Готові списки джерел за темами / Laser keyhole

Добірка наукової літератури з теми "Laser keyhole"

Автор: Grafiati
Опубліковано: 7 липня 2024
Оновлено: 7 липня 2024

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Статті в журналах з теми "Laser keyhole":

1

Cunningham, Ross, Cang Zhao, Niranjan Parab, Christopher Kantzos, Joseph Pauza, Kamel Fezzaa, Tao Sun, and Anthony D. Rollett. "Keyhole threshold and morphology in laser melting revealed by ultrahigh-speed x-ray imaging." Science 363, no. 6429 (February 21, 2019): 849–52. http://dx.doi.org/10.1126/science.aav4687.

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We used ultrahigh-speed synchrotron x-ray imaging to quantify the phenomenon of vapor depressions (also known as keyholes) during laser melting of metals as practiced in additive manufacturing. Although expected from welding and inferred from postmortem cross sections of fusion zones, the direct visualization of the keyhole morphology and dynamics with high-energy x-rays shows that (i) keyholes are present across the range of power and scanning velocity used in laser powder bed fusion; (ii) there is a well-defined threshold from conduction mode to keyhole based on laser power density; and (iii) the transition follows the sequence of vaporization, depression of the liquid surface, instability, and then deep keyhole formation. These and other aspects provide a physical basis for three-dimensional printing in laser powder bed machines.
2

Al-Aloosi, Raghad Ahmed, Zainab Abdul-Kareem Farhan, and Ahmad H. Sabry. "Remote laser welding simulation for aluminium alloy manufacturing using computational fluid dynamics model." Indonesian Journal of Electrical Engineering and Computer Science 27, no. 3 (September 1, 2022): 1533. http://dx.doi.org/10.11591/ijeecs.v27.i3.pp1533-1541.

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The process of remote laser welding is simulated in this study to identify the keyhole-induced porosity generation mechanisms and keyhole. Three processes are simulated and discussed: laser power levels, laser-beam shaping configurations, and laser keyhole process. The simulation finding reveals that pore development is caused by strong melt flow behind the keyhole. As verification, the equivalent experimental test is also carried out. According to the findings, a welding speed with a high level helps to keep the keyholes released and prevents the flow of strong melt; a big advanced leaning-angle also provides inactive molten pool flow, making it difficult for bubbles to float to the backside of the molten pool. The conclusions of this study offer crucial insight into the method of porosity of aluminum (Al) alloys laser welding, as well as advice on how to avoid keyhole-induced porosity. It is also obtained that a smaller laser beam with constant power raises the velocity, welding pool depth, and liquid metal temperature.
3

Fabbro, Remy. "Depth Dependence and Keyhole Stability at Threshold, for Different Laser Welding Regimes." Applied Sciences 10, no. 4 (February 21, 2020): 1487. http://dx.doi.org/10.3390/app10041487.

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Depending of the laser operating parameters, several characteristic regimes of laser welding can be observed. At low welding speeds, the aspect ratio of the keyhole can be rather large with a rather vertical cylindrical shape, whereas at high welding speeds, low aspect ratios result, where only the keyhole front is mainly irradiated. For these different regimes, the dependence of the keyhole (KH) depth or the keyhole threshold, as a function of the operating parameters and material properties, is derived and their resulting scaling laws are surprisingly very similar. This approach allows us to analyze the keyhole behavior for these welding regimes, around their keyhole generation thresholds. Specific experiments confirm the occurrence and the behavior of these unstable keyholes for these conditions. Furthermore, recent experimental results can be analyzed using these approaches. Finally, this analysis allows us to define the aspect ratio range for the occurrence of this unstable behavior and to highlight the importance of laser absorptivity for this mechanism. Consequently, the use of a short wavelength laser for the reduction of these keyhole stability issues and the corresponding improvement of weld seam quality is emphasized.
4

Zhao, Cang, Niranjan D. Parab, Xuxiao Li, Kamel Fezzaa, Wenda Tan, Anthony D. Rollett, and Tao Sun. "Critical instability at moving keyhole tip generates porosity in laser melting." Science 370, no. 6520 (November 26, 2020): 1080–86. http://dx.doi.org/10.1126/science.abd1587.

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Laser powder bed fusion is a dominant metal 3D printing technology. However, porosity defects remain a challenge for fatigue-sensitive applications. Some porosity is associated with deep and narrow vapor depressions called keyholes, which occur under high-power, low–scan speed laser melting conditions. High-speed x-ray imaging enables operando observation of the detailed formation process of pores in Ti-6Al-4V caused by a critical instability at the keyhole tip. We found that the boundary of the keyhole porosity regime in power-velocity space is sharp and smooth, varying only slightly between the bare plate and powder bed. The critical keyhole instability generates acoustic waves in the melt pool that provide additional yet vital driving force for the pores near the keyhole tip to move away from the keyhole and become trapped as defects.
5

Ur Rehman, Asif, Muhammad Arif Mahmood, Fatih Pitir, Metin Uymaz Salamci, Andrei C. Popescu, and Ion N. Mihailescu. "Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation." Nanomaterials 11, no. 12 (December 3, 2021): 3284. http://dx.doi.org/10.3390/nano11123284.

