thermo-capillary convection is primarily responsible for the intricate convex-concave melt pool shape and pool enlargement near the plate surfaces. The calculated and experimental molten pool dimensions are in close agreement.
The shape of the weld pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. The aim of the present work was its experimental and numerical investigation. To visualize the geometry of the melt pool in the longitudinal section a butt joint configuration of 15 mm thick structural steel and transparent quartz glass was used. The weld pool shape was recorded by means of a high-speed video camera and two thermal imaging MWIR and VIS cameras. The observations show that the dimensions of the weld pool vary depending on the depth. The regions close to the surface form a teardrop shaped weld pool. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a transient numerical simulation was performed until reaching a steady state to obtain the weld pool shape and to understand the formation mechanism of the observed bulging phenomena. A fixed keyhole with an experimentally obtained shape was used to represent the full-penetration laser beam welding process. The model considers the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. It was found that the Marangoni convection and the movement of the laser heat source are the dominant factors for the formation of the bulging-region. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and the time-temperature curves on the upper and bottom surface were found.
The shape of the weld pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. The aim of the present work was its experimental and numerical investigation. To visualize the geometry of the melt pool in the longitudinal section a butt joint configuration of 15 mm thick structural steel and transparent quartz glass was used. The weld pool shape was recorded by means of a high-speed video camera and two thermal imaging MWIR and VIS cameras. The observations show that the dimensions of the weld pool vary depending on the depth. The regions close to the surface form a teardrop shaped weld pool. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a transient numerical simulation was performed until reaching a steady state to obtain the weld pool shape and to understand the formation mechanism of the observed bulging phenomena. A fixed keyhole with an experimentally obtained shape was used to represent the full-penetration laser beam welding process. The model considers the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. It was found that the Marangoni convection and the movement of the laser heat source are the dominant factors for the formation of the bulging-region. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and the time-temperature curves on the upper and bottom surface were found.
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.
The geometrical characteristics of the weld end crater are commonly used for the validation of numerical results in welding simulation. A semi-analytical model calculating the cooling stage of the welding process after the moving energy source is turned off has been developed. A solution for various combinations of heat sources and workpieces has been found. The theoretical limits for the heat transfer of the absorbed energy during cooling in a thin plate and a semi-infinite body were studied. It is shown that after turning off the energy source, an additional melting of the base material in longitudinal direction may occur. The developed technique is applied to complete-penetration keyhole laser beam welding of a 2 mm thick austenitic chromium-nickel 316L steel plate at a welding speed of 20 mm/s and a laser power of 2.3 kW. The results show a theoretical increase of the weld end crater length in comparison to the length of the steady-state weld pool of up to 19 %. A shift of the centre of the end crater, in which the solidification of the liquid metal ends, towards the tail of the end crater relative to the axis of the heat source at the time of its termination, was computed. The speed and the direction of crystallization of the molten material in the weld pool and the end crater were found to be different. A good agreement between the computational results and the welding experiments was achieved.
The geometrical characteristics of the weld end crater are commonly used as a means of validating numerical results in welding simulations.
In this paper, an analytical model is developed for calculating the cooling stage of the welding process after the moving energy source is turned off. Solutions for various combinations of heat sources and heated bodies are found. It is shown that after turning off the Energy source, additional melting of the base material in the longitudinal direction may occur due to the overheated liquid metal. The developed technique is applied to complete-penetration keyhole laser beam welding of 2 mm thick austenitic stainless-steel plate 316L at a Welding speed of 20 mm/s and a laser power of 2.3 kW. The results show a theoretical increase in the weld end crater length of up to 19% compared to the length of the steady-state weld pool. It is found that at the moment of switch off, the weld end crater center, where solidification of the liquid metal ends, is shifted from the heat source axis toward the weld pool tail. The solidification rate and the direction of crystallization of the molten material during the welding process and those in the weld end crater differ significantly. A good agreement between the computational results and the welding experiments is achieved.