• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.31-38
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• 1989

This paper concentrates on the analysis of reinforced concrete(R/C) structures subjected to monotonic loading, from zero to ultimate loads. Tensile cracking, the nonlinear stress-strain relationship for concrete and reinforcement are taken into account the concrete is assumed to be elastic in tension region and elasto-hardening plastic in compression region. The Kupfer's failure criteria and associated flow rule are adopted to govern the plastic behavior of the concrete. The reinforcing bar is considered as a elasto-hardening platic material. The tension stiffening effect of the concrete between cracks is also considered. The numerical error depends on the used finite element mesh size is reduced by correcting the slope of strain softening region of the concrete according to the developed energy criteria.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.128-134
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• 1996

In this study, the thermal and optical properties of multicomponent glass optical fiber by adding heavy metal oxide Ga$_2$O$_3$were investigated. The fiber samples were made by rod in tube method. The optical loss of fiber was measured in 0.3~1.8${\mu}{\textrm}{m}$ wavelength region. As Ga$_2$O$_3$increased up to 20wt%, the transition and softening temperature of bulk glass were increased from 495$^{\circ}C$ to 579$^{\circ}C$ and from 548$^{\circ}C$ to 641$^{\circ}C$respectively. Whereas the thermal expansion coefficient was decreased from 102 to 79.1$\times$10$^{-7}$ $^{\circ}C$. The refractive index was increased from 1.621 to 1.665, and IR cut-off wavelength was enlarged from 4.64${\mu}{\textrm}{m}$ to 6.1${\mu}{\textrm}{m}$. The optical loss of fiber was decreased and more remarkably decreased in 1.146${\mu}{\textrm}{m}$~1.8${\mu}{\textrm}{m}$ wavelength region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.91-91
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• 2008

$SnO_2-B_2O_3-P_2O_5$ system were prepared by melt-quenching technique in the compositional series containing 50, 55 aod 60mol.% of $SnO_2$. A large glass-forming region was found at the phosphate side of the ternary system with homogeneous glasses containing up to 5-25mol.% of $B_2O_3$. For these glasses, thermal expansion coeffient($\alpha$), glass transition temperature(Tg), and glass softening temperature(Ts), were determined. The values a decrease with increasing $B_2O_3$ content, while Tg and Ts increased. The reason for the observed changes is local structure of the glasses. Local structure of the glasses was investigated by Raman and FT-IR measurements, suggesting that the number of bridging oxygens decreased whereas the non-bridging oxygen concentration increased with increasing $SnO_2$ content in the glasses.

• Structural Engineering and Mechanics
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• v.56 no.6
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• pp.917-938
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• 2015

The nonlinear numerical analysis of the impact response of reinforced concrete/mortar beam incorporated with the updated Lagrangian method, namely the Smoothed Particle Hydrodynamics (SPH) is carried out in this study. The analysis includes the simulation of the effects of high mass low velocity impact load falling on beam structures. Three material models to describe the localized failure of structural elements are: (1) linear pressure-sensitive yield criteria (Drucker-Prager type) in the pre-peak regime for the concrete/mortar meanwhile, the shear strain energy criterion (Von Mises) is applied for the steel reinforcement (2) nonlinear hardening law by means of modified linear Drucker-Prager envelope by employing the plane cap surface to simulate the irreversible plastic behavior of concrete/mortar (3) implementation of linear and nonlinear softening in tension and compression regions, respectively, to express the complex behavior of concrete material during short time loading condition. Validation upon existing experimental test results is conducted, from which the impact behavior of concrete beams are best described using the SPH model adopting an average velocity and erosion algorithm, where instability in terms of numerical fragmentation is reduced considerably.

• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.119-127
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• 1996

Objection of this study is to present the three-dimensional material nonlinear analysis of reinforced concrete. A concrete is idealized with three-dimensional 16-node solid element including triaxial nonlinear stress-strain behavior, cracking, crushing and strain softening: a steel with three-dimensional 3 node truss element including elastic-plastic behavior with strain hardening. The cracked shear retention factor is introduced to estimate the effective shear modulus con sidering aggregate interlock after c:racking and a modified newton method is used to obtain a nu merical solution. Numerical results in a gauss point is displayed graphically. Numerical examples of Krahl's reinforced concrete beam and Hedgreds shell are selected to compare with the experimental and numerical results.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.4
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• pp.180-186
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• 2018

