• Steel and Composite Structures
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• v.2 no.4
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• pp.247-258
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• 2002

The high-temperature material properties of steel are very important to the fire resistance analysis of high-strength bolt connections. This paper reports on the results of the experimental studies on the high-temperature properties of 20 MnTiB steel which is widely used in high-strength bolts, and the friction coefficient of 16Mn steel plates at elevated temperature which is a necessary parameter for bolted frictional connection analysis. The test data includes yield strength, limit strength, modulus of elasticity, elongation and expansion coefficient of 20MnTiB steel at elevated temperature, and the friction coefficients between two 16Mn steel plates under elevated temperatures and after cooling. Based on the data from the tests, the mathematical models for predicting the mechanical properties of 20MnTiB steel and friction coefficients of 16Mn steel plates have been established.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3581-3590
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• 2023

High-temperature design evaluations were conducted on Type 316L stainless steel piping for a 700 ℃ large-capacity thermal energy storage verification test loop (TESET) under construction at KAERI. The hot leg piping with sodium coolant at 700 ℃ connects the main components of the loop heater, hot storage tank, and air-to-sodium heat exchanger. Currently, the design rules of ASME B31.1 and RCC-MRx provide design procedures for high-temperature piping in the creep range for Type 316L stainless steel. However, the design material properties around 700 ℃ are not available in those rules. Therefore, a number of material tests, including creep tests at various temperatures, were conducted to determine the insufficient material properties and relevant design coefficients so that high-temperature design on the 700 ℃ piping may be possible. It was shown that Type 316L stainless steel can be used in a 700 ℃ high-temperature piping system of Generation IV reactor systems or a renewable energy systems, such as thermal energy storage systems, for a limited operation time.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.31-36
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• 2003

Recently, composite materials are widely used for nozzle, pressure vessel, skins of satellite and many structures under condition of high temperature due to good thermal characteristics such as low CTE, heat-resistance, etc. Fiber optic sensors, especially FBG(fiber Bragg grating) sensors, can be a good counterproposal of strain gages for the measurement of material properties of composites under high temperature. In this research, T700/Epoxy specimens with embedded FBG sensors were fabricated and tested at the Instron with thermal chamber from room temperature to $400^{\circ}C$. The effects of embedding optical fiber on material properties were also verified. And, the experimental results were discussed and analyzed by microphotographs of the composite specimen.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.135-140
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• 2001

In metal cutting at the tool-chip interface, friction generates considerable amount of heat. Thus, tile .knowledge of wear properties or the cutting tool material in high temperature has been known as one of tile important factors in need of clarification. The authors presented the wear properties of 5%V-5%Co-1%Nb high speed steel, fabricated by powder metallurgy, in room temperature in a previous article. The objective of this paper is to clarify tile effects of temperature ell its wear properties. Wear tests in sliding conditions under various temperatures have been conducted. The results indicate that tile wear properties of tile tool material in high temperature as well as in room temperature are excellent. It may be deduced that the oxide layer formed on the vol-n surface at high temperature is stable enough to prevent wear due to tile high temperature strength of its matrix.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.59-62
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• 2001

Flow induced vibration in steam generators has caused dynamic interactions between tubes and contacting materials resulting in fretting wear . Series of experiments have been performed to examine the wear properties of Inconel 690 steam generator tubes in various environmental conditions. For the present study, the test rig was designed to examine the fretting wear and rolling wear properties in high temperature(room temperature - 290。C) water. The test was performed at constant applied load and sliding distance to investigate the effect of test temperature on wear properties of the steam generator tube materials. To investigate the wear mechanism of material, the worn was observed using scanning electron microscopy. The weight loss increase at higher test temperature was caused by the decrease of water viscosity and the mechanical property change of tube material. The mechanical property changes of steam generator tube material, such as decrease of hardness or yield stress in the high temperature tests. From the SEM observation of worn surfaces, the severe wear scars were observed in specimens tested at the higher temperature.

