Absorptivity of several metals at 106 μm: empirical expressions for the temperature dependence computed from Drude theory

Arnold, Graham S.

doi:10.1364/ao.23.001434

Cited by 40 publications

(27 citation statements)

References 5 publications

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“…58,[72][73][74] Figure 3a shows the dependence of absorptivity on temperature 72 for several pure materials irradiated at a wavelength of 10?6 mm. As the temperature of the workpiece increases, absorptivity increases, and once a material melts, absorptivity increases significantly, resulting in the discontinuities shown in each curve.…”

Section: Role Of Power Density Distributionmentioning

confidence: 99%

Problems and issues in laser-arc hybrid welding

Ribic

Palmer

DebRoy

2009

International Materials Reviews

202

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Hybrid welding, using the combination of a laser and an electrical arc, is designed to overcome problems commonly encountered during either laser or arc welding such as cracking, brittle phase formation and porosity. When placed in close contact with each other, the two heat sources interact in such a way as to produce a single high intensity energy source. This synergistic interaction of the two heat sources has been shown to alleviate problems commonly encountered in each individual welding process. Hybrid welding allows increased gap tolerances, as compared to laser welding, while retaining the high weld speed and penetration necessary for the efficient welding of thicker workpieces. A number of simultaneously occurring physical processes have been identified as contributing to these unique properties obtained during hybrid welding. However, the physical understanding of these interactions is still evolving. This review critically analyses the recent advances in the fundamental understanding of hybrid welding processes with emphases on the physical interaction between the arc and laser and the effect of the combined arc/laser heat source on the welding process. Important areas for further research are also identified. List of symbols and acronymsa coefficient in the surface tension pressure term A area of the transverse weld cross-section (mm 2 ) B magnetic flux (kg s 22 A 21 ) c molar concentration of vapour inside keyhole (mol cm 23 ) C concentration of surface active elements (wt-%) C p heat capacity or specific heat (J kg 21 K 21 ) DCEN direct current electrode negative DCEP direct current electrode positive D LA horizontal distance between laser focal point and arc electrode tip dT/dy spatial temperature gradient on the weld pool surface (K mm 21 ) E A attenuated incident radiation (W) f distribution factor F b buoyancy force (N m 23 ) F emf Lorentz or electromagnetic force (N m 23 ) g acceleration due to gravity (m s 22 ) GMA gas metal arc GMAW gas metal arc welding GTA gas tungsten arc GTAW gas tungsten arc welding h depth of keyhole (mm) H heat input per unit length (J mm 21 ) HAZ heat affected zone HCP hexagonal close packed H f latent heat of fusion (J kg 21 ) I arc current (A) I a attenuated laser beam intensity (W) I m imaginary portion of the complex refractive index I o initial laser beam intensity (W) J flux of evaporating particles in keyhole (mol cm 22 s 21 ) J c current density (A m 22 ) k e extinction coefficient k thermal conductivity (W m 21 K 21 ) L characteristic length (half of the weld pool width) (mm) L P length of the plasma (mm) L R characteristic length of the weld pool (mm) m complex refractive index n refractive index N number density of scattering particles (no./mm) Nd:YAG neodymium:yttrium aluminium garnet P incident heat source power (W) P d power density (W mm 22 ) Pe Peclet number P r recoil pressure (Pa) P v vapour pressure (Pa) P n power or nominal power (W) P t total power of the heat source (W) International Materials Reviews 2009 VOL 54 NO 4223 P c pressure due to surfa...

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Section: Role Of Power Density Distributionmentioning

confidence: 99%

Problems and issues in laser-arc hybrid welding

Ribic

Palmer

DebRoy

2009

International Materials Reviews

202

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“…),   is the vacuum permittivity, e is electron charge, N represents the charge carrier density and  is angular frequency of the incident light. 50,51 However, the earliest results showed that the Drude's free electron theory didn't fit the experiment results in the visible and near-ultraviolet regions. 52 Normally, in the quantum theory, the absorption in the visible and ultraviolet regions may be due to the transition from the filled d bands to the sp conduction bands.…”

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confidence: 99%

Magnetoresistive polyaniline–silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity

Guo

Khan

et al. 2016

Phys. Chem. Chem. Phys.

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The Drude model modified by Debye relaxation time was introduced to determine the plasma frequency (ωp) in the surface initiated polymerization (SIP) synthesized β-silicon carbide (β-SiC)/polyaniline (PANI) metacomposites. The calculated plasma frequency for these metacomposites with different loadings of β-SiC nanoparticles was ranging from 6.11 × 10(4) to 1.53 × 10(5) rad s(-1). The relationship between the negative permittivity and plasma frequency indicates the existence of switching frequency, at which the permittivity was changed from negative to positive. More interestingly, the synthesized non-magnetic metacomposites, observed to follow the 3-dimensional (3-D) Mott variable range hopping (VRH) electrical conduction mechanism, demonstrated high positive magnetoresistance (MR) values of up to 57.48% and high MR sensitivity at low magnetic field regimes.

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“…The temperature dependence of DC conductivity DC for different metals is available in literatures, [37][38][39] and the optical conductivity o in frequency range of the thermal radiation ͑mostly infrared͒ can be obtained using a correction factor f, so that DC = f o . [29][30][31]40 Using the conductivity o , we obtain the complex index of refraction of dust material as function of the temperature using the Drude theory, and then calculate Q abs using Mie theory computational code. 41 For integration of Eq.…”

Section: Model C: Using Mie Theorymentioning

confidence: 99%

“…25 They used the Mie theory to calculate light absorption efficiency factor 26,27 and Drude theory to estimate the temperaturedependent optical constants, [28][29][30][31] and calculated the total emissivity of the metallic dust particle. As a result, it has been found that the temperature and radius dependences of the emissivity was relatively large, and the emissivity can vary by a factor of more than 100 as a function of dust radius and temperature in a particular case.…”

Section: Introductionmentioning

confidence: 99%

Influence of emissivity on behavior of metallic dust particles in plasmas

et al. 2008

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Influence of thermal radiation emissivity on the lifetime of a dust particle in plasmas is investigated for different fusion relevant metals ͑Li, Be, Mo, and W͒. The thermal radiation is one of main cooling mechanisms of the dust in plasmas especially for dust with evaporation temperature higher than 2500 K. In this paper, the temperature-and radius-dependent emissivity of dust particles is calculated using Mie theory and temperature-dependent optical constants for the above metallic materials. The lifetime of a dust particle in uniform plasmas is estimated with the calculated emissivity using the dust transport code DUSTT ͓A. Pigarov et al., Physics of Plasmas 12, 122508 ͑2005͔͒, considering other dust cooling and destruction processes such as physical and chemical sputtering, melting and evaporation, electron emission etc. The use of temperature-dependent emissivity calculated with Mie theory provides a longer lifetime of the refractory metal dust particle compared with that obtained using conventional emissivity constants in the literature. The dynamics of heavy metal dust particles are also presented using the calculated emissivity in a tokamak plasma.

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Absorptivity of several metals at 106 μm: empirical expressions for the temperature dependence computed from Drude theory

Cited by 40 publications

References 5 publications

Problems and issues in laser-arc hybrid welding

Problems and issues in laser-arc hybrid welding

Magnetoresistive polyaniline–silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity

Influence of emissivity on behavior of metallic dust particles in plasmas

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