• Title, Summary, Keyword: isotropic immersion

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SCREEN ISOTROPIC LEAVES ON LIGHTLIKE HYPERSURFACES OF A LORENTZIAN MANIFOLD

  • Gulbahar, Mehmet
    • Bulletin of the Korean Mathematical Society
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    • v.54 no.2
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    • pp.429-442
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    • 2017
  • In the present paper, screen isotropic leaves on lightlike hypersurfaces of a Lorentzian manifold are introduced and studied which are inspired by the definition of isotropic immersions in the Riemannian context. Some examples of such leaves are mentioned. Furthermore, some relations involving curvature invariants are obtained.

The Wave Propagation in Transversely Isotropic Composite Laminates (가로 등방성 복합재료의 초음파에 관한 연구)

  • Kim Hyung-Won
    • Journal of the Korean Society of Propulsion Engineers
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    • v.10 no.2
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    • pp.62-69
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    • 2006
  • In transversely isotropic composite laminates, the velocities, the particle directions and the amplitudes of reflected and transmitted waves were obtained using the equation of motion, the constitutive equation, and the displacement equation expressed by wave number and frequency. Eigenvalue problem involving a velocity was solved by Snell's law. Finally, the results were confirmed by 7300 Carbon fiber/5208 Epoxy materials. This approach could be applied to the detection of flaws in transversely isotropic composite laminates by the water immersion C-scan procedure.

The Wave Propagation in transversely isotropic composite laminates (가로 등방성 복합재료의 파동전파에 관한 연구)

  • Kim Hyung-Won
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.422-425
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    • 2005
  • In an transversely isotropic composite laminates, the velocities, the particle directions and the amplitudes of reflected and transmitted waves were obtained using the equation of motion, the constitutive equation, and the displacement equation expressed by wave number and frequency Eigenvalue problem involving a velocity was solved by Snell's law. Finally, the results were confirmed by T300 Carbon fiber/5208 Epoxy materials. This approach could be applied to the detection of flaws in a transversely isotropic composite laminates by the water immersion C-scan procedure.

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Determination of the elastic properties in CFRP composites: comparison of different approaches based on tensile tests and ultrasonic characterization

  • Munoz, Victor;Perrin, Marianne;Pastor, Marie-Laetitia;Welemane, Helene;Cantarel, Arthur;Karama, Moussa
    • Advances in aircraft and spacecraft science
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    • v.2 no.3
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    • pp.249-261
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    • 2015
  • The mechanical characterization of composite materials is nowadays a major interest due to their increasing use in the aeronautic industry. The design of most of these materials is based on their stiffness, which is mainly obtained by means of tensile tests with strain gauge measurement. For thin laminated composites, this classical method requires adequate samples with specific orientation and does not provide all the independent elastic constants. Regarding ultrasonic characterization, especially immersion technique, only one specimen is needed and the entire determination of the stiffness tensor is possible. This paper presents a study of different methods to determine the mechanical properties of transversely isotropic carbon fibre composite materials (gauge and correlation strain measurement during tensile tests, ultrasonic immersion technique). Results are compared to ISO standards and manufacturer data to evaluate the accuracy of these techniques.

Evaluation of Elastic Properties of Anisotropic Cylindrical Tubes Using an Ultrasonic Resonance Scattering Spectroscopy

  • Kim, Jin-Yeon;Li, Zheng
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.6
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    • pp.548-557
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    • 2010
  • An ultrasonic resonance scattering spectroscopy technique is developed and applied for reconstructing elastic constants of a transversely isotropic cylindrical component. Immersion ultrasonic measurements are performed on tube samples made from a boron/aluminum composite material to obtain resonance frequencies and dispersion curves of different guided wave modes propagating in the tube. Theoretical analysis on the acoustic resonance scattering from a transversely isotropic cylindrical tube is also performed, from which complete backscattering and resonance scattering spectra and theoretical dispersion curves are calculated. A sensitive change of the dispersion curves to the elastic properties of the composite tube is observed for both normal and oblique incidences; this is exploited for a systematic evaluation of damage and elastic constants of the composite tube samples. The elastic constants of two boron/aluminum composite tube samples manufactured under different conditions are reconstructed through an optimization procedure in which the residual between the experimental and theoretical phase velocities (dispersion curves) is minimized.

Wave Propagation in Unidirectionally Reinforced Composites

  • Hyung-Won Kim;Seong-Eun Kim
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.121-129
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    • 1997
  • Wave propagation was studied for an unidirectionally reinforced composite materials. The velocities, the particle directions and the amplitudes of reflected and transmitted waves were obtained. This analysis involves an immersion C-scan procedure. Snell's law was modified to get the velocities of waves. This analysis could be applied to the detection of flaws in a transversely isotropic composite motor case.

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Measurements of Ultrasonic Velocity and Attenuation by Signal Processing Techniques in Time and Frequency Domains (시간 및 주파수 영역에서의 신호 처리 기술에 의한 초음파 속도와 감쇠의 측정)

  • Jang, Young-Su;Kim, Jin-Ho;Jeong, Hyun-Jo;Nam, Young-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.2
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    • pp.118-128
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    • 1999
  • There are many ultrasonic measurement methods that are used in nondestructive testing applications. Some typical applications include material property determination, microstructural characterization. and flaw detection. Ultrasonic parameters such as velocity and attenuation are most commonly required in these applications. The accuracy and repeatability of testing results are dependent on both the hardware used to generate and receive the ultrasonic waves and on the analysis software for calculating these parameters. In this study, five analysis algorithms were implemented on a computer for measuring wave speed in a pulse echo. immersion testing configuration. In velocity measurements comparisons were made between the overlap. cross-correlation. Fourier transform. Hilbert transform, wavelet transform algorithms. Velocity measurement was applied to an isotropic steel sample using the five analysis algorithms. Frequency-dependent phase/group velocity and attenuation were also measured using the Fourier transform and wavelet transform algorithms on a composite laminate containing voids.

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