Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Dokumenttyp
- Zeitschriftenartikel (88) (entfernen)
Sprache
- Englisch (88) (entfernen)
Referierte Publikation
- ja (88) (entfernen)
Schlagworte
- Laser beam welding (28)
- Microstructure (9)
- Laser metal deposition (8)
- Additive manufacturing (7)
- Mechanical properties (7)
- Resistance spot welding (7)
- Laser welding (5)
- Liquid metal embrittlement (5)
- Solidification cracking (5)
- Artificial neural network (4)
- Hybrid laser-arc welding (4)
- Numerical modeling (4)
- Numerical simulation (4)
- 9%Ni steel (3)
- Crack (3)
- DED (3)
- Hybrid laser arc welding (3)
- Magnetic field (3)
- Magnetohydrodynamics (3)
- Mechanical mismatching (3)
- Multi-physical modelling (3)
- Porosity (3)
- Solidification (3)
- Welding simulation (3)
- Advanced high strength steels (2)
- Critical strain (2)
- Deep penetration (2)
- Dimensional accuracy (2)
- Dissimilar metal weld overlays (2)
- Dual phase steel (2)
- Electron beam welding (2)
- Element transport (2)
- Equivalent heat source (2)
- Full penetration (2)
- Grain refinement (2)
- Grain size (2)
- High power laser beam welding (2)
- High-power laser beam welding (2)
- Hot crack (2)
- Inconel 718 (2)
- Laser energy distribution (2)
- Matching ferritic welding electrode (2)
- Melt pool dynamics (2)
- Metal mixing (2)
- Process simulation (2)
- Quality assurance (2)
- Ray tracing (2)
- Refill friction stir spot welding (2)
- Simulation (2)
- Thick-walled steel (2)
- Ti-6Al-4V (2)
- Wire arc additive manufacturing (2)
- AC magnetic field (1)
- AGIL (1)
- AHSS (1)
- AM (1)
- AM feature integration (1)
- Adaptive control (1)
- Adaptive welding beam oscillation (1)
- Advanced high strength steel (1)
- Advanced high-strength steel (1)
- Advanced high-strength steels (1)
- AlMg0.7SiTiB filler wire (1)
- Aluminum alloys (1)
- Aluminum bronze (1)
- Artificial Intelligence (1)
- Austenitic welding electrode (1)
- Automotive application (1)
- Bending test (1)
- Boundary element method (1)
- Build-up strategy (1)
- Bulge effect (1)
- Bulge formation (1)
- Bulging effect (1)
- Bulging effects (1)
- CFD model (1)
- Carbon dioxide footprint (1)
- Circumferential weld (1)
- Clad steels (1)
- Clustering (1)
- Coarse grained heat affected zone (1)
- Coarse-grained heat-affected zone (1)
- Columnar crystal growth (1)
- Computer vision (1)
- Convolutional neural network (1)
- Cracking (1)
- Crater (1)
- Crystal branch development (1)
- DED-EB (1)
- DIC (1)
- Damage prediction (1)
- Data preparation (1)
- Deep learning (1)
- Deep penetration laser beam welding (1)
- Deformed geometry (1)
- Dendrite growth (1)
- Density measurement (1)
- Deposition rate (1)
- Deposition welding (1)
- Design of experiments (1)
- Die-cast aluminum (1)
- Die-casted aluminum (1)
- Digitalization (1)
- Directed energy deposition (1)
- Dissimilar joints (1)
- Duplex AISI 2205 (1)
- Duplex steels (1)
- EBAM (1)
- EBSD (1)
- Edge quality (1)
- Electro-thermomechnical model (1)
- Electrode geometry (1)
- Electromagnetic (1)
- Electromagnetic influence (1)
- Electromagnetic stirring (1)
- Electromagnetic support (1)
- Electromagnetic supported degassing (1)
- Electromagnetic weld pool support (1)
- End crater (1)
- Environmental impact categories (1)
- Ferromagnetic steels (1)
- Fiber laser (1)
- Filler wire mixing (1)
- Finite element method (1)
- Finite element method (FEM) (1)
- Finite element simulation (1)
- Flange width (1)
- Flüssigmetallinduzierte Rissbildung (1)
- Fresnel reflection (1)
- Fusion zone (1)
- Fusion zone profile (1)
- Fusion zone size (1)
- Fusion zone, nickel alloys (1)
- GMA welding (1)
- GTAW (1)
- Galvanized steel (1)
- Gap bridgeability (1)
- Gap bridging (1)
- General analytical solutions (1)
- Gleeble testing (1)
- Grade S960QL steel (1)
- Grain structure (1)
- HSLA (1)
- Hardly separable problem (1)
- Hardness (1)
- Heat conduction (1)
- Heat flow (1)
- Heat input (1)
- Heat source models (1)
- High brightness (1)
- High power (1)
- High process speeds (1)
- High strength steels (1)
- High-Power Welding (1)
- High-power laser beam (1)
- High-strength low-alloy steel (1)
- High-strength steel sheets (1)
