PEID를 利用한 中型 프레스의 設備總合效率 向上에 關한 硏究

徐昌敏,李文煥,徐德榮 경북대학교 산업기술연구소 1993 産業技術硏究誌 Vol.21 No.-

In recent years a serious interruption loss often occurs at highly expensive developed equipment. To maximize the total equipment efficiency of the Midium-Press it is essential to reveal and improve the potential loss of equipment based on these 6 kinds of chronic loss. Further, the way to minimize the investment in equipment has been presented by applying the PEID(Program for Equipment Improvement & Development).

기기구조물의 열화와 인간의 노화

서창민 대한기계학회 1993 大韓機械學會誌 Vol.33 No.4

각종 기기 구조물이나 인간은 세월이 흐를수록 원래 그들이 가지고 있는 최적의 상태에서 점차로 열화 및 노화되어 간다. 이와 더불어 가혹한 주변환경이나 무리한 작동 및 활동으로 인한 피로, 관리 및 유지의 소홀함등과 같은 이유가 열화 및 노화현상을 더욱 가속화시키고 있다. 그림 8에 서로간의 연관성을 정리하여 나타내고 있다. 특히 막대한 자금으로 여러 가지 목적으로 설비된 기계구조물이 노후화되어감에 따라 유지, 검사 및 보수의 허로 인한 대형사고의 결과는 국가경 제뿐만 아니라 수많은 인명의 위험이 뒤따르므로 그것들의 방지책으로는 정확한 수명예측을 위한 기술적 터득과 더불어 데이터의 축적, 신뢰성 있는 평가방법들의 개발에 관한 투자와 연구가 시급한 실정이며, 인체의 노화에 대해서도 인적자원의 관리면에서 투자와 연구가 긴요하다는 것은 설명의 여지가 없다. 이러한 목적을 위해서는 각 전문분야의 학술적 교류와 더불어 산 . 학. 연의 공동연구를 통한 지속적 연구노력이 계속되어야 할 것이다.

세라믹 코팅된 1Cr-1Mo-0.25V강의 피로균열성장 특성

서창민,김경렬,Seo, Chang-Min,Kim, Gyeong-Ryeol 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.10

Fatigue tests were performed to investigate the effect of ceramic coatings as in TiN and TiCN on fatigue crack growth properties of ceramic coated 1Cr-1Mo-0.25V steel with different coating thickness in laboratory air conditions. The experimental results are described with respect to a Paris equation, da/dN=C(.DELTA.K)$^{m}$ , where the crack growth rate of coated specimens provided as similar growth rate as that of the uncoated specimen regardless of coating thickness. Furthermore, it was observed that the type of coating layer had virtually no effect on crack growth rate in the full region of stress intensity factor range. And it was also appeared that the final crack length of TiCN coated specimens was short compared to that of TiN coated, and the substrate specimens, in which it was inferred due to lowering the toughness of coated material from high hardness of TiCN coating layer itself.

Fatigue characteristics of bearing steel in very high cycle fatigue

서창민,김종형 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.2

Very high cycle fatigue (VHCF) tests were carried out to find the fatigue characteristics of a super-long life range by using a cantilever type rotational bending fatigue test machine on three kinds of specimens in bearing steel which were quenched and tempered in air (A: non-shot peened and B: shot peened after heat treatment) and under vacuum environment(C: non-shot peened) in this study. S-N curves obtained from the VHCF tests of the B and C specimens tend to come down again in the super-long life (109 cycles) range due to fish-eye type cracking, while most of the A and B specimens were fractured by surface defects such as scratches and slip lines. This duplex S-N behavior of bearing steel has to be reviewed by the change of the fracture modes.

세라믹 코팅된 1Cr-1Mo-0.25V강재의 피로균열의 발생 성장거동 ( Fatigue Crack Initiation and Growth Behavior of Ceramic-Coated 1Cr-1Mo-0.25V Steel )

서창민,김경렬,권현욱 대한기계학회 1995 대한기계학회 춘추학술대회 Vol.- No.-

표면거칠기를 가진 유리의 입자충격 손상기구에 관한 실험적 연구

서창민,정성묵,이문환,Suh, Chang-Min,Chung, Seong-Muk,Lee, Mun-Hwan 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.7

The damage mechanism by the impact of steel ball on the soda-lime glass having a different surface roughness was investigated. An initiation and a propagation behavior of cracks formed by each impact velocity were quantitatively studied. A 4-point bending test was carried out to evaluate the remaining bending strength of a scratched soda-lime glass which impacted by the steel ball. As the surface roughness was increased, the shape of cracks became more irregular rather than those of the smooth specimens. The phenomenon of turning up in the wing of cone cracks occurred even at the lower velocity than the critical velocity caused the crushing. The threshold velocity of cracks initiation generally became lower than those of smooth specimen. An initiation and a propagation behavior of radial cracks had no relation with the direction of scratch on the surface. The remaning benidng strength of the scratched specimen according to impact velocity had no big difference compared with those of the smooth specimen.