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In the laser powder bed fusion (LPBF) process, the operating conditions are essential in determining laser-induced keyhole regimes based on the thermal distribution. These regimes, classified into shallow and deep keyholes, control the probability and defects formation intensity in the LPBF process. To study and control the keyhole in the LPBF process, mathematical and computational fluid dynamics (CFD) models are presented. For CFD, the volume of fluid method with the discrete element modeling technique was used, while a mathematical model was developed by including the laser beam absorption by the powder bed voids and surface. The dynamic melt pool behavior is explored in detail. Quantitative comparisons are made among experimental, CFD simulation and analytical computing results leading to a good correspondence. In LPBF, the temperature around the laser irradiation zone rises rapidly compared to the surroundings in the powder layer due to the high thermal resistance and the air between the powder particles, resulting in a slow travel of laser transverse heat waves. In LPBF, the keyhole can be classified into shallow and deep keyhole mode, controlled by the energy density. Increasing the energy density, the shallow keyhole mode transforms into the deep keyhole mode. The energy density in a deep keyhole is higher due to the multiple reflections and concentrations of secondary reflected beams within the keyhole, causing the material to vaporize quickly. Due to an elevated temperature distribution in deep keyhole mode, the probability of pores forming is much higher than in a shallow keyhole as the liquid material is close to the vaporization temperature. When the temperature increases rapidly, the material density drops quickly, thus, raising the fluid volume due to the specific heat and fusion latent heat. In return, this lowers the surface tension and affects the melt pool uniformity.
6

Dong, William, Jason Lian, Chengpo Yan, Yiran Zhong, Sumanth Karnati, Qilin Guo, Lianyi Chen, and Dane Morgan. "Deep-Learning-Based Segmentation of Keyhole in In-Situ X-ray Imaging of Laser Powder Bed Fusion." Materials 17, no. 2 (January 21, 2024): 510. http://dx.doi.org/10.3390/ma17020510.

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In laser powder bed fusion processes, keyholes are the gaseous cavities formed where laser interacts with metal, and their morphologies play an important role in defect formation and the final product quality. The in-situ X-ray imaging technique can monitor the keyhole dynamics from the side and capture keyhole shapes in the X-ray image stream. Keyhole shapes in X-ray images are then often labeled by humans for analysis, which increasingly involves attempting to correlate keyhole shapes with defects using machine learning. However, such labeling is tedious, time-consuming, error-prone, and cannot be scaled to large data sets. To use keyhole shapes more readily as the input to machine learning methods, an automatic tool to identify keyhole regions is desirable. In this paper, a deep-learning-based computer vision tool that can automatically segment keyhole shapes out of X-ray images is presented. The pipeline contains a filtering method and an implementation of the BASNet deep learning model to semantically segment the keyhole morphologies out of X-ray images. The presented tool shows promising average accuracy of 91.24% for keyhole area, and 92.81% for boundary shape, for a range of test dataset conditions in Al6061 (and one AliSi10Mg) alloys, with 300 training images/labels and 100 testing images for each trial. Prospective users may apply the presently trained tool or a retrained version following the approach used here to automatically label keyhole shapes in large image sets.
7

Jin, Xiangzhong, Yuanyong Cheng, Licheng Zeng, Yufeng Zou, and Honggui Zhang. "Multiple Reflections and Fresnel Absorption of Gaussian Laser Beam in an Actual 3D Keyhole during Deep-Penetration Laser Welding." International Journal of Optics 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/361818.

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In deep penetration laser welding, a keyhole is formed in the material. Based on an experimentally obtained bending keyhole from low- and medium-speed laser penetration welding of glass, the keyhole profiles in both the symmetric plane are determined by polynomial fitting. Then, a 3D bending keyhole is reconstructed under the assumption of circular cross-section of the keyhole at each keyhole depth. In this paper, the behavior of focused Gaussian laser beam in the keyhole is analyzed by tracing a ray of light using Gaussian optics theory, the Fresnel absorption and multiple reflections in the keyhole are systematically studied, and the laser intensities absorbed on the keyhole walls are calculated. Finally, the formation mechanism of the keyhole is deduced.
8

Lai, Wai Jun, Supriyo Ganguly, and Wojciech Suder. "Study of the effect of inter-pass temperature on weld overlap start-stop defects and mitigation by application of laser defocusing." International Journal of Advanced Manufacturing Technology 114, no. 1-2 (March 8, 2021): 117–30. http://dx.doi.org/10.1007/s00170-021-06851-8.

