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X-선 회절에 의한 SS41 불림재와 M.E.F. 복합 조직강의 피로 파단면 해석에 관한 연구
허선철,박영철,박수영,김득진,오세욱 韓國非破壞檢査學會 1996 한국비파괴검사학회지 Vol.16 No.1
본 연구에서는 SS41 불림재와 M.E.F. 복합 조직강에 대해서 파괴 역학 파라미터와 X-선 피라미터 사이의 관계를 규명하였다. 피로 균열 진전 실험이 수행되었고, X-선 회절 방법이 피로 파단면에 적용되었다. 피로 파단면을 순차적으로 전해 연마하면서 깊이에 따른 X-선 파라미터(잔류응력, 반가폭)의 변화를 관찰하였다. 최대 소성역 깊이 Wy는 SS41 불림재에서는 반가폭의 분포로, M.E.F. 복합 조직강에 대해서는 잔류 응력의 분포로 결정할 수 있었다. 피로 파단면의 깊이 방향에 따른 X-선 파라미터의 분포로부터 Kmax와 Wy의 관계식이 실험 데이터로부터 얻어지고, 이 식들로부터 Kmax은 Wy의 측정에 의하여 추정되어질 수 있다. This study verified the relationship between fracture mechanics parameters and X-ray parameters for normalized SS41 steel with homogeneous crystal structure and M.E.F. dual phase steel(martensite encapsulated islands of ferrite). The fatigue crack propagation test were carried out and X-ray diffraction technique was applied to fatigue fractured surface. The change in X-ray parameters(residual stress, half-value breadth) according to the depth of fatigue fractured surface were investigated. The depth of maximum plastic zone, Wy, were determined on the basis of the distribution of the half-value breadth for normalized SS41 steel and that of the residual stress for M.E.F. dual phase steel. Kmax could be estimated by the measurement of Wy.
CO₂용접과 TIG 용접에 의한 복합 용접재의 피로크랙전파속도에 대한 연구
허정원,오세욱,도영민 동아대학교 공과대학 부설 한국자원개발연구소 1995 硏究報告 Vol.19 No.1
A structural steel(SB41) was welded in complex by TIG and CO₂welding, where complex meaned that the rest welded by CO₂welding after 2∼3 pass by TIG welding. In base metal, HAZ and deposit metal part of this weldment, the behavior of fatigue crack propagation was examined. In the hardness distribution along vertical direction to thickness in the weldment, hardness was the highest in deposit metal and got low gradually as position went from deposit metal to base metal. In the base metal, the rate of fatigue crack propagation was constant regardless of stress ratio(R-0.1, 0.3, 0.5). This was because of tensile residual stress made in rolling work. The residual stress was considerable tensile residual stress in deposit metal and small tensile stress in HAZ and compressive stress in bass metal. The rate of fatigue crack propagation was slower in deposit metal and HAZ than in base metal and slower in deposit metal than in HAZ.
Ti-Ni합금의 반복변형특성에 미치는 pre-strain의 효과
박영철,조용배,허선철 東亞大學校 海洋資源硏究所 1995 硏究論文集 Vol.8 No.1
In SMA(Shape Memory Alloy), the degradation by fatigue is one of the most important problems tobe overcome, when SMA is used for robot-actuator materials. The actuator is operated repetitively for long time and its repeating operation develops the fatigue degradation of SMA. The fatigue degradation changes the transformation temperature and deformation behavior and results in inaccurate operation control of robot. Accordingly, the changing behavior of transformation temperature and deformation which results from repeating operation is to be investigated in advance and the scheme to resolve those problems have to be made for the design of actuator. In this paper, for the improvement of the fatigue degradation by repetive movement and better control of the correct movement by the stability of martensite transformation in the developement of Robots actuator, Pre-strain(0,1.5,5,8%) are loaded in the specimens and fatigue testing were carried out by the method of heating and cooling in direct condition. From the results of these experiments, the effects on pre-strain which affect the transformation characteristic and fatigue degradation phenomena were correctly investigated.