HSS-Co와 SM55C 이종 마찰용접재의 피로강도에 관한 연구(1)

서창민,서덕영,이동재 대한기계학회 1995 대한기계학회논문집 Vol.19 No.4

This paper deals with the various mechanical properties and fatigue strength in the FRW1 (friction welded interface) of high speed steel (HSS-Co) to SM55C through the tensile test, hardness test and fatigue test. The data of FRW specimens are also compared with those of the base materials (HSS-Co and SM55C steel). Three kinds of specimens used in this study are the friction welded joints, HSS-Co and SM55C carbon steel with circumferential notch, saw notch and smooth, respectively. It is confirmed that the applied welding conditions are optimum methods in order to minimize the heat affected zone (HAZ) and hardness distribution at the HAZ. The fatigue strengths at N = 10$^{6}$ cycles of smooth, circumferential notch and saw notch specimens in the FRW joints are about 299.2 MPa, 123.8 MPa and 247.5 MPA, respectively. The fatigue strength of the friction welded joints is almost equal to that of the SM55C carbon steel in the optimum welding conditions. The fatigue cracks initiated at the welded zone are propagated along the side of SM55C steel.

Wear behavior of diamond wheel for grinding optical connector ferrule - FEA and wear test -

서창민,배규석,서민수 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.11

The grinding characteristics and the wear behavior of diamond wheel for grinding the optical connector ferrule were investigated by finite element analysis (FEA) and wear test. FEA of contact between diamond wheel and ferrule shows that the subsurface damage area of ferrule is 13μm from the interface of abrasive particle and matrix. Fallout of abrasive particle is affected by the stress state at the interface. A 2-D finite element model was established to calculate the distribution of stress at the interface. As the result of FEA, fallout condition of abrasive was concerned with the ratio of the critical protrusion; the ratio of particle size is about 0.6. FE model was established to investigate the effects of the diamond concentration of wheel. The FEA result shows that the lower concentration of it has larger wear volume due to the small stress propagation.. To investigate grinding performance, the pin-on-disc wear test was carried out for three types of concentrations 75%, 100% and 125%. Through the wear test, it was confirmed that the 75% wheel concentration has the highest amount of wear volume. This result shows good agreement with that of FEA. And 100% concentration by considering the grinding ratio of the wheel shows the best optimized result for the grinding performance.

표면균열의 거동과 피로수명예측에 관한 연구

서창민,이정주,정은화,박희범 대한기계학회 1988 대한기계학회논문집 Vol.12 No.5

본 연구에서는 이 좁은 벤트내에 자료가 모이는 피로균열의 특성을 이용하여 표면피로균열의 성장거동을 파괴역학적으로 해석, 연구하여 균열의 성장특성과 $S-N_{f}$ 곡선의 추정을 마이크로 컴퓨터로 계산하였다. This paper deals with surface crack behavior and the fatigue life prediction of notched specimens using the relation between surface crack length, a, and the cycle ratio, $N/N_{f}$. From the $a-N\;/\;N_{f}$ curves, UC(the upper limit curve), LC(the lower limit curve) and MC(the middle limit curve) were assumed and utilized to predict the fatigue life and crack growth rate. The data computed from the three assumed curves were compared with the experimental data. It has been found that in the stable crack growth region ($N/N_{f}=0.3-0.8$) fatigue life can be predicted within 20% errors. Using the characteristics of $a-N\;/\;N_{f}$ curve, it is possible to predict the $da/dN-K_{max}$ curve, the $da/dN-{\Delta}K_{{\varepsilon}_t}$ curve, and the $S-N_{f}$ curve.

장시간 사용된 1Cr-0.5Mo 강의 피로균열진전 특성

서창민,고영태,남승훈,장상엽 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.9

As the service time of power plant approaches its design life, the crack initiation and growth in boiler components becomes major concerns. Though there are many research effort for finding out the properties of used materials with the materials artificially aged by heat treatment, the obtained results are nothing but the estimated values to be verified. In this study, characteristics of the crack growth behavior for 1Cr-0.5Mo steel which was served for a boiler header for about 30 years were studied by performing fatigue crack growth tests at 538℃ and room temperature under triangular and trapezoidal wave-shapes. In order to evaluate hold time effect at elevated temperatures, the fatigue test with 10 second hold time (0.083Hz) was performed. From the experimental results, it was found that the increase of the fatigue test temperature had a significant effect on the increase of the rate of fatigue crack propagation. In the case of hold time testing, the oxidation layer formed at the crack wake was thicker than in the case without hold time.