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AbstractLaser keyhole initiation and termination-related defects, such as cracking and keyhole cavities due to keyhole collapse, are a well-known issue in laser keyhole welding of thick section steels. In longitudinal welding, run-on and run-off plates are used to avoid this problem. However, such an approach is not applicable in circumferential welding where start/stop defects remain within the workpiece. These issues can hinder industry from applying laser keyhole welding for circumferential welding applications. In this paper, the effect of inter-pass temperature on laser keyhole initiation and termination at the weld overlap start-stop region was investigated. This study has identified that defects occurring within this region were due to laser termination rather than laser initiation because of keyhole instabilities regardless of the thermal cycle. The laser termination defects were mitigated by applying a laser defocusing termination regime to reduce the keyhole depth gradually and control the closure of the keyhole.
9

Hao, Zhongjia, Huiyang Chen, Xiangzhong Jin, and Zuguo Liu. "Comparative Study on the Behavior of Keyhole in Analogy Welding and Real Deep Penetration Laser Welding." Materials 15, no. 24 (December 16, 2022): 9001. http://dx.doi.org/10.3390/ma15249001.

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In deep penetration laser welding, the behavior of the keyhole has an important influence on the welding quality. As it is difficult to directly observe the keyhole and detect the pressure inside the keyhole during metal laser welding, theoretical analysis and numerical simulation methods are commonly used methods in studying keyhole behavior. However, these methods cannot provide direct real information on keyhole behavior. In this paper, a method of analogy welding is proposed, in which high speed gas is used to blow the liquid to generate the keyhole. Relevant process experiments were conducted to explore keyhole behavior in analogy welding and real deep penetration laser welding. The pressure balance of the keyhole, both in analogy welding and real deep penetration laser welding, were analyzed. The laws obtained in analogy welding and real deep penetration laser welding are similar, which indicates that studying keyhole formation and the maintenance principle using the analogy welding method proposed in this paper may be helpful for deep understanding of the keyhole formation and maintenance mechanisms in real deep penetration laser welding.
10

Henze, Insa, and Peer Woizeschke. "Laser Keyhole Brazing." PhotonicsViews 18, S1 (February 2021): 30–31. http://dx.doi.org/10.1002/phvs.202100013.

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Статті в журналах

Дисертації з теми "Laser keyhole":

1

Holbert, Roy Kyle. "An investigation of the keyhole penetration mode in carbon dioxide laser welding /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849377292756.

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2

Blackburn, Jonathan. "Understanding porosity formation and prevention when welding titanium alloys with 1μm wavelength laser beams". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/understanding-porosity-formation-and-prevention-when-welding-titanium-alloys-with-1-micro-metre-wavelength-laser-beams(d8708b46-50ac-42f1-8f5e-a26ebdfc8ae6).html.

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Keyhole laser welding is a joining technology characterised by the high focussed power density applied to the workpiece, facilitating deep penetration at high processing speeds. High aspect-ratio welds produced using this process invariably have narrow heat-affected-zones and minimal thermal distortion compared with traditional arc welding processes. Furthermore, the ability to process out of vacuum and the easy robotic manipulation of fibre optically delivered 1μm wavelength laser beams, allow keyhole laser welding to process geometrically complex components. The widespread uptake of keyhole laser welding for the production of titanium alloy components in the aerospace industry has been limited by the stringent weld quality requirements. Producing welds with levels of subsurface weld metal porosity content meeting the required weld quality criteria has been the primary obstacle. Here, three techniques for controlling the levels of weld metal porosity when welding titanium alloys with Nd:YAG rod lasers have been developed. Characterisation of the welding processes using high speed photography and optical spectroscopy, have allowed an original scientific understanding of the effects these methods have on the keyhole, melt pool and vapour plume behaviour. Combining this with a thorough assessment of the weld qualities produced, has enabled the effects of these process behaviours on the formation of weld metal porosity to be determined. It was found that with the correct process parameters a directed gas jet and a dual focus laser welding condition can both be used to reduce the occurrence of keyhole collapse during Nd:YAG laser welding. The directed gas jet prevents the formation of a beam attenuating vapour plume and interacts with the molten metal to produce a stable welding condition, whereas the dual focus laser welding condition reduces fluctuations in the process due to an enlarged keyhole. When applied, both techniques reduced the occurrence of porosity in the weld metal of full penetration butt welds produced in titanium alloys. A modulated Nd:YAG laser output, with the correct waveform and modulation frequency, also reduced the occurrence of porosity in the weld metal compared with welds produced with a continuous-wave output. This was a result of an oscillating wave being set-up in the melt pool which manipulated the keyhole geometry and prevented instabilities in the process being established. In addition, the potential for welding titanium alloys to the required weld quality criteria with state-of-the-art Yb-fibre lasers has been assessed. It was found that the high power densities of suitably focussed laser beams with excellent beam quality, were capable of producing low-porosity full penetration butt welds in titanium alloys without the techniques required for laser beams with a lower beam quality. These new techniques for keyhole laser welding of titanium alloys will encourage the uptake of keyhole laser welding for producing near-net-shape high-performance aerospace components. The advantages offered by this joining technology include high productivity, low heat input and easy robotic automation.
3

Ros, García Adrián, and Silva Luis Bujalance. "Laser welding for battery cells of hybrid vehicles." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-17588.

