Strain-rate effects in dry and partially-saturated sand under one-dimensional compression at high pressures

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.

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One-dimensional elastic-plastic calculations involving strain-hardening and strain-rate effects for aluminum. [2 to 10 GPa]

10.2172/5130082 ◽

1974 ◽

Author(s):

R Swanson ◽

C Mader

Keyword(s):

Strain Rate ◽

Strain Hardening ◽

Strain Rate Effects ◽

One Dimensional ◽

Elastic Plastic ◽

Rate Effects

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

Canadian Geotechnical Journal ◽

10.1139/cgj-2019-0717 ◽

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.

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Strain-Rate Effect in the Endochronic Theory of Viscoplasticity

Journal of Applied Mechanics ◽

10.1115/1.3423803 ◽

1976 ◽

Vol 43 (1) ◽

pp. 92-96 ◽

Cited By ~ 17

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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