Elastic viscoplastic modelling of the time-dependent stress-strain behaviour of soils

1999 ◽  
Vol 36 (4) ◽  
pp. 736-745 ◽  
Author(s):  
Jian-Hua Yin ◽  
James Graham
Keyword(s):  
Strain Rate ◽  
Creep Test ◽  
Triaxial Compression ◽  
Constant Strain Rate ◽  
Time Dependent ◽  
Model Parameters ◽  
Stress Strain ◽  
Equivalent Time ◽  
Strain Behaviour ◽  
Modified Cam Clay

This paper presents a new framework for elastic viscoplastic (EVP) constitutive modelling. In developing the model, a general one-dimensional elastic viscoplastic (1D EVP) relationship is first derived for isotropic stressing conditions using an "equivalent-time" concept. This 1D EVP model is then generalized into a three-dimensional EVP model based on Modified Cam-Clay and viscoplasticity. Fitting functions are proposed for fitting data when model parameters are being determined. Using these functions, a specific EVP model is developed which describes the time-dependent stress-strain behaviour of soils under triaxial stress states. This model has been calibrated using data from a densely compacted sand-bentonite mixture. The calibrated model is used to compute time-dependent (or strain rate dependent) stress-strain curves from a multistage shear creep test and a step-changed, constant strain rate undrained triaxial compression test. Predictions from the EVP model are in general agreement with measured values. It is demonstrated that the model can simulate accelerating creep when deviator stresses are close to the shear strength envelope in a q creep test. It can also model the behaviour in unloading-reloading and relaxation. Limitations and possible improvements are also indicated.Key words: equivalent time, stress-strain, time dependent, elastic, viscoplastic, triaxial.

A New Nonlinear Stress-Strain Model for Soils at Various Strain Levels

2013 ◽  
Vol 631-632 ◽  
pp. 782-788
Author(s):  
Cheng Chen ◽  
Zheng Ming Zhou
Keyword(s):  
Compression Test ◽  
Triaxial Compression ◽  
Small Strain ◽  
Empirical Formulas ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Proposed Model ◽  
Nonlinear Stress ◽  
London Clay ◽  
Strain Model

Soils have nonlinear stiffness and develops irrecoverable strains even at very small strain levels. Accurate modeling of stress-strain behaviour at various strain levels is very important for predicting the deformation of soils. Some existing stress-strain models are reviewed and evaluated firstly. And then a new simple non-linear stress-strain model is proposed. Four undetermined parameters involved in the proposed model can be obtained through maximum Young’s module, deformation module, and limit deviator stress and linearity index of soils that can be measured from experiment directly or calculated by empirical formulas indirectly. The effectiveness of the proposed stress-strain model is examined by predicting stress-strain curves measured in plane-strain compression test on Toyota sand and undrained triaxial compression test on London clay. The fitting results of the proposed model are in good agreement with experimental data, which verify the effectiveness of the model.

Tensile Stress-Strain Curves Modeling of Four Kinds of Solders with Temperature and Rate Dependence

2005 ◽  
Vol 297-300 ◽  
pp. 905-911 ◽  
Author(s):  
Xu Chen ◽  
Li Zhang ◽  
Masao Sakane ◽  
Haruo Nose
Keyword(s):  
Tensile Stress ◽  
Constitutive Model ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Strain Rate Range ◽  
Rate Dependence ◽  
Strain Rates ◽  
Stress Strain ◽  
Rate Range

A series of tensile tests at constant strain rate were conducted on tin-lead based solders with different Sn content under wide ranges of temperatures and strain rates. It was shown that the stress-strain relationships had strong temperature- and strain rate- dependence. The parameters of Anand model for four solders were determined. The four solders were 60Sn-40Pb, 40Sn-60Pb, 10Sn-90Pb and 5Sn-95Pb. Anand constitutive model was employed to simulate the stress-strain behaviors of the solders for the temperature range from 313K to 398K and the strain rate range from 0.001%sP -1 P to 2%sP -1 P. The results showed that Anand model can adequately predict the rate- and temperature- related constitutive behaviors at all test temperatures and strain rates.

