Forced oscillations of the keyhole in penetration laser beam welding

Klein, Torsten; Vicanek, M.; Simon, Gerhard

doi:10.1088/0022-3727/29/2/008

Cited by 70 publications

(55 citation statements)

References 23 publications

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“…Table 1 gives an overview of material parameters and physical constants used for the numerical simulations in Chap. 3 [3,4]. The material parameters are taken for iron welded by a laser with a wavelength of 1,064 nm.…”

Section: Process Modelmentioning

confidence: 99%

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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

Geiger

Leitz

Koch

et al. 2009

Prod. Eng. Res. Devel.

143

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In order to get a deeper understanding of laser beam welding, a process model was developed at the Chair of Manufacturing Technology. It is based on the continuity equation, the equation of heat conduction and the NavierStokes equation. The model includes effects of Fresnel absorption, vapor pressure, surface tension, melting and evaporation enthalpy and energy loss due to evaporating material. This paper presents the results of a three-dimensional, transient finite volume simulation of a laser beam deep penetration welding process based on this model. The simulations show periodic keyhole oscillations and the complex fluid dynamics of the melt pool. A comparison of the evaporation rates calculated from the simulations and the experimentally observed process emissions shows good correlation. Furthermore, the simulations show pore formation at higher feed rates, the influence of a gap on the welding process and give an explanation for the welding behavior of zinc coated steel sheets.

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Section: Process Modelmentioning

confidence: 99%

“…The vapor pressure p V is in balance with the surface tension of the liquid melt. The pressure p r due to surface tension depends on the surface tension coefficient r and the local surface curvature c of the keyhole [3]:…”

Section: Physical Effectsmentioning

confidence: 99%

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

Geiger

Leitz

Koch

et al. 2009

Prod. Eng. Res. Devel.

143

View full text Add to dashboard Cite

show abstract

“…The high stability of the output radiation is one of the important advantages of high power fiber lasers in comparison with CO 2 -lasers, as it is well known that even small variations of the laser output power in the kHz-range of the frequency can lead to resonance generation of the melt pool macro oscillations and form defects in the weld seam [29,30]. This problem can be especially important in case of thick metal welding with a laser power of 10 kW and more, when the window of the technological parameters becomes narrow.…”

Section: Plume Attenuation Of Fiber Laser Radiationmentioning

confidence: 99%

Plume attenuation of laser radiation during high power fiber laser welding

et al. 2011

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Abstract:The results of an in-situ plume-laser interaction measurement during welding of mild steel with a 5 kW ytterbium fiber laser are reported. A measurement of the attenuation of probe laser beam passing through the plume has allowed to estimate the plume characteristics like the size of the extinction area and the spatial distribution of the extinction coefficient. The power loss of the fiber laser radiation propagating through the whole plume length was calculated. Together with a measured temporal characteristics of extinction the result indicates a significant decreasing of the laser radiation stability, which can lead to the formation of the macroscopic welding defects. Verification of the extinction coefficient distribution model with experimental data of the extinction signal depending on the plume height

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“…However, the FPH exhibits rapid fluctuations with frequencies of several kHz [8,9]. Therefore, the approach of measuring the contrast of image intensity between the full penetration hole and the surrounding laser interaction zone at frame rates below 1 kHz seemed inappropriate.…”

Section: Introductionmentioning

confidence: 99%

The full penetration hole as a stochastic process: controlling penetration depth in keyhole laser-welding processes

Blug

Abt²,

Nicolosi³

et al. 2012

Appl. Phys. B

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Although laser-welding processes are frequently used in industrial production the quality control of these processes is not satisfactory yet. Until recently, the "full penetration hole" was presumed as an image feature which appears when the keyhole opens at the bottom of the work piece. Therefore it was used as an indicator for full penetration only. We used a novel camera based on "cellular neural networks" which enables measurements at frame rates up to 14 kHz. The results show that the occurrence of the full penetration hole can be described as a stochastic process. The probability to observe it increases near the full penetration state. In overlap joints, a very similar image feature appears when the penetration depth reaches the gap between the sheets. This stochastic process is exploited by a closedloop system which controls penetration depth near the bottom of the work piece ("full penetration") or near the gap in overlap joints ("partial penetration"). It guides the welding process at the minimum laser power necessary for the required penetration depth. As a result, defects like spatters are reduced considerably and the penetration depth becomes independent of process drifts such as feeding rate or pollution on protection glasses.

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Forced oscillations of the keyhole in penetration laser beam welding

Cited by 70 publications

References 23 publications

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

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

Plume attenuation of laser radiation during high power fiber laser welding

The full penetration hole as a stochastic process: controlling penetration depth in keyhole laser-welding processes

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