A Simple Effective Stress Approach for Modeling Rate-Dependent Strength of Soft Clay

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Jiang Tao Yi ◽  
Yu Ping Li ◽  
Shan Bai ◽  
Yong Fu ◽  
Fook Hou Lee ◽  
...  
Keyword(s):  
Strain Rate ◽  
Effective Stress ◽  
Large Strain ◽  
Soft Clay ◽  
Yield Locus ◽  
Submarine Landslides ◽  
Fine Grained ◽  
Rate Dependent ◽  
Modified Cam Clay ◽  
Free Falling

This paper proposes a simple effective stress method for modeling the strain rate-dependent strength behavior that is experienced by many fine-grained soils in offshore events when subjected to rapid, large strain, undrained shearing. The approach is based on correlating the size of the modified Cam-Clay yield locus with strain rate, i.e., yield locus enlarging or diminishing dependent on the strain rate. A viscometer-based method for evaluating the needed parameters for this approach is provided. The viscometer measurements showed that strain rate parameters are largely independent of water content and agree closely with data from a previous study. Numerical analysis of the annular simple shear situation induced by the viscometer shows remarkable agreement with the experimental data provided the remolding-induced strength degradation effect is accounted for. The proposed method allows offshore foundation installation processes such as dynamically installed offshore anchors, free-falling penetrometer, and submarine landslides to be more realistically analyzed through effective stress calculations.

Modeling the viscoplastic behaviour of clays during consolidation: application to Berthierville clay in both laboratory and field conditions

2001 ◽  
Vol 38 (3) ◽  
pp. 484-497 ◽  
Author(s):  
Yun Tae Kim ◽  
S Leroueil
Keyword(s):  
Strain Rate ◽  
Effective Stress ◽  
Soft Clay ◽  
Field Conditions ◽  
Combined Processes ◽  
Natural Clay ◽  
Viscoplastic Strain ◽  
Proposed Model ◽  
The Difference ◽  
Predicted Values

To analyze the effects of strain rate and viscoplastic strain on consolidation of natural clay, this paper presents a nonlinear viscoplastic model in which viscoplastic behaviour is modeled by a unique effective stress (σ'v) – viscous strain (εv) – viscous strain rate (ε·v) relationship. The proposed model can consider the effects of strain rate and viscoplastic strain on consolidation, to take into account the difference in strain rate between laboratory and field conditions, and the combined processes of generation and dissipation of pore pressure during consolidation. This model can also predict the behaviour of clay during stepwise loading, constant rate of strain, and relaxation of effective stress. The predicted values using numerical analysis are compared with measured values in laboratory tests and in situ, under an embankment built on soft clay at Berthierville, Quebec. It is possible to estimate the consolidation behaviour of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.Key words: consolidation, soft clay, strain rate, viscoplastic, relaxation.

Effects of Extrusion Speed on the Deformation of Copper Using ECAP Based on FEM

2015 ◽  
Vol 1088 ◽  
pp. 729-732 ◽  
Author(s):  
Chun Ling Wu ◽  
Zhong Ren Wang ◽  
Wen Zhang
Keyword(s):  
Plastic Deformation ◽  
Effective Stress ◽  
Metal Forming ◽  
Large Strain ◽  
Effective Strain ◽  
Extrusion Speed ◽  
Fine Grained ◽  
Ecap Process ◽  
Friction Extrusion ◽  
Forming Methods

Severe plastic deformation is defined as metal forming methods in which a very large strain is imposed to a bulk in order to make an ultra-fine grained metal. ECAP is one of the most effective methods in SPD. The influences of main parameters on deformation include extrusion route, extrusion pass, die corner, friction, extrusion speed and so on. In this investigation, a model of ECAP process has been developed based on FEM and effects of extrusion speed on effective strain, load and effective stress imposed in the copper road are researched. The results of simulation have shown that lower extrusion speed can lead to higher load of top die and effective stress while the effect of extrusion speed on effective strain of copper road is slight.

Analysis of large-strain shear in rate-dependent face-centred cubic polycrystals: correlation of micro- and macromechanics

1989 ◽  
Vol 328 (1600) ◽  
pp. 443-500 ◽  
Keyword(s):  
Strain Rate ◽  
Finite Strain ◽  
Large Strain ◽  
Kinematic Hardening ◽  
Texture Evolution ◽  
Rate Sensitivity ◽  
Rate Dependent ◽  
Crystallographic Slip ◽  
Physically Based ◽  
Constitutive Response

Micro- and macroscopic aspects of large-strain deformation are examined through analyses of shear by using physical and phenomenological models. Past experiments and analyses are first reviewed to reveal current issues and put the present work in perspective. These issues are addressed by a complete set of simulations of large-strain shear with a finite-strain, rate-dependent polycrystal model. The model is based on a rigorous constitutive theory for crystallographic slip that accounts for the development of crystallographic texture and the effects of texture on constitutive response. The influences of strain hardening, latent hardening, strain-rate sensitivity, boundary constraints, and initial textures on texture evolution and constitutive response are studied. Coupled stress and strain effects such as axial elongation during unconstrained shear and the development of normal stresses during constrained shear are related to material properties, boundary constraint and texture. The formation of ideal textures and their role in determining polycrystalline behaviour is discussed in quantitative terms. Large-strain shear is also studied by using several phenomenological constitutive theories including J 2 -flow theory, J 2 -corner theory, and two versions of finite-strain kinematic hardening theory. The behaviours predicted by these phenomenological theories and the physically based polycrystal model are directly compared. A noteworthy outcome is the close correspondence found between the predictions of J 2 -corner theory and those of the micromechanically based physical model.

