Implementation of real-time multiple reflection and Fresnel absorption of laser beam in keyhole

Cho, Jungho; Na, Suck-Joo

doi:10.1088/0022-3727/39/24/039

Cited by 271 publications

(76 citation statements)

References 19 publications

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“…These solid-liquid and liquid-gas interfacial conditions are of importance to be comprehensively understood as they can contribute to the formation of residual stresses and distortions during the welding operation. 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.…”

mentioning

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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mentioning

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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“…We note that most of previous theoretical modeling studies of LW process [10][11][12][13][14][15][16][17][18][19] were based on the recoil pressure model independent on ambient pressure shown in Eq. (1) (similarly to the vacuum case of our modified recoil pressure model).…”

Section: Resultsmentioning

confidence: 99%

“…The concept of recoil pressure, first proposed by Anisimov 50 years ago, 9 has been widely used for mechanism explanation and theoretical modeling of laser material processing. [10][11][12][13][14][15][16][17][18][19] However, this widely applied model has been rested on an assumption that the ambient gas does not influence the evaporation process in laser material interaction. With this model, the recoil pressure is expressed as…”

Section: Theorymentioning

confidence: 99%

Explanation of penetration depth variation during laser welding under variable ambient pressure

Pang¹,

Hirano²,

Fabbro³

et al. 2015

Journal of Laser Applications

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Science Arts & Métiers (SAM)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 has been observed that the penetration depth during laser welding (LW) under vacuum or reduced ambient pressure could be significantly greater than that during welding under atmospheric pressure. Previous explanations of this phenomenon usually limit to specific wavelength laser welding and have difficulties in explaining why the variation will disappear, as the welding speed increases. Here, we propose that this variation is caused by the temperature difference of keyhole wall under variable ambient pressure based on a correct physical description of related processes.A new surface pressure model, dependent on ambient pressure, is proposed for describing the evaporation process during laser material interaction under variable ambient pressure. For laser welding of a 304 stainless steel with 2.0 kW laser power and 3 m/min welding speed, it is shown that the average keyhole wall temperature is around 2900 K under atmospheric pressure, and only around 2300 K under vacuum, which results in significant penetration depth variations. Interestingly, it is also shown that as the welding speed increases, the average temperature of the front keyhole wall gradually rises due to the reduction of the mean incident angle of laser, and the magnitude of this increase is larger in welding under vacuum than under atmospheric pressure. It allows us to explain why the penetration depth improvement decreases to zero with the increase of welding speed.

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“…In recent years, research on keyhole formation, molten pool dynamics, and welding defects such as the formation of porosity and spatter has become a heavily researched topic. Na et al [3,4] and Pang et al [5][6][7] obtained the shape of a real-time keyhole, the model of which used a ray tracing method to simulate multiple laser reflections along the keyhole wall. Their study suggested that the formation of the keyhole was a result of the interaction of the recoil pressure caused by metal vaporization, the surface tension, and hydrostatic pressure.…”

Section: Introductionmentioning

confidence: 99%

3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials

Jiazhou

Zhang

Feng

et al. 2018

Metals

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Abstract:A three-dimensional multiphysical transient model was developed to investigate keyhole formation, weld pool dynamics, and mass transfer in laser welding of dissimilar materials. The coupling of heat transfer, fluid flow, keyhole free surface evolution, and solute diffusion between dissimilar metals was simulated. The adaptive heat source model was used to trace the change of keyhole shape, and the Rayleigh scattering of the laser beam was considered. The keyhole wall was calculated using the fluid volume equation, primarily considering the recoil pressure induced by metal evaporation, surface tension, and hydrostatic pressure. Fluid flow, diffusion, and keyhole formation were considered simultaneously in mass transport processes. Welding experiments of 304L stainless steel and industrial pure titanium TA2 were performed to verify the simulation results. It is shown that spatters are shaped during the welding process. The thickness of the intermetallic reaction layer between the two metals and the diffusion of elements in the weld are calculated, which are important criteria for welding quality. The simulation results correspond well with the experimental results.

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Implementation of real-time multiple reflection and Fresnel absorption of laser beam in keyhole

Cited by 271 publications

References 19 publications

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

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

Explanation of penetration depth variation during laser welding under variable ambient pressure

3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials

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