• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.172-175
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• 2001

The high temperature deformation behavior of two-phase gamma TiAl alloy has been investigated with the variation of temperature and ${\gamma}/{\alpha}_2$ volume fraction. For this purpose, a series of load relaxation tests and tensile tests have been conducted at temperature ranging from 800 to $1050^{\circ}C$. In the early stage of the deformation as in the load relaxation test experimental flow curves of the fine-grained TiAl alloy are well fitted with the combined curves of two processes (grain matrix deformation and dislocation climb) in the inelastic deformation theory. The evidence of grain boundary sliding has not been observed at this stage. However, when the amount of deformation is large (${\epsilon}{\approx}$ 0.8), flow curves significantly changes its shape indicating that grain boundary sliding also operates at this stage, which has been attributed to the occurrence of dynamic recrystallization during the deformation. With the increase in the volume fraction of ${\alpha}_2$-phase, the flow stress for grain matrix deformation increases since ${\alpha}_2$-Phase is considered as hard phase acting as barrier for dislocation movement. It is considered that cavity initiation is more probable to occur at ${\alpha}_2/{\gamma}$ interface rather than at ${\gamma}/{\gamma}$ interface.

• Journal of Powder Materials
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• v.8 no.3
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• pp.168-173
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• 2001

The effect of grain refinement of the strength and ductility of metallic materials is investigated. A model in which a single phase material is considered as an effectively two-phase one is discussed. A distinctive feature of the model is that grain boundaries are treated as a separate phase deforming by a diffusion mechanism. Deformation of the grain interior phase is assumed to be carried by two concurrent mechanism. Deformation of the grain interior phase is assumed to be carried by two concurrent mechanisms: dislocation glide and mass transfer by diffusion. The model was exemplified by simulating uniaxial tensile deformation of Cu down to the nanometer grain size. The results confirm the observed strain hardening behaviour and a trend for reduction of ductility with decreasing grain size at room temperature.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.174-179
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• 2004

The effect of grain refinement on the plastic deformation behaviour of nanocrystalline metallic materials is investigated. A phase mixture model in which a single phase material is considered as an effectively two-phase one is discussed. A distinctive feature of the model is that grain boundaries are treated as a separate phase deforming by a diffusion mechanism. For the grain interior phase two concurrent mechanisms are considered: dislocation glide and mass transfer by diffusion. The proposed constitutive model was implemented into a finite element code (DEFORM) using a semicoupled approach. The finite element method was applied to simulating room temperature tensile deformation of Cu down to the nanoscale grain size in order to investigate the pre- and post-necking behaviour.

• Advances in concrete construction
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• v.13 no.5
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• pp.361-365
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• 2022

The objective of this study is to simulate the two-phase flow in pipes with various two-fluid models and determinate the shear stress. A hyperbolic shear deformation theory is used for modelling of the pipe. Two-fluid models are solved by using the conservative shock capturing method. Energy relations are used for deriving the motion equations. When the initial conditions of problem satisfied the Kelvin Helmholtz instability conditions, the free-pressure two-fluid model could accurately predict discontinuities in the solution field. A numerical solution is applied for computing the shear stress. The two-pressure two-fluid model produces more numerical diffusion compared to the free-pressure two-fluid and single-pressure two-fluid models. Results show that with increasing the two-phase percent, the shear stress is reduced.

• Transactions of Materials Processing
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• v.11 no.5
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• pp.447-456
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• 2002

A study has been made to investigate the boundary sliding and its accommodation mode with respect to the variation of $\alpha$$_2$/$eta$ volume fraction during superplastic deformation of two-phase Ti$_3$Al-xNb intermetallics. Step strain rate and load relaxation tests have been performed at 950, 970 and 99$0^{\circ}C$ to obtain the flow stress curves and to analyze the deformation characteristics by the theory of inelastic deformation. The results show that the grain matrix deformation and boundary sliding of the three intermetallics containing 21, 50 and 77% in $eta$ volume fractions are well described by the plastic deformation and viscous flow equations. Due to the equal accommodation of both $a^2$ and $\beta$ phases, the accommodation modes for fine-grained materials are in good agreement with the iso-strain rate models. The sliding resistance analyzed for the different boundaries is the lowest in the $\alpha$$_2$/$\alpha$$_2$ boundary, and increases in the order of $\alpha$$_2$/$\alpha$$_2$<< $\alpha$$_2$/$\beta$ = $\beta$/$\beta$, which plays an important role in controlling the superplasticity of the alloys with the various $\alpha$$_2$/$\beta$ phase ratio.

