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  • A sign control method for fitting and interconverting material functions for linearly viscoelastic solids
    Bradshaw, R. D. ; Brinson, L. C.
    The multidata method was originally proposed to fit a Prony exponential series function to experimental viscoelastic modulus and compliance data; this was accomplished by the application of a linear ... least squares solver. This paper considers a similar approach, but extended in two key ways. First, it has been applied to the solution of convolution integral equations; specifically those used for material function interconversion. Second, it has been modified to force the signs of the Prony series coefficients to be positive; this is an essential criterion for the proper physical interpretation of a Prony series material function, which is typically not satisfied by multidata method solutions. Sign control is implemented by an iterative Levenberg-Marquardt solution algorithm with an appropriate constraint, and can be used for both fitting experimental data and interconversion. To use the method, a Prony series must be capable of adequately representing the applicable functions. The method is demonstrated by first fitting and converting experimental modulus data. Formulation for a composite lamina is also shown, in which a system of integral equations is reduced to a single integral equation; this can then be solved using the new method. Finally, application of the new method to frequency domain transformations is demonstrated, along with comparisons to other techniques.
    Vir: Mechanics of time-dependent materials : an international journal devoted to the time-dependent behaviour of materials and structures. - ISSN 1385-2000 (Vol. 1, no. 1, 1997, 85-108)
    Vrsta gradiva - članek, sestavni del
    Leto - 1997
    Jezik - angleški
    COBISS.SI-ID - 4037915

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