Anisotropic behaviour of a sensitive clay

1979 ◽  
Vol 16 (2) ◽  
pp. 335-350 ◽  
Author(s):  
R. N. Yong ◽  
V. Silvestri
Keyword(s):  
Mechanical Response ◽  
Plastic Material ◽  
Anisotropic Elasticity ◽  
True Triaxial ◽  
Anisotropic Behaviour ◽  
Strain Behaviour ◽  
Preconsolidation Pressure ◽  
Confining Pressures ◽  
Sensitive Clay ◽  
Elastic Plastic Material

This paper presents the results of a study carried out to determine the drained stress–strain behaviour of a sensitive clay from St-Louis de Bonsecours (Quebec), tested under conventional axisymmetric (σ′1 > σ′2 = σ′3) and complex true-triaxial (σ′1 ≠ σ′2 ≠ σ′3) stress states.The data reported herein show that, for confining pressures below the preconsolidation pressure of the clay, the influence of cementation bonds and anisotropy results in deviation from the Mohr–Coulomb theory and causes the clay to behave as an anisotropic pseudo-elastic, plastic material. It is shown that constitutive relationships derived from the theories of anisotropic elasticity and plasticity represent very well the mechanical response of the clay.

A novel technique of electrical strengthening of soft sensitive clays by dielectrophoresis

1992 ◽  
Vol 29 (4) ◽  
pp. 599-608 ◽  
Author(s):  
K. Y. Lo ◽  
K. S. Ho ◽  
I. I. Inculet
Keyword(s):  
Shear Strength ◽  
Electric Field ◽  
High Voltage ◽  
Alternating Current ◽  
Novel Technique ◽  
Strain Behaviour ◽  
Preconsolidation Pressure ◽  
Electro Osmosis ◽  
Sensitive Clay ◽  
Applied Electric Potential

A novel technique of electrical strengthening of soil by dielectrophoresis was developed. The process employs an alternating current at high voltage, generating a converging electric field towards the electrode by which a net resultant movement of water in the clay mass is produced towards the direction of stronger electric field intensity. Laboratory tests were developed to investigate the mechanism of this process and to explore the possibility of its application in electrical strengthening of soft sensitive clays. The preliminary results of this study showed that the process is effective, and the shear strength of the treated clay (Wallaceburg clay) increased drastically by several times with a reduction of moisture content of approximately 25% at an applied electric potential of 20 kV for 28 days. When compared with electro-osmosis, similar results are obtained in dielectrophoresis, such as the increase in preconsolidation pressure, decrease in sensitivity, and improvement of stress–strain behaviour. It is also shown that the improvement of soil properties can be greatly enhanced by increasing the applied voltage and electrode depth. Key words : dielectrophoresis, alternating current, converging electric field, high-voltage electrode, dielectric constant, electro-osmosis, soft sensitive clay, shear strength, consolidation.

Anisotropic Behaviour of AZ31B Sheet at High Strain Rates

2012 ◽  
Vol 151 ◽  
pp. 726-730 ◽  
Author(s):  
Iram Raza Ahmad ◽  
Dong Wei Shu
Keyword(s):  
Maximum Stress ◽  
Mechanical Response ◽  
High Strain ◽  
Rate Sensitivity ◽  
Tensile Loading ◽  
Strain Rates ◽  
High Strain Rates ◽  
Anisotropic Behaviour ◽  
Strain Behaviour ◽  
Tension Compression Asymmetry

The anisotropic effects on the mechanical response of AZ31B sheet at high strain rates have been analyzed. The experimental results indicate that the stress-strain behaviour of the alloy is highly anisotropic and rate sensitive. However, anisotropy of the mechanical properties of the alloy is less significant at higher strain rates. Under tensile loading, the anisotropic behaviour of the alloy is less significant as compare to its behaviour under compression. In both compression and tensile loading the alloy shows significant rate sensitivity as compare to quasi-static strain rates but at higher rates it is less significant. The maximum stress is observed to reach nearly 600 MPa for transverse direction impact. The tension-compression asymmetry is observed in the alloy.

Electroosmotic strengthening of soft sensitive clays

1991 ◽  
Vol 28 (1) ◽  
pp. 62-73 ◽  
Author(s):  
K. Y. Lo ◽  
I. I. Inculet ◽  
K. S. Ho
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Strength Increase ◽  
Sample Length ◽  
Voltage Distribution ◽  
Steady Current ◽  
Preconsolidation Pressure ◽  
Sensitive Clay ◽  
Pressure Stress

A comprehensive experimental investigation on the electroosmotic strengthening of soft sensitive clay was performed to assess the effectiveness of the treatment and to study the mechanism of the process. A specially designed electroosmotic cell was developed to prevent gas accumulation near the electrodes, to allow better electrode-soil contact, and to improve the treatment efficiency. This apparatus also enables the monitoring of the generated negative pore-water pressure along the sample length, settlement, voltage distribution, and current variation during treatment. The investigation covered two different types of soil trimmed at different orientations: the vertically and horizontally trimmed overconsolidated Wallaceburg clay and the vertically trimmed slightly overconsolidated soft sensitive Gloucester (Leda) clay. Results of this study showed that the voltage distribution and induced negative pore pressure at equilibrium along the sample are linear with steady current flow across the sample, indicating that the electrode design in the electroosmosis test apparatus is efficient. The electroosmotic consolidation curve is similar to that of the conventional consolidation curve, and the preconsolidation pressure was increased by 51–88% with an applied voltage up to 6 V. The undrained shear strength increased to a maximum of 172%, and the moisture content decreased by 30%. The technique of electrode reversal is employed, and a relatively uniform strength increase between the electrodes is observed. Key words: electroosmosis, electroosmotic cell, soft sensitive clay, negative pore-water pressure, preconsolidation pressure, stress–strain behaviour.