• Korean Journal of Materials Research
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• v.23 no.10
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• pp.568-573
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• 2013

The deformation properties of a TiC-Mo eutectic composite were investigated in a compression test at temperatures ranging from room temperature to 2053 K and at strain rates ranging from $3.9{\times}10^{-5}s^{-1}$ to $4.9{\times}10^{-3}s^{-1}$. It was found that this material shows excellent high-temperature strength as well as appreciable room-temperature toughness, suggesting that the material is a good candidate for high-temperature application as a structure material. At a low-temperature, high strength is observed. The deformation behavior is different among the three temperature ranges tested here, i.e., low, intermediate and high. At an intermediate temperature, no yield drop occurs, and from the beginning the work hardening level is high. At a high temperature, a yield drop occurs again, after which deformation proceeds with nearly constant stress. The temperature- and yield-stress-dependence of the strain is the strongest in this case among the three temperature ranges. The observed high-temperature deformation behavior suggests that the excellent high-temperature strength is due to the constraining of the deformation in the Mo phase by the thin TiC components, which is considerably stronger than bulk TiC. It is also concluded that the appreciable room-temperature toughness is ascribed to the frequent branching of crack paths as well as to the plastic deformation of the Mo phase.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.20 no.1
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• pp.75-83
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• 2024

In this study, high temperature design and integrity evaluation methodology have been developed for Type 316L stainless steel air-to-sodium heat exchanger which uses 700℃ sodium as coolant. Currently the only design rules that take creep effects into consideration explicitly for the 316L stainless steel subjected to high temperature in the creep range are French RCC-MRx, where elevated temperature designs are possible around 550℃. Absent design coefficients at high temperature were determined based on the material properties newly determined in previous studies, and high-temperature design evaluation methodologies were developed based on 3D finite element analyses on the 700℃ class heat exchanger. In addition, works were conducted on the web-based design evaluation program of HITEP_RCC-MRx including incorporation of material properties and design coefficients up to 700℃. Methodologies on high temperature design evaluations on Type 316L stainless steel high-temperature heat exchanger were suggested.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.370-373
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• 2008

Small size gas turbine disk requires good mechanical strength and creep properties at high temperature. In this study, Waspaloy was used as a superalloy to satisfy these specifications. The control of microstructure was needed to satisfy material properties at high temperature. In order to do this, we studied forging conditions and material analysis. Therefore die and preform design conducted so that hot forged gas turbine disk could have a good microstructure. The die and preform shapes are designed with consideration of the predefined hydraulic press capacity and the microstructure of forging product. Also we carried out the hot compression test for Waspaloy in various test conditions. From these results, we obtained the forging conditions as material temperature, die velocity etc. To verify these forging conditions, we conducted FE simulations by means of the DEFORM 2D-HT. In this study, the hot closed die and preform designs were completed to offer high temperature material properties of a small size gas turbine.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.440-447
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• 2011

To improving the mechanical properties of Mg alloys at high temperature, we investigated the mechanical properties at high temperature and the change of microstructure of Mg-6 wt%Zn-0.4 wt%Mn and Mg-6 wt%Zn-0.4 wt%Mn-1 wt%Ag alloys on age treatment that have a stable MgZn phase at high temperature and $AgMg_4$ improving yield stress. In order to predict thermodynamic data of Mg alloys, a phase diagram and precipitation phase were calculated using a thermodynamic program, and it was confirmed that the MgZn and $AgMg_4$ phase existed as main precipitation in this alloys. The experimental data examined using DSC and XRD were comparable with the calculated data for reliability. In order to analysis the microstructure and precipitate phase during aging treatment, it was measured by SEM/EDS and TEM. Lastly, mechanical properties of the MgZn and $AgMg_4$ phase were measured by a tensile test at high temperature.

• Tribology and Lubricants
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• v.19 no.3
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• pp.151-158
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• 2003

In metal cutting at the tool-chip interface, friction generates considerable amount of heat. Thus, the knowledge of wear properties of cutting tool material in high temperature has been as one of important factors in need of clarification. The authors presented the wear properties of 5%Co-5%V-1%Nb high speed steel, fabricated by powder metallurgy, in room temperature in previous articles. The objective of this paper is to clarify the effects of temperature on its wear properties. Wear tests in sliding conditions under various temperatures have been conducted using the pin-on-disc type wear test machine. The results indicate that the wear properties of 5%Co-5%V-1%Nb high speed steel in high temperature as well as in room temperature are excellent. It may be deduced that the oxide layer formed on worn surface at high temperature is stable enough to prevent wear due to the high temperature strength of its matrix.