A 3D transient model of keyhole and melt pool dynamics in laser beam welding applied to the joining of zinc coated sheets

Geiger, Manfred; Leitz, Karl-Heinz; Koch, Holger; Otto, Andreas

doi:10.1007/s11740-008-0148-7

Cited by 138 publications

(56 citation statements)

References 13 publications

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“…The same discussion applies also to boundary condition of pressure in numerical simulations of a keyhole welding process, which have already been reported by several groups [16,17,33]. The result of our study highlights the importance of imposing the ambient atmospheric pressure P amb to non-evaporating surfaces, although this boundary condition was not clearly described in these papers.…”

Section: Weldingsupporting

confidence: 79%

Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric pressure

Hirano¹,

Fabbro²,

Muller³

2011

J. Phys. D: Appl. Phys.

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. . It is thus essential to estimate the recoil pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the recoil pressure near the boiling temperature (T v ), which is particularly important in welding process. In this study we experimentally investigated the recoil pressure of pure iron around T v . The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach T v to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over T v . It is indicated also that, in normal gas-assisted laser cutting process, the recoil pressure hardly contributes to material ejection when the surface temperature is lower than T v , as opposed to commonly believed presumption.

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Section: Weldingsupporting

confidence: 79%

Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric pressure

Hirano¹,

Fabbro²,

Muller³

2011

J. Phys. D: Appl. Phys.

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“…Over the last two decades, literature has been reported on sophisticated modeling approaches [7][8][9][10][11][12] and experimental techniques [13][14][15][16][17][18] to study the dynamics of the keyhole phenomena during high power density fusion welding technologies, such as laser welding. From a modeling perspective, the interface deformation that leads to keyhole formation during the laser welding has been studied intensively using various numerical techniques, including a volume-of-fluid approach [13,14] and a level set method. [9] Recently, Courtois et al [9] have proposed a level set approach and included the influence of the electromagnetic field to accurately capture the energy reflection inside the keyhole.…”

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confidence: 99%

An Integrated Modeling Approach for Predicting Process Maps of Residual Stress and Distortion in a Laser Weld: A Combined CFD–FE Methodology

Turner

Panwisawas

Sovani

et al. 2016

Metall Mater Trans B

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Laser welding has become an important joining methodology within a number of industries for the structural joining of metallic parts. It offers a high power density welding capability which is desirable for deep weld sections, but is equally suited to performing thinner welded joints with sensible amendments to key process variables. However, as with any welding process, the introduction of severe thermal gradients at the weld line will inevitably lead to process-induced residual stress formation and distortions. Finite element (FE) predictions for weld simulation have been made within academia and industrial research for a number of years, although given the fluid nature of the molten weld pool, FE methodologies have limited capabilities. An improvement upon this established method would be to incorporate a computational fluid dynamics (CFD) model formulation prior to the FE model, to predict the weld pool shape and fluid flow, such that details can be fed into FE from CFD as a starting condition. The key outputs of residual stress and distortions predicted by the FE model can then be monitored against the process variables input to the model. Further, a link between the thermal results and the microstructural properties is of interest. Therefore, an empirical relationship between lamellar spacing and the cooling rate was developed and used to make predictions about the lamellar spacing for welds of different process parameters. Processing parameter combinations that lead to regions of high residual stress formation and high distortion have been determined, and the impact of processing parameters upon the predicted lamellar spacing has been presented.

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“…In the numerical simulation presented by Geiger et al [28] it was shown that as the gap at the interface between two uncoated sheets welded in an overlap configuration increases to 0.05-0.1 mm, the liquid metal on the keyhole front wall tends to separate; i.e. a channel opens connecting the interface gap to the keyhole.…”

Section: Zinc Vapour Evacuation Through the Keyhole Front Wallmentioning

confidence: 99%

Keyhole behaviour during laser welding of zinc-coated steel

Pan¹,

Richardson²

2011

J. Phys. D: Appl. Phys.

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The production of consistent, high-quality laser welds on zinc-coated steels for the automotive industry remains a challenge. A simple overlap joint geometry is desirable in these applications but has been shown to be extremely detrimental to laser welding because the zinc vapour formed at the interface between the two sheets expands into the keyhole and disrupts fluid flow in the melt pool, which often leads to metal ejection. In this work, laser welding on sheets with various coating thicknesses has been performed and it is observed that the sheets with thick coatings (∼20 µm) show surprisingly good weldability. High speed video camera visualizations of the keyhole provide insight into the keyhole dynamics during the process. It appears that the dynamic pressure of zinc vapour can effectively elongate the keyhole and the process can reach a stable state when an elongated keyhole is continuously present. A simple analytical model has been developed to describe the influence of zinc vapour on keyhole elongation.

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A 3D transient model of keyhole and melt pool dynamics in laser beam welding applied to the joining of zinc coated sheets

Cited by 138 publications

References 13 publications

Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric pressure

Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric pressure

An Integrated Modeling Approach for Predicting Process Maps of Residual Stress and Distortion in a Laser Weld: A Combined CFD–FE Methodology

Keyhole behaviour during laser welding of zinc-coated steel

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