Measurement of Power Flow in Uniform Beams and Plates

The Journal of the Acoustical Society of America (Impact Factor: 1.5). 01/1970; 47. DOI: 10.1121/1.1911472
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    • "Of course, derivation of experimentally obtained distributions is an implementation problem, since it amplifies errors inherent in measurements. Because the displacement field can only be measured at discrete points, the usual derivation techniques consist in applying finite differences (see for example: (Pezerat and Guyader 1995, Pezerat and Guyader 2000, Pavic 1976 or Noiseux 1970) or using expansions of the field in a basis of analytical and differential continuous distributions, like eigen shapes (Pezerat and Guyader 1995), Chebyshev polynomials (Chochol et al. 2013), plane waves (Zhang and Mann 1999), etc. Since these operations approximate derivatives, they amplify the measurement noises, Corresponding author, Associate Professor, E-mail: "
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    ABSTRACT: This paper deals with the experimental validation of the use of PVDF Patches for the assessment of spatial derivatives of displacement field. It focuses more exactly on the shear Force Identification by using Specific forms of PVDF patcHes (FISH) on beams. An overview of the theoretical approach is exposed. The principle is based on the use of the weak form of the equation of motion of the beam which allows the shear forces to be extracted at one edge of the sensor when this last has a specific form. The experimental validation is carried out with a cantilever steel beam, excited by a shaker at its free boundary. The validation consists in comparing the shear force measured by the designed sensor glued at the free edge and the directly measured force applied by the shaker. The sensor is made of two patches, called the "stiffness" patch and the "mass" patch. The use of both patches allows one to identify correctly the shear force on a large frequency domain. The use of only the stiffness patch is valid in the low frequency domain and has the advantage to have a frequency-independent gain that allows its use in real time.
    SMART STRUCTURES AND SYSTEMS 05/2015; 15(5):1203-1214. DOI:10.12989/sss.2015.15.5.1203 · 1.37 Impact Factor
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    • "In [1], the proof of concept was presented on beams with numerical and experimental validations. Close to structural intensity techniques [2] [3], the basic principle of FAT consists in measuring displacement fields on a given meshgrid and to inject it in the equation of motion discretized by finite difference schemes. Extensions to plates [4] and shells [5] [6] were made few years later. "
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    ABSTRACT: The paper aims to combine two objectives of the Force Analysis Technique (FAT): vibration source identification and material characterization from the same set of measurement. Initially, the FAT was developed for external load location and identification. It consists in injecting measured vibration displacements in the discretized equation of motion. Two developments exist: FAT and CFAT (Corrected Force Analysis Technique) where two finite difference schemes are used. Recently, the FAT was adapted for the identification of elastic and damping properties in a structure. The principal interests are that the identification is local and allows mapping of material characteristics, the identification can be made at all frequencies, especially in medium and high frequency domains. The paper recalls the development of FAT and CFAT on beams and plates and how it can be possible to extract material characteristics in areas where no external loads are applied. Experimental validations are shown on an aluminum plate with arbitrary boundary conditions, excited by a point force and where a piece of foam is glued on a sub-surface of the plate. Contactless measurements were made using a scanning laser vibrometer. The results of FAT and CFAT are compared and discussed for material property identifications in the regions with and without foam. The excitation force identification is finally made by using the identified material properties. CFAT gives excellent results comparable to a direct measurement obtained by a piezoelectric sensor. The relevance of the corrected scheme is then underlined for both source identification and material characterization from the same measurements.
    Journal of Sound and Vibration 05/2015; 351. DOI:10.1016/j.jsv.2015.04.025 · 1.81 Impact Factor
    • "the complex wave number. To analyse the energy flow in plates at mid-and high-frequencies, the far-field assumption [13] can be applied to the harmonic solution of the homogeneous form of Eq. (3), to obtain: "
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    ABSTRACT: At mid- and high-frequency bands, displacement-based approaches such as the finite element method (FEM) create too large models, while energy-based methods, such as statistical energy analysis, produce smaller ones, but without spatial variation. Energy flow analysis (EFA) can produce compact models that include spatial variation; however, their analytical solution makes them difficult to handle for built-up structures. To overcome this issue, the energy finite element method (EFEM), a finite element solution of EFA, was proposed. A more accurate alternative to EFEM is the energy spectral element method (ESEM). It is a matrix methodology applied to EFA similar in style to FEM, with one significant difference being the use of the analytical solution as interpolation functions. Simulated results obtained by EFEM and ESEM are analysed and compared with each other and with the spectral element method, which is used as a reference.
    Computers & Structures 04/2014; 134:48–61. DOI:10.1016/j.compstruc.2013.11.006 · 2.13 Impact Factor
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