scholarly journals Evolution of specimen strain rate in split Hopkinson bar test

2019 ◽  
Vol 233 (13) ◽  
pp. 4667-4687 ◽  
Author(s):  
Hyunho Shin ◽  
Jong-Bong Kim
Keyword(s):  
Strain Rate ◽  
Rate Equation ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Hopkinson Bar ◽  
Stress Strain ◽  
Split Hopkinson Bar ◽  
Specimen Diameter ◽  
Strain And Strain Rate ◽  
Split Hopkinson

The specimen strain rate in the split Hopkinson bar (SHB) test has been formulated based on a one-dimensional assumption. The strain rate is found to be controlled by the stress and strain of the deforming specimen, geometry (the length and diameter) of specimen, impedance of bar, and impact velocity. The specimen strain rate evolves as a result of the competition between the rate-increasing and rate-decreasing factors. Unless the two factors are balanced, the specimen strain rate generally varies (decreases or increases) with strain (specimen deformation), which is the physical origin of the varying nature of the specimen strain rate in the SHB test. According to the formulated strain rate equation, the curves of stress–strain and strain rate–strain are mutually correlated. Based on the correlation of these curves, the strain rate equation is verified through a numerical simulation and experiment. The formulated equation can be used as a tool for verifying the measured strain rate–strain curve simultaneously with the measured stress–strain curve. A practical method for predicting the specimen strain rate before carrying out the SHB test has also been presented. The method simultaneously solves the formulated strain rate equation and a reasonably estimated constitutive equation of specimen to generate the anticipated curves of strain rate–strain and stress–strain in the SHB test. An Excel® program to solve the two equations is provided. The strain rate equation also indicates that the increase in specimen stress during deformation (e.g., work hardening) plays a role in decreasing the slope of the strain rate–strain curve in the plastic regime. However, according to the strain rate equation, the slope of the strain rate–strain curve in the plastic deformation regime can be tailored by controlling the specimen diameter. Two practical methods for determining the specimen diameter to achieve a nearly constant strain rate are presented.

scholarly journals Constant Strain-Rate Tensile Testing of Natural Snow

1980 ◽  
Vol 26 (94) ◽  
pp. 519 ◽  
Author(s):  
H. Singh ◽  
F.W. Smith
Keyword(s):  
Strain Rate ◽  
Strain Gage ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Strain Rates ◽  
Strain Gages ◽  
Compression Tests ◽  
Snow Sample ◽  
Stress Strain ◽  
Natural Snow

Abstract In conducting tension and compression tests on snow samples, strains and strain-rates are usually determined from the displacements of the ends of the samples. In this work, a strain-gage which mounts directly onto the snow sample during testing, was developed and was found to give accurate and direct measurements of strain and strain-rates. A commercially available 0-28 pF variable capacitor was modified to perform the required strain measurements. It is a polished metallic plunger sliding inside a metal-coated glass tube. The plunger and tube were each soldered to the end of a spring-steel wire arm. To the other end of these arms were soldered to 10 mm square pads made of thin brass shim stock. The whole device weighs 2.5 g and the low coefficient of friction in the capacitor resulted in a very low actuation force. To mount the strain gage, the pads are wetted and frozen onto the snow sample. A high degree of sensitivity was achieved through the use of “phase-lock-loop” electronic circuitry. The capacitance change caused by the strain in the sample, changes the frequency of output signal from an oscillator and thus causes the change in output from the system. In the locked state, to which the system is constantly driven by a feed-back loop, the system output is almost ripple free. The strain gages were calibrated in the field in order to take into account the effects of very low field temperatures. The calibration curves were almost linear over the travel of 15 mm, the maximum limit. The sensitivity of the system is 4 mV per strain unit, but this could be increased by an order of magnitude by minor adjustments in the circuit. Constant strain-rate tensile tests were performed on natural snow at Berthoud Pass, Colorado, U.S.A., in the density range of 140-290 kg m-3. Four strain gages were mounted onto the samples to sense any non-uniform deformation which otherwise would have gone unnoticed or caused scatter in the data. The average indication of these gages was used to construct stress—strain curves for various types of snow at different strain-rates. The effect of strain-rate on the behavior of snow was studied. “Ratcheting” in the stress-strain curve in the region where the snow becomes plastic was observed first by Kinosita in his compression tests. A similar phenomenon was observed in these tension tests. It was found that directly measured strain is quite different from that which would be calculated from sample end movement. Strain softening was not observed in these tests up to total strains of 8%. The strain-rate effects found were comparable to the results of other investigators.

