• Journal of Welding and Joining
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• v.22 no.4
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• pp.50-58
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• 2004

In this study, high temperature tensile properties of high strength steels(POSTEN60, POSTEN80) were investigated. The three-dimensional thermal elastic-plastic analyses were conducted to investigate the characteristics of welding residual stresses in welds of high strength steels on the basis of thermal and mechanical properites at high temperature obtained from the experiment. According to the results, high temperature tensile strength of POSTEN60 steel deteriorated slowly to 10$0^{\circ}C$. As the temperature went up, the tensile strength became better because of blue shortness, and it deteriorated radically after reaching to the maximum value around 30$0^{\circ}C$. For the POSTEN80 steel, high temperature tensile strength deteriorated slowly to 20$0^{\circ}C$. As the temperature went up the tensile strength became better and it deteriorated slowly to $600^{\circ}C$ after reached to the maximum value around 30$0^{\circ}C$. Strain of high strength steels at the elevated temperature increased radically after the mercury rose to $600^{\circ}C$. The strain hardening ratio of POSTEN60 steel was larger then that of POSTEN80 steel at the elevated temperature as in the case at the room temperature and it became smaller radically after the mercury rose to 40$0^{\circ}C$. And, in the welding of high strength steels, increasing tensile strength of the steel (POSTEN60

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.643-651
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• 2017

Four types of high Mn TWIP(Twinning Induced Plasticity) steels were fabricated by varying the Mn and Al content, and the tensile properties were measured at various strain rates and temperatures. An examination of the tensile properties at room temperature revealed an increase in strength with increasing strain rate because mobile dislocations interacted rapidly with the dislocations in localized regions, whereas elongation and the number of serrations decreased. The strength decreased with increasing temperature, whereas the elongation increased. A martensitic transformation occurred in the 18Mn, 22Mn and 18Mn1.6Al steels tested at $-196^{\circ}C$ due to a decrease in the stacking fault energies with decreasing temperature. An examination of the tensile properties at $-196^{\circ}C$ showed that the strength of the non-Al added high Mn TWIP steels was high, whereas the elongation was low because of the martensitic transformation and brittle fracture mode. Although a martensitic transformation did not occur in the 18Mn1.9Al steel, the strength increased with decreasing temperature because many twins formed in the early stages of the tensile test and interacted rapidly with the dislocations.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.1
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• pp.10-16
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• 2021

Exhaust manifold is a very important component that is directly connected to air environment pollution and that requires strict mechanical properties such as high temperature fatigue and oxidation. Among stainless steels, the ferritic stainless steel with body-centered cubic structure shows excellent resistance of stress-corrosion cracking, ferromagnetic at room temperature, very excellent cold workability and may not be enhanced by heat treatment. The microstructural characteristics of four cast ferritic stainless steels which are high heat-resistant materials, were analyzed. By comparing and evaluating the mechanical properties at room temperature and high temperature in a range of 400℃~800℃, a database was established to control and predict the required properties and the mechanical properties of the final product. The precipitates of cast ferritic stainless steels were analyzed and the high-temperature deformation characteristics were evaluated by comparative analysis of hardness and tensile characteristics of four steels at room temperature and from 400℃ to 800℃.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.260-262
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• 2003

In this study, high temperature tensile properties of high tensile strength steels(POSTEN60, POSTEN80) were investigated by elevated temperature tensile test. According toe the results, high temperature tensile strength of POSTEN60 deteriorated slowly to 100$^{\circ}C$. As the temperature went up the tensile strength became better because of blue shortness and it deteriorated radically after reached to the maximum value around 300$^{\circ}C$. For the POSTEN80, high temperature tensile strength deteriorated slowly to 200$^{\circ}C$.As the temperature went up the tensile strength became better and it deteriorated slowly to 600$^{\circ}C$ after reached to the maximum value around 300$^{\circ}C$. Strain of high tensile strength steels at the elevated temperature increased radically after the mercury rose to 600$^{\circ}C$. The strain hardening ratio of POSTEN60 was larger then that of POSTEN80 at the elevated temperature as in the case at the room temperature and it became smaller radically after the mercury rose to 400$^{\circ}C$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.77-84
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• 2015

Tensile tests were conducted on the GFRP reinforcement exposed to high temperature. The exposure condition for this study was below $200^{\circ}C$ for about 3 minutes. This conditioning is minor compared with that presented in experimental program conducted by other researchers. The residual tensile strength and elastic modulus of GFRP reinforcing bars at high temperature and after exposure to high temperature were compared. In results, tensile properties were decreased at high temperatures, but those after exposure to high temperature were recovered to pre-heating level almost completely. These results could be valuable for evaluating GFRP reinforced structure damaged by fire accident.

