• 한국정밀공학회지
• /
• 제26권1호
• /
• pp.71-81
• /
• 2009

Die steel for plastic molding were used as mold material of automobile parts and electronic component industry. The material of this paper has superior to mechanical properties, such as repair weldability, corrosion resistance and high temperature strength, required mold parts for semitransparent. Laser-induced surface hardening technology is widely adopted to improver fatigue life and wear resistance via localized hardening at the surface of mold parts. The objective of this research work is to investigate on the characteristics of surface hardening of the laser process parameters, such as beam travel speed, laser power and defocsued spot position, for the case of die steel for plastic molding. Lens for surface hardening of large area is plano-convex type with elliptical profile to maintain uniform laser irradiation. According to the experimental results, large size of hardened layer at the surface of die steel for plastic molding was achieved, and microstructure of this layer was lath martensite. Optimal surface status and mechanical property of hardened layer could be obtained at 1095Watt, $0.25{\sim}0.3m/min$, 0mm (focal length: 232mm) for laser power, beam travel speed, and focal position. Where, heat input was $0.793{\times}10^{3}J/cm^2$, and width of hardened layer was 27.58mm.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
• /
• pp.58-58
• /
• 2010

The purpose of this study is to evaluate the structural safety at the topside weldment of hull structure, which was welded after launching. For it, the variations of residual stress and distortion at the topside weldment with loading conditions such as hull girder hogging bending moment after launching and free initial loading state was evaluated by using FEA. And the maximum stress range at the weldment under design loads specified by classification society was evaluated by FEA. In this case, the residual stress and welding distortion at the topside weldment was assumed to be initial imperfection. In accordance with FEA results, regardless of initial loading condition, tensile residual stress was found. However, the residual stress and welding distortion at the topside weldment produced under hogging condition was less than those of topside weldment under free loading state. That is, the amount of residual stress at the topside weldment decreased with an increase in the amount of tension load caused by hogging condition. It was because the compressive thermal strain at the topside weldment produced during welding was reduced by tensile load. However, the maximum stress range at the topside weldment under maximum hull girder bending moment was almost similar regardless of initial loading condition. So, if the problem related to the soundness of weldment is not introduced by initial load, the effect of initial loading condition during welding on fatigue strength of topside weldment could be negligible.

• 대한기계학회논문집B
• /
• 제38권4호
• /
• pp.311-320
• /
• 2014

풍력터빈 블레이드는 바람의 운동에너지를 기계적 에너지로 변환하는 장치로써 풍력발전시스템의 출력성능, 에너지변환효율, 하중 및 동적 안정성에 영향을 미칠 수 있기 때문에 주요부품으로 분류된다. 따라서 최적의 블레이드 설계결과를 얻기 위해서는 시스템 특성이 고려된 공력-구조 통합설계가 중요하며, 국제표준 또는 인증기관의 가이드라인에 따른 설계평가를 통해 구조건전성의 검증이 요구된다. 본 연구에서는 블레이드 설계 인증 시 요구되는 평가항목 및 판정기준에 대한 상세해설과, (사)한국선급의 인증기준에 따른 2 MW 급 블레이드(KR40.1b)에 대한 설계평가 결과를 제시하였다. 유한요소 해석에 의한 극한 강도, 좌굴 안정성, 한계 허용 팁 변형과 누적 손상 법에 의한 피로 강도 해석결과가 검토되었으며, KR40.1b 블레이드는 모든 평가항목에 대한 구조 건전성을 만족하는 것으로 확인되었다.

• 대한기계학회논문집A
• /
• 제41권11호
• /
• pp.1119-1124
• /
• 2017

차량 하부에 장착된 스테빌라이저바는 차량이 곡선 구간을 선회할 때 차량의 자체를 유지해 줌으로서 차량 주행을 보다 편안하게 해 준다. 스테빌라이저바는 중실과 중공 타입 2가지가 있으며, 차량의 경량화를 위해 중공 형태의 스테빌라이저바의 적용이 늘고 있다. 차량의 경량화를 위한 중공 스테빌라이저바는 중실에 비해 무게가 34% 이상 경량화가 가능하지만 경량화 비율이 높아질수록 제품의 내구 수명은 급격하게 감소하는 경향을 나타낸다. 이러한 내구 수명 감소에 대한 대책으로서 소재의 고강도 및 고경도 소재를 적용하거나 쇼트피닝 공법을 개선 하는 등의 노력을 통해 내구 수명을 보장할 수 있다.

