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  • 1
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    Determination of the elastic properties of layered materials using laser excitation of ultrasound (2010)
    Springer
    Details
    Publication Date: 2010-12-01
    Print ISSN: 1541-308X
    Electronic ISSN: 1934-807X
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Photoacoustic study of the transmission of wide-band ultrasonic signals through periodic one-dimensional structures (2000)
    Springer
    Acoustical physics 46 (2000), S. 439-444 
    Details
    ISSN: 1562-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The propagation of wide-band acoustic pulses in one-dimensional periodic structures consisting of alternating plexiglas and water layers is studied theoretically and experimentally. The experiment is carried out with the use of the wide-band photoacoustic spectroscopy based on the laser excitation of ultrasound and a wide-band signal detection. The fact that the transmission spectrum of a periodic structure has alternating pass and stop bands is confirmed experimentally. The width and localization of the stop bands strongly depend on the thickness of the layers and on the phase velocity of ultrasound in them. It is demonstrated that defects of the structure periodicity give rise to one or several local transmission maxima in the stop band and to a modification of the pass band. The amplitude and position of a local maximum in the stop band strongly depend on the position of the defective layer. The experimental data agree well with the results of numerical simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.29906
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  • 3
    Electronic Resource
    Electronic Resource
    Laser ablation of aqueous solutions with spatially homogeneous and heterogeneous absorption (1994)
    Springer
    Applied physics 59 (1994), S. 73-81 
    Details
    ISSN: 1432-0649
    Keywords: 79.20.Ds ; 83.70.Hq ; 83.70.Gp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ablation efficiency of aqueous solutions with different concentrations and spatially homogeneous (CuCl2 solution) and heterogeneous (ink solution) absorption was studied as a function of the pulse-energy fluence (Nd:YAG laser, λ=1064 nm, τp = 20 ns). The latter was varied over a wide range from 0.15 J/cm2 to 8.00 J/cm2. The ablation threshold of solutions with heterogeneous absorption was found to be much lower (3 to 4 times) than the ablation threshold of solutions with homogeneous absorption and with the same average absorption coefficient. The ablation efficiency of heterogeneous solutions was higher by more than an order of magnitude. It was found that the ablation efficiency increases drastically for both types of solutions as the pulse energy fluence was raised to exceed the ablation threshold by 2 or 3 times. At such energy fluences, along with small droplets, larger droplets (1.5–2 mm cross section) could be ejected. This points to the ablation of solutions being affected by a hydrodynamic shock formed as a result of the pulsed recoil pressure excerted by the ablation products. The differences between the ablation processes for solutions with homogeneous and heterogeneous absorption as well as the hydrodynamic destruction at high energy fluences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081730
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  • 4
    Electronic Resource
    Electronic Resource
    Time-resolved laser optoacoustic tomography of inhomogeneous media (1996)
    Springer
    Applied physics 63 (1996), S. 545-563 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 79.20.Ds ; 87.71.Rh ; 87.73.Ca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract.  The methods of time-resolved laser optoacoustic tomography of inhomogeneous media and related problems are reviewed. Time-resolved laser optoacoustic tomography allows one to measure the distribution of light absorption in turbid media with depth resolution up to several microns in real time. The theory of laser excitation of acoustic waves by absorbing of light in particles, dispersed in transparent, light-absorbing or scattering media, is developed. The distribution of light absorption can be obtained from the temporal course of acoustic pressure. Two schemes of acoustic wave detection – in the medium under testing (direct detection) and in transparent medium, coupled to the investigated one (indirect detection) – are discussed. In both cases the reconstruction of light absorption can be made by simple calculations. Test experiments with homogeneous and layered media confirm the proposed theoretical models and the possibility of using the proposed experimental schemes. Light absorption in homogeneous, inhomogeneous media and in absorbing particles dispersed in turbid media was investigated. The experimental setup allows one to measure the absorption coefficients over the range 1–500 cm-1 with the depth resolution 10–15 μm over the depth 1–1.5 mm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01830994
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  • 5
    Electronic Resource
    Electronic Resource
    Direct measurement of the spatial distribution of light intensity in a scattering medium (1999)
    Springer
    JETP letters 70 (1999), S. 183-188 
    Details
    ISSN: 1090-6487
    Keywords: 42.25.Fx ; 43.35.Sx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A direct nonperturbative measurement of the spatial distribution of the light intensity in a strongly scattering medium is performed using an optoacoustic method. It is shown that near a surface the intensity can be five times greater than the incident intensity, and the absolute maximum of the intensity is observed at a depth ℓ(1–R)(1–4.0R) determined by the photon transport mean free path ℓ and the effective light reflection coefficient R of the boundary separating the scattering and external media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.568150
