AUTHOR=Lin Che-Yu 

TITLE=Alternative Form of Standard Linear Solid Model for Characterizing Stress Relaxation and Creep: Including a Novel Parameter for Quantifying the Ratio of Fluids to Solids of a Viscoelastic Solid

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.00011

DOI=10.3389/fmats.2020.00011

ISSN=2296-8016

ABSTRACT=<p>The standard linear solid model (SLSM) is a typical and useful model for analyzing stress relaxation and creep behaviors of viscoelastic solids for obtaining the corresponding viscoelastic properties. However, the analysis results cannot be directly compared to the parameters commonly adopted for defining the mechanical properties of viscoelastic solids in the finite element simulation package such as the modulus of elasticity (<italic>E</italic><sub><italic>e</italic></sub>) and the two parameters in the dimensionless form of the relaxation modulus (<italic>g</italic> and τ<sub>1</sub>). The purpose of this paper is to introduce an alternative form of SLSM in terms of <italic>E</italic><sub><italic>e</italic></sub>, <italic>g</italic>, and τ<sub>1</sub> for characterizing stress relaxation and creep behaviors. A series of stress relaxation and creep curves with different <italic>E</italic><sub><italic>e</italic></sub>, <italic>g</italic>, and τ<sub>1</sub> was simulated by finite element simulation. The derived alternative form of SLSM was used to curve fit the simulated stress relaxation and creep curves to obtain the corresponding values of <italic>E</italic><sub><italic>e</italic></sub>, <italic>g</italic>, and τ<sub>1</sub>. The results showed that the values of <italic>E</italic><sub><italic>e</italic></sub>, <italic>g</italic>, and τ<sub>1</sub> obtained from the simulation were approximately equal to the theoretical ones (i.e., those set in the simulation), showing that the alternative form of SLSM can accurately evaluate the corresponding <italic>E</italic><sub><italic>e</italic></sub>, <italic>g</italic>, and τ<sub>1</sub>. In conclusion, the alternative form is formulated in terms of the parameters used to define the mechanical properties in the finite element simulation package, so that the parameters obtained by curve fitting can be directly compared to those set in the finite element simulation package. It was also found that the physical meaning of <italic>g</italic> is associated with the ratio of viscous fluids to solids of a viscoelastic solid.</p>