1,720,974 research outputs found
Constitutive issues associated with LAOS experimental techniques
No full textLarge amplitude oscillatory shear (LAOS) is a rheological test method for the characterization of viscoelastic nonlinear materials. The correlation between the characteristic parameters obtained from measurements and theoretical models is a complex issue, one that requires the extraction of significant data from the measurements in order to identify corresponding models. Alternatively, a process of deductive logic may be useful in predicting typical behaviors of the materials through modeling which can then be verified by the analysis of measured data. The aim of this work is to highlight the potential of this logical deductive approach regarding LAOS testing. For this purpose, a LAOS is analytically simulated for an isotropic viscoelastic material of a differential type, with cubic nonlinearities and a correspondence of the Fourier coefficients. This is how nonlinearity parameters of the model are obtained. It can be seen that each nonlinearity parameter depends on Fourier coefficients through one of the new measures introduced by Ewoldt et al. [J. Rheol. 52, 1427–1458 (2008)] in 2008. Analysis of the function which represents shear stress suggests new interpretations of the experimental results and highlights how characteristics of the model can be compared with typical behaviors of the Lissajous–Bowditch plots
The Anti-Plane Shear Problem in Nonlinear Elasticity Revisited
No full textA classical problem in the framework of nonlinear elasticity theory is the characterization of the materials that may sustain a pure state of anti-plane shear in the absence of body forces. This problem has been solved by Knowles and by Hill in the framework of isotropic and incompressible elasticity in the seventies. Here we provide a simpler and shorter proof of these classical results. Moreover, we extend these results to nonlinear elastodynamics and we provide some new special solutions
Some remarks about a simple history dependent nonlinear viscoelastic model
No full textA simple model for history dependent nonlinear viscoelasticity is considered. The determining equation governing shear motions is derived and investigated in the quasistatic approximation and under the traveling waves ansatz. Traveling waves are possible only if an inequality involving the constitutive parameters is satisfied. This fact is in contrast to what happens in viscoelasticity of the Kelvin–Voigt type. On the other hand, in the quasi-static approximation (classical creep and recovery experiments) the behavior of the history dependent model is similar to analogous rate dependent models
On a Special Class of Nonlinear Viscoelastic solids
No full textWe investigate some possible nonlinear generalizations of the Kelvin—Voigt viscoelastic models. We use the usual idealization of creep and recovery experiments to discuss the mechanical significance of some constitutive requirements and we show that in the case of a shear-rate dependent viscosity localization of the solution is possible under a simple constitutive characterization
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