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The report is an overview article, as a result of our investigation at the field of laser welding applied to electromobility cells manufactured in an aluminium housing. This project was proposed by the University of Skövde in collaboration with ASSAR Centre. The key results presented are based on the study of the following parameters: laser type and power, shielding gases, welding modes, patterns and layout. The conclusions of the project define the final selection of each parameter in order to achieve minimum defects and optimal electrical performance by minimizing the contact resistance.
4

Folchitto, Edoardo. "Saldatura laser di componenti in rame per la produzione di motori elettrici nel settore automotive." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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Il settore automotive ha visto un repentino sviluppo di auto con motori elettrici, date le sempre più stringenti leggi sulle emissioni inquinanti: risulta quindi indispensabile sviluppare nuove architetture per migliorare le prestazioni dei motori elettrici. Gli avvolgimenti tradizionali vengono sostituiti da nuovi avvolgimenti chiamati “hairpin”, realizzati in rame, in grado di essere attraversati da elevati flussi di corrente che consentono di erogare una potenza nettamente maggiore. Il rame è un materiale che gode di ottime proprietà di duttilità, conducibilità elettrica e termica; quest’ultima è la ragione principale della scarsa saldabilità del rame mediante tecniche tradizionali. Le saldature realizzate sono, inoltre, afflitte dalla problematica delle porosità. In questo contesto la scelta di una sorgente laser garantisce una risposta efficace: consente di determinare alcune problematiche fornendo un elevato apporto di calore in maniera localizzata. Elevata produttività, grande flessibilità e possibilità di automatizzare completamente l’operazione, sono ulteriori caratteristiche fortemente apprezzate “nell’industria 4.0”. L’obiettivo dell’attività sperimentale è: valutare l’utilizzo della saldatura laser a profonda penetrazione, operante in continuo con una lunghezza d’onda caratteristica nel campo dell’infrarosso e indagare l’influenza dei parametri energetici sui risultati morfologici ottenuti, valutando al contempo, l’effetto sulla problematica delle porosità. Sono state realizzate prove di resistenza meccanica per valutare le caratteristiche del giunto ottenuto. Vengono portate avanti due diverse strategie di scansione, al fine di indagare l’opportuna quantità di energia da fornire al pezzo ed eventuali incrementi di efficienza, causati da una differente modalità di trasferimento di energia. Sono stati individuati i parametri che regolano il processo e la strategia di scansione che permette di incrementare la resistenza meccanica del giunto.
5

Tirand, Guillaume. "Etude des conditions de soudage laser d'alliages à base aluminium par voie expérimentale et à l'aide d'une simulation numérique." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14482/document.

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Le développement du soudage laser dans divers secteurs industriels particulièrement dans l’aéronautique au cours de la dernière décennie, a nécessité bien des études encore insuffisantes en nombre pour bien comprendre et contrôler les conditions de soudage laser que ce soit au niveau interaction laser/matière, au niveau des transferts thermiques ou au niveau métallurgique. La démarche suivie dans cette étude consiste (1) à mettre en évidence expérimentalement la problématique du soudage laser d’alliage base aluminium, c'est-à-dire le couplage des effets entre les différents paramètres de soudage, (2) à décrire l’histoire thermique d’une opération de soudage laser à partir d’une modélisation et d’une simulation numérique et (3) à exploiter la connaissance de l’évolution thermique d’un assemblage encours de soudage pour optimiser les performances mécaniques de l’assemblage en terme de résistance statique, de résistance à la fissuration à chaud, de tenue à la fatigue et de résistance à la corrosion. Les déficits de performance par exemple en terme de résistance sont principalement attribuable à des vitesses de refroidissement trop faibles au cours du soudage comparativement à des trempes ce qui justifie l’efficacité d’un traitement de mise en solution post soudage préalablement à un traitement de durcissement par précipitation
The development of laser welding in various branches of industry particularly in the aeronautics during the last decade, required many studies still insufficient in number to understand and control the conditions of laser welding concerning laser / material interaction,as well as thermal transfers or metallurgical aspects. The approach followed in this study consists (1) to bring to light experimentally the problem of laser welding of aluminium based alloy, that is the coupling of the effects between the various welding parameters, (2) to describe the thermal history of an operation of laser welding from a modelling and from a numerical simulation and (3) to exploit the knowledge of the thermal evolution of an assembly all along welding operation to optimize the mechanical performance of the assembly in term of static resistance, resistance to hot cracking, fatigue and corrosion resistance. The deficit of performance for example in term of tensile resistance is mainly related to too low speeds of cooling during welding compared with quenching. It justifies the efficiency of a post welding solution heat treatment before a precipitation hardening treatment
6

Zajíc, Jiří. "Porovnání vlastností tupých svarů svařených laserem a plazmou pro austenitickou a feritickou korozivzdornou ocel." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382469.

