Papers by Author: Young Shin Lee

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Authors: Young Shin Lee, Hyun Soo Kim, Young Jin Choi, Jae Hoon Kim
Abstract: The laminated composite structures applied to the wing and the speed brake of an aircraft or the turbine blade of a compressor. These structures may be impacted by birds and hails during operation. They may also be impacted by drop of a tool during manufacture or repair. Unlike high velocity impact damage, which can be easily found by the naked eye, the damage due to low velocity impact may be difficult to detect. Damage which is not detected may cause failure of a structure and result in damage propagation. Growth of damage means reduction of stiffness on the structure. So, exact prediction of damage caused by a low velocity impact is very important in order to guard against sudden failure of the structure. In this study, modified delamination failure criterion has suggested in order to predict the failure behavior of a composite plate subjected to low-velocity impact. The criterion includes the assumption which is matrix cracking mode causes delamination failure. Predicted damage using supposed delamination criterion is similar to experiment results.
Authors: Young Shin Lee
Abstract: An advanced way of treating livestock wastewater made use of both Autothermal Thermophilic Aerobic Digestion (ATAD), as a pre-step, and Expanded Granular Sludge Blanket (EGSB), as the post-step. As a result, the chemical oxygen demand (COD) concentration flowing out of the post step, including the EGSB, was 89mg/ℓ, while the suspended solid (SS) concentration was 28mg/ℓ, and the total nitrogen (TN) and total phosphorus (TP) concentrations were 62mg/ℓ and 5.7mg/ℓ, respectively. To maintain a high temperature in the ATAD reactor without external heating, the characteristics of influent were found to be very critical. The temperature of the ATAD reactor was significantly elevated only when the influent TSS was more 50,000mg/ℓ. The EGSB reactor was fed with increasingly higher livestock wastewater loading rates up to 6kg chemical oxygen demand (COD)/ m3/day and an average of 84.7% of the COD and 85.4% of the SS were removed in EGSB. Biogas was generated on the 47th day of operation in the EGSB after startup and its production increased at a rapid rate. The methane percentage within the biogas was initially low but it also increased rapidly, up to 73%. When the HRTs were 0.5-3 days, the COD removal efficiency was over 80%, but did show a increase as the HRT increased to 3 days.
Authors: Young Jin Choi, Young Shin Lee, Jae Hoon Kim, Won Shik Park, Hyun Soo Kim
Abstract: The hot gas casing of the gas turbine has operated in high temperatures and thermal gradients. The structure safety of hot gas casing will be highly depend on the thermal stress. In this paper, flow and thermal stress analysis of the hot gas casing is carried out using ANSYS program. The obtained temperature data by flow analysis of hot gas casing is applied to the load condition of the thermal analysis. The thermal stress analysis is carried out the elastic-plasticity analysis. The pressure, temperature and velocity of the flow and thermal stress of the hot gas casing are presented
Authors: Young Shin Lee, Young Jin Choi, Kyu Hyun Han, Je Wook Chae, Eui Jung Choi, In Woo Kim
Abstract: The rifle impact on human body is affected by the posture of human for rifling. The interaction human-rifle system influences on a firing accuracy. In this paper, impact analysis of human model for standing posture is carried out. ADAMS code and LifeMOD are used in impact analysis of human model and modeling of the human body, respectively. At the shooting, human model is affected by rifle impact during 0.001 second. Performed simulation time for shooting is 0.3second. Applied constraint condition to human-rifle system is rotating and spherical condition. As the results, displacement of the rifle and transfer path analysis of impact on human model is presented.
Authors: Sang Youn Jeon, Kyu Tae Kim, Young Shin Lee
Abstract: This study contains several estimation methods of the static buckling load for the spacer grid of nuclear fuel assembly in pressurized water reactor. Three different estimation methods were proposed for the calculation of the static buckling loads of spacer grid. The linear and non-linear static buckling analyses were performed to estimate the static buckling load of the spacer grids using ANSYS program. The analyses results were compared with the static buckling test results. Based on the analysis and test results, the applicability of the proposed estimation method for the static buckling load of the spacer grid was investigated.
Authors: Taek Joon Son, Young Shin Lee
Abstract: The strength of micro heat exchanger under pressure is studied in this paper. Micro heat exchanger is made with brazing technology. It is constructed of stainless steel thin plates with micro channels and in/out port for fluid flow. Micro channels in thin plates are formed by etching and all parts including thin plates are joined by brazing. The study on the strength under pressure is performed by structural analysis. For structural analysis, one layer of micro heat exchanger body is considered. It is composed of thin plate with micro channel and brazing filler which is used to join thin plates. This paper shows the tendency of stress behavior and gives design guideline of micro heat exchanger.
Authors: Young Shin Lee, Je Jun Lee, Youn Ki Kang, Sun Young Song
Abstract: The strain distribution around the unstiffened and stiffened circular cutout of the isotropic stainless steel (ANSI type 304) and the GFRP laminated composite cylindrical shells subjected to axial compression are studied. The experimental results are obtained and compared with numerical analysis. In experiment, the strain is measured around the circular cutout by strain measuring system under the axial uniform compression loading. The numerical analysis is performed by the commercial finite element code ANSYS. The strain concentration factor (SCF) is defined to investigate the strain concentration around the circular cutout. The SCF of the stainless steel cylindrical shell with a stiffened cutout is decreased 39% in experiment and 50 % in numerical analysis. The SCF of GFRP laminated composite cylindrical shell is decreased 22% in experiment and 31 % in numerical analysis.
Authors: Je Wook Chae, Sung Bae Lee, Chan Lee, Hyun Jun Kim, Young Shin Lee
Abstract: This paper includes a study on the surface treatments of the barrel of small arms with an aim at improving resistance of corrosion and wear. The inner surface of the barrel is Cr plated or nitrided to improve the performance under the firing. The endurance test was conducted to compare the wear resistance of standard barrel (the non surface treatment barrel), the Cr plating barrel and the nitriding barrel. The wear resistance is evaluated by inner diameter of the barrel, muzzle velocity and dispersion during the firing. And the salt water immersion test was conducted to estimate the corrosion resistance. As the results of the tests, the Cr plating barrel is superior to the NST barrel and the nitriding barrel in a view of corrosion and wear.
Authors: Young Shin Lee, Hyun Soo Kim, C.H. Han
Abstract: An experimental modal analysis is the process to identify structure's dynamic characteristics. For investigating vibrational characteristics of cylindrical shell with multiple supports, modal testing is performed using impact exciting method. The frequency response function(FRF) measurements are also made on the experimental model within the frequency range from 0 to 4kHz. Modal parameters are identified from resonant peaks in the FRF’s and animated deformation patterns associated with each of the resonances are shown on a computer screen. The experimental results are compared with analytical and FEA results.
Authors: Sang Youn Jeon, Young Shin Lee
Abstract: This study contains an estimation of the dynamic buckling load for the spacer grid of fuel assembly in pressurized water reactor. Three different estimation methods were proposed for the calculation of the dynamic buckling loads of spacer grid. The dynamic impact tests and analyses were performed to evaluate the impact characteristics of the spacer grids and to predict the dynamic buckling load of the full size spacer grid. The estimation results were compared with the test results for the verification of the estimation methods.
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