Papers by Author: Seong In Moon

Abstract: In this paper, conservatisms of current plugging criteria on steam generator tubes are reviewed and six new failure prediction models for dual through-wall cracks are proposed. In order to determine the optimum ones among these local or global failure prediction models, a series of plastic collapse tests and corresponding finite element analyses are carried out with respect to two adjacent axial through-wall cracks in thin plates. Then, reaction force model, plastic zone contact model and COD (Crack Opening Displacement) base model were selected as the optimum ones for integrity assessment of steam generator tubes with dual cracks.

Abstract: Recently, mechanical shock failures of a flat display unit such as TFT-LCD device have been an important concern of designers. In order to achieve the mechanical shock requirement, it is necessary to perform the detailed FE analyses which could be very expensive either by the lengthy computation or by the complicated geometry modeling. The objective of this study is to propose a simplified analysis methodology to simulate impact behavior of thin glass plates. The static problem equivalent to the impact one is found from the concept of solid mechanics to estimate the maximum deflection and stress under impact loading. To show the plausibility of the proposed approach, it is applied to the idealized problem which is a two dimensional beam subjected to impact loading. Based on explicit FE analyses using the LS-DYNA FE program, it was shown that the impact problem can be solved by the equivalent static analysis which is much easier to solve in practice. Therefore, the proposed approach provides significant advantages in design optimization of a TFT-LCD device against shock failure, and enables the designer to avoid ad hoc modeling of the transient dynamics so that product design cycle could be shortened.

Abstract: In this work, a simple way was contrived to enhance the rate capability and cycle life of LiNixMnyCo(1-x-y)O2 by doping Zr into the material. Zr-doped LiNixMnyCo(1-x-y)O2 was synthesized by solution-based synthetic route, and its electrochemical performance was investigated as 2016 coin-type half cell. With doping, some impurity peaks appeared in the XRD pattern, which seems to be related to Zr containing oxides. The enhanced characteristics in the rate capability and cycle life might be the result of the protective effect of Zr oxide against the decomposition of electrolyte and a faster Li diffusion rate.