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The thesis is focused on evaluation and comparison of welds made by welding technologies using laser and plasma. For the purpose of comparing those technologies, were chosen austenitic stainless steel x5CrNi18-18 and ferritic stainless steel X6Cr17. These materials were chosen for their diversity in properties gained by high temperatures that go along with most welding processes. First part of the thesis is focused on description of welded materials and technologies of laser and plasma welding. In following experimental section, the thesis is focused on evaluation of welded samples, made for this purpose. Samples were examined for metallography, specifically macrostructure and microstructure. Followed by tensile test of mechanical properties and microhardness test.
7

Heiderscheit, Timothy Donald. "Comparative study of near-infrared pulsed laser machining of carbon fiber reinforced plastics." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5946.

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Carbon fiber-reinforced plastics (CFRPs) have gained widespread popularity as a lightweight, high-strength alternative to traditional materials. The unique anisotropic properties of CFRP make processing difficult, especially using conventional methods. This study investigates laser cutting by ablation as an alternative by comparing two near-infrared laser systems to a typical mechanical machining process. This research has potential applications in the automotive and aerospace industries, where CFRPs are particularly desirable for weight savings and fuel efficiency. First, a CNC mill was used to study the effects of process parameters and tool design on machining quality. Despite high productivity and flexible tooling, mechanical drilling suffers from machining defects that could compromise structural performance of a CFRP component. Rotational feed rate was shown to be the primary factor in determining the axial thrust force, which correlated with the extent of delamination and peeling. Experimental results concluded that machining quality could be improved using a non-contact laser-based material removal mechanism. Laser machining was investigated first with a Yb:YAG fiber laser system, operated in either continuous wave or pulse-modulated mode, for both cross-ply and woven CFRP. For the first time, energy density was used as a control variable to account for changes in process parameters, predicting a logarithmic relationship with machining results attributable to plasma shielding effects. Relevant process parameters included operation mode, laser power, pulse overlap, and cross-ply surface fiber orientation, all of which showed a significant impact on single-pass machining quality. High pulse frequency was required to successfully ablate woven CFRP at the weave boundaries, possibly due to matrix absorption dynamics. Overall, the Yb:YAG fiber laser system showed improved performance over mechanical machining. However, microsecond pulses cause extensive thermal damage and low ablation rates due to long laser-material interaction time and low power intensity. Next, laser machining was investigated using a high-energy nanosecond-pulsed Nd:YAG NIR laser operating in either Q-Switch or Long Pulse mode. This research demonstrates for the first time that keyhole-mode cutting can be achieved for CFRP materials using a high-energy nanosecond laser with long-duration pulsing. It is also shown that short-duration Q-Switch mode results in an ineffective cutting performance for CFRP, likely due to laser-induced optical breakdown. At sufficiently high power intensity, it is hypothesized that the resulting plasma absorbs a significant portion of the incoming laser energy by the inverse Bremsstrahlung mechanism. In Long Pulse mode, multi-pass line and contour cutting experiments are further performed to investigate the effect of laser processing parameters on thermal damage and machined surface integrity. A logarithmic trend was observed for machining results, attributable to plasma shielding similar to microsecond fiber laser results. Cutting depth data was used to estimate the ablation threshold of Hexcel IM7 and AS4 fiber types. Drilling results show that a 2.2 mm thick cross-ply CFRP panel can be cut through using about 6 laser passes, and a high-quality machined surface can be produced with a limited heat-affected zone and little fiber pull-out using inert assist gas. In general, high-energy Long Pulse laser machining achieved superior performance due to shorter pulse duration and higher power intensity, resulting in significantly higher ablation rates. The successful outcomes from this work provide the key to enable an efficient high-quality laser machining process for CFRP materials.
8

Métais, Alexandre. "Simulation numérique des phénomènes thermohydrauliques et de diffusion des éléments chimiques lors du soudage laser d'aciers de nature différente." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK052/document.

