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Aging estimation of reactor pressure vessel in the field using magnetic properties
Baek, Un Bong,Ryu, Kwon Sang,Kim, Amkee,Nahm, Seung Hoon Elsevier 2009 Journal of loss prevention in the process industri Vol.22 No.6
<P><B>Abstract</B></P><P>Many researchers have been interested in the nondestructive measurement methods for estimating components damage in order to assure the safe service of steel structures. It is recognized that the evaluating techniques based on magnetic measurement can offer a great potential because of high susceptibility to the change of several metallurgical factors. Magnetic property such as coercive force was measured. The coercive force at room temperature monotonously increased with the increase of frequency. The correlation between the magnetic properties of used material and that of un-used material was studied. The coercive force gradient at room temperature increased with the increase of aging. Hence the estimating method using magnetic properties allows one to evaluate the extent of material aging for reactor pressure vessel.</P>
Baek, Seung-Wook,Song, Eun Ju,Kim, Jung Hyun,Jung, Myungsik,Baek, Un Bong,Nahm, Seung Hoon Elsevier 2017 Scripta materialia Vol.130 No.-
<P><B>Abstract</B></P> <P>Metal additive manufacturing (AM) technology as the emerging future manufacturing technology can be applied to the hydrogen service including hydrogen energy utilized industry. Direct metal tooling (DMT), one of the 3-D printing technologies, was used to manufacture an austenitic stainless steel part, and its mechanical properties and hydrogen embrittlement (HE) behavior were studied using the small specimen test technique under 10-MPa pressurized hydrogen gas. This part showed high HE resistance with minimal strain-induced transformation of austenite to martensite. This result indicates that parts produced using DMT are suitable for use in facilities for hydrogen service and hydrogen infrastructure.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Magnetic Shielding Effect on Halbach Cylinder used in Magnetic Refrigerators
Un Bong Baek,Jong Suk Lee,Seong-Cho Yu,Kwon-Sang Ryu 한국자기학회 2014 Journal of Magnetics Vol.19 No.4
The system for producing magnetic field constitutes an important component of magnetic refrigerator. Many researchers have directed significant effort to increase the magnetic field intensity, because the magnetocaloric effect at the Curie temperature increases with the power of 2/3 of the magnetic field. In this study, we report the simulation of the magnetic field intensity at polar axis of a Halbach cylinder (HC) by i) changing the length and thickness of the HC, ii) having with or without gap of the HC, and iii) surrounding the HC with a soft magnet shell, acting as a shielding. We simulated the field distribution of a HC with a finite size. Furthermore, the detailed numerical results of the magnetic field distribution and its dependence on shielding are presented in this study.
A Study on Fatigue Properties of Sc Added Al 2519 Alloy
Baek, Un Bong,Park, Jong Seo,Chung, In Hyun,Nahm, Seung Hoon,Ma, Young Hwa,Lee, Yong Yun Trans Tech Publications, Ltd. 2005 Key Engineering Materials Vol.297 No.-
<P>The high cycle fatigue properties of two kinds of wrought Al 2519 alloys without and with scandium of 0.10% were investigated. The fatigue strength was determined at R = 0.1 under constant amplitude loading conditions in air. The alloy with scandium of 0.10% showed a little lower tensile yield strength and higher fatigue strength values. The fine grained Al-0.10Sc alloy exhibited a higher resistance against fatigue crack nucleation despite the lower yield stress in comparison to the coarse grained Al 2519 alloy. The results can be explained mainly with the microstructural differences between both alloys. This results are due to the presence of coherent Al3 (Sc, Zr) precipitates and a very fine subgrain structure.</P>
스테인리스강 316L 수소가압-인장시험의 수소취성균열과 상변태
백운봉 ( Un Bong Baek ),최병학 ( Byung Hak Choe ),심종헌 ( Jong Hun Shim ),김영욱 ( Young Uk Kim ),김영석 ( Young Suk Kim ),김성수 ( Sung Soo Kim ),남승훈 ( Sung Hoon Nam ),홍기용 ( Key Yong Hong ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.2
The aim of this investigation is to prove the mechanism of hydrogen induced crack (HIC) of 316L stainless steels in hydrogen pressured tensile test. Microstructures like twin, planar slip, and abnormal phase transformation around the HIC were analyzed by transmission electron microscopy. Deformation twin accompanied by planar slip could be related to the main cause of HIC in the hydrogen pressured tensile condition, because intragranular HICs were mainly observed along the boundaries of twins and planar slip lines. An abnormal forbidden diffraction was also accompanied by HIC in the hydrogen attacked area. Examination of the HIC mechanism in austenitic stainless steel can be applied to the fitness of use for alloys with the possibility of various susceptible cracks in a hydrogen and stress atmosphere.
용접부 균열의 크리프-피로 균열성장 수명평가 연구 (Ⅰ)
백운봉(Un Bong Baek),윤기봉(Kee Bong Yoon),서창민(Chang Min Suh),이해무(Hae Moo Lee) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
High temperature material properties of a welded joint were experimentally studied. Tensile and creep properties were measured for each part of weld metal, HAZ(heat affected zone) and parent metal at 538℃. HAZ metal was obtained by a simulated heat treatment. Results showed that the order of tensile strength is weld>HAZ>parent both at 24℃ and at 538℃. Creep resistance was also the highest for weld metal and lowest for parent metal. Creep rupture life curves were obtained and converted to Monkman-Grant relation which is useful for life assessment. Use of the data obtained in this study is discussed.