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  • 1
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    Fundamentals of microcrack nucleation mechanics (1985)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A foundation for ultrasonic evaluation of microcrack nucleation mechanics is identified in order to establish a basis for correlations between plane strain fracture toughness and ultrasonic factors through the interaction of elastic waves with material microstructures. Since microcracking is the origin of (brittle) fracture, it is appropriate to consider the role of stress waves in the dynamics of microcracking. Therefore, the following topics are discussed: (1) microstress distributions with typical microstructural defects located in the stress field; (2) elastic wave scattering from various idealized defects; and (3) dynamic effective-properties of media with randomly distributed inhomogeneities.
    Schlagwort(e): QUALITY ASSURANCE AND RELIABILITY
    Materialart: NASA-CR-3851 , E-2296 , NAS 1.26:3851 , RFP763340/714952
    Format: application/pdf
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  • 2
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    The transmission or scattering of elastic waves by an inhomogeneity of simple geometry: A comparison of theories (1982)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The extended method of equivalent inclusion developed is applied to study the specific wave problems of the transmission of elastic waves in an infinite medium containing a layer of inhomogeneity, and of the scattering of elastic waves in an infinite medium containing a perfect spherical inhomogeneity. The eigenstrains are expanded as a geometric series and the method of integration for the inhomogeneous Helmholtz operator given by Fu and Mura is adopted. The results obtained by using a limited number of terms in the eigenstrain expansion are compared with exact solutions for the layer problem and for a perfect sphere. Two parameters are singled out for this comparison: the ratio of elastic moduli, and the ratio of the mass densities. General trends for three different situations are shown.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: NASA-CR-169034 , NAS 1.26:169034 , TR-104
    Format: application/pdf
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  • 3
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    Ultrasonic wave propagation in two-phase media - Spherical inclusions (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The scattering theory, recently developed via the extended method of equivalent inclusion, is used to study the propagation of time-harmonic waves in two-phase media of elastic matrix with randomly distributed elastic spherical inclusion materials. The elastic moduli and mass density of the composite medium are determined as functions of frequencies when given properties and concentration of the spheres and the matrix. Velocity and attenuation of ultrasonic waves in two-phase media are determined for cases of distributed spheres and localized damage. An averaging theorem that requires the equivalence of the strain energy and the kinetic energy between the effective medium and the original matrix with spherical inhomogeneities is employed to derive the effective moduli and mass density. The functional dependency of these quantities upon frequencies and concentration provides a method of data analysis in ultrasonic evaluation of material properties. Numerical results or moduli, velocity and/or attenuation as functions of concentration of inclusion material, or porosity, are graphically displayed.
    Schlagwort(e): COMPOSITE MATERIALS
    Materialart: Composite Structures (ISSN 0263-8223); 2; 4 19; 289-303
    Format: text
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  • 4
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    Ultrasonic wave propagation in two-phase media: Spherical inclusions (1983)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The scattering theory, recently developed via the extended method of equivalent inclusion, is used to study the propagation of time-harmonic waves in two-phase media of elastic matrix with randomly distributed elastic spherical inclusion materials. The elastic moduli and mass density of the composite medium are determined as functions of frequencies when given properties and concentration of the spheres and the matrix. Velocity and attenuation of ultrasonic waves in two-phase media are determined for cases of distributed spheres and localized damage. An averaging theorem that requires the equivalence of the strain energy and the kinetic energy between the effective medium and the original matrix with spherical inhomogeneities is employed to derive the effective moduli and mass density. The functional dependency of these quantities upon frequencies and concentration provides a method of data analysis in ultrasonic evaluation of material properties. Numerical results or moduli, velocity and/or attenuation as functions of concentration of inclusion material, or porosity, are graphically displayed.
    Schlagwort(e): QUALITY ASSURANCE AND RELIABILITY
    Materialart: NASA-CR-3732 , NAS 1.26:3732
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Unbekannt
    The transmission or scattering of elastic waves by an inhomogeneity of simple geometry: A comparison of theories (1983)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The extended method of equivalent inclusions is applied to study the specific wave problems: (1) the transmission of elastic waves in an infinite medium containing a layer of inhomogeneity, and (2) the scattering of elastic waves in an infinite medium containing a perfect spherical inhomogeneity. Eigenstrains are expanded as a geometric series and a method of integration based on the inhomogeneous Helmholtz operator is adopted. This study compares results, obtained by using limited number of terms in the eigenstrain expansion, with exact solutions for the layer problem and that for a perfect sphere.
    Schlagwort(e): QUALITY ASSURANCE AND RELIABILITY
    Materialart: NASA-CR-3659 , E-1394 , NAS 1.26:3659 , RF-TECH-104
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
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