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La formulation de nouvelles nuances d’aciers présentant des caractéristiques mécaniques équivalentes pour des épaisseurs moindres et la plus-value associée à la possibilité d'assembler deux nuances différentes, nécessitent le développement et la maîtrise des procédés d’assemblage. Grâce à sa haute précision et à sa flexibilité, le procédé de soudage par laser est devenu une des principales techniques pour le raboutage des flans d'aciers de nature différente. La prédiction de la composition chimique locale de la zone fondue formée entre deux aciers en fonction des paramètres de soudage est de grande importance, puisque la dilution et la distribution des éléments d'alliage conditionnent la résistance mécanique finale du cordon. La présente étude a pour objectif la conception et la validation d’un modèle numérique multi-physiques décrivant la formation du mélange dans le cordon de soudure entre des aciers de nature différente, obtenu par fusion laser. Pour une meilleure compréhension du mélange issu de la diffusion et de la convection dans le bain liquide formé lors d'un soudage laser débouchant, une simulation 3D à l'aide du code de calcul commercial Comsol Multiphysics®, couplant les transferts thermiques, l’écoulement du métal liquide, et la diffusion des espèces, a été réalisée afin de prédire la géométrie du bain liquide et d'obtenir des informations sur la distribution des éléments chimiques à l'intérieur du cordon. Afin de réduire le temps de calcul, le modèle a été développé avec les hypothèses simplificatrices suivantes : le capillaire de vapeur a une géométrie fixe et l’ensemble des équations est résolu sous forme pseudo-stationnaire. Un modèle d’écoulement turbulent est utilisé pour le calcul du champ de vitesse. La loi de Fick est introduite pour modéliser le transport des espèces dans le bain liquide. Dans un premier temps et afin de valider les hypothèses sur les phénomènes de convection, une série d’essais de soudage avec des inserts de nickel pur, utilisés comme traceur chimique, a été réalisée pour cartographier post-mortem la distribution du nickel dans le cordon de soudure. Les résultats de la simulation numérique ont été trouvés en bon accord avec les résultats expérimentaux. Par la suite, le modèle a été appliqué au cas du soudage entre un acier Dual Phase et un acier TWIP riche en manganèse et enfin adapté à l'étude du mélange des revêtements dans le bain de métal liquide formé durant le soudage laser
The design of new steel grades offering equivalent mechanical performances for lower thicknesses and the added value with the possibility to join two different steel grades, require development and control of joining processes. Thanks to high precision and good flexibility, the laser welding became one of the most used processes for joining of dissimilar welded blanks. The prediction of local chemical composition in the weld formed between dissimilar steels in function of the welding parameters is essential because the dilution rate and the distribution of alloying elements in the melted zone determine the final tensile strength of the weld. The goal of the present study is to create and to validate a multiphysical numerical model studying the mixing of dissimilar steels in laser weld pool. For a better understanding of materials mixing based on convection-diffusion process in the melted pool in case of full penetrated laser welding, a 3D simulation developed within COMSOL Multiphysics®, including heat transfer, fluid flow and transport of species has been performed to provide the weld geometry and quantitative mapping of elements distributions in the melted zone. In order to reduce computation time, the model has been developed basing on the following hypothesis: a steady keyhole approximation and solved in quasi-stationary form. Turbulent flow model was used to calculate velocity field. Fick law for diluted species was integrated to simulate the transport of alloying elements in the weld pool. In parallel, to validate the model, a number of experiments using pure Ni foils as tracers have been performed to obtain mapping post-mortem of Ni distribution in the melted zone. The results of simulations have been found in good agreement with experimental data. Afterwards the model was applied to laser welding between Dual Phase steel (DP) and high Mn steel (TWIP) and finally it was adapted to the study of coating dissolution in laser weld pool
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Křivan, Miloš. "Simulace geometrie key hole v závislosti na svařovacích parametrech při laserovém penetračním svařování." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230461.

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The diploma thesis is focused on simulation of keyhole creation in laser deep penetration welding and on the effect of welding parameters on the geometry of keyhole (weld). With reference to this issue theories of keyhole creation are described. 2D simulation model that is created in mathematical software Matlab is verified pursuant welding results of non-alloy constructional steel 1. 0122 and stainless steel 1.4301. Effect of welding parameters on the geometry of keyhole and on the quality of weld is investigated through the welds in non-alloy steel 1.0122.
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Mostafa, Massaud. "Etude du perçage et du soudage laser : dynamique du capillaire." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00692412.