• Journal of Welding and Joining
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• v.26 no.5
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• pp.60-65
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• 2008

Ferritic stainless steels of the 400 series have been available for automotive exhaust system, heat exchanger, radiater etc. in various industrial because heat resistance, corrosion resistance and strength are excellent. Especially, automotive exhaust system is required good heat resistance because typical temperature of exhaust system exposed during operation of engine is reach up to $800^{\circ}C$. However, research for effect of high temperature in ferritic stainless steels is not enough. In this study, high temperature tensile properties of lap weld of ferritic stainless steels(STS 429) were investigated. In accordance with heat input, lap welds had been produced and were evaluated at high temperature($800^{\circ}C$) to compare high temperature tensile properties. In addition, room temperature tensile tests were carried out for non-aging and aging specimens. As a result of R.T tensile test, non-aging specimens were fractured in base metal except for low heat input specimen and aging specimens were fractured in weld metal. Also high temperature tensile test were carried out by aging specimen. After high temperature tensile test, fracture of aged specimen was occurred in base metal except for low heat input specimen. Fracture surface of low heat input specimen in weld metal was confirmed as brittle fracture with observation using scanning electron microscope(SEM). Significant decrease in ultimate tensile strength (between 82 and 85%) was observed for aged ferritic stainless steels(STS 429) when tested at high temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.4 s.235
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• pp.600-605
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• 2005

In this study, the ring tensile test at high temperature was suggested to evaluate the hoop tensile properties of small tube such as the cladding in the nuclear reactor Using the Arsene's ring model, the ring tensile test was performed and the test data were calibrated. From the result of the ring test with strain gauge and the numerical analysis with 1/8 model, LCRR(load-displacement conversion relationship of ring specimen) was determined. We could obtain the hoop tensile properties by means of applying the LCRR to the calibrated data of the ring tensile test. A few difference was observed in view of the shape of fractured surface and the fracture mechanism between at the high temperature and at the room temperature.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.1
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• pp.21-28
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• 2014

Recently, several researchers made their endeavor to manufacture the photobioreactor(PBR) with characteristic shapes form vacuum and blow forming process. Hence, behaviors of the transparent polycarbonate(PC) plate in the high temperature region should be examined to obtain the desired PBR case via vacuum and blow forming processes. The aim of this paper is to investigate tensile behavior of PC plate in the high temperature. Various tensile tests were performed using high temperature tensile testing machine. The influence of tensile speed, thickness and ambient temperature on tensile behavior in the high temperature was examined. The flow stress and tensile strength augmented when the tensile speed increased. In order to obtain proper flow curves with strain rate effects for different temperature of specimen, G'sell-Jonas model was adopted. The material constants of the G'sell-Jonas model were estimated. The flow curves of the PC plate considering the tensile speed, specimen thickness and temperature were obtained.

• Journal of Korea Foundry Society
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• v.40 no.4
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• pp.118-127
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• 2020

Microstructural evolution during a heat treatment and high-temperature tensile properties have been investigated in conventionally cast CM247LC. In as-cast specimens, MC carbides with high amounts of Ta, Ti, Hf, and W were found to exist in the interdendritic regions, and γ' was observed in the form of cubes and octocubes prior to decomposition into cubes. In the heat-treated condition, some portion of eutectic γ-γ' remained, and uniform cubic γ' was observed in both interdendritic regions and dendrite core. Three types of carbides with different stoichiometries and compositions were found at the grain boundaries. MC carbides with high Hf contents were observed in the vicinity of eutectic γ-γ'. The highest tensile strength value was found at 750℃, whereas the greatest ductility appeared at 649℃. The effect of the temperature on the tensile properties was closely related to the dislocation structure. With increase in the test temperature, the density of dislocations inside γ' decreased, whereas that in the γ matrix increased. Stacking faults generated in γ' at 750℃ had a strengthening effect, whereas thermally activated dislocation motion at a high temperature was considered to have the opposite effect.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.228-233
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• 2004

The characteristics of the probability distribution for mechanical properties, e.g. tensile strength, reduction of area ana elongation, for STS304 stainless steel in elevated temperature were investigated from tensile test performed by constant cross head speea controls with 1mm/min, Recently, in order to clarify the strengthening mechanisms at high temperature, a new scheme to improve high temperature mechanical properties is desired. Therefore, the test ,technique development of high temperature creep behaviors for this material is very important. In this paper, the creep praperties and creep life prediction by Larson-Miller parameter method for STS304 stainless steel to be used for other high temperature components were presented at the elevated temperatures of 600, 650 and $700^{\circ}C$.