Viscoelastic behavior of plasticized polyvinyl chloride at large deformations. I. Stress relaxation

1963 ◽  
Vol 1 (8) ◽  
pp. 2497-2510 ◽  
Author(s):  
Raffaele Sabia ◽  
F. R. Eirich
Keyword(s):  
Stress Relaxation ◽  
Polyvinyl Chloride ◽  
Large Deformations ◽  
Viscoelastic Behavior

Viscoelastic Behavior of High Polymers at Large Deformations

1969 ◽  
Vol 42 (2) ◽  
pp. 373-380 ◽  
Author(s):  
G. W. Becker ◽  
H.-J. Rademacher
Keyword(s):  
Stress Relaxation ◽  
Entire Range ◽  
Large Deformations ◽  
Viscoelastic Behavior ◽  
Stress Dependence ◽  
Plasticized Pvc ◽  
Stress Region ◽  
Deformation Dependence ◽  
Different Strains ◽  
High Polymers

Abstract Stress relaxation at different strains, and retarded deformation at different stresses were measured for rod-shaped test specimens of plasticized PVC in tension. Temperature was varied in such a way that changes in properties of the material, within the entire range from the glassy-amorphous to the quasi rubber-elastic states, could be comprehended. From results of the two types of experiment it was concluded that outside of the linear stress region, and at all temperatures, the time and deformation dependence of stress could be separated, but this was not possible for the time and stress dependence of strain.

Nonseparable Behavior in Rubber Viscoelasticity

1989 ◽  
Vol 62 (1) ◽  
pp. 68-81 ◽  
Author(s):  
J. L. Sullivan ◽  
K. A. Mazich
Keyword(s):  
Stress Relaxation ◽  
Relaxation Spectrum ◽  
Loss Modulus ◽  
Large Strain ◽  
Viscoelastic Behavior ◽  
Strain Effects ◽  
Mixed Response ◽  
Strain Stress ◽  
Necessary And Sufficient ◽  
Solid Liquid

Abstract New large-strain rubber viscoelasticity results for a filled and an unfilled IIR vulcanizate and previously published results for two NR gum vulcanizates have been discussed. The data show that the “mixed” response functions of large-strain stress relaxation, and the incremental storage and relaxation moduli do not demonstrate factorizability of time and strain effects. This is a consequence of the elastic and relaxation contributions in each of the mixed functions being different. The incremental dynamic data also show that the loss modulus for the filled IIR and unfilled NR vulcanizates (unavailable for the unfilled IIR) are separable functions of time and strain. This directly shows that the relaxation spectra for the filled IIR and unfilled NR vulcanizates are independent of strain for the deformations studied. In fact, it is argued that a necessary and sufficient condition for the relaxation spectrum to be independent of strain is that the loss modulus is a factorizable function of time and strain effects. The quantitative success of the Generalized Solid-Liquid (GSL) model in representing the viscoelastic behavior of the gum NR vulcanizate has been reviewed. Although the GSL model applies only to unfilled vulcanizates, it has also been successfully used to qualitatively interpret the results for the filled IIR compounds. Both successes are attributed to the physical assumptions intrinsic to the GSL model; more specifically, 1) the relaxation spectrum is independent of the state of strain, and 2) the deformational dependences of elastic and relaxation contributions to the overall response of the system need not be the same. Physical arguments justifying these assumptions have been covered. It has also been shown with the aid of the GSL model, that a material might exist which demonstrates factorizability in stress relaxation and incremental loss modulus behaviors but nonfactorizability in the incremental storage and relaxation moduli.

Study on Nonlinear Viscoelastic Properties of Asphalt Mixture Based on Stress Relaxation Test

2014 ◽  
Vol 563 ◽  
pp. 48-52
Author(s):  
Lei Chen ◽  
Zhi Xin Yu ◽  
Wei Ping Cui ◽  
Li Juan Qin
Keyword(s):  
Stress Relaxation ◽  
Asphalt Mixture ◽  
Viscoelastic Behavior ◽  
Exponential Model ◽  
Relaxation Test ◽  
Asphalt Binders ◽  
Stress Relaxation Test ◽  
Nonlinear Viscoelastic ◽  
Low Temperature Cracking ◽  
Relaxation Experiments

Development of normal stress in the direction perpendicular to the asphalt mixture is an important feature of the nonlinear viscoelastic behavior of asphalt binders. In this paper, this phenomenon was studied with the help of stress-relaxation experiments in torsion.  Results indicate that stress relaxation test by controlling strain could be used to evaluate the stress relaxation ability of asphalt mixture. With the aging degree of asphalt mixtures increased, the low temperature cracking resistance got worse; the higher the temperature is, the faster the stress relaxed; the smaller the initial strain, the worse the stress relaxation ability also. The viscoelasticity of asphalt mixture could be simulated by exponential model fractional and the experiments well supported the modeling results.

scholarly journals Constitutive Modeling of Time-Dependent Response of Human Plantar Aponeurosis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
P. G. Pavan ◽  
P. Pachera ◽  
C. Stecco ◽  
A. N. Natali
Keyword(s):  
Experimental Data ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Transverse Isotropy ◽  
Model Fitting ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Plantar Aponeurosis ◽  
Structural Conformation ◽  
Dependent Behavior