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L'objectif de ce travail est d'étudier expérimentalement la formation du capillaire durant le perçage et le soudage par faisceau laser, et de développer une simulation numérique permettant de reproduire la dynamique de formation et d'évolution du capillaire. Nous avons fait le choix d'utiliser comme matériau test le Zinc, en raison de ses propriétés thermodynamiques. Afin de simplifier le problème, nous avons étudié dans un premier temps le mécanisme de perçage. Deux méthodes expérimentales ont été utilisées pour caractériser l'évolution de la géométrie du capillaire : La méthode DODO (Direct Observation of Drilled hOle ) permet de visualiser le capillaire après perçage pour différentes durées et la méthode Zn-Quartz permet d'observer directement son évolution temporelle par camera rapide à travers une lame de quartz. Puis nous avons utilisé cette évolution pour mettre au point une simulation du mécanisme de perçage. Après avoir étudié le dépôt de puissance à l'intérieur d'un capillaire en tenant compte des réflexions multiples et estimé l'importance de la perte d'énergie et de matière lors du processus, nous avons développé une simulation en utilisant le logiciel Comsol Multiphysics couplant l'équation thermique, l'équation de Navier Stokes et prenant en compte le déplacement du métal fondu sous l'action de la pression de recul. Dans ce cas, on observe la formation d'un bourrelet important au bord du trou et une augmentation de la profondeur du capillaire. Ensuite nous avons étudié la formation du capillaire durant le soudage laser, c'est-à-dire avec déplacement de la source. A partir des techniques mises en œuvre pour l'étude du perçage nous avons obtenu l'évolution de la forme du capillaire dans le cas du soudage Zn/Quartz. Nous avons réalisé une simulation relativement simple en supposant la géométrie et la température du capillaire connues a priori. Nous avons constaté qu'un modèle simple, modélisant uniquement les transferts thermiques par conduction, permet de bien simuler la forme de la zone fondue pour les couples Zn/Zn et Zn-quartz.

Частини книг з теми "Laser keyhole":

1

Dowden, John. "Laser Keyhole Welding: The Vapour Phase." In The Theory of Laser Materials Processing, 113–51. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56711-2_5.

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2

Dowden, John. "Laser Keyhole Welding: The Vapour Phase." In The Theory of Laser Materials Processing, 95–128. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9340-1_4.

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3

Dowden, John Michael. "Simple Models of Laser Keyhole Welding." In The Mathematics of Thermal Modeling, 151–89. 2nd ed. Boca Raton: CRC Press, 2024. http://dx.doi.org/10.1201/9781032684758-6.

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4

Kaplan, Alexander. "Keyhole Welding: The Solid and Liquid Phases." In The Theory of Laser Materials Processing, 89–112. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56711-2_4.

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5

Kaplan, Alexander. "Keyhole Welding: The Solid and Liquid Phases." In The Theory of Laser Materials Processing, 71–93. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9340-1_3.

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6

Gong, Shuili, Shengyong Pang, Hong Wang, and Linjie Zhang. "Simulation of Transient Keyhole and Weld Pool." In Weld Pool Dynamics in Deep Penetration Laser Welding, 107–40. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0788-2_4.

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7

Gong, Shuili, Shengyong Pang, Hong Wang, and Linjie Zhang. "Dynamic Behaviors of Metal Vapor/Plasma Plume Inside Transient Keyhole." In Weld Pool Dynamics in Deep Penetration Laser Welding, 141–63. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0788-2_5.

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8

Gong, Shuili, Shengyong Pang, Hong Wang, and Linjie Zhang. "Keyhole and Weld Pool Dynamics in Dual-Beam Laser Welding." In Weld Pool Dynamics in Deep Penetration Laser Welding, 183–201. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0788-2_7.

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9

Gong, Shuili, Shengyong Pang, Hong Wang, and Linjie Zhang. "Dynamical Behaviors of Keyhole and Weld Pool in Vacuum Laser Welding." In Weld Pool Dynamics in Deep Penetration Laser Welding, 253–73. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0788-2_9.

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10

Gong, Shuili, Shengyong Pang, Hong Wang, and Linjie Zhang. "Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires." In Weld Pool Dynamics in Deep Penetration Laser Welding, 203–51. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0788-2_8.

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Тези доповідей конференцій з теми "Laser keyhole":

1

Kaplan, Alexander F. H., Masami Mizutani, Seiji Katayama, and Akira Matsunawa. "Keyhole laser spot welding." In ICALEO® 2002: 21st International Congress on Laser Materials Processing and Laser Microfabrication. Laser Institute of America, 2002. http://dx.doi.org/10.2351/1.5066203.

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2

Cho, M. H., D. Farson, J. Y. Lee, and C. D. Yoo. "Laser weld keyhole dynamics." In ICALEO® 2001: Proceedings of the Laser Materials Processing Conference and Laser Microfabrication Conference. Laser Institute of America, 2001. http://dx.doi.org/10.2351/1.5059953.

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3

Zhou, J., H. L. Tsai, P. C. Wang, and R. Menassa. "Melt Flow and Porosity Formation in Pulsed Laser Keyhole Welding." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56732.

