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원전 배관의 LBB 개념 적용을 위한 간략 설계기법 개발
이철형,김영진,표창률,석창성,허남수 한국산업안전학회 1999 한국안전학회지 Vol.14 No.2
If the Leak-Before-Break (LBB) concept is applicable to the nuclear piping design, it is not necessary to consider the dynamic effect due to pipe rupture. Therefore, the construction cost can be significantly reduced by eliminating unnecessary pipe whip restraints and jet impingement devices. The objective of this paper is to develop the Piping Evaluation Diagram (PED) for efficient application of LBB concept to piping system at an initial piping design stage. For this purpose, the 3-D finite element analyses were performed to evaluate the crack stability. And the stress-strain curve based on the pipe material tests were used to calculate the detectable leakage crack length. Finally, the present PED which was composed as a function of NOP load and allowable SSE load, was developed for an application of LBB concept to the safety injection and shutdown cooling line in Korean Next Generation Reactor (KNGR).
초내열합금 Mar-M 247 LC 에서 열처리에 의한 미세조직의 변화와 크리프특성과의 관계
김일호,최병학,강수현,조종춘,허보영,김학매 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.3
Creep-rupture properties of a cast type Superalloy, Mar-M247LC. were studied in 760℃ and 980℃. The shape and size of γ′ particles in grains were known to have significant influence on the creep behavior and rupture life in relation to the micro-mechanism of plastic deformation. It was found that the creep properties were also affected by the cast structure which is composed of dendrite matrix and eutectic boundaries. The hardening effect of boundaries by solute segregation and eutectic phases may improve the creep resistance of grain or eutectic boundaries during creep-rupture.
김경자,허동섭,김중석,안병국,서수교 한국고무학회 1986 엘라스토머 및 콤포지트 Vol.21 No.4
This survey reports on the extensive examination of the quality of 14 jogging and tennis shoes separately, availavable in the domestic market. Both jogging and tennis shoes were catagorised in two groups, namely the general goods (less expensive ones) and the exclusive goods (expensive models). The detailed classification are shown below; (도표) The domestic products meet the general purpose just as that of the foreign products. Due to the adhesion technology, the domestic tennis shoes consist of rubber sole with natural leather upper; In fact, the desirable combination, as foreign products, must be polyurethane/natural leather. The expensive models were heavier than the less expensive ones. The greater weight difference of right and left shoes are shown in the expensive models than that of the less expensive ones. The moisture absorption ratio of the expensive model is far superior in comparison with the less expensive model. The reason is identified by the material supplyed to produce the expensive model consisted of the natural leather and proper parts. The abrasion resistance of the expensive models were excellent that of the less expensive ones, because the rubber soles were showed the properties better than polyurethane sole which was used in the less expensive model.
김현철,조성윤,허무영 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.8
The evolution of the through-thickness textures in a ferritic stainless steel sheet was investigated by means of texture measurements and microstructure observations. Pronounced through-thickness texture gradients were found in the hot band where the rotated cube orientation prevailed at the center layer and the Goss-orientation developed in the near-surface layers. The cold rolling texture was strongly dependent on initial preferred orientations of the hot band. The rotated cube orientation was quite stable during cold rolling. The weak initial texture of the hot band led to the formation of the typical bcc rolling texture. Upon annealing, the {557}$lt;583$gt; developed at the expense of the rotate cube orientation and the {111} fiber texture formed from the typical bcc rolling texture components. The evolution of texture gradients during rolling was discussed by means of the orientation stability based on the Taylor deformation theory. The recrystallization textures were explained in terms of the nucleation and the growth selection.
오스테나이트계 스테인리스강에 대한 질소 고용화 처리 및 그 효과
남태운,허정 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.5
As a case hardening process for stainless steels, nitriding is more preferred and widely used than carburizing which deterioates corrosion resistance severely. In order to add the nitrogen into the stainless steels, passive film on the surface must be removed effectively before nitriding. Conventional gas nitriding process is performed in the temperature range of 500 to 600℃ with NH₃ gas, which often leads to sensitization of stainless steels. In this study, we tried to activate passive film of austenitic stainless steels by heating at low pressure.(900℃, 5×10^(-2) Torr.) Nitriding was performed at the solution treatment temperature of 1100℃ with nitrogen molecules instead of NH₃gas. An attainable nitrogen content in a case depends on the nitrogen gas pressure at constant nitriding temperature. A case depth is proportional to the square not of solution time, which suggests that inward diffusion of nitrogen follows the Fick's 2nd law. Surface nitrogen atoms are dissolved as interstitial solutes, or precipitated in the form of MN, M₂N nitrides, which increase the case hardeness. Dissolved nitrogen in the case enhances the cavitation resistance of austenitic stainless steels dramatically.