Viscous–elastic–plastic modelling of one-dimensional time-dependent behaviour of clays

1989 ◽  
Vol 26 (2) ◽  
pp. 199-209 ◽  
Author(s):  
J.-H. Yin ◽  
J. Graham
Keyword(s):  
Strain Rate ◽  
Constitutive Models ◽  
Constitutive Modelling ◽  
Time Dependent ◽  
Creep Tests ◽  
Strain Rate Effects ◽  
One Dimensional ◽  
Elastic Plastic ◽  
Constant Rate ◽  
Rate Effects

Increased attention has recently been directed towards the influence of time and strain-rate effects on the behaviour of clays in one-dimensional (1-D) laboratory consolidation. The improved understanding coming from these studies must now be incorporated into improved constitutive models that can be used for analysis of foundation settlements. This paper presents a 1-D model for stepped loading using a new concept for establishing "equivalent times" during time-dependent straining. This model is then developed into a general constitutive equation for continuous loading. The model uses three parameters, λ, κ, and ψ, that can be easily found using conventional oedometer tests.The general model has been used to develop analytical solutions for creep tests, relaxation tests, constant rate of strain (CRSN) tests, and tests with constant rate of stress (CRSS). Results from three different clays have been used to examine the validity of the model. Key words: consolidation, constitutive modelling, elastic-plastic, viscous, time, creep, strain rate, relaxation.

TIME-DEPENDENT MECHANICAL BEHAVIOR OF CARBON BLACK FILLED ELASTOMERS

2011 ◽  
Vol 84 (3) ◽  
pp. 296-324 ◽  
Author(s):  
Aparajita Bhattacharya ◽  
Grigori A. Medvedev ◽  
James M. Caruthers
Keyword(s):  
Cyclic Loading ◽  
Stress Relaxation ◽  
Constitutive Models ◽  
Large Change ◽  
Time Dependent ◽  
Tangent Modulus ◽  
Strain Rate Effects ◽  
Damage Models ◽  
Filled Elastomers ◽  
Rate Effects

Abstract An extensive set of time-dependent mechanical data was obtained for several filled SBR elastomers, including Mullins experiments, cyclic loading experiments, and stress relaxation. These comprehensive data enable critical evaluation of three classes of constitutive models. Viscoelastic models can naturally describe the hysteresis upon loading/reloading, but are unable to capture the large change in tangent modulus between the initial loading and the modulus just as the specimen is being unloaded. Elastic-damage models can capture the large change in tangent modulus just prior versus subsequent to unloading of a virgin sample, but can only parameterize the hysteresis on cyclic loading and are unable to predict strain rate effects and stress relaxation. A viscoelastic-damage model can predict the large change in tangent modulus upon reversal of the strain, hysteresis, strain rate effects, and stress relaxation; however, viscoelastic-damage models are unable to simultaneously predict the modest amount of hysteresis observed in cyclic experiments and the large amount of stress relaxation observed after loading to large deformations. The analysis indicates that constitutive models that include different deformation mechanics than the traditional elastic, viscoelastic, and damage processes will be needed to describe the full range of mechanical behavior exhibited by carbon black filled elastomers.

Strain rate behaviour of Saint-Jean-Vianney clay

1979 ◽  
Vol 16 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Y. P. Vaid ◽  
P. K. Robertson ◽  
R. G. Campanella
Keyword(s):  
Undrained Shear Strength ◽  
Shear Tests ◽  
Creep Tests ◽  
One Dimensional ◽  
Sustained Loading ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Rate Effects ◽  
Undrained Strength ◽  
Rate Behaviour

Rate effects on one-dimensional compressibility and undrained shear strength of a heavily overconsolidated naturally cemented clay have been studied. It is shown that in constant rate-of-strain consolidation tests the compressibility increases and the apparent preconsolidation pressure decreases with progressive decrease in rate of strain. Also a decrease in undrained strength is shown to occur with slower rates of strain in constant rate-of-strain shear and with increased time of sustained loading in creep tests. Undrained strengths from the two types of shear tests have been correlated.

