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Infrared laser based contacting of bar-wound windings in the field of electric drives production
摘要： Driven by electric mobility innovative winding methods increasing the copper fill ratio and thus the power density of electrical drives gain in importance. Compared to conventional windings, bar-wound windings based on rectangular cross sections besides optimized copper fill ratios also offer advantages in terms of automated production. Because of the high number of joints necessary for the manufacturing of the winding, contacting efforts increase significantly wherefore the process of laser welding, due to its short process times and high reproducibility shows potentials to realize the process step. This paper examines the most important interactions within the process of laser welding of insulated copper wires with rectangular cross sections in the context of electric drives production. Besides workpiece specific factors, the focus is set on process parameters, beam guidance strategies and specific quality requirements. For this purpose, a parameter study based on design of experiments is executed in which suitable measuring technologies are used to quantify the properties of the samples.
关键词： hairpin windings,infrared lasers,electrical contacts,insulated copper conductors,laser beam welding
更新于2025-09-12 10:27:22
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Laser Beam Welding of a Low Density Refractory High Entropy Alloy
摘要： The effect of laser beam welding on the structure and properties of a Ti1.89NbCrV0.56 refractory high entropy alloy was studied. In particular, the effect of different pre-heating temperatures was examined. Due to the low ductility of the material, laser beam welding at room temperature resulted in the formations of hot cracks. Sound butt joints without cracks were produced using pre-heating to T ≥ 600 °C. In the initial as-cast condition, the alloy consisted of coarse bcc grains with a small amount of lens-shaped C15 Laves phase particles. A columnar microstructure was formed in the welds; the thickness of the grains increased with the temperature of pre-heating before welding. The Laves phase particles were formed in the seams after welding at 600 °C or 800 °C, however, these particles were not observed after welding at room temperature or at 400 °C. Soaking at elevated temperatures did not change the microstructure of the base material considerably, however, “additional” small Laves particles formed at 600 °C. Tensile test of welded specimens performed at 750 °C resulted in the fracture of the base material because of the higher hardness of the welds. The latter can be associated with the bcc grains refinement in the seams.
关键词： microstructure,mechanical properties,laser beam welding,high entropy alloys
更新于2025-09-12 10:27:22
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Numerical simulation of the weld pool dynamics during pulsed laser welding using adapted heat source models
摘要： 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.
关键词： weld pool dynamics,multiple reflections,pulsed laser beam welding,vaporization
更新于2025-09-12 10:27:22
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A study on change point detection methods applied to beam offset detection in laser welding
摘要： This paper presents an experimental study where a photodiode integrated into a laser beam welding tool is used to monitor laser beam spot deviations from the joint, the beam offset. The photodiode system is cost effective and typically easy to implement in an industrial system. The selected photodiode is a silicon detector sensitive in the spectral range between 340-600 nm which corresponds to the spectral emissions from the plasma plume. The welding application is closed-square-butt joint welding where a laser beam offset can cause lack of fusion in the resulting weld. The photodiode signal has been evaluated by two different change point detection methods, one off-line and one on-line method, with respect to their detection performance. Off-line methods can be used to guide post weld inspection and on-line methods have the potential to enable on-line adaptive control or the possibility to stop the process for repair. The performance of the monitoring system and the change point detection methods have been evaluated from data obtained during laser beam welding experiments conducted on plates of stainless steel. The results clearly indicates the possibility to detect beam offsets by photodiode monitoring.
关键词： change point detection,monitoring,photodiode,Laser beam welding
更新于2025-09-12 10:27:22
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Distortion minimization of laser beam welded components by the use of finite element simulation and Artificial Intelligence
摘要： Welded components often require costly efforts to compensate for the thermally induced distortions. This is usually done by applying a specific pre-deformation or by reworking, for example by thermal straightening. These approaches are not practicable for joining complex structures. Therefore, a method that is capable of minimizing the distortions of a complex frame structure with multiple welds is presented. A meta-model by means of an Artificial Neural Network is used to predict the local distortions depending on the welding parameters within sub-areas. A genetic algorithm is utilized to efficiently find suitable welding parameters for the global structure. It could be shown that by applying the method, distortion minimized parameters from more than one billion potential parameter combinations are identified both efficiently and reliably.