- Highspeed-plasma-laser-cladding (1)
- Hochfester Stahl (1)
- Hold time (1)
- Hot Cracks (1)
- Hot cracking (1)
- Hybrid Laser-Arc Welding (1)
- Impact absorbed energy (1)
- In situ strain (1)
- Inconel 625 (1)
- Inconel 939 (1)
- Instumented indentation test (1)
- Integrated alignment features (1)
- Keyhole collapse (1)
- Keyhole mode welding (1)
- Keyhole stability (1)
- L-PBF (1)
- LMD (1)
- LME (1)
- Lamé curves (1)
- Lamé curves approximation (1)
- Laser Powder Bed Fusion (1)
- Laser cutting (1)
- Laser hybrid welding (1)
- Laser keyhole welding (1)
- Laser melting (1)
- Laser powder-based directed energy deposition (1)
- Laser surfacing (1)
- Life cycle assessment (1)
- Liquid Metal Embrittlement (1)
- Low feed rates (1)
- Low heat input GMA welding (1)
- Low heat input Gma welding (1)
- MHD (1)
- Magnesium Alloy (1)
- Magnesium alloy (1)
- Matching ferritic filler metal (1)
- Material modeling (1)
- Mathematical modeling (1)
- Mechanical property (1)
- Mechanical-technological properties (1)
- Metallic vapour plume (1)
- Microstructure Tensile strength (1)
- Model calibration (1)
- Model order reduction (1)
- Molten pool dynamics (1)
- Multi-materials joining (1)
- Narrow gap welding (1)
- Neural networks (1)
- Ni-based austenitic filler metal (1)
- Ni-based austenitic welding electrode (1)
- Ni-based superalloy (1)
- NiCrBSi (1)
- Nickel (1)
- Nickel alloys (1)
- Numerical analysis (1)
- Numerical process simulation (1)
- Numerical simulations (1)
- Numerical welding simulation (1)
- Numerical welding simulations (1)
- Open science (1)
- Open source (1)
- Optical measurement (1)
- Optical measurment technique (1)
- Oscillating magnetic field (1)
- Oscillating vapor plume (1)
- Partial penetration (1)
- Partial penetration welding (1)
- Path planning (1)
- Periodic solidification pattern (1)
- Phase field method (1)
- Pipe Welding (1)
- Pipe weld preparation (1)
- Pipeline steel of grade X120 (1)
- Plasma cutting (1)
- Plastic deformation (1)
- Plume heating (1)
- Porosity reduction (1)
- Post-weld heat treatment (1)
- Precipitation hardening aluminum alloys (1)
- Preheating (1)
- Process monitoring (1)
- Proper generalized decomposition (1)
- RSW (1)
- Ray teacing (1)
- Ray-tracing methods (1)
- Research data management (1)
- Residual stress (1)
- SMAW (1)
- Seam geometry (1)
- Secondary heat source (1)
- Selective Laser Melting (1)
- Sensor (1)
- Ship building (1)
- Shipbuilding steel (1)
- Software (1)
- Stainless steels (1)
- Steady-state weld pool (1)
- Steel and Al (1)
- Strain fields prediction (1)
- Strain rate (1)
- Strain-rate (1)
- Stress-strain behavior (1)
- Submerged arc welding (1)
- Superalloy (1)
- Surface cracks (1)
- TIG welding (1)
- Temperature distribution (1)
- Tensile properties (1)
- Tensile resistance spot welding experiment (1)
- Testing method (1)
- Texture (1)
- Thermal analysis (1)
- Thermal cycles (1)
- Thermo-fluid dynamics (1)
- Thermo-fluid flow (1)
- Thick materials (1)
- Thick-Walled Steel (1)
- Titanium alloy (1)
- Toughness (1)
- Transformable steels (1)
- Transient heat transfer (1)
- Tungsten carbide (1)
- Turbine components (1)
- Two-dimensional solidification (1)
- Two-run welding technique (1)
- Vapor recondensation (1)
- Viscoplasticity (1)
- Wear resistance (1)
- Weld end crater (1)
- Weld pool (1)
- Weld pool behavior (1)
- Weld pool dynamics (1)
- Weld pool shape (1)
- Weld root (1)
- Welding (1)
- Welding parameter (1)
- Welding process simulation (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)
- Zinc (1)
- Zinc coated steel (1)
- Zink (1)
- digital image correlation (1)
- dual phase steel (1)
- resistance spot welding (1)
Organisationseinheit der BAM
- 9.3 Schweißtechnische Fertigungsverfahren (88) (entfernen)
In this contribution, we present a physically motivated heat source model for the numerical modeling of laser beam welding processes. Since the calibration of existing heat source models, such as the conic or Goldak model, is difficult, the representation of the heat source using so-called Lamé curves has been established, relying on prior Computational Fluid Dynamics (CFD) simulations.
