Papers by Author: J.H. Park

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Authors: Dong Ho Bae, J.H. Park
Abstract: In order to develop a corrosion fatigue design method and estimate reliability of TMCP steel using as the material of heavy industries and plants, its electrochemical corrosion characteristics and determination of corrosion fatigue design criterion were investigated. And, a corrosion fatigue design method of TMCP steel was also investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. Corrosion fatigue strength in 25°C, 3.5wt.% NaCl solution is very lower than that of in air. And also, it was decreased with loading frequency decrease in the same environment. It was found that corrosion fatigue strength and life of TMCP steel is predictable by using the S-N curve of fatigue strength in air. Therefore, it is expected that the developed corrosion fatigue design method for TMCP steel will be useful for safe design and reliability assessment of the industrial facilities and structures.
Authors: Woong Ho Bang, C.S. Kang, J.H. Park, Kyu Hwan Oh
Abstract: Under a high-pressure condition, the wear characteristics of alloyed and unalloyed ductile cast iron were investigated. Mn, Cu, Si and Mo were chosen as alloying elements, and their effects on mechanical properties of hardness and toughness were correlated with wear properties. In most cases, high-pressure wear of alloyed and unalloyed DCI were sequentially developed by mild wear region followed by severe wear. The transition of wear mode was indicated by the drastic increase of friction coefficient and wear rate. The observation of worn surface at mild-wear region suggested that wear had been concentrated at graphite phases, whereas severe wear mode damaged both of graphite and matrix. It was found that DCI alloyed with Si-Mo exhibited the most prominent resistance to the beginning of severe wear while the toughness of DCI was also a crucial factor.
Authors: Young Rang Uhm, Geun Hee Lee, J.H. Park, Wheung Whoe Kim, Chang Kyu Rhee
Abstract: Al2O3 compacts with various phases were prepared by hydrolysis and spark plasma sintering (SPS) process of Al powder. The bayerite (-Al(OH)3) phase was derived by hydrolysis of commercial Al powder with micron size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate nano powder into dense compacts with a rapid heating rate of about 100 °C per min. under the pressure of 50 MPa. After compaction in the temperature ranges from 350 °C to 1100 °C, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows the phase transition of Al(OH)3  -Al2O3  -Al2O3  -Al2O3 sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to  -Al2O3 at 350 °C showing AlO(OH)   -Al2O3  -Al2O3  -Al2O3  -Al2O3 sequences.
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