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Instead of CW (continuous wave) mode, pulsed mode laser welding has been popularly used in industry especially for Nd: YAG lasers. In pulsed mode laser keyhole welding, pores have been frequently observed near the root of the solidified weld. Our previous studies have indicated that the formation of porosity is caused by two competing mechanisms during the keyhole collapse process, and they are 1) the speed of solidification process for the melt surrounding the keyhole and 2) the speed of melt backfilling the keyhole. If the solidification process is too fast and completed before the keyhole is filled, pores will be formed. A technique to control the laser power trailing when it is turned off during the keyhole collapse process has been proposed and experimentally validated to postpone the solidification speed and, as a result, to prevent the porosity formation. However, this method fails for a “deep” keyhole. In this study, an electromagnetic force is used to control the melt backfill flow which is proved to be very effective in preventing porosity from occurring. A mathematical model has been developed to calculate the transient heat transfer and fluid flow during the keyhole formation and collapse processes in pulsed laser welding. The continuum model is used to handle the entire domain including solid phase, liquid phase and mush zone. The enthalpy method is employed to handle the absorption and release of latent heat during melting and solidification. The laser induced plasma inside the keyhole due to the Inverse Bremsstrahlung (IB) absorption is considered and the temperature distribution inside the keyhole is calculated. Both the Fresnel absorption and multiple reflections of laser beam energy at the keyhole walls are also considered. Parametric studies to determine the desired strength of the electromagnetic force and its duration under several laser welding conditions have been conducted. Computer animations showing the keyhole formation and collapse, metal flow, and possible formation of pores will be presented.
4

Pang, Shengyong, Liliang Chen, Yajun Yin, Tao Chen, Jianxin Zhou, Dunming Liao, and Lunji Hu. "Three-dimensional simulation transient keyhole evolution during laser keyhole welding." In Photonics and Optoelectronics Meetings 2009, edited by Dianyuan Fan, Horst Weber, Xiao Zhu, Dongsheng Jiang, Xiaochun Xiao, Weiwei Dong, and Desheng Xu. SPIE, 2009. http://dx.doi.org/10.1117/12.843202.

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5

Poueyo-Verwaerde, Anne, B. Dabezies, and Remy Fabbro. "Thermal coupling inside the keyhole during welding process." In Europto High Power Lasers and Laser Applications V, edited by Eckhard Beyer, Maichi Cantello, Aldo V. La Rocca, Lucien D. Laude, Flemming O. Olsen, and Gerd Sepold. SPIE, 1994. http://dx.doi.org/10.1117/12.184720.

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6

Gärtner, Philipp, and Rudolf Weber. "Spatter formation and keyhole observation with high speed cameras - Better understanding of the keyhole formation." In ICALEO® 2009: 28th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing. Laser Institute of America, 2009. http://dx.doi.org/10.2351/1.5061576.

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7

Metzbower, E. A. "Absorption in the keyhole." In ICALEO® ‘97: Proceedings of the Laser Materials Processing Conference. Laser Institute of America, 1997. http://dx.doi.org/10.2351/1.5059719.

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8

Bardin, Fabrice, Adolfo Cobo, Jose M. Lopez-Higuera, Olivier Collin, Pascal Aubry, Thierry Dubois, Mats Högström, et al. "Process control of laser keyhole welding." In ICALEO® 2004: 23rd International Congress on Laser Materials Processing and Laser Microfabrication. Laser Institute of America, 2004. http://dx.doi.org/10.2351/1.5060185.

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9

Tan, Wenda, and Wenkang Huang. "Numerical Modeling of Thermo-Fluid Flow and Metal Mixing in Laser Keyhole Welding of Dissimilar Metals." In ASME 2018 13th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/msec2018-6640.

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In laser keyhole welding of dissimilar metals, the thermo-fluid flow in the molten pool has decisive effects on the compositional mixing of different chemical elements and hence the formation of detrimental intermetallic compounds. A numerical model is developed in this work to investigate the composition mixing in laser keyhole welding of dissimilar metals. The model takes into account multiple important physics in the process, including dynamic keyhole evolution, laser matter-interaction, phase change, thermo-fluid flow, and composition diffusion/advection. The preliminary simulation results demonstrate that the keyhole behavior is strongly affected by the properties of the dissimilar metals, and the keyhole fluctuation causes an unstable flow in the molten pool that facilitates the compositional mixing through advection.
10

Matsunawa, Akira, Naoki Seto, Masami Mizutani, and Seiji Katayama. "Liquid motion in keyhole laser welding." In ICALEO® ‘98: Proceedings of the Laser Materials Processing Conference. Laser Institute of America, 1998. http://dx.doi.org/10.2351/1.5059193.

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Звіти організацій з теми "Laser keyhole":

1

Wood, B. C., T. A. Palmer, and J. W. Elmer. Comparison Between Keyhole Weld Model and Laser Welding Experiments. Office of Scientific and Technical Information (OSTI), September 2002. http://dx.doi.org/10.2172/15006362.

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2

Ahlquist, E., V. Castillo, and Y. Hu. Keyhole-mode Microscopy Dataset for Laser Powder-bed Fusion Modeling. Office of Scientific and Technical Information (OSTI), June 2022. http://dx.doi.org/10.2172/1878448.

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