Large Strain, High Strain Rate Testing of Copper

1980 ◽  
Vol 102 (4) ◽  
pp. 376-381 ◽  
Author(s):  
U. S. Lindholm ◽  
A. Nagy ◽  
G. R. Johnson ◽  
J. M. Hoegfeldt
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Large Strain ◽  
Shear Banding ◽  
Testing Machine ◽  
Shear Instability ◽  
Large Strains ◽  
Rate Dependent ◽  
Torsional Testing ◽  
Strain Hardening Behavior

This paper describes the development of a high-speed torsional testing machine and results obtained on the strain-rate dependent strength of copper at large shear strains. Test techniques and data obtained are intended to be useful in applications such as ballistics and machining. For copper, the results indicate positive strain hardening behavior to very large strains under low rate, isothermal conditions and the transition to adiabatic thermal softening, shear instability and localization (shear banding) at high rates.

scholarly journals Bounding Surface Elasto-Viscoplasticity: A General Constitutive Framework for Rate-Dependent Geomaterials

2018 ◽  
Author(s):  
Zhenhao Shi ◽  
James Hambleton ◽  
Giuseppe Buscarnera
Keyword(s):  
Strain Rate ◽  
Axial Strain ◽  
Constitutive Law ◽  
Strain Rates ◽  
Bounding Surface ◽  
Rate Dependent ◽  
Wide Range ◽  
Modified Cam Clay ◽  
Constitutive Parameters ◽  
New Framework

A general framework is proposed to incorporate rate and time effects into bounding surface (BS) plasticity models. For this purpose, the elasto-viscoplasticity (EVP) overstress theory is combined with bounding surface modeling techniques. The resulting constitutive framework simply requires the definition of an overstress function through which BS models can be augmented without additional constitutive hypotheses. The new formulation differs from existing rate-dependent bounding surface frameworks in that the strain rate is additively decomposed into elastic and viscoplastic parts, much like classical viscoplasticity. Accordingly, the proposed bounding surface elasto-viscoplasticity (BS-EVP) framework is characterized by two attractive features: (1) the rate-independent limit is naturally recovered at low strain rates; (2) the inelastic strain rate depends exclusively on the current state. To illustrate the advantages of the new framework, a particular BS-EVP constitutive law is formulated by enhancing the Modified Cam-clay model through the proposed theory. From a qualitative standpoint, this simple model shows that the new framework is able to replicate a wide range of time/rate effects occurring at stress levels located strictly inside the bounding surface. From a quantitative standpoint, the calibration of the model for over-consolidated Hong Kong marine clays shows that, despite the use of only six constitutive parameters, the resulting model is able to realistically replicate the undrained shear behavior of clay samples with OCR ranging from 1 to 8, and subjected to axial strain rates spanning from 0.15%/hr to 15%/hr. These promising features demonstrate that the proposed BS-EVP framework represents an ideal platform to model geomaterials characterized by complex past stress history and cyclic stress fluctuations applied at rapidly varying rates.

Development of a one-dimensional constitutive equation for metals subjected to high strain rate and large strain

1994 ◽  
Vol 29 (2) ◽  
pp. 117-127 ◽  
Author(s):  
M S J Hashmi ◽  
A M S Hamouda
Keyword(s):  
Constitutive Equation ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Numerical Technique ◽  
Large Strain ◽  
Mechanical Energy ◽  
Pure Copper ◽  
One Dimensional ◽  
Rate Dependent

This paper outlines a simple technique to establish rate dependent stress-strain properties for metallic materials. The materials considered are commercially pure copper and mild steel. The deformation of materials at high strain rate leads to the conversion of mechanical energy into heat. The temperature rise produced during these processes can be significant and can lead to phase transformation. A combined experimental and numerical technique has been used to establish the one-dimensional constitutive equation, which takes account of the effects of strain, strain hardening, strain rate, inertia, and temperature.

Strain-rate dependent material properties of selective laser melted AlSi10Mg and AlSi3.5Mg2.5

2020 ◽  
Vol 62 (6) ◽  
pp. 573-583
Author(s):  
Andreas Lutz ◽  
Lukas Huber ◽  
Claus Emmelmann
Keyword(s):  
Strain Rate ◽  
Material Properties ◽  
Rate Dependent
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