음향방출특성에 의한 탄소섬유강화 복합재의 손상파괴거동에 관한 연구

권오헌 한국산업안전학회 2002 한국안전학회지 Vol.17 No.1

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

Batteries: Cable‐Type Flexible Lithium Ion Battery Based on Hollow Multi‐Helix Electrodes (Adv. Mater. 38/2012)

Kwon, Yo Han,Woo, Sang‐,Wook,Jung, Hye‐,Ran,Yu, Hyung Kyun,Kim, Kitae,Oh, Byung Hun,Ahn, Soonho,Lee, Sang‐,Young,Song, Seung‐,Wan,Cho, Jaephil,Shin, Heon‐,Cheol,Kim, Je Y WILEY‐VCH Verlag 2012 Advanced Materials Vol.24 No.38

<P>The first ever demonstration of a cable‐type lithium ion battery architecture with outstanding omni‐directional flexibility is described by Je Young Kim, Heon‐Cheol Shin, and co‐workers on page 5192. The Front Cover image illustrates the unique battery architecture comprising a skeleton frame surrounding an empty space, that is, a hollow‐spiral anode with a multi‐helical structure. This design enables the battery to reliably power an LED screen or an MP3 player even under severe mechanical twisting and bending. </P>

프랙탈차원을 이용한 고인성 균열진전거동의 평가에 관한 연구

권오헌,윤유성 釜慶大學校 1998 釜慶大學校 論文集 Vol.3 No.2

The application of fractal concept provides an useful method in the study for the quantitative analysis of highly irregular fracture surfaces and crack profiles. Fractal curves have a characteristic that erpresents a self similarity as an invariant based on the fractal dimension. The fractal dimensions were obtained by the method of a box counting. In this report, we obtained the nearly stable fractal dimensions of fracture crack profiles for the STS316 with CT specimen as the crack advances and the relationship between fractal extension crack lenght and fractal dimension. From the results, we concluded that the crack profile of high toughness material shows the fractal characteristic also, which can be used in order to evaluate more precise prediction of the crack life.

노령의 대퇴 전자간 골절 치료에서 압박고 나사못의 안정성 및 유용성

김종오,노권재,윤여헌,고영도,유재두,정준모,방한천,정재학 대한골절학회 2003 대한골절학회지 Vol.16 No.2

목 적: 노령의 대퇴 전자간 골절에서 압박고 나사못의 안정성에 영향을 주는 인자들간의 상관 관계와 골절 양상에 따른 술후 고관절 기능을 평가 및 분석하였다. 대상 및 방법: 압박고 나사를 이용하여 수술적 치료를 시행한 231명의 환자 중 6개월 이상 추시가 가능하였던 60세 이상 84명의 환자들을 대상으로 했다. 방사선적 계측은 압박고 나사못의 활강 길이 및 내반각, 가압 나사 위치, 정복 상태, 원위 골편의 내측 전위를 측정하였으며 술후 기능은 Clawson의 기능 평가표로 하였고 골절 양상에 따라 방사선 계측과 기능 회복과의 상관 관계를 평가하였다. 결 과: 임상 결과는 불안정 골절에서 양호가 10례, 불량이 23례, 안정 골절에서는 양호 40례, 불량이 11례로 안정 골절에서 임상 결과가 좋았고(p<0.001), 압박고 나사 활강은 10 ㎜ 이상일 때 양호가 4례, 불량이 21례, 10 ㎜ 이하에서 양호가 46례, 불량이 13례로 10 ㎜ 이상 활강시에 술후 결과가 불량했다(p<0.001). 다르 방사선적 계측 요인은 결과에 의미있는 차이를 보이지 않았다. 또한, 불안정 골절 중에서 전위 양상 골절의 경우 10㎜ 이상 활강이 12례, 10㎜ 이하 활강이 8례, 분쇄 양상 골절의 경우는 10㎜ 이상이 11례, 10㎜ 이하가 2례로 분쇄 양상의 불안정 골절에서 10㎜ 이상 활강이 의미있게 많았다 (p<0.001). 결 론: 10㎜ 이상의 지연 나사 활강은 고관절 기능 회복 약화를 유발시킬 수 있으며 불안정 골절 분쇄 양상 골절은 이런 지연 나사의 활강이 과도하게 유발될 수 있으므로 불안정 분쇄 양상 골절에서 압박고 나사의 단독 사용은 재고해 보아야 할 것이다. Purpose: To evaluate the relationship between fracture stability and functional results, and analyze the correlation between stability factors and the outcome in intertrochanteric fracture of the elderly. Materials and Methods: Of the 231 patients, 84 patients with age above 60 were able to follow up for minimum 6 months. We measured the sliding length of the lag screw, varus degree, position of lag screw, reduction status and medialization of distal fragment radiologically. The functional outcome of the treatment was evaluated with the Clawson's result classification and we evaluated the correlation between the radiological results of measurement and the functional recovery depending on the Evans fracture classification. Results: There were good results in 40 cases out of 51 stable fractures, and in 10 cases out of 33 unstable fractures (p<0.001). In case of sliding of lag screw more than 10㎜, good results were obtained in 4 cases, and poor in 21. And in case of sliding less than 10㎜, good results were obtained in 46, and poor in 13. (p<0.001).But there was no relationship between other radiologic factors and clinical results. In unstable type, there were 12 cases with lag screw sliding more than 10㎜ and 10 cases with less than 10㎜. In comminuted type, there were 11 cases with lag screw sliding more than 10㎜ and 2 cases with less than 10㎜(p<0.001). Conclusion: The sliding of lag screw more than 10㎜ may result in poor outcome. As in comminuted unstable pattern, sliding of lag screw might be excessive, the use of compression hip screw alone is not good treatment option.

