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Juan Luis Gonzalez-Santander

Publications and source records attributed to Juan Luis Gonzalez-Santander.

3 recordsLinked to original sources

Energy dissipation in linear viscoelasticity

We compare the specific dissipation $Q^{-1}\left( ω\right) $ for the Becker, Lomnitz, and Lambert models in linear viscoelasticity. Graphically, the specific dissipation of these models behaves similarly as $ω\rightarrow 0^{+}$ and $ω\rightarrow +\infty$. Furthermore, we obtain analytic formulas for the asymptotic behavior of $Q^{-1}\left( ω\right) $ in the Becker and Lomnitz models as $ω\rightarrow 0^{+}$ and $ω\rightarrow +\infty$, where the latter limit coincides with the specific dissipation of the Maxwell model. We also derive a novel closed-form expression for the specific dissipation in the generalized Becker model, $Q_{ν}^{-1}\left( ω\right) $, when the parameter $ν\in \left( 0,1\right] $ is rational. When $ν\rightarrow 0$, we recover the specific dissipation of the Maxwell model, whereas when $ν=1$, we recover that of the original Becker model. In addition, we derive two new closed-form expressions for the specific dissipation for the extended Jeffreys--Lomnitz model $Q_{α}^{-1}\left( ω\right) $, the first being valid for $α\in \left( 0,1\right] $, and the second for $α\in \left( -\infty ,1\right] $. When $α\rightarrow 0$, we recover the specific dissipation of the Lomnitz model, whereas when $α=1$, we recover that of the Maxwell model. Finally, we conclude that the asymptotic behavior of $Q_{α}^{-1}\left( ω\right) $ as $ω\rightarrow +\infty $ coincides with the specific dissipation of the Maxwell model. Keywords:

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Delta-pulse solution in Zener viscoelastic model

We derive the integral representation of the solution for the propagation of a delta-pulse (impulsive wave) in a semi-infinite, homogeneous, linear viscoelastic medium governed by the Zener model. Starting from the Bromwich integral representation of the response function, we obtain a closed-form integral representation by analytically inverting the relevant Laplace transforms. The result is expressed in terms of modified Bessel functions of the first kind and Macdonald functions of half-integer order, and is shown to reduce to the known Maxwell model solution in the appropriate limit. As an independent computational approach, we derive the steepest descent path (SDP) associated with the phase function of the Bromwich integral, characterizing its saddle points and showing that the SDP can be expressed explicitly as the zero locus of a sixth-degree polynomial in the imaginary part of the complex variable. The two methods are compared numerically for several values of the model parameters, confirming their agreement. While the integral representation provides analytical insight into the structure of the solution, the steepest descent method requires no explicit inversion of the Laplace transform and may therefore prove especially valuable in more general viscoelastic settings where a closed-form integral representation is not available.

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Pulse waves in the viscoelastic Kelvin-Voigt model: a revisited approach

We calculate the mechanical response $r(x,t$) of an initially quiescent semi-infinite homogeneous medium to a pulse applied at the origin, and this is achieved within the framework of the Kelvin-Voigt model. Although this problem has been extensively studied in the literature because of its wide range of applications -- particularly in seismology -- here, we present a solution in a novel integral form. This integral solution avoids the numerical computation of the solution in terms of the inverse Laplace transform; that is, numerical integration in the complex plane. In particular, we derive integral form expressions for both delta-pulse and step-pulse excitations which are simpler and more computationally efficient than those previously reported in the literature. Furthermore, the obtained expressions allow us to obtain simple asymptotic formulas for $r(x,t$ as $x,t \to 0,\infty$ for both step- and delta-type pulses.

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