The attention is focused on the viscoelastic behavior of human plantar aponeurosis tissue. At this purpose, stress relaxation tests were developed on samples taken from the plantar aponeurosis of frozen adult donors with age ranging from 67 to 78 years, imposing three levels of strain in the physiological range (4%, 6%, and 8%) and observing stress decay for 240 s. A viscohyperelastic fiber-reinforced constitutive model with transverse isotropy was assumed to describe the time-dependent behavior of the aponeurotic tissue. This model is consistent with the structural conformation of the tissue where collagen fibers are mainly aligned with the proximal-distal direction. Constitutive model fitting to experimental data was made by implementing a stochastic-deterministic procedure. The stress relaxation was found close to 40%, independently of the level of strain applied. The agreement between experimental data and numerical results confirms the suitability of the constitutive model to describe the viscoelastic behaviour of the plantar aponeurosis.

Analysis of Fabric Deformation in a Roll-Making Operation Part III: Effect of Viscoelasticity

1992 ◽  
Vol 62 (11) ◽  
pp. 669-676 ◽  
Author(s):  
T. K. Ghosh ◽  
H. Peng ◽  
P. Banks-Lee
Keyword(s):  
Stress State ◽  
Stress Relaxation ◽  
Continuum Model ◽  
Present Model ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Plane Stress State ◽  
Numerical Examples ◽  
Fabric Deformation ◽  
The Relationship

The relationship between various parameters of roll making, fabric properties, and the resultant stresses developed within a fabric roll has been discussed in Parts I and II of this series. A discrete continuum model was used to describe fabric deformation during roll making. In the present model, the fabric is assumed to be in plane stress state and the effect in the filling direction is entirely neglected. The fabric is considered as anisotropic in warp and thickness directions. The effect of fabric viscoelasticity in the warp direction is also considered. A simple two-term Maxwell viscoelastic model is used to describe the fabric viscoelastic behavior. The stress relaxation process within fabric rolls during and after roll formation is discussed through numerical examples.

An Improved Method to Analyze the Stress Relaxation of Ligaments Following a Finite Ramp Time Based on the Quasi-Linear Viscoelastic Theory

2004 ◽  
Vol 126 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Steven D. Abramowitch ◽  
Savio L.-Y. Woo
Keyword(s):  
Stress Relaxation ◽  
Soft Tissues ◽  
Viscoelastic Behavior ◽  
Cyclic Stress ◽  
Elastic Response ◽  
Curve Fit ◽  
Order Of Magnitude ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Theory ◽  
Experimental Values

The quasi-linear viscoelastic (QLV) theory proposed by Fung (1972) has been frequently used to model the nonlinear time- and history-dependent viscoelastic behavior of many soft tissues. It is common to use five constants to describe the instantaneous elastic response (constants A and B) and reduced relaxation function (constants C, τ1, and τ2) on experiments with finite ramp times followed by stress relaxation to equilibrium. However, a limitation is that the theory is based on a step change in strain which is not possible to perform experimentally. Accounting for this limitation may result in regression algorithms that converge poorly and yield nonunique solutions with highly variable constants, especially for long ramp times (Kwan et al. 1993). The goal of the present study was to introduce an improved approach to obtain the constants for QLV theory that converges to a unique solution with minimal variability. Six goat femur-medial collateral ligament-tibia complexes were subjected to a uniaxial tension test (ramp time of 18.4 s) followed by one hour of stress relaxation. The convoluted QLV constitutive equation was simultaneously curve-fit to the ramping and relaxation portions of the data r2>0.99. Confidence intervals of the constants were generated from a bootstrapping analysis and revealed that constants were distributed within 1% of their median values. For validation, the determined constants were used to predict peak stresses from a separate cyclic stress relaxation test with averaged errors across all specimens measuring less than 6.3±6.0% of the experimental values. For comparison, an analysis that assumed an instantaneous ramp time was also performed and the constants obtained for the two approaches were compared. Significant differences were observed for constants B, C, τ1, and τ2, with τ1 differing by an order of magnitude. By taking into account the ramping phase of the experiment, the approach allows for viscoelastic properties to be determined independent of the strain rate applied. Thus, the results obtained from different laboratories and from different tissues may be compared.

Comparison of a Novel Nonlinear Viscoelastic Finite Ramp Time Correction Method to a Heaviside Step Assumption

2011 ◽  
Author(s):  
Kevin L. Troyer ◽  
Christian M. Puttlitz
Keyword(s):  
Stress Relaxation ◽  
Soft Tissues ◽  
Viscoelastic Behavior ◽  
Relaxation Modulus ◽  
Correction Method ◽  
Nonlinear Viscoelastic ◽  
Instantaneous Strain ◽  
Relaxation Experiments ◽  
Time Correction

Connective soft tissues exhibit time-dependent, or viscoelastic, behavior. In order to characterize this behavior, stress relaxation experiments can be performed to determine the tissue’s relaxation modulus. Theoretically, the relaxation modulus describes the stress relaxation behavior of the tissue in response to an instantaneous (step) application of strain. However, a step increase in strain is experimentally impossible and a pure ramp load is intractable due to the inertial limitations of the testing device. Even small deviations from an instantaneous strain application may cause significant errors in the determination of the tissue’s relaxation modulus.

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