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The one-dimensional constitutive equations of strain-hardening materials subject to nonlinear creep are derived. The solution is found using the hypothesis of unified deformation curve based on the similarity of the tensile and isochronic creep curves. A generalized rheological model is constructed which accounts for the instantaneous strain rate, loading rate, and the mode of strain hardening. This model is used to derive one-dimensional constitutive equations for linear viscoelastic, nonlinear viscoelastic, and linear- and nonlinear-hardening viscoelastoplastic materials. It is shown that the creep of linear viscoelastic and linear-hardening viscoelastoplastic materials is transient. For nonlinear viscoelastic and nonlinear-hardening viscoelastoplastic materials, all the characteristic stages of creep are present 相似文献
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The creep strains in linear viscoelastic materials under nonstationary loading of various types (incremental loading, complete
unloading, and cyclic loading) are determined. Boltzmann–Volterra hereditary theory with fractional exponential kernel is
used. Nonstationary loads are specified by Heaviside functions. The calculated results are validated by experimentally determining
nonstationary creep strains of glass-reinforced plastic, plastic laminate, polymer concrete, duralumin, and nylon 相似文献
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The nonlinearity of the creep of nylon fibers is justified based on the similarity of a set of isochronous creep curves, which
also includes the instantaneous deformation curve. Nonlinear hereditary constitutive equations of creep are derived. The real
values of the influence function are determined as the basic rheological characteristic of the material. The applicability
of Boltzmann's, Abel's, Rzhanitsyn's, and Rabotnov's kernels is estimated quantitatively. The choice of an Abel-type kernel
is justified. The calculated and experimental data are in satisfactory agreement for a loading duration of up to 1,000 hours
and an order of magnitude change in the stresses
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 7, pp. 102–115, July 2005. 相似文献
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The linearity domain for the viscoelastic properties of high-molecular organic fibers is determined. The linearity criteria are coincidence of experimental compliance curves and linearity of isochronic creep curves. Statistical criteria are used to establish linearity. The influence function in the constitutive equation of linear viscoelasticity is an Abel-type power kernel. The calculated and experimental creep strains are in good agreement both at the initial stage of deformation and after long-term loading__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 5, pp. 97–106, May 2005. 相似文献
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The parameters of the fractional exponential creep and relaxation kernels of linear viscoelastic materials are determined.
Methods that approximate the kernel by using the Mittag-Leffler function, the Laplace-Carson transform, and direct approximation
of the creep function by the original equation are analyzed. The parameters of fractional exponential kernels are determined
for aramid fibers, parapolyamide fibers, glass-reinforced plastic, and polymer concrete. It is shown that the kernel parameters
calculated through the direct approximation of the creep function provide the best agreement between theory and experiment.
The methods are experimentally validated for constant-stress and variable-stress loading in the modes of additional loading
and complete unloading
Translated from Prikladnaya Mekhanika, Vol. 44, No. 9, pp. 12–25, September 2008. 相似文献