• Journal of the Korean Society for Heat Treatment
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• v.24 no.4
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• pp.193-198
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• 2011

Effect of CaO addition on age hardening response has been studied by using optical microscopy, scanning electron microscopy and differential thermal analysis in AZ91 and CaO-containing ECO-AZ91 alloys. After solution treatment, the ${\beta}$($Mg_{17}Al_{12}$) phase formed during solidification mostly disappeared in the microstructure in the AZ91 alloy, whereas numerous ${\beta}$ precipitates containing Ca were still observed in the ECO-AZ91 alloy due to its enhanced thermal stability. The ECO-AZ91 alloy showed the delayed peak aging time and higher peak hardness compared with those of the AZ91 alloy. The activation energies for ${\beta}$ precipitation calculated by means of Kissinger method increased from 71.4 to 85.6 kJ/mole by the addition of CaO, which implies that CaO plays a role in reducing ${\beta}$ precipitation rate in the AZ91 alloy.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.28-35
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• 1998

The seismic overstrength factor $\Omega$ is evaluated for 4-story reinforced concrete buildings in Korea(of which seismic intensity is low). The study model is designed according to aseismic guideline research - phase II in Korea. The effect of variation of span length and bay number, dead load is considered, especially including the variation of hardening ration after yielding. And push-over analysis is performed, in which the external and internal frame is connected by rigid-link and the $\Omega$ is calculated using the roof drift ratio at 2%. For Zone I, the mean value of $\Omega$ is ranged form 2.3 to 2.5, For Zone II, from 3.1 to 3.4. For low hardening ratio(3%) after yielding, $\Omega$ has little relations with the number of bay, like as the results of other research. But for 5% hardening ratio, $\Omega$ is increased as the number of bay is increased. Within general gravity-load bound, the variation of D.L. has variation of D. L. has no effect on $\Omega$. And, $\Omega$ is increased as the span length is increased.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.11
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• pp.490-492
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• 2005

A study on radiation hardening of infrared(IR) detector, the chief component of IR camera was performed. The radiation test on IR sensor passivated with the ZnS by Co$^{60}$ gamma-ray over 1 Mrads showed the reduction in Ro by 1/100 which was related to the noise level. This effect that was caused by carrier trapping in the ZnS passivation layer increased the leakage current and resulted in degradation in the device performance. For the radiation hardening of IR devices we suggested the ones with CdTe passivation layer which had a tendency to reluctant to carrier trapping in its layer and developed test patterns. Radiation test to the patterns showed that the our CdTe passivated device could survived over 1 Mrad gamma-ray dose.

• The Journal of Information Technology
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• v.8 no.4
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• pp.43-50
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• 2005

In this paper, we describe a study on the relationship between photographic emulsion manufacture and hardening test of color paper. The hardener was prepared by the reaction of cyanuric chloride with sodium hydroxide, disodium hydrogenphosphate-12-water and trisodium phosphate-12-water in the presence of water. The hardener used in this study is a 2,4-dichloro-6-hydroxy-1,3,5-triazine mono sodium salt. The hardening test of photographic emulsion was studied respectively at pH 5.5, 7, 8.5 and about increasing temperature. Novel hardener can be used in photo-graphic emulsion of color paper and showed very good hardening effect.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.144-147
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• 2003

In order to evaluate spring-back behavior in automotive sheet forming processes, a panel shape idealized as a SS-rail has been investigated. After spring-back kas been predicted fer SS-rails using the finite element analysis, results has been compared with experimental measurements for three automotive sheets. To account for hardening behavior such as the Bauschinger and transient effects in addition to anisotropic behavior, the combined isotropic-kinematic hardening law based on the Chaboche type single-surface model and a recently developed non-quadratic anisotropic yield function have been utilized, respectively.

• Journal of the Korean Society of Safety
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• v.23 no.1
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• pp.12-17
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• 2008

The earn shaft is very important for the safety of automobiles. The earn shaft needs a surface hardening process by high frequency induction to have both strength and toughness. It is required for safety of automobile to consider how the characteristics of tensile strength and toughness are changed according to the condition of surface hardness. In this study, we prepared surface hardened SM53C which is used as cam shaft materials. We examined the tensile strengths according to the depth of surface hardening and the effect of tempering. We also investigated the fracture toughnesses according to the depth of surface hardening(1mm, 2mm).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.40-43
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• 2000

A process optimal design methodology applicable to steady-state forming with a strain-hardening material is presented. in this approach the optimal design problem is formulated on the basis of a rigid-viscoplastic finite element process model and a derivative based approach is adopted as an optimization technique The process model the schemes for the evaluation of the design sensitivity considering the effect of strain-hardening and an iterative procedure for design optimization are described. the validity of the proposed approach is demonstrated through application to die shape optimal design in extrusion.

• Transactions of Materials Processing
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• v.26 no.6
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• pp.333-340
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• 2017

The cyclic hardening behavior of transformation-induced plasticity (TRIP) steels shows tension-compression asymmetry known to be attributed to transformation of retained austenite into martensite during deformation. In this work, YoshidaUemori hardening model was used to represent the asymmetric hardening behavior of TRIP1180 steel. Yoshida-Uemori hardening model parameters were obtained from three sets of data: tension-compression, compression-tension, and a combination of the two. Material models were validated for U-bending and springback.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.64-71
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• 1988

A special set of constitutive equations is formulated to predict elastic-plastic strain hardening responses of porous metals. Including the effect of the material's strain hardening in the yield function, the constitutive equations are capable of showing no dip phenomena in uniaxial strain compression and prediction work-hardening response for plastically precyled porous metal. The proposed constitutive equations are compared with experimental data for porous tungsten.

• Journal of Ocean Engineering and Technology
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• v.18 no.4 s.59
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• pp.46-51
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• 2004

The surface layer in dredged and reclaimed marine clay is improved by mixing of shallow soils and hardening agents, which is made of cement, containing some other special admixtures. Tests in both laboratory and field settings are performed to investigate the improvement effect and strength properties of cement-stabilized soils. The test results show that the hardening agent sufficiently improves the soil properties of the surface layer, while increasing the load-carrying capacity. The strength of cement-stabilized soils depends, primarily, on water-to-cement ratio and curing temperature. That is, the higher curing temperature and the longer curing time, the higher the strength in cement-stabilized soils. The high ratio of water-ta-cement results in a lower strength.