Papers by Author: Jung Kyu Kim

Paper TitlePage

Authors: Jung Kyu Kim, Cheon Soo Jang, Chul Su Kim
Authors: Ki Weon Kang, Byeong Choon Goo, J.H. Kim, Heung Seob Kim, Jung Kyu Kim
Abstract: This paper deals with the fatigue behavior and its statistical properties of SM490A steel at various temperatures, which is utilized in the railway vehicle. For these goals, the tensile ad fatigue tests were performed by using a servo-hydraulic fatigue testing machine at three temperatures: +20°C, -10°C and -40°C. The static strength and fatigue limits of SM490A steel were increased with decreasing of test temperature. The probabilistic properties of fatigue behavior are investigated by means of probabilistic stress-life (P-S-N) curve and they are well in conformance with the experimental results regardless of temperature. Also, based on P-S-N curves, the variation of fatigue life is investigated and as the temperature decreases, the variation of fatigue life increases moderately.
Authors: Chul Su Kim, Jung Kyu Kim, Tae Seong Kim
Abstract: In order to evaluate the variation of fatigue data of turbine blade steel in low pressure (LP) steam, it is important to estimate probabilistic stress-life (P-S-N) curve to accurately define the probability distribution. In this study, a new procedure was introduced to determine the expression of P-S-N curves. For this purpose, 3-parameter Weibull distribution was found to be the most appropriate among assumed distributions when the probability distributions of the fatigue life were examined by a comparative analysis. Furthermore, the parameter of P-S-N curve was evaluated using various optimization techniques to maximize the correlation coefficient. As a result, the sequential linear program method is used for estimation of P-S-N curve.
Authors: Ki Weon Kang, B.J. Lee, Kyung Young Jhang, Jung Kyu Kim
Abstract: This study was aimed at identifying failure mechanism and strength of brazed copper pipe used in household air conditioner. For these ends, the brazed joints with various brazing length were manufactured according to manufacturer’s recommended methods. The 3-dimensional X-ray technique was used to identify internal flaws and their failure mechanism in brazed joints. And, strength of brazed joint was evaluated by static tests. To evaluate the effect of heat on the brazed joints, the micro-Vickers hardness is measured. Also, bursting tests were performed for burst pressure of brazed joints by using of self-designed internal pressure bursting tester.
Authors: Ki Weon Kang, Hee Jin Shim, C.M. Kim, Jung Kyu Kim
Abstract: The study aimed at the failure analysis and strength evaluation of brazed joints used in household air conditioner. For these goals, the failure modes were investigated through the fractographic analysis and micro-Vickers hardness test. The failure modes were classified into two different types and their mechanism was influenced by heat and internal flaws such as incomplete penetration and pin holes. Also, a finite element analysis was performed to evaluate the strength behavior of the brazed joints according to the heat and internal flaws.
Authors: Chul Su Kim, Cheon Soo Jang, Seung Ho Jang, Jung Kyu Kim
Abstract: To reduce the cost and time of transport due to the different track gauges(narrow, standard, broad) in the Eurasian railroad network such as TKR(Trans-Korea Railway), TCR(Trans-China Railway) and TSR(Trans-Siberia Railway), it is very necessary to develop and adapt the gauge-adjustable wheelsets system. The freight trains’ with gauge-adjustable system could operate on the different track gauges in the transcontinental railway. Therefore, to assure the safety of the newly developed gauge-adjustment wheelsets system, it is essential to evaluate integrity of locking parts in the system by using fatigue analysis. In this study, it was performed that contact stress analysis of locking parts by using FEM(Finite Element Method) in the case both the gauge changeover operation and freight trains' service in the curved track, respectively. Besides, to consider the variation of fatigue data, the crack initiation life was statistically evaluated.
Authors: Ki Weon Kang, Jung Kyu Kim, Yong Su Kim, Young Min Do
Abstract: The paper presents the fatigue behavior of carbon/epoxy laminates with impact-induced damage under 2-stage block loading. The impact damage parameter is proposed to evaluate the effect of impact damage on fatigue life. Based on this parameter, the model is developed to predict the residual life at second block. Also, the model for equivalent stress is proposed to estimate the fatigue life under 2-stage block loading based on the S-N curves under constant amplitude loading. For these models, the 2-stage block loading fatigue tests were performed on the impacted composite laminates. The effect of impact damage on fatigue life under 2-stage block loading can be characterized by the impact damage parameter. Additionally, the results by the present residual life prediction model agree with experimental results regardless of applied impact energy. Also, the equivalent stress and corresponding fatigue life by the present model agrees well with the experimental results.
Showing 1 to 10 of 23 Paper Titles