Lamé curves, which describe the melting isotherm, are used in a subsequent finite-element (FE) simulation to define a moving Dirichlet boundary condition, which prescribes a constant temperature in the melt pool. As an alternative to this approach, we developed a physically motivated heat source model, which prescribes the heat input as a body load directly. The new model also relies on prior CFD simulations to identify the melting isotherm. We demonstrate numerical results of the new heat source model on boundary-value problems from the field of laser beam welding and compare it with the prior CFD simulation and the results of the Lamé curve model and experimental data.
A fundamental study of physical mechanisms of wineglass-shaped fusion zone profile in laser melting
(2024)
The fusion zone geometry in laser melting processes e.g., laser welding and laser-based additive manufacturing, of metallic materials has commonly a wineglass-shaped profile which is critical to the grain orientation and stress distribution. Hereby, we adopt for the first time a decoupling work through a combination of multi-physics modelling and experiments to reveal the fundamental mechanisms of this special morphology. Two physicsbased easy-to-use metal vapour models are proposed to consider the vapour’s momentum and thermal effects separately. It is found that the direct laser energy absorption and Marangoni shear stress which are widely hypothesised to dominate the wineglass-shape formation show only a minor influence. The additional heating from the metallic vapour plume rather than its momentum impact contributes predominantly to the enlarging of the molten pool top region, resulting directly in the formation of the wineglass-shaped fusion zone. The generality of the plume heating effect is also validated in two types of materials (steel and Al) in a wide range of parameters.
Despite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibility and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in the form of a beadon-plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is developed, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control, and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the temperature.
The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data.
Numerical and experimental assessment of liquid metal embrittlement in externally loaded spot welds
(2024)
Zinc-based surface coatings are widely applied with high-strength steels in automotive industry. Some of these base materials show an increased brittle cracking risk during loading. It is necessary to examine electrogalvanized and uncoated samples of a high strength steel susceptible to liquid metal embrittlement during spot welding with applied external load. Therefore, a newly developed tensile test method with a simultaneously applied spot weld is conducted. A fully coupled 3D electrical, thermal, metallurgical and mechanical finite element model depicting the resistant spot welding process combined with the tensile test conducted is mandatory to correct geometric influences of the sample geometry and provides insights into the sample’s time dependent local loading. With increasing external loads, the morphology of the brittle cracks formed is affected more than the crack depth. The validated finite element model applies newly developed damage indicators to predict and explain the liquid metal embrittlement cracking onset and development as well as even ductile failure.
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.
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.
AbstractLaser beam welding has become widely applied in many industrial fields in recent years. Solidification cracks remain one of the most common welding faults that can prevent a safe welded joint. In civil engineering, convolutional neural networks (CNNs) have been successfully used to detect cracks in roads and buildings by analysing images of the constructed objects. These cracks are found in static objects, whereas the generation of a welding crack is a dynamic process. Detecting the formation of cracks as early as possible is greatly important to ensure high welding quality. In this study, two end-to-end models based on long short-term memory and three-dimensional convolutional networks (3D-CNN) are proposed for automatic crack formation detection. To achieve maximum accuracy with minimal computational complexity, we progressively modify the model to find the optimal structure. The controlled tensile weldability test is conducted to generate long videos used for training and testing. The performance of the proposed models is compared with the classical neural network ResNet-18, which has been proven to be a good transfer learning model for crack detection. The results show that our models can detect the start time of crack formation earlier, while ResNet-18 only detects cracks during the propagation stage.
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.
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.
The amount of absorbed energy in the keyhole as well as its spatial and temporal distribution is essential to model the laser beam welding process. The recoil pressure, which develops because of the evaporation process induced by the absorbed laser energy at the keyhole wall, is a key determining factor for the macroscopic flow of the molten metal in the weld pool during high-power laser beam welding. Consequently, a realistic implementation of the effect of laser radiation on the weld metal is crucial to obtain reliable and accurate simulation results. In this paper, we discuss manyfold different improvements on the laser-material interaction, namely, the ray tracing method, in the numerical simulation of the laser beam welding process. The first improvement relates to locating the exact reflection points in the ray tracing method using a so-called cosine condition in the determination algorithm for the intersection of reflected rays and the keyhole surface. A second correction refers to the numerical treatment of the Gaussian distribution of the laser beam, whose beam width is defined by a decay of the laser intensity by a factor of 1/e2, thus ignoring around 14% of the total laser beam energy. In the third step, the changes in the laser radiation distribution in the vertical direction were adapted by using different approximations for the converging and the diverging regions of the laser beam, thus mimicking the beam caustic. Finally, a virtual mesh refinement was adopted in the ray tracing routine. The obtained numerical results were validated with experimental measurements.