Void ratio redistribution in undrained triaxial extension tests on Ottawa sand

1998 ◽  
Vol 35 (2) ◽  
pp. 351-359 ◽  
Author(s):  
A Ayoubian ◽  
P K Robertson
Keyword(s):  
Phase Transformation ◽  
Void Ratio ◽  
Large Strains ◽  
Ultimate State ◽  
Ratio Distribution ◽  
Ottawa Sand ◽  
Effective Stresses ◽  
Softening Behavior ◽  
Triaxial Extension Test ◽  
Triaxial Extension

Water-pluviated samples of Ottawa sand were tested in monotonic, undrained triaxial extension tests. The specimens exhibited similar "limited strain softening" behavior, and they all experienced phase transformation from contraction to dilation at small axial strains. The tests were stopped at different stages and the samples were frozen to obtain void ratio distribution along the length of the specimens. It was shown that void ratio redistribution can start at very low axial strains in an undrained triaxial extension test. Before phase transformation, void ratio redistribution was very small, but after phase transformation void ratio redistribution started rapidly and continued until the end of the tests at ultimate state. The location of the ultimate state line in a void ratio - mean normal effective stress plot was shown to be affected by localized failure at large strains in undrained triaxial extension tests. The actual ultimate state line with respect to void ratios and effective stresses within the failure zone in the samples can be located above the average ultimate state line obtained from average measurements of void ratios and effective stresses of the entire specimens.Key words: liquefaction, testing, void ratio.

Mode of shear effects on yield and liquefied strength ratios

2008 ◽  
Vol 45 (4) ◽  
pp. 574-587 ◽  
Author(s):  
Scott M. Olson ◽  
Benjamin B. Mattson
Keyword(s):  
Simple Shear ◽  
Void Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
Sloping Ground ◽  
Direct Simple Shear ◽  
Flow Failure ◽  
Triaxial Extension Test ◽  
Triaxial Extension ◽  
Rotational Shear

A database of 386 laboratory triaxial compression, direct simple shear, rotational shear, and triaxial extension test results was collected to examine yield and liquefied strength ratio concepts used in liquefaction analysis of sloping ground. These data envelope the yield and liquefied strength ratios obtained from back-analyses of liquefaction flow failure case histories. Generally, triaxial compression exhibits the highest yield and liquefied strength ratios, triaxial extension yields the lowest ratios, and direct simple shear – rotational shear shows intermediate responses. However, mode of shear appears to have a considerably smaller effect on laboratory-measured liquefied strength ratios for specimens with a positive state parameter (i.e., difference in consolidation void ratio and steady state void ratio at the same effective stress).

Specimen nonuniformities in water-pluviated and moist-tamped sands under undrained triaxial compression and extension

2008 ◽  
Vol 45 (7) ◽  
pp. 939-956 ◽  
Author(s):  
P. R. Thomson ◽  
R. C.K. Wong
Keyword(s):  
Computed Tomography ◽  
Axial Load ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Stress Path ◽  
Saturated Sand ◽  
Ratio Distribution ◽  
X Ray ◽  
X Ray Computed ◽  
Insight Into

X-ray computed tomography (CT) methods and specialized triaxial equipment were developed to quantify void ratio distribution within saturated sand specimens reconstituted by water pluviation and moist tamping methods during undrained triaxial compression and extension. The CT measurements were obtained at several points along the stress path of each specimen without significant removal of axial load. It was observed that two reconstitution methods yielded very different void ratio distributions within specimens. Significant void ratio redistribution occurred within each specimen during the undrained shearing tests. The influences of void ratio redistribution on globally observed specimen responses are discussed. The findings of this research investigation provide unique insight into fundamental aspects of saturated sand behaviour during undrained triaxial shearing.

Application of the Shape Memory Effect to Restore Smoothness

2015 ◽  
Author(s):  
Paul Braden ◽  
Kaitlyn Gainer
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Complex Problem ◽  
Large Strains ◽  
National Archives ◽  
Cylindrical Tubes ◽  
Reverse Method ◽  
The U.S

A major worldwide industry is the display and preservation of historical and rare documents, paintings, canvases, tapestries and other works of art. Many private collectors and museums pay large amounts, such as the $23 million for the U.S. National Gallery and $8 million for the U.S. National Archives. There is an even greater demand for many consumers who desire an affordable way to safely maintain their images in top condition for viewing and enjoyment. Another industry where the smoothness of the paper documents is important is in the shipping and delivery business. Here, many shipments are done with cylindrical tubes that cause the paper to appear bent and not flat. In some cases, this can pose a major problem for scanning and electronic devices which need a flat surface for optimal performance. A novel new alternative to traditional conservation methods is the use of Shape Memory Alloys (SMA’s) to remove wrinkles and other surface anomalies. SMA’s use a thermoelastic property called the Shape Memory Effect (SME) to recover large strains by phase transformation. In this process, the SMA is stretched until the polycrystalline microstructure is detwinned Martensite. Then, energy in the form of heat is applied to the SMA which causes the phase transformation to the more compact Austenite. Thus, a reverse method is the proposed solution for the complex problem faced by art preservation experts. Instead of using large clamps and having to wait for results, we demonstrate how embedded SMA wires in a robust picture frame can provide a continuous restorative force that maintains the picture’s smoothness. Using proper simple wiring from the SMA wires to the picture, it is possible to remove the strains in the paper and hold the picture to the proper smoothness long term. We provide experimental results and offer suggestions for the future use of SMA’s in this new field of art restoration.