Strain-Rate Effects in the Dynamic Buckling of a Simple Elastic-Plastic Model

1997 ◽  
Vol 64 (1) ◽  
pp. 193-200 ◽  
Author(s):  
D. Karagiozova ◽  
N. Jones
Keyword(s):  
Strain Rate ◽  
Plastic Material ◽  
Rate Sensitivity ◽  
Dynamic Buckling ◽  
Strain Rate Effects ◽  
Plastic Model ◽  
Elastic Plastic ◽  
Rate Effects ◽  
Elastic Plastic Material ◽  
The Impact

The phenomenon of dynamic buckling is examined when the influence of material strain-rate sensitivity is retained in the basic equations for a simple elastic-plastic model with linear strain hardening when subjected to an impact by a mass. Two approaches are proposed for taking into account the material strain-rate effects and both use the Cowper-Symonds constitutive equation. The critical impact velocities depend on the impact mass and are determined for a wholly elastic material, a strain-rate insensitive elastic-plastic material and an elastic-plastic material with a dynamic yield force together with linear or nonlinear hardening due to the strain-rate effects. The results obtained show that both strain-rate sensitive models predict impact velocities which are higher than those predicted by the strain-rate insensitive idealization and that the influence of any initial imperfections is important for the three material models considered.

Integration of Viscoplastic Effects in a One-Dimensional Constitutive Model for Ground Response Analysis

2020 ◽  
Author(s):  
Samuel Yniesta ◽  
Mallak Janati-Idrissi
Keyword(s):  
Strain Rate ◽  
Stress Component ◽  
Response Analysis ◽  
Shear Strain Rate ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Strain Rate Effects ◽  
One Dimensional ◽  
Rate Effects ◽  
Modulus Reduction

During an earthquake, strain-rate effects affect both the stiffness and damping behaviour of soils, yet existing constitutive models for ground response analysis are typically formulated within a rate-independent framework. In this paper, a one-dimensional viscoplastic stress-strain model is presented to introduce strain rate effects in ground response analysis. Its constitutive equations are based on a model that uses a cubic spline fit of the modulus reduction curve and a coordinate transformation technique to match any input modulus reduction and damping curve. A viscous stress component is added to model the effect of strain rate on the mechanical behaviour of soils using a single input parameter. The model is able to reproduce the linear increase in shear strength with the logarithm of shear strain rate, and allows to introduce viscous effects in 1D ground response analysis with control over damping and modulus reduction behaviour. The model is implemented in a software for ground response analysis and used to predict the results of a centrifuge test modeling one-dimensional wave propagation. The results show that the model predicts accurately the amplification and attenuation of shear waves, in a context where strain rates impact significantly the response of the model.

Strain-Rate Effect in the Endochronic Theory of Viscoplasticity

1976 ◽  
Vol 43 (1) ◽  
pp. 92-96 ◽  
Author(s):  
H.-C. Lin ◽  
H.-C. Wu
Keyword(s):  
Strain Rate ◽  
Quantitative Agreement ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strain Rate Effects ◽  
Endochronic Theory ◽  
One Dimensional ◽  
Time Profiles ◽  
Rate Effects ◽  
Theoretical Stress

An explicit function of material parameter β1 is proposed to accommodate the strain-rate effect in the endochronic theory of viscoplasticity developed by Valanis. The strain-rate effects are treated in a manner that includes strain-rate history dependence. The theoretical stress-strain curves at constant strain rates are presented and compared with the existing experimental data. Based on this constitutive equation, the solution of one-dimensional plastic wave propagation in thin rods is obtained for annealed aluminum and copper. The theoretical strain-time profiles are in qualitative and quantitative agreement with the experimental results. It has been shown theoretically that the consideration of the strain-rate effect in the endochronic theory lowers the final constant strain states in the strain-time profiles.

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