Papers by Author: Seon Jin Kim

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Authors: C.K. Lee, Bong-Soon Chang, D.H. Lee, Ki Sup Hong, Hyun Seung Ryu, Seon Jin Kim
Authors: Hyun Seung Ryu, H.J. Youn, Ki Sup Hong, Seon Jin Kim, D.H. Lee, Bong-Soon Chang, C.K. Lee, S.S. Chung
Authors: Woo Gon Kim, Jae Young Park, Song Nan Yin, Yong Wan Kim, Seon Jin Kim
Abstract: This study aimed to assess creep crack growth rates on the base and welded metals of modified 9Cr-1Mo steel. For this purpose, welded specimens were prepared by the Shielded Metal Arc Weld method. To obtain mechanical properties concerning the base and welded metals, a series of creep and tensile tests were conducted at 600 °C, and creep crack growth tests were also performed under different applied loads using 1/2" compact tension specimens at 600 °C. Their creep crack growth rates were calculated using the empirical equation of the da/dt vs. C* parameter and compared. It appeared that, for a given value of C*, the rate of creep crack propagation was about 2.0 times faster in the welded metal than the base metal. This reason was that the welded metal was faster in the creep strain rate than the base metal.
Authors: Song Nan Yin, Woo Gon Kim, Ik Hee Jung, Yong Wan Kim, Seon Jin Kim
Abstract: An isochronous stress-strain curve (ISSC) needs to be generated for a creep design application for high-temperature materials. To generate the ISSC for type 316LN stainless steel (SS), a series of creep data, which was obtained from creep tests with different stress levels at 600oC, was used. Creep curves were modeled by means of a nonlinear least square fitting (NLSF) of the Garofalo model. In the fitting of the creep curve, a secondary creep region was separated into first and second phases, and its fitting range was suitable to use for the first phase. The Garofalo model revealed a good agreement with the experimental creep data, and its parameters, P1, P2 and P3 revealed a good linear relationship as a function of a stress. The ISSCs for type 316LN SS at 600oC were successfully generated up to 300,000 hours.
Authors: Yu Sik Kong, Han Ki Yoon, Yi Hyun Park, Seon Jin Kim
Abstract: The high temperature creep behaviors of heat machine systems such as aircraft engines, boilers and turbines in power plants and nuclear reactor components have been considered as an important and needful fact. There are considerable research results available for the design of high temperature tube materials in power plants, based on uni-axial tension creep tests. However, few studies on the Initial Strain Method (ISM) capable of securing repair, maintenance, cost loss and life loss have been made. In this method, a long time prediction of high temperature creep characteristics can be dramatically reduced through a short time experiment. The purpose of present study is to investigate the high temperature creep life of 1Cr-0.5Mo steel using the Initial Strain Method. The creep test was performed at 500°C, 550°C and 600°C under a pure loading. In the prediction of creep life for 1Cr-0.5Mo steel, the equation of ISM was superior to those of LMP. Especially, the long time prediction of creep life was identified to improve the reliability.
Authors: Seon Jin Kim, Yu Sik Kong, Won Taek Jung, Jong Taek Yeom, Nho Kwang Park
Abstract: The purpose of this study is to investigate the high temperature creep life of Waspaloy using the Initial Strain Parameter Technique (ISPT). The creep tests were performed at the elevated temperatures from 550oC to 700 oC. Constant stress creep tests were carried out in the experiment. The initial strain was measured for one minute after loading. The creep life of Waspaloy was calculated using the creep life prediction equation of ISPT. The confidence level between the experimental rupture time and the calculated rupture time using the ISPT is within 95%. So, the results show that the creep life prediction by the ISPT was a good agreement with LMP method.
Authors: Seon Jin Kim, Seok Hwan Ahn, Yu Sik Kong, Sang Woo Kwon
Abstract: Constant K fatigue crack growth tests were performed by applying an intermediate multiple overloads for S45C steel. The purpose of this study is to investigate effects of specimen thickness at various baseline stress intensity factor range levels (Kb), the application position of the overload (a/W) and the application frequency of the overload (OLHz) on fatigue crack growth retardation behavior. The principal results are summarized as follows. The number of retardation cycles for the constant baseline stress intensity factor level (Kb ) decreases with increasing specimen thickness. The normalized number of retardation cycles ( Nd / Nc ) decreases with increasing specimen thickness. But, at Kb = 45 MPa(m)1/2, the cycle increases with increasing specimen thickness.
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