Influence of Void Ratio Distribution on Permeability of Porous Layer

2018 ◽  
Vol 2018.93 (0) ◽  
pp. 809
Author(s):  
Yoshiyuki YAMAGUCHI ◽  
Kimitaka WATANABE ◽  
Satoshi DOI
Keyword(s):  
Porous Layer ◽  
Void Ratio ◽  
Ratio Distribution

A Numerical Investigation of Interface Dynamics during Martensitic Transformation in a Shape Memory Alloy Using the Level-Set Method

2007 ◽  
Vol 340-341 ◽  
pp. 1199-1204 ◽  
Author(s):  
Takeshi Iwamoto ◽  
Mohammed Cherkaoui ◽  
Esteban P. Busso
Keyword(s):  
Phase Transformation ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Level Set Method ◽  
Level Set ◽  
Dissipation Function ◽  
Large Strains ◽  
Normal Velocity ◽  
Kinetics Of

In this study, the simulation of the motion of an interface during the stress-induced martensitic transformation of a shape memory alloy is performed using the level-set method. The kinetics of the phase transformation is defined as an anisotropic kinetic relation between the rate at which the weak discontinuity moves, given by its normal velocity, and the thermodynamics driving force. The latter is derived from a dissipation function, which obeys the 1st and 2nd law of thermodynamics and accounts for large strains. Furthermore, a hyperelastic constitutive framework is used to describe the constitutive behavior of the material. The model is implemented into the finite element method and is then used to solve a 2D phase transformation problem in a shape memory alloy.

scholarly journals Simulations of Fine-Meshed Biaxial Tests with Barodesy

Geosciences ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 20
Author(s):  
Gertraud Medicus ◽  
Barbara Schneider-Muntau
Keyword(s):  
Shear Band ◽  
Void Ratio ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Triaxial Tests ◽  
Biaxial Test ◽  
Average Response ◽  
Stress Strain ◽  
Ratio Distribution ◽  
Biaxial Tests

Recent experimental studies showed that shear band development starts at the beginning of triaxial tests. In experimental testing, it is impossible to obtain a soil sample with a homogeneous void ratio. Therefore, a homogeneous deformation, i.e., an element test, is questionable well before the peak. In this article we carry out finite element simulations of fine-meshed biaxial tests with the constitutive model barodesy, where the stress rate is formulated as a function of stress, stretching and void ratio. The initial void ratio in the simulations is normally distributed over all elements in a narrow range. In this article, we evaluate the pre-peak shear band development. We further compare stress paths and stress-strain curves of the biaxial test of relevant elements (e.g., in- and outside the shear band) with the results of the average response of all elements. We show how the response in an element test differs from the average response of the fine-meshed test. We present the resulting potential for understanding (early) shear band development and stress-strain behaviour in a biaxial test: The inhomogeneous void ratio distribution in a sample favours early shear band development. This effect is modelled with barodesy. The obtained stress paths and stress-strain curves show that the maximum deviatoric stress is higher in the element test than it is in the average response of the fine-meshed test.

Static Softening Behaviour in High Aluminum Steels

2012 ◽  
Vol 706-709 ◽  
pp. 2764-2769 ◽  
Author(s):  
Z. Aretxabaleta ◽  
B. Pereda ◽  
S.V. Parker ◽  
Beatriz López
Keyword(s):  
Phase Transformation ◽  
Base Composition ◽  
Static Recrystallization ◽  
Ferrite Phase ◽  
Softening Behaviour ◽  
Recrystallization Kinetics ◽  
Softening Behavior ◽  
Base Steel ◽  
Static Softening ◽  
High Aluminum

The effect of Al addition on the static softening behavior of C-Mn steels was investigated. The compositions of the steels studied are representative of the recently developed TRIP-assisted steels: a base composition of 0.2%C, 2%Mn, 50ppm N and three different Al levels, 0.03 (base steel), 1 and 2%. Double-hit torsion tests were performed at different deformation temperatures, in the range 950°C to 1100°C, and pass-strains, =0.2 and 0.35. It was found that solute Al produced a significant retardation on static recrystallization kinetics, equivalent to that exerted by 0.026%Nb for the 1%Al steel and to 0.05%Nb for the 2%Al steel. Additionally, at the lowest temperatures (950-1000°C) and 2%Al level, austenite to ferrite phase transformation was found to be concurrent with softening, enhancing retardation in the mechanical softening.

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