Multiple Wavelength Extinction Technique for Particle Characterization in Dense Particle Clouds

Dittmann, Rolf; Feld, Heinz-Juergen; Samenfink, Wolfgang; Wittig, Sigmar

doi:10.1002/ppsc.19940110505

Cited by 12 publications

(8 citation statements)

References 12 publications

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“…24,25,36,37 In this case, the attenuation of three probe beams by passing a particle collective was evaluated under the application of the Mie theory. The corresponding weld seam with a weld length of 70 mm is shown below the diode signal.…”

Section: Particle Formationmentioning

confidence: 99%

Effect of process parameters on the formation of laser-induced nanoparticles during material processing with continuous solid-state lasers

Scholz

Dickmann

Ostendorf

et al. 2015

Journal of Laser Applications

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Articles you may be interested inEffect of process parameters in laser cladding on substrate melted areas and the substrate melted shape J. Laser Appl. 27, S29201 (2015); 10.2351/1.4906376 Effect of laser and laser hybrid welding on the corrosion performance of a lean duplex stainless steel J. Laser Appl. 22, 150 (2010); 10.2351/1.3533146 Visualization of refraction and attenuation of near-infrared laser beam due to laser-induced plume J. Laser Appl. 21, 96 (2009); 10.2351/1.3110058Interaction between laser beam, process effects, and structural properties during welding using models based on the finite element analysis During laser material processing with high laser beam intensities, a laser-induced vapor formation can occur. Due to the shockwave behavior of the vapor plume and the associated rapid cooling, a significant particle formation can be initiated by nucleation. The laser radiation interacts with the particles which can result in a dynamic change of the intensity distribution on the surface. Especially in the field of laser remote processing, the attenuation of laser radiation by nanoparticles can influence the process stability and reduce the processing quality. The presented work is focused on the particle formation at a height of 10 mm above the material surface during the laser welding of stainless steel with a fiber laser. The laser beam intensity on the surface was varied between 1.3 and 5.1 MW/cm 2 . Transmission electron microscopy images of the nanoparticles and high speed images of the vapor propagation in the ambient atmosphere were analyzed. The attenuation of a probe beam in the vapor plume was evaluated in dependence on the wavelength. The results indicate a linear connection between the laser beam power and the particle formation rate. V C 2015 Laser Institute of America. [http://dx.

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Section: Particle Formationmentioning

confidence: 99%

Effect of process parameters on the formation of laser-induced nanoparticles during material processing with continuous solid-state lasers

Scholz

Dickmann

Ostendorf

et al. 2015

Journal of Laser Applications

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“…The incident, scattered, and internal electric fields of the j th sphere can then be expanded as follows: The superscript (1) defines the generating function to be the spherical Bessel function of the first kind, while the superscript (3) designates the spherical Hankel function of the first kind. The formulations for the magnetic fields are similar.…”

Section: Theorymentioning

confidence: 99%

“…Online or inline setups for sensors are mostly based on light extinction or backscattering. To extract information about a particle size distribution, multiple wavelengths or multiple angles are used [1][2][3]. Such sensor systems are typically employed in precipitation and crystallization processes because the final particle size of the product essentially controls the system properties.…”

Section: Introductionmentioning

confidence: 99%

Light extinction at agglomerates of spheres—A practical test on the submicroscale

Kätzel

Gruy

Babick

et al. 2005

Journal of Colloid and Interface Science

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“…Also, the extinction ratio is not a function only of the particle diameter but also of the refractive index. However, this is not relevant to this paper, and solutions to these problems have been presented previously [22,23,28,291. Figure 7, the error Ad, which arises if measurements are performed within real combustion systems with agglomerates present and the data evaluation is based on the Mie theory can be determined.…”

Section: Optical Characterization Of Combustion Aerosolsmentioning

confidence: 99%

Optical Cross‐Sections of Soot Agglomerates: The model of the virtual refractive index and first‐order multiple scattering

Dittmann

1996

Part & Part Syst Charact

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A new technique for the calculation of the optical properties of agglomerated spherical primary particles is presented. By means of the so-called virtual refractive index, the multiple scattering within the agglomerate is described by a modified Mie solution, thus avoiding restrictions with respect to the primary particle size. An additional benefit of the method is the small numerical expense required, permitting practical use for complex agglomerate structures such as real combustion aerosols. Utilizing this method, attention is focused on the calculation of the extinction cross-section of real combustion aerosols in order to discuss the results of multiple-wavelength extinction measurements within combustion systems. It is found that approximately the primary particle diameter is determined. Furthermore, the error that occurs can be avoided by means of the method presented without a detailed knowledge of the agglomerate size. Thus, the present work eliminates some current uncertainties inherent in optical combustion aerosol characterization.

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Multiple Wavelength Extinction Technique for Particle Characterization in Dense Particle Clouds

Cited by 12 publications

References 12 publications

Effect of process parameters on the formation of laser-induced nanoparticles during material processing with continuous solid-state lasers

Effect of process parameters on the formation of laser-induced nanoparticles during material processing with continuous solid-state lasers

Light extinction at agglomerates of spheres—A practical test on the submicroscale

Optical Cross‐Sections of Soot Agglomerates: The model of the virtual refractive index and first‐order multiple scattering

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