Determination of the Creep Parameters of Linear Viscoelastic Materials

Abstract

Creep process of linear viscoelastic materials is described by the integral equation of Boltzmann-Volterra in which creep kernel is approximated by Rabotnov’s fractional exponential function. The creep equation contains four unknown parameters: $\alpha$, singularity parameter; $\beta$, fading parameter; $\lambda$, rheological parameter; and ${\epsilon }_0$, conditionally instantaneous strain. Two-stage determination method of creep parameters is offered. At the first stage, taking into account weak singularity properties of Abel’s function at the initial moment of loading, parameters ${\epsilon }_0$ and $\alpha$ are determined. At the second stage, using already known parameters ${\epsilon }_0$ and $\alpha$, parameters $\beta$ and $\lambda$ are determined. Analytical expressions for calculating these parameters are obtained. An accuracy evaluation of the offered method with using experimentally determined creep strains of material Nylon 6 and asphalt concrete showed its high accuracy.