• Economic and Environmental Geology
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• v.16 no.2
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• pp.111-123
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• 1983

The studied area is situated in tho southern part of the Ogcheon fold belt, where the "Ogcheon Group" is widespread with Jurassic and Cretaceous intrusions. The regional stratigraphy may be divided into three formations, the lower pebble bearing phyllitic, the middle dark grey phyllitic, and the upper black phyllitic formations. For the purposes of the present study, the area has been partitioned to three structural subareas based on major fold axes and fault line. The main subjects of the research have been discussed from two different points, multiple deformation and minor-micro fold styles. The former is analyzed by pebble elongation, folding and lineation in a pebbly formation as well as schistosity, crenulation cleavage and crenulated lineation in the phyllitic formation. The later describes the characteristic features of fold style in each formation and structural subarea. Although minor fold axes within broad pelitic rocks usually tend to trend northeast and to plunge northward, most of these were probably formed by two stages, first a similar fold phase and second a kink fold phase. Measured structural elements indicate that crenulation cleavage in phyllite formed parallel to fold axes of folded pebble followed a NE phase of first deformation and a fold axes of pebbles diagonal to bedding of phyllite are represented by a NW phase of a second deformation. Microscopically, quartz and mica grains form a micro fold enabling one to establish tectonic levels which occur in different deformation modes in each stratigraphic sequence. Microtextures such as crenulation cleavage, kink band, aggregate band of mica and pressure shadows of porphyroblast of quartz related to qarnet and staurolite may suggest the time relation of crystallization and tectonism. The result of this study may conform that three deformation phase, NE first phase-NE second phase-NW phase, occurred in the area.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.103-110
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• 2011

A two-dimensional immiscible droplet deformation phenomena on moving wall in a channel has been investigated by using lattice Boltzmann method involving two-phase model. The dependence of the deformation of the droplet with different sizes on the contact angle and the velocity of bottom wall has studied. When the bottom wall starts to move, the deformation of the droplet occurs. For the largest bottom wall velocity, eventually, the deformation of the droplet is classified into the three patterns according to the contact angle.

• Journal of the Korean Society of Visualization
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• v.18 no.3
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• pp.35-41
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• 2020

We conduct numerical simulations of the interaction of a deformable structure with two-phase compressible flow. The finite volume method (FVM) is used to simulate fluid phenomena including a shock wave, a gas bubble, and the deformation of free surface. The deformation of a floating structure is computed with the finite element method (FEM). The compressible two-phase volume of fluid (VOF) method is used for the generation and development of a cavitation bubble, and the immersed boundary method (IBM) is used to impose the effect of the structure on the fluid domain. The result of the simulation shows the generation of a shock wave, and the expansion of the bubble. Also, the deformation of the structure due to the hydrodynamic loading by the explosion is identified.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.114-120
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• 2013

This study was carried out to investigate the relationship between mechanical properties and damping capacity in high manganese austenitic stainless steel with two phase mixed structure of reversed austenite and deformation induced martensite. Reversed austenite of ultra-fine grain size less than $0.3{\mu}m$ was obtained by reversion treatment. Two phase structure of deformation induced martensite and reversed austenite was obtained by annealing treatment at range of $500^{\circ}C{\sim}700^{\circ}C$ for various time in cold rolled high manganese austenite stainless steel. In stainless steel with two phase mixed structure of martensite and austenite, damping capacity decreased rapidly with the increasing hardness and strength. With the increasing elongation, damping capacity was increased rapidly and then, slowly increased.

• Korean Journal of Materials Research
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• v.25 no.1
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• pp.9-15
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• 2015

The effect of retained and reversed austenite on the damping capacity in high manganese stainless steel with two phases of martensite and austenite was studied. The two phase structure of martensite and retained austenite was obtained by deformation for various degrees of deformation, and a two phase structure of martensite and reverse austenite was obtained by reverse annealing treatment for various temperatures after 70 % cold rolling. With the increase in the degree of deformation, the retained austenite and damping capacity rapidly decreased, with an increase in the reverse annealing temperature, the reversed austenite and damping capacity rapidly increased. With the volume fraction of the retained and reverse austenite, the damping capacity increased rapidly. At same volume of retained and reversed austenite, the damping capacity of the reversed austenite was higher than the retained austenite. Thus, the damping capacity was affected greatly by the reversed austenite.