• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.759-772
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• 2009

Amorphous alloys, in addition to being promising materials for a variety of practical applications, provide an excellent test bed for evaluating our understanding of the underlying physics on deformation in amorphous solids. Like many amorphous materials, amorphous alloys can exhibit either homogeneous or inhomogeneous deformation depending on the stress level. The mode of deformation has a strong influence on whether the material behavior is classified as ductile or brittle. It was observed that the characteristics of these deformations are largely dependent on the atomic-scale structures of the alloys and determine the amount of the plastic deformation prior to failure. In this study, the structural features that control the homogeneous deformation of amorphous alloys are outlined on the basis on experiments and molecular dynamics simulations.

• Korea-Australia Rheology Journal
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• v.15 no.1
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• pp.9-17
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• 2003

The rheological behaviour of anatase $TiO_2$ with organic coating has been investigated extensively in this study. The yield stress was measured over a wide range of solids concentration and pH using stress-controlled and speed-controlled rheometers. The organic treatment leads to a shift of the isoelectric point (IEP) from around pH 5.5 to pH 2.4. A maximum yield stress occurs in the vicinity of the isoelectric point determined by electrokinetic measurements. The transition of rheological behaviour between elastic solid and viscous liquid is represented by a stress plateau in a plot of stress against strain. It is hypothesised that the slope of the stress plateau reflects the uniformity of the structure, and hence the distribution of bond strength. Altering the concentration and the surface chemistry can vary the bond strength and its distribution. therefore, resulting in different type of failure: "ductile-type" or "brittle-type". pH and volume fraction dependence of yield stress could be described quantitatively using existing models with reasonable agreement.easonable agreement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.2
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• pp.33-56
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• 2001

It is well known fact that all rocks exhibit brittle properties and time depends strain properties (creep). An understanding of the time dependent deformation behaviour of rocks is believed to be essential in the field of civil and tunnelling. The rock and concrete creep in various forms of loading conditions and physical environment are reviewed. A comparison of creep behaviour between rocks and concrete is provided, in order to bring two existing relatively independent methods of predicting creep strain closer together. It was felt that the physical process in the creep of rocks would be similar to the process in creep of concrete. Since experiments and observations have shown that non-elastic (creep) mechanical behaviour of all crystalline solids (i.e., concrete, rocks, ceramics and refractories) and single materials have a common base. Also a comparison of the results for the accepted methods of estimating creep in rocks and concrete under - multiaxial loading was attempted to extend the knowledge of deformational characteristics of these two materials.