Linear viscoelastic behaviour of isotropic materials I - Transient measurements
article
The linear viscoelastic behaviour of isotropic materials under three dimensional stress distributions is treated by means of a generalised superposition principle, which yields the state of stress under known strain history and vice versa. The material is completely characterised mechanically, if two independent characteristic material functions are determined. As such we may choose: 1. the creep compliances in simple shear, isotropic compression and linear extension J(t), B(t) and F(t) (monotonously increasing functions of time). 2. the stress relaxation moduli in simple shear, isotropic compression and linear extension G(t), K(t) and E(t) (monotonously decreasing functions of time), 3. a time dependent Poisson's ratio v(t) (varying unrestrictedly between 0 and 1/2). The relationships between these functions are given. The shear modulus G(t) as well as the bulk K(t) may show independent dispersion regions. A dispersion in the shear modulus without dispersion in the bulk modulus leads to an increase in Poisson's ratio, a dispersion in the bulk modulus without dispersion in the shear modulus would lead to a decrease in Poisson's ratio. If the "relaxation strengths" in shear modulus and bulk modulus are equal, Poisson's ratio remains constant. From the consideration of the experimental facts on high polymers known to day, it is emphasized that a transition region in shear modulus will generally be accompanied by an increase in Poisson's ratio and may perhaps be followed by a slight relaxation of the bulk modulus. © 1956 Verlag von Dr. Dietrich Steinkopff.
TNO Identifier
226654
ISSN
0303402X
Source
Kolloid-Zeitschrift, 148(1-2), pp. 47-57.
Publisher
Springer-Verlag
Pages
47-57
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