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  • 6
    Electronic Resource
    Electronic Resource
    Laser ultrasonic investigation of the elastic properties of unidirectional graphite-epoxy composites (1998)
    Springer
    Mechanics of composite materials 34 (1998), S. 575-582 
    Details
    ISSN: 1573-8922
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An ultrasonic method is proposed for the determination of the elastic constants of orthotropic solids with a laser source of ultrasound and wide-band registration of acoustic pulses. The propagation of acoustic transients in unidirectional fiber-reinforced graphite-epoxy composites is investigated. The experimental data show that the model of orthotropic solids is valid for the description of the mechanical properties of these materials. The absence of frequenc dispersion of the phase velocity in the spectral range of 1–15 MHz for every direction of propagation of ultrasound waves in the composite was confirmed. A complete set of elastic constants of unidirectional fiber-reinforced graphite-epoxy composites is calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02254668
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  • 7
    Electronic Resource
    Electronic Resource
    Nondestructive Evaluation of Graphite-Epoxy Composites by the Laser Ultrasonic Method (2000)
    Springer
    Mechanics of composite materials 36 (2000), S. 497-500 
    Details
    ISSN: 1573-8922
    Keywords: graphite-epoxy composite ; structural defect ; nondestructive evaluation ; laser ultrasonic method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A laser ultrasonic method for nondestructive evaluation of the structure of composite materials is proposed. Specimens of graphite-epoxy composites with compaction-type defects and air cavities are investigated. The method is based on the laser thermooptical generation of wide-band acoustic pulses - optoacoustic (OA) signals - in the material investigated. The acoustic pulses backscattered by structural ingomogeneities and defects are registered by a wide-band piezotransducer, which makes it possible to detect acoustic pulses in the frequency range from 0.1 to 30 MHz. Since the generation and detection of acoustic pulses takes place on the front surface of the specimen, this method allows us to carry out nondestructive evaluation with one-sided access to the object under study. The spectral and correlation analyses of backscattered OA signals are used for mathematical processing of the experimental data. The method developed makes it possible to determine the type of defects and the depth of their location.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006714818203
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  • 8
    Electronic Resource
    Electronic Resource
    Nondestructive evaluation of fatigue-induced changes in the structure of composites by an ultrasonic method using a laser (1995)
    Springer
    Mechanics of composite materials 31 (1995), S. 301-304 
    Details
    ISSN: 1573-8922
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Studies were conducted to nondestructively evaluate the damage to a glass-fiber-reinforced plastic during cyclic and static loading. The evaluation was made by an ultrasonic method employing a laser. In both the unloaded and loaded specimens, the ultrasound attenuation spectrum has a resonance peak attributable to the periodic nature of the structure of the composite. This peak is shifted to the low-frequency region during static loading, due to a decrease in the elastic modulus. The spectra obtained after cyclic loading have no resonance peaks, due to attenuation of the ultrasound over a broad range of frequencies by a large number of fatigue cracks. Additional static loading results in concentration of the cracks near the boundary between the glass fibers and the polymer matrix, which leads to the formation of a resonance peak in the high-frequency region of the spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615645
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  • 9
    Electronic Resource
    Electronic Resource
    Unsteady quasi-one-dimensional transonic gas flows (1984)
    Springer
    Fluid dynamics 19 (1984), S. 169-172 
    Details
    ISSN: 1573-8507
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01090931
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of layered composites by laser optoacoustic transducers (1999)
    Springer
    Mechanics of composite materials 35 (1999), S. 89-94 
    Details
    ISSN: 1573-8922
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An ultrasonic method for evaluation of composite structures by laser-excited wide-band acoustic pulses is proposed. Two types of laser optoacoustic transducers, in transmission and reflection modes, are used in the spectral range of 0.1–10 MHz. In the first case, the frequency dependence of the attenuation factor of ultrasound is measured. In the reflection mode, the optoacoustic transducer allows us to obtain the time-dependent shape and spectrum of the backscattered acoustic signal with one-sided access to a specimen or product. Specimens of a layered graphite-epoxy composite of different porosity (up to 1.2%) are studied. In the frequency range of 1–5 MHz, the attenuation factor of ultrasound measured in the transmission mode is the greater the higher the porosity of the specimen. The “noise” part of the backscattered acoustic pulse is found to increase with increasing porosity of the specimens. A 1% growth in porosity causes a threefold increase in the noise power. The results obtained confirm the advantages of the laser optoacoustic method for evaluation of composite materials and products during their manufacturing and operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260816
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