1.1 Fundamentals of laser-induced processes

Hügel, H.; Dausinger, Friedrich

doi:10.1007/10877768_1

Cited by 7 publications

(7 citation statements)

References 42 publications

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“…the table in [1]), but since it is mainly the temperature gradient that enters in the absolute value of (6), the value of the voltage is not much affected even if a lower value of n e is assumed taking into account a mixing with the surrounding air or gas.…”

Section: Discussionmentioning

confidence: 99%

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Electrical potential difference during laser welding

2014

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Abstract:We present a new model for the generation of thermoelectric currents during laser welding, taking into account sheath effects at both contact points as well as the potential drop within the quasi-neutral plasma generated by the laser. We show that the model is in good agreement with experimentally measured electric potential difference between the hot and the cold part of the welded workpiece. In particular, all three elements of the model are needed to correctly reproduce the sign of the measured voltage difference. The mechanism proposed relies on the temperature dependence of the electron flux from the plasma to the workpiece and hence does not need thermoemission from the workpiece surface to explain the experimentally observed sign and magnitude of the potential drop.

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Section: Discussionmentioning

confidence: 99%

“…Plasma production during laser welding is a commonly observed phenomenon due to the high local power deposited by the laser [1]. The plasma above the weld pool can scatter, diffract or absorb laser light and hence, the understanding of the formation of this plasma has received attention [2].…”

Section: Introductionmentioning

confidence: 99%

Electrical potential difference during laser welding

2014

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“…According to [11] the calculated absorptivity of pure iron at room temperature and perpendicular incidence is roundly 44 % at 532 nm and 36 % at 1064 nm. However, the absorptivity of laser radiation in metal surfaces does not only depend on wavelength, but also on polarization, workpiece temperature, angle of incidence, alloying elements, surface roughness and oxidation (see [11] for a general discussion). At microdrilling with ultrashort laser pulses, several of the aforementioned influencing values, if at all, are only known within wide limits.…”

Section: Drilling Rate and Completion Timementioning

confidence: 99%

“…It is stated in [10] that for pulse durations above 5 ps, a certain fraction of the pulse energy is absorbed by lasergenerated plasma. Absorption by inverse bremsstrahlung is strongly reduced with decreasing laser wavelength (α ~ λ 3 ) [11]. Provided that the laser-plasma interaction is governed by inverse bremsstrahlung absorption in the investigated parameter regime, drilling with frequency-doubled laser radiation can be expected to be beneficial from both quality and process efficiency aspects.…”

Section: Introductionmentioning

confidence: 99%

Microdrilling in Steel with Frequency-doubled Ultrashort Pulsed Laser Radiation

Kraus¹,

Collmer²,

Sommer³

et al. 2008

JLMN

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In this paper we study the influence of the processing wavelength on process efficiency and quality at picosecond microdrilling in steel. Possible optical setups for utilizing the second harmonic will be presented, and the influence of wavelength on the drilling rate will be discussed. The potential of helical drilling with the second harmonic in 1 mm thick CrNi-steel will be investigated with regard to process efficiency and hole quality. An analysis will be given of the role of particle-ignited atmospheric plasma and the relation between isophote contour and hole morphology. Our study reveals that a substantial enhancement of both precision and productivity can be achieved by using frequency-doubled instead of infrared radiation. It is shown that plasma ablation and melt production can be minimized by drilling with the second harmonic.

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“…In recent years, lasers have been increasingly used in the processing of metals. Lasers can be used for cutting, drilling, marking, engraving, cleaning, welding and other operations [5][6][7][8][9]. The advantages of laser application in metal processing are significant: the process is contactless, precise and fast, and does not cause deformation in the material [10].…”

Section: Introductionmentioning

confidence: 99%

Corrosion characteristics of laser-cleaned surfaces on iron artefact

Radojković¹,

Jegdić²,

Bobić³

et al. 2020

Zaštita materijala

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Nd:YAG laser was used for cleaning surfaces of cultural heritage iron artefacts covered with corrosion products. The corrosion products were removed without damaging the base material. Three different electrochemical techniques were used for the determination of the corrosion rate of mechanically prepared iron, laser-cleaned iron and laser-cleaned iron with Paraloid B44 coating. The morphology of the tested surfaces was analysed by SEM. The linear polarization resistance technique, electrochemical impedance spectroscopy and linear sweep voltammetry have shown that the corrosion rate of the laser-cleaned iron is approximately 50 % higher than the corrosion rate of the mechanically prepared iron. Electrochemical impedance spectroscopy has shown that the pore resistance of the Paraloid coating on the laser-cleaned iron sample decreases at the beginning of the test and remains approximately constant after this period. At the beginning of the test, the charge transfer resistance value is constant and then decreases rapidly i.e. the corrosion rate of the iron in the Paraloid coating pores increases with time. During the linear sweep voltammetry test of the iron sample with Paraloid coating, it was noticed that the anodic polarisation curve shows an unusual shape at the potentials more positive than-0.5 V.

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1.1 Fundamentals of laser-induced processes

Cited by 7 publications

References 42 publications

Electrical potential difference during laser welding

Electrical potential difference during laser welding

Microdrilling in Steel with Frequency-doubled Ultrashort Pulsed Laser Radiation

Corrosion characteristics of laser-cleaned surfaces on iron artefact

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