• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.473-474
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.380-381
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• 2005

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.58-59
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• 2018

• Korean Journal of Materials Research
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• v.14 no.8
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• pp.558-564
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• 2004

In order to improve the low hardness and low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment and CrN film coating were carried out. Effects of the plasma carburization and CrN coating were analyzed and compared with the non-treated alloy by mechanical and creep tests. After plasma carburization and CrN coating treatments, the carburized layer was about 150 ${\mu}m$ in depth and CrN coated layer was about 7.5 ${\mu}m$ in thickness. Hardness value of about $H_{v}$ 402 of the non-treated alloy was improved to $H_{v}$ 1600 and 1390 by plasma carburization and CrN thin film coating, respectively. Stress exponent(n) was decreased from 9.10 in CrN coating specimen to 8.95 in carburized specimen. However, the activation energy(Q) was increased from 242 to 250 kJ/mol. It can be concluded that the static creep deformation for Ti-6Al-4V alloy is controlled by the dislocation climb over the ranges of the experimental conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1580-1587
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• 2005

To calculate the long-term allowable strength of geosynthetic reinforcement, replacement method was recommended. The isochronous creep curve by S. Turner was used to define the relation between creep strain and allowable strength. In isochronous curve at given time, one can read the allowable strength at allowable creep strain. The allowable strain gets from specification by directors or manufacturers according to the allowable displacement of reinforced structures. The allowable strength can be determined in relation to the allowable horizontal displacement each structures case by case. The effect of install damage on isochronous behaviors of geosynthetic reinforcement was little. In previous study, install damage increase the creep strain slightly. And the degradation was not identified. But it is supposed that degradation increase the creep strain. In conclusion, The recommended model to determine long-term allowable strength of geosynthetic reinforcements considering tensile deformation of reinforcement and soil is fit for proper, correct and economic design for reinforced earth walls.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.253-259
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• 2007

A new material tester has been developed to measure mechanical properties of thin film specimens at high temperature. It is useful for observing oxide film growth or local deformation on the surface, and for measuring creep strength. Main characteristics of the tester is as follows; First, high temperature is achieved by Joule heating generated by electricity passing through the specimen, which does not need to enclose the specimen by a furnace or a heating chamber. The exposed specimen enables one to observe the surface during the test. Because the overall size of the test rig is compact, the whole test rig can be placed in a chamber for environmental controlled tests. The loading device is from a level scales. Not only static load with fixed counter weight, but also variable load by moving counter weight controlled remotely can be applied for an ordinary creep test and creep-fatigue test, respectively. The detail of the construction, operation principle, and the specification are described. And also, an example of test result obtained using the creep tester is presented.

• Computers and Concrete
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• v.28 no.5
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• pp.441-450
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• 2021

This study presents the first analysis system and fast-access cloud database for shrinkage and creep of concrete in the world, named "shrinkage and creep database in Taiwan", SCDT. SCDT not only has the most comprehensive experimental data, including NU, JSCE, Europe, and TW databases, but provides a design tool for researchers and engineers. It can further facilitate the development of prediction models for localized concrete. Users can obtain the shrinkage and creep curves based on their selected prediction models in SCDT. Comparisons of the predicted results of selected models and test results in the chosen database can be generated in seconds. One example of the development of basic creep prediction model in Taiwan based on model B4 by using SCDT to reflect concrete characteristics in Taiwan is also presented in this study. Users anywhere in the world can easily access SCDT to browse and upload data, receive predictive results, or develop predictive models.

• Journal of the Korean GEO-environmental Society
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• v.14 no.11
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• pp.33-46
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• 2013

Recently, the projects which are to increase the capacity of the flood control are being actively performed because of the abnormal climate changes throughout the country. In this study, the regression analysis was performed using both Kelvin model and the real settlement measured at the crest of the existing concrete face rockfill dam(CFRD) to estimate the long-term deformation behavior characteristics such as creep which occurs without additional load. In addition, the effects on changes in physical properties (E, G, K) of the dam construction materials by deformation characteristics of the dam were evaluated, and the reasonable stability analysis method of the dam was proposed to obtain the long-term stability considering the changes in physical properties induced by the long-term deformation behavior in case of heightening the existing dams.

• Korean Journal of Materials Research
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• v.18 no.6
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• pp.326-333
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• 2008

Since the 1990s, the second generation of Zirconium alloys containing main alloy compositions of Nb, Sn and Fe have been used as a replacement of Zircaloy-4 (Zr-Sn-Fe-Cr), a first-generation Zirconium alloy, to meet severe and rigorous reactor operating conditions characterized by high-burn-up, high-power and high-pH operations. In this study, the mechanical properties and creep behaviors of Zr-Sn-Fe-Cr and Zr-Nb-Sn-Fe alloys were investigated in a temperature range of $450{\sim}500^{\circ}C$ and in a stress range of $80{\sim}150\;MPa$. The mechanical testing results indicate that the yield and tensile strengths of the Zr-Nb-Sn-Fe alloy are slightly higher compared to those of Zr-Sn-Fe-Cr. This can be explained by the second phase strengthening of the $\beta$-Nb precipitates. The creep test results indicate that the stress exponent for the steady-state creep rate decreases with the increase in the applied stress. However, the stress exponent of the Zr-Sn-Fe-Cr alloy is lower than that of the Zr-Nb-Sn-Fe alloy in a relatively high stress range, whereas the creep activation energy of the former is slightly higher than that of the latter. This can be explained by the dynamic deformation aging effect caused by the interaction of dislocations with Sn substitutional atoms. A higher Sn content leads to a lower stress exponent value and higher creep activation energy.

• Journal of the Korean Geosynthetics Society
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• v.9 no.4
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• pp.75-84
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• 2010

In this study, the long-term performance tests, which have extensibility, creep deformation, installation resistance and durability characteristic, is conducted to apply geosynthetic strip in field. The strength reduction factors using the test results are evaluated in order to calculate long-term design tensile strength. First, the creep deformation was evaluated by both the stepped isothermal method(SIM) and the time-temperature superposition(TTS) method. The creep reduction factor is reasonable to apply 1.6. Second, the result of installation damage test had little damage of yarn, which affected strength of reinforcement. Therefore, it can be analyzed that the installation damage of geosynthetic strip has little effect of long-term design tensile strength. Finally, the durability reduction factor considering chemical, biological and outdoor exposure resistance is reasonable to apply 1.1, which is considered the stability and economic efficiency of reinforced earth wall using geosynthetic strip.