소규모 베이커리에서의 HACCP적용을 위한 미생물학적 위해도 평가

엄애선,권성희,정덕화,오상석,이헌옥 한국조리과학회 2003 한국식품조리과학회지 Vol.19 No.4

Recently, the HACCP(Hazard Analysis Critical Control Point) system has been emphasized in food processing industries throughout the world. However, the system has, as yet, not been applied very well to domestic food industries. Due to the increase in the consumption of bakery products, more studies are required on the application of HACCP to establish the system in small-scale bakeries. This study was designed to provide basic data for setting management standards for HACCP, based on microbiological hazard evaluations of bakery products. Red bean paste filled breads, custard cream filled breads and cakes covered with fresh whipping cream were collected, and microbiological evaluations conducted on the raw materials, the manufacturing processes and potential hazards. The result showed the presence of coliforms in fresh cream of cakes and the soybean paste of soybean paste breads at levels as high as 105 CFU/g on the hazard analysis of the raw materials. Moreover, the general levels of bacteria and coliforms were over those of the standards during the intermediate fermentation and molding processes. Furthermore, high levels of coliforms were detected on the hands of the salesmen and bakers themselves. This suggests that the CCPs (Critical Control Points), such as fresh cream and red bean paste manufacturing process desperately require better management. There is also a requirement for education relating to personal hygiene for the production of hygienic bakery products and for the publics health.

숏피닝 가공재의 저온 피로 강도 평가

박경동,권오헌 한국안전학회 2003 한국안전학회지 Vol.18 No.3

In this study, CT specimens were prepared from spring steel(SPS5) processed shot peening. The fatigue crack growth tests were carried out in the environment of the room temperature and low temperature at 25℃, -30℃, -50℃, -70℃ -100℃ and -150℃ in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range ΔKth in the early stage of fatigue crack growth (Region Ⅰ) and stress intensity factor range ΔK in the stable of fatigue crack growth (Region Ⅱ) were decreased in proportion to descend temperature. It was shown that the fatigue resistance characteristics and fracture strength at low temperature are considerable higher than those of room temperature in the early stage and stable of fatigue crack growth region.

평직구조 CFRP 적층판 복합재의 강도 및 균열진전특성에 대한 AE 평가

윤유성,권오헌 한국안전학회 2004 한국안전학회지 Vol.19 No.1

The mechanical strength and crack propagation of plain woven carbon fiber fabric laminate composites are examined by acoustic emission(AE). AE signals are measured during the tensile test and fracture tests. Thus, the relationship between AE signal and load-displacement curves and crack extension length are shown. Also the fracture mechanisms in terms of AE characteristics are discussed in viewpoint of crack propagation behavior.

승객용 승강기의 재해예방에 관한 연구

윤유성,권오헌,고성석 한국산업안전학회 2002 한국안전학회지 Vol.17 No.2

Recently the car and elevator accidents as well as the fire, explosion and collapse increased. The passenger elevator accident from 1993 year to 2001 has about 56.7% of total accidents and the human victims of 180according to the Korea Elevator Safety Institute. Accident cause and prevention were investigated for the elevator having the fall, impact and narrowness accident types. The prevention and protection methods of the elevator accident from analysis results were suggested by comparing and analogizing the accident statistics about the accident investigation of the passenger elevator according to the elevator accidents.

측면 홈을 가지는 STS316 CT시험편의 정적 성장균열에 대한 프랙탈 기하학의 응용

윤유성,권오헌 한국산업안전학회 2002 한국안전학회지 Vol.17 No.4

The application of fractal concept provides an useful method in the study for the quantitative analysis of irregular variations like fracture surfaces and crack profiles. Fractal curves have characteristics that represents a self-similarity based on the fractal dimension. The fractal dimensions were obtained by the box counting method. In this report, we obtained the nearly stable fractal dimensions of fracture crack profiles for STS316 with CT specimens as the crack advances and the relationships between crack length and fractal dimension. Moreover fractal fracture parameter that corresponds to J-R curve is shown by the relationships between fractal dimension and crack extension. From the results, we concluded that the crack extension of high toughness material also shows the fractal characteristics, which can be used in order to evaluate the crack life precisely.

횡하중을 받는 SiC/Ti-15-3 MMC 복합재 계면영역에서의 탄소성 응력장분포거동(Ⅰ)

강지웅,김상태,권오헌 한국안전학회 2004 한국안전학회지 Vol.19 No.4

Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions (5-60%) were studied numerically. The interface was treated as three thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.