김규수,남덕현,최영희 龍仁大學校 武道硏究所 2004 武道硏究所誌 Vol.14 No.2
The study is designed to find out the physical factors for decision of records of play in senior highschool judo players under planned training and to identify physical factors of play performance of judo players. The the subject of the study were the senior highschool players registered in Korea sports council and experienced in participation in various judo plays, and total 72 players served as the subject of the study divided into two groups; 36 excellent players awarded in private competition; and not-excellent players with no award record. SPSS V11.0 ststistic program was used in processing of data in this study. discriminant analysis was performed to identify the combinations of variables for physical strength expression that is the difference between the groups, and the contribution levels of variabilities were assessed. 1. In determination of excellent or not-excellent players by physical strength, statistic showed statistical significance with 5% of significance level. 2. The order of contribution of variables that determine the performance of play was muscular strength, muscular endurance, agility, flexibility, explosive power, and cardiovascular endurance in the six physical strength factors. 3. In therms of accuracy of the reclassification of determination factors of play performance, the reclassification into six physical factors, 74.3%.
근골격계 질환 예방을 위하여 새로이 제시된 세탁기 디자인에 대한 생체역학적 평가
조영근(Young Kuen Cho),최희석(Hue Seok Choi),김현동(Hyun Dong Kim),최현호(Hyun Ho Choi),윤종인(join In Youn),김영호(Young Ho Kim),신태민(Tae Min Shin),김한성(Han Sung Kim),임도형(Dohyung Lim) 대한인간공학회 2008 大韓人間工學會誌 Vol.27 No.4
Recently, many studies have reported the fact that an excessively accumulated psychological and physical burden induced from physical labor conducted routinely in home and industry can be one of main reasons of musculoskeletal disorders in the working population. This fact makes increase interests in studies to reduce a risk of musculoskeletal disorders through grafting ergonomic considerations on working environment. However, there are currently limited methodologies in quantitative evaluations of new ergonomic suggestions to reduce a risk of musculoskeletal disorders. The current study is therefore performed to evaluate quantitatively effects of a design of washing machine as a new ergonomic suggestion onto prevention of musculoskeletal disorders, through application of a biomechanical evaluation methodology, For this, three-dimensional motion analysis by using musculoskeletal models with Rapid Entire Body Assessment (REBA), which has been generally used for a simple evaluation of a degree of harmfulness of the human body at specific working postures to be considered, was performed, The results of REBA did not give us enough information and their results were somewhat simple and inaccurate, but the results of the three-dimensional motion analysis give us enough information such as alteration of main muscle forces and joint moments required during washing work. All results showed that the main muscle strengths and joint moments were decreased effectively for reduction of a risk of musculoskeletal disorders during the washing work with newly designed washing machine evaluated in the current study, compared with those generated during the washing work with general washing machine. From these results, it can be concluded that a risk of the musculoskeletal disorders, which may be induced by a repetitive washing work, may be reduced through using the washing machine designed ergonomically and newly. Also, it is thought that if our ergonomic design can be applied for improvement of working environment in lifting and laying works conducted repeatedly for a treatment work of goods, which have a strong resemblance to the behaviors generated frequently during the washing work, a possibility of occurrence of the musculoskeletal disorders by the lifting and laying works may be reduced highly.
세라믹/금속접합재의 고온피로에 따른 접합계면의 응력분포
박영철(Young-Chul Park),허선철(Sun-Chul Hue),김현수(Hyun-Su Kim),윤두표(Doo-Pyo Yun),김광영(Kwang-Young Kim) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.2
The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low specific weight, low thermal expansibility, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductility in order to compensate the weakness of ceramic.<br/> The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strength of joint to a large amount by forming a singular stress field.<br/> In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined.<br/> In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.
김선희 ( Sun Hue Kim ),나기복 ( Ki Book Na ),양승민 ( Seung Min Yang ),유제용 ( Jae Yong You ),배영재 ( Young Jae Bae ),최영태 ( Young Te Choi ) 한국가축위생학회 2003 韓國家畜衛生學會誌 Vol.26 No.1
In order to monitoring the chicken meat hygiene, 165 chicken samples were tested for contamination agents such as the total bacterial counts, coliform bacterial counts and falling bacterial counts. The prevalence of level on number of standard plate count(SPC), total bacterial counts in less than 103cfu/cn, 103~l04cfu/cm2 and 104~l05cfu/cm2 were 30 samples (18.2%), 98 samples(59.4%) and 37 samples(22.4%), respectively. The coliform bacterial counts in less than l02cfu/cm2, 102~l03cfu/cm2 and 103~l04cfu/cm2 were 7 samples(4.2%), 66 samples (40.0%), 92 samples(55.8%), respectively. The falling bacterial counts in plants were higher 9.1, in summer 8.4, in fall 7.2 in spring and 6.7 in winter decreased.