• Journal of Welding and Joining
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• v.26 no.3
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• pp.37-44
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• 2008

Charpy V-Notch test is commonly used to evaluate fracture toughness. However, since the region to be evaluated is limited to bulk material due to the specimen size required, individual evaluation of micro-structures on weldment is very difficult. In this study, ASP(Advanced Small Punch) test was carried out to evaluate material degradation and fracture toughness on the B.M, W.M and each micro-structures of HAZ for X20CrMoV121 and 2.25Cr1Mo steels with artificial aging time. In addition, to evaluate fracture toughness and material degradation of B.M and W.M of X20CrMoV121 steels with aging times, CVN (Charpy V-notch) test was performed. And then the correlation between ASP and CVN test on X20CrMoV121 steels was obtained. Furthermore, through this correlation, material degradation property of each micro-region of the HAZ in weldment, which was impossible to be evaluated by the CVN test, can be estimated and determined.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.207-215
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• 1997

The miscellaneous variables observed by OGLE Project of searching for dark matter in our Galaxy have been analyzed to find their characteristics. We investigated evolutionary status, shape of light curve, relationship between orbital period and amplitude of light variation for the miscellaneous variables. The miscellaneous variables except ellipsoidal variables are subgiants or giants. The shapes of the light curves are similar to those of nearby RS CVn type stars. The amplitudes of the light variations decrease rapidly as increasing their orbital periods for the variables whose periods are shorter than 30 days, while the amplitudes decrease slowly for the variables whose periods are longer that 30 days. Thus the OGLE miscellaneous variables are classified as the RS CVn type stars.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.233-234
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• 2015

We present results of a new high-resolution spectroscopic study of the RS CVn-type binary system EI Eridani (HD26337). We used high S/N ratio LSD profiles to measure a new RV orbit of the primary component and new orbital parameters. We found evidence of strong spectral line profile variations at time intervals indicating the existence of short-lived (few days) spots on the surface of the primary component. We measured a projected rotation velocity of star of 53.2 km/s.

• Bulletin of the Korean Space Science Society
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• 1994.09a
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• pp.20-20
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• 1994

• The Bulletin of The Korean Astronomical Society
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• v.29 no.2
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• pp.65.2-65.2
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• 2004

• The Bulletin of The Korean Astronomical Society
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• v.7
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• pp.10.3-11
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• 1982

• The Bulletin of The Korean Astronomical Society
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• v.8
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• pp.6.1-6.1
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• 1983

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.195-197
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• 2001

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.62-66
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• 2015

Considering for plants and structure under extreme conditions is required for the successful design, especially temperature and pressure. The ductile-brittle transition temperature (DBTT) for the materials under extreme condition needs to be considered. In this study, A-grade mild steel for the LNG carrier and offshore plant was examined by performing low-temperature Charpy V-notch (CVN) impact tests to investigate DBTT and the fracture toughness. The absorbed energy decreased gradually with the experimental temperature, which showed an upper-shelf energy region, lower shelf energy region, and transition temperature indicating DBTT. In addition, the fracture surface morphologies of the mild steels indicated ductile fractures at the upper-shelf energy level, with wide and large-sized dimples, whereas a brittle fracture surface, where was observed at the lower-shelf energy level, with both large and small cleavage facets. Based on the experimental results, ductile brittle transition temperature was estimated in about $-60^{\circ}C$.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.268-276
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• 2016

This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s⁻¹ and 100 s⁻¹. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.