9 research outputs found

    Non-ambiguous recovery of Biot poroelastic parameters of cellular panels using ultrasonic waves

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    a b s t r a c t The inverse problem of the recovery of the poroelastic parameters of open-cell soft plastic foam panels is solved by employing transmitted ultrasonic waves (USW) and the Biot-Johnson-Koplik-Champoux-Allard (BJKCA) model. It is shown by constructing the objective functional given by the total square of the difference between predictions from the BJKCA interaction model and experimental data obtained with transmitted USW that the inverse problem is ill-posed, since the functional exhibits several local minima and maxima. In order to solve this problem, which is beyond the capability of most off-the-shelf iterative nonlinear least squares optimization algorithms (such as the Levenberg Marquadt or Nelder-Mead simplex methods), simple strategies are developed. The recovered acoustic parameters are compared with those obtained using simpler interaction models and a method employing asymptotic phase velocity of the transmitted USW. The retrieved elastic moduli are validated by solving an inverse vibration spectroscopy problem with data obtained from beam-like specimens cut from the panels using an equivalent solid elastodynamic model as estimator. The phase velocities are reconstructed using computed, measured resonance frequencies and a time-frequency decomposition of transient waves induced in the beam specimen. These confirm that the elastic parameters recovered using vibration are valid over the frequency range of study

    Técnica para Calibração Primária em Campo Livre de Microfones de Medição

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    Este artigo apresenta a técnica de medição, desenvolvida e implementada no Inmetro, para a calibração primária em campo livre de microfones de medição. Nesta técnica, a diafonia (crosstalk) é removida por subtração e o interespalhamento (multiple backscattering) e as demais reflexões são removidos por um procedimento de seleção no tempo

    Characterization of Acoustic Oscillations in Fuel Supply Lines

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    Técnica para Calibração Primária em Campo Livre de Microfones de Medição

    No full text
    Este artigo apresenta a técnica de medição, desenvolvida e implementada no Inmetro, para a calibração primária em campo livre de microfones de medição. Nesta técnica, a diafonia (crosstalk) é removida por subtração e o interespalhamento (multiple backscattering) e as demais reflexões são removidos por um procedimento de seleção no tempo
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