High temperature flow behaviors of Fe-Cr-Mo-V-W-C tool steel were investigated using isothermal compression tests on a Gleeble simulator. The compressive test temperature was varied from 850 to $1,150^{\circ}C$ with the strain rate ranges of 0.05 and $10s^{-1}$. The maximum height reduction was 45%. The dynamic softening related to the dynamic recrystallization was observed during hot deformation. The constitutive model based on Arrhenius-typed equation with the Zener-Hollomon parameter was proposed to simulate the hot deformation behavior of Fe-Cr-Mo-V-W-C steel. An artificial neural network (ANN) model was also developed to compare with the constitutive model. It was concluded that the ANN model showed more accurate prediction compared with the constitutive model for describing the hot compressive behavior of Fe-Cr-Mo-V-W-C steel.

• Food Science and Preservation
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• v.2 no.1
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• pp.173-183
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• 1995

This paper was carried out to investigate changes in chromatograms of polysacctatides and soluble pectins on Sephadex G-50 and non-cellulosic neutral sugars of polysaccharides isolated from cell wall of persimmon fruits treated with polygalacturonase and $\beta$-galactosidase in vitro. The chromatogram pattern of soluble pectins extracted from cell wall treated with $\beta$-galactosidase on Sephacryl S-500 column were similar to those of untreatment, but contents of soluble pectins treated with $\beta$-galactosidase were different from those of untreatment. The patterns of chromatograms In soluble pectins extracted from cell wall treated with polygalacturonase were more complex and lower molecular polymer than those of other cell wall-degrading enzyme treatments. Non-cellulosic neutral sugar of polysaccharides in fraction I of soluble material treated with polygalacturonase was rhamnose, those in fraction II were similar to those in fraction III and contents of arabinose, xylose and glucose were higher than contents of other non-cellulosic neutral sugars. Non-cellulosic neutral sugars of polysaccharides in fraction I in soluble material by $\beta$-galactosidase treatment were rhamnose, arabinose, galactose and mannose. Content of glucose of polysaccharides in fraction II was higher than that in fraction I . Non-cellulosic neutral sugars treated with mixed enzyme were rhamnose, fucose, arabinose, xylose, mannose, galactose and glucose. Compositions of non-cellulosic neutral sugars of polysaccharides in fraction I were similar to those in fraction II and III.

• Structural Engineering and Mechanics
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• v.14 no.4
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• pp.435-454
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• 2002

The paper proposes analytical forms able to represent with very good approximation the constitutive law experimentally deducible by means of uniaxial cyclic compressive tests on material having softening post-peak behaviour in compression and negligible tensile strength. The envelope, unloading and reloading curves characterizing the proposed model adequately approach structural responses corresponding to different levels of nonlinearity and ductility, requiring a not very high number of parameters to be calibrated experimentally. The reliability of the model is shown by comparing the results that it is able to provide with the ones analytically deduced from two reference models (one for concrete, another for masonry) available in the literature, and with experimental results obtained by the authors in the framework of a research in progress.

• Structural Engineering and Mechanics
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• v.22 no.3
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• pp.351-370
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• 2006

In this study, the earthquake damage response of the concrete arch dams was investigated including dam-reservoir interaction. A continuum damage model which is a second-order tensor and includes the strain softening behavior was selected for the concrete material. Fluid-structure interaction problem was modeled by Lagrangian approach. Sommerfeld radiation condition was applied to the truncated boundary of reservoir. The improved form of the HHT-${\alpha}$ time integration algorithm was used in the solution of the equations of motion. The arch dam Type 5 was selected for numerical application. For the dynamic input, acceleration records of the 10 December 1967 Koyna earthquake were chosen. These records were scaled with earthquake acceleration scale factor (EASF) and then used in the analyses. Solutions were obtained for empty and full reservoir cases. The effects of EASF and damping ratio on the response of the dam were studied.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.191-194
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• 2003

The results from a systematic study of the response of a Ti-6Al-4V alloy under quasi-static and dynamic loading at different strain rates and temperatures are presented. It has been shown that the work-hardening rate decreased as the strain rate and the strain increased. The correlations and predictions using modified KHL (Khan-Huang-Liang) viscoplastic constitutive model are compared with those from JC (Johnson-Cook) model and experimental observations. Overall, KHL model correlations and predictions compared much more favorably than the corresponding JC model predictions and correlations.