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음향방출법에 의한 SM45C 고주파 열처리 강의 기계적 특성 평가
이장규,김봉각 대한안전경영과학회 2009 대한안전경영과학회 학술대회논문집 Vol.2009 No.11
This study is deal with the high frequency induction hardening (HF at 850℃, 120kHz & 50kW condition) SM45C steel. (1) The HF specimen which was tempered at 150℃, did not appear any tempering effect. A brittle fracture occurred at rounded area of the tensile specimen. AE amplitude distribution showed between 45~60dB. (2) The HF specimen which was tempered at 300℃, slip and fracture occurred at the hole area of the tensile specimen. As it passes the yield point, the AE energy increased intermittently and AE amplitude distribution showed between 70~85dB. In addition, after the maximum tensile load, it showed high amplitude and energy distribution. The AE amplitude showed between 45~70dB. (3) The HF specimen which was tempered at 450℃, a brittle fracture occurred as if it is torn in the direction of 45℃ on parallel area over the both sides of the tensile specimen, which led to several peak to be appeared in AE energy. It was found that the AE amplitude was relatively low and the AE energy was high.
황수철,김봉각 충북대학교 건설기술연구소 1988 建設技術論文集 Vol.6 No.2
In most structural configuration, beams are supported by other structural members which provide elastic types of restraints at the end of the beam. The variation of critical load as a functions of the positions of lateral elastic constraint $quot;a$quot; and the spring constant $quot;L$quot; has been studied when the beam is under the lateral elastic constraint. The governing equation of this study has been derived from the beam-column theory and the critical load has been evaluated by equilibrium method.
전단박화유체의 수직상향 난류유동시 저항감소에 관한 연구
차경옥,김봉각,김재근,Cha, Kyong-Ok,Kim, Bong-gag,Kim, Jea-Geun 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.12
The drag reduction is the phenomenon that occurs only when the shear stress from the wall of pipe is beyond the critical point. The drag reduction increase as the molecular weight, concentration of the polymer and Reynolds number increase, but it is limited by Virk's maximum drag reduction asymptote. Because of the strong shear force for the polymer on the turbulent flow, the molecular weight and the drag reduction do not decrease. Such mechanical degradation of the polymer occurs in all polymer solvent systems. This paper is to identify and develop high performance polymer additives for fluid transportations with the benefits of turbulent drag reduction. In addition, drag reduction in vertical flow by measuring the pressure drop and local void fraction on vertical-up flow of close system is evaluated.
구봉근,김홍용,김봉각 충북대학교 건설기술연구소 1991 建設技術論文集 Vol.10 No.1
In most structural configuration, beans are supported by other structural members which provide types of restraints at the end of the beam. The change of critical load was examined when one end simply supported and the other end under rotational constraint. The variation of critical load as a function of the positions lateral elastic constraint $quot;a$quot;, and the spring constant $quot;L$quot; has lien studied when the beau is under the lateral elastic constraint. The governing equation of this study has been derived from the beat-column theory and the critical load has been evaluated by equilibrium method.
음향방출을 이용한 일방향 탄소섬유강화 플라스틱의 손상평가에 관한 연구
이장규,박성완,김봉각,우창기 한국공작기계학회 2005 한국생산제조학회지 Vol.14 No.1
This study is to investigate a damage estimation of single edge notched tensile specimens as a function of acoustic emission(AE) according to the uni-directionally oriented carbon fiber/epoxy composites, CFRP. In fiber reinforced composite materials, AE signals due to several types of failure mechanisms are typically observed. These are due to fiber breakage, fiber pull-out, matrix cracking, delamination, and splitting or fiber bundle breaking. And these are usually discriminated on the basis of amplitude distribution, event counts, and energy related parameters. In this case, AE signals were analyzed and classified 3 regions by AE event counts, energy and amplitude for corresponding applied load. Bath-tub curve shows 3 distinct periods during the lifetime of a single-edge-notch(SEN) specimen. The characterization of AE generated from CFRP during SEN tensile test is becoming an useful tool for the prediction of damage failure or/and failure mode analysis.
線形系와 2乘特性系의 結合 모델에 대한 스펙트럼 解析에 관한 硏究
李焌瑞,張宇種,金鳳珏,車京玉 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-
This Paper describes a number of theoretical formulas to analyze the frequency domain properties of Gaussian input data passing through non-linear square-law systems. From measurement of input data and output data only, results are obtained to identify the separate frequency response functions for two models of linear systems in parallel with non-linear square-law systems. This formulas indicates also how to analyze other types of non-linear models by employing similar techniques.