关键词： Component distortions,Artificial Intelligence,Metamodeling,Genetic algorithms,FEM simulation,Artificial Neural Networks,Laser beam welding
更新于2025-09-12 10:27:22
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Numerical and experimental investigation of thermo-fluid flow and element transport in electromagnetic stirring enhanced wire feed laser beam welding
摘要： The introduction of electromagnetic stirring to laser beam welding can bring several beneficial effects e.g. element homogenization and grain refinement. However, the underlying physics has not been fully explored due to the absence of quantitative data of heat and mass transfer in the molten pool. In this paper, the influence of electromagnetic stirring on the thermo-fluid flow and element transport in the wire feed laser beam welding is studied numerically and experimentally. A three-dimensional transient heat transfer and fluid flow model coupled with dynamic keyhole, magnetic induction and element transport is developed for the first time. The results suggest that the Lorentz force produced by an oscillating magnetic field and its induced eddy current shows an important influence on the thermo-fluid flow and the keyhole stability. The melt flow velocity is increased by the electromagnetic stirring at the rear and lower regions of molten pool. The keyhole collapses more frequently at the upper part. The additional elements from the filler wire are significantly homogenized because of the enhanced forward and downward flow. The model is well verified by fusion line shape, high-speed images of molten pool and measured element distribution. This work provides a deeper understanding of the transport phenomena in the laser beam welding with magnetic field.
关键词： Laser beam welding,Element transport,Thermo-fluid flow,Numerical analysis,Magnetohydrodynamics
更新于2025-09-12 10:27:22
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Process control using capillary depth measurement
摘要： One important characteristics of laser beam welding is the penetration depth. Traditionally, it is determined by time-consuming and destructive cross-sectioning, but an online monitoring and eventually control system is desired. The measurement of the capillary depth in deep-penetration laser welding by optical coherence tomography (OCT), an interferometry measuring method, has been shown to be a sensing principle that allows an online in-situ measurement. It works in a wide range of industrial applications and delivers accurate data. In this paper we investigate the capability of the method and determine its restrictions.
关键词： optical coherence tomography,penetration depth,interferometry,capillary depth,laser beam welding
更新于2025-09-11 14:15:04
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Laser beam welding of DP980 dual phase steel at high temperatures
摘要： Dual phase steels have been used in safety components for the automotive industry and represents a standard in terms of energy absorbing steel alloys. After welding, these components present a martensitic transformation in the fusion and heat-a?ected zones with an intrinsic brittleness. The current contribution presents a procedure where the DP980 steel sheet is kept at a given temperature during and after the laser weld in order to generate bainite instead of martensite. The results using an isothermal treatment at 527 °C shown a microstructure composed by grain boundary and bainitic ferrite and retained austenite with a constant hardness in the base material and heat-a?ected and fusion zones of 280 HV. The room temperature welds present hardness values between 320 and 500 HV. The high-temperature welds also shown a decrease in the maximum residual stress at the weld centerline by 1/3, with a consequential reduction in the warp of the joined component.
关键词： Heat treatment,Hardness testing,Laser beam welding,Dual phase steels
更新于2025-09-11 14:15:04
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Effect of heat input in pulsed Nd:YAG laser welding of titanium alloy (Ti6Al4V) on microstructure and mechanical properties
摘要： In the present investigation, titanium alloy Ti6Al4V of 1.4 mm thickness has been laser-welded in butt joint configuration using pulsed Nd:YAG laser system. The effects of heat input on weld bead shape, fusion zone width (top, middle, and bottom), heat-affected zone (HAZ) width (top, middle, and bottom), and fusion zone area have been studied. The microstructure and mechanical properties of laser-welded specimens at various heat inputs (43.7–103.5 J/mm) have also been investigated. Microstructures of the fusion zone, HAZ, and parent material have been compared at various heat inputs using optical microscope and field emission scanning electron microscope (FESEM). The mechanical properties such as microhardness and tensile strength of the welded joints at varying heat inputs have been studied. Tensile tests of the welded specimen and base metal have been conducted for analyzing ultimate tensile strength and percentage elongation. Surface topography of the tensile fractured specimen of the welded joints and base metal has been examined to analyze the ductile and brittle behavior. EDS analyses of base metal and fusion zone of the welded specimen have been studied. XRD of the as-received base metal and welded specimen have been measured in the range of 30 to 85° to study the crystallographic structure.
关键词： Ti6Al4V,Microstructure,Laser beam welding,Pulsed Nd:YAG laser,Microhardness,Porosity
更新于2025-09-04 15:30:14