An Improved Method of Determining the Disturbed State Concept Model Parameters

2014 ◽  
Vol 919-921 ◽  
pp. 1345-1349
Author(s):  
Wei Lu ◽  
Jia Jun Pan
Keyword(s):  
Triaxial Compression ◽  
Model Parameters ◽  
Improved Method ◽  
Stress Strain ◽  
Material Parameters ◽  
Concept Model ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Disturbed State Concept

The method of postulate of relatively intact model in the disturbed concept model is reached. Because it is more difficult to assume relatively intact curve by observed experimental data, a method which could automatically calculate the stress strain relation curve of relative intact by triaxial compression test data is raised, so that the determination of material parameters becomes easier, and the improved method is verified by numerical calculation. The results show that this method can effectively determine the stress strain relation curve of relative intact.

Measured and predicted time-dependent stress-strain behaviour of Hong Kong marine deposits

1999 ◽  
Vol 36 (4) ◽  
pp. 760-766 ◽  
Author(s):  
Jian-Hua Yin ◽  
Jun-Gao Zhu
Keyword(s):  
Hong Kong ◽  
Technical Note ◽  
Time Dependent ◽  
Practical Significance ◽  
Stress Strain ◽  
Analysis And Design ◽  
Marine Deposits ◽  
Modelling Framework ◽  
Strain Behaviour ◽  
Dependent Behaviour

Hong Kong marine deposits (HKMD) are considered to be difficult (or weak) soils for civil projects because of low shear strength and time-dependent high compressibility. Understanding and modelling the time-dependent stress-strain behaviour of HKMD are of practical significance in the analysis and design of civil structures on and in HKMD. In this technical note, test data on the time-dependent behaviour of a remoulded HKMD are presented and analysed. An existing elastic viscoplastic (EVP) modelling framework is used to describe the time-dependent stress-strain behaviour of HKMD. The modelling results are compared with the measured results.Key words: stress-strain, time dependent, creep, viscoplastic, triaxial, soil.

High Temperature Plastic Behaviour of Icosahedral AlCuFe Quasicrystals.

2000 ◽  
Vol 643 ◽  
Author(s):  
Jan Fikar ◽  
Joël Bonneville ◽  
Nadine Baluc ◽  
Pierre Guyot
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Friction Stress ◽  
Dislocation Model ◽  
Compression Tests ◽  
Creep Tests ◽  
Flow Strength ◽  
Stress Strain ◽  
Softening Effect ◽  
Dislocation Interaction

AbstractIcosahedral AlCuFe poly-quasicrystalline specimens were deformed in constant strain rate compression tests at temperatures ranging between 300K - 1020K. Below nearly 0.7 Tm (Tm is the melting temperature) the specimens were brittle. Above the brittle-to-ductile transition temperature, after the elastic stage the stress-strain curves exhibit a marked yield-point followed by a stage of strain softening only. Transient creep tests were performed at different given stress/strain levels after interrupting the constant strain-rate deformation tests. After the transient tests, the flow strength of the specimens was investigated anew at constant strain rate. The results are interpreted in the framework of a dislocation model, where two effects opposing dislocation movement are considered: firstly, the usual elastic dislocation interaction, yielding a work-hardening contribution, and, secondly, a friction stress specific to the quasiperiodic lattice, leading to a softening effect.

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