Structural Integrity Research for Reactor Pressure Vessel Under In-Vessel Retention of a Core Melt

2016 ◽  
Author(s):  
Yongjian Gao ◽  
Yinbiao He ◽  
Ming Cao ◽  
Yuebing Li ◽  
Shiyi Bao ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Material Properties ◽  
Power Plants ◽  
Structural Integrity ◽  
Plastic Material ◽  
Plastic Region ◽  
Reactor Pressure Vessel ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Reactor Pressure

In-Vessel Retention (IVR) is one of the most important severe accident mitigation strategies of the third generation passive Nuclear Power Plants (NPP). It is intended to demonstrate that in the case of a core melt, the structural integrity of the Reactor Pressure Vessel (RPV) is assured such that there is no leakage of radioactive debris from the RPV. This paper studied the IVR issue using Finite Element Analyses (FEA). Firstly, the tension and creep testing for the SA-508 Gr.3 Cl.1 material in the temperature range of 25°C to 1000°C were performed. Secondly, a FEA model of the RPV lower head was built. Based on the assumption of ideally elastic-plastic material properties derived from the tension testing data, limit analyses were performed under both the thermal and the thermal plus pressure loading conditions where the load bearing capacity was investigated by tracking the propagation of plastic region as a function of pressure increment. Finally, the ideal elastic-plastic material properties incorporating the creep effect are developed from the 100hr isochronous stress-strain curves, limit analyses are carried out as the second step above. The allowable pressures at 0 hr and 100 hr are obtained. This research provides an alternative approach for the structural integrity evaluation for RPV under IVR condition.

On Determining Elastic Modulus from Instrumented Indentation

2013 ◽  
Vol 668 ◽  
pp. 616-620
Author(s):  
Shuai Huang ◽  
Huang Yuan
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Plastic Material ◽  
Instrumented Indentation ◽  
Computational Simulations ◽  
Elastic Plastic ◽  
Modified Method ◽  
Plastic Materials ◽  
Elastic Plastic Material ◽  
Elastic Plastic Materials

Computational simulations of indentations in elastic-plastic materials showed overestimate in determining elastic modulus using the Oliver & Pharr’s method. Deviations significantly increase with decreasing material hardening. Based on extensive finite element computations the correlation between elastic-plastic material property and indentation has been carried out. A modified method was introduced for estimating elastic modulus from dimensional analysis associated with indentation data. Experimental verifications confirm that the new method produces more accurate prediction of elastic modulus than the Oliver & Pharr’s method.

scholarly journals Relationship Between Rockwell C Hardness and Inelastic Material Constants

2002 ◽  
Vol 124 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Akihiko Hirano ◽  
Masao Sakane ◽  
Naomi Hamada
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Strain Hardening ◽  
Yield Stress ◽  
Plastic Material ◽  
Stress And Strain ◽  
Material Constants ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Hardening Coefficient

This paper describes the relationship between Rockwell C hardness and elastic-plastic material constants by using finite element analyses. Finite element Rockwell C hardness analyses were carried out to study the effects of friction coefficient and elastic-plastic material constants on the hardness. The friction coefficient and Young’s modulus had no influence on the hardness but the inelastic materials constants, yield stress, and strain hardening coefficient and exponent, had a significant influence on the hardness. A new equation for predicting the hardness was proposed as a function of yield stress and strain hardening coefficient and exponent. The equation evaluated the hardness within a ±5% difference for all the finite element and experimental results. The critical thickness of specimen and critical distance from specimen edge in the hardness testing was also discussed in connection with JIS and ISO standards.

Integral Representation of Energy Release Rate in Graded Materials

2006 ◽  
Vol 74 (5) ◽  
pp. 1046-1048 ◽  
Author(s):  
Z.-H. Jin ◽  
C. T. Sun
Keyword(s):  
Potential Energy ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Plastic Material ◽  
Contour Integral ◽  
Material System ◽  
Graded Materials ◽  
Elastic Plastic Material ◽  
Graded Interlayer

It is well known that, for homogeneous materials, the path-independent J contour integral is the (potential) energy release rate. For general nonhomogeneous, or graded materials, such a contour integral as the energy release rate does not exist. This work presents a rigorous derivation of the extended J integral for general graded materials from the potential energy variation with crack extension. Effects of crack shielding and amplification due to a graded interlayer in an elastic-plastic material system are discussed in terms of this integral.

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