• 한국표면공학회지
• /
• 제32권2호
• /
• pp.144-156
• /
• 1999

Thermal Barrier Coating with Functional Gradient Materials (FGM-TBC) can play an important role to protect the parts from harmful environments in high temperatures such as oxidation, corrosion, and wear and to improve the efficiency of aircraft engine by lowering the surface temperature on turbine blade. FGM-TBC can increase the life spans of product and improve the operating properties. Therfore, in this study the evaluations of mechanical and thermal properties of FGM-TBC such as fatigue, oxidation and wear-resistance at high temperatures have been conducted. The samples of both the TBC with 2, 3, 5 layers (YSZ/NiCrAlY) to be produced by Air Plasma Spray method (APS) and the bulk TBC with 6 layers to be produced by Plasma Assisted Sintering method (PAS) were used. Furthermore, residual stress, bond strength, and thermal conductivity were evaluated. The average thickness of the APS was 500$\mu\textrm{m}$ to 600$\mu\textrm{m}$ and the average thickness of the PAS was 3mm. The hardness number of the top layer of APS was 750 Hv to 810Hv and that of PAS was 950 Hv to 1440Hv. The $ZrO_2$ coating layer of APS was composed of tetragonal structure after spraying as the result of XRD analysis. As shown in the results of the high temperature wear test, the 3 layer coating of APS had the best wear resistance at $800^{\circ}C$ and the 5 layer coating of APS had the best wear resistance at $600^{\circ}C$. But, these coatings had the tendency of the low-temperature softening at $300^{\circ}C$. The main mechanism of wear was the adhesive wear and the friction coefficient of coatings was increased as increasing the test temperatures. A s results of thermal conductivity test, the ${\Delta}T$ of the APS coating was increased as number of layer and the range of thermal conductivity of the PAS was $800^{\circ}C$ to $1000^{\circ}C$.

• 한국철도학회논문집
• /
• 제11권3호
• /
• pp.326-333
• /
• 2008

본 논문은 누적통과톤수에 의한 레일교체기준 개정을 위한 기초 데이터를 제시하는데 목적이 있다. 본 연구에서는 국외의 누적통과톤수에 의한 레일교체기준의 산정근거를 조사하였으며, 일본에서 조사된 레일용접부 결합유형 및 원인과 국내 철도운영기관인 서울메트로의 궤도유지관리이력을 조사하여 실제 레일절손과 누적통과톤수의 상관관계를 분석하였다. 또한, 누적통과톤수 기준치에 도래한 노후레일 용접부를 현장에서 발췌하여 레일용접부 휨시험을 수행하였다. 그 결과, 누적통과톤수와 레일절손간의 상관관계는 뚜렷하지 않았으며 레일용접부의 시공불량에 의한 절손사례가 많은 것으로 분석되었다. 또한, 노후레일휨시험 결과 신규레일용접부에 비해 파괴강도가 $17{\sim}18%$만이 저하된 것으로 나타나 레안교체기준에 도래한 노후레일은 사용성 측면에서 충분한 내구성 및 내하력을 확보하고 있는 것으로 분석되었다.

• 근관절건강학회지
• /
• 제18권2호
• /
• pp.270-281
• /
• 2011

Purpose: This study was done to determine if osteoarthritis (OA) patients living in rural Korea would have a benefit from a structured group program focused on self-help strategies. Methods: A hundred and twenty-six patients with OA were recruited from nine Primary Health Care Posts. The experimental group received a 6-week self-help education program while the control group received usual care. T-tests and c2-tests were used to determine the homogeneity between the experimental and control groups. Independent sample t-tests were performed to determine the effect of the treatment program. To guard against such likelihood, the level of significance of t-test was determined by Bonferroni correction within the study constructs. When significant group differences were found in study variables at baseline, analysis of covariances (ANCOVAs) were used for group comparisons of outcome variables. Results: The experimental group reported more significant improvement in fatigue, difficulty with physical activity, depression, quality of life, self-efficacy, and health behaviors than did the control group. The experimental group also showed improvements in range of motion and muscle strength as compared to the control group. Conclusion: A self-help group education program was an effective and powerful strategy to promote physical and psychosocial health in OA patients

• Journal of Korean Biological Nursing Science
• /
• 제17권2호
• /
• pp.104-113
• /
• 2015

Purpose: This study aimed to analyze physical activity as measured by the International Physical Activity Questionnaire (IPAQ) and an actigraph in breast cancer survivors, as well as to identify their intention to participate in a physical activity program. Methods: Breast cancer patients who had been diagnosed for more than six months (N=135) at a university hospital participated from June 2012 to May 2013. Physical activity was measured using the Korean version of the IPAQ-Short Form and Actigraph GT3X plus an accelerator for seven consecutive days. Data analyses were conducted using the SPSS WIN 19.0 program. Results: Mean total physical activity was 2298.21 metabolic equivalent task (MET)-min/week as assessed by IPAQ and 150,140.57 counts/day as measured by an actigraph. There were statistically significant correlations between moderate physical activity from IPAQ and light intensity of physical activity from the actigraph (r=.735, p<.001), vigorous physical activity from IPAQ and vigorous intensity of physical activity from the actigraph (r=.871, p<.001), total physical activity from IPAQ and light intensity of physical activity from the actigraph (r=.825, p<.001), respectively. Most (80.7%) cancer survivors reported a positive attitude toward physical activity and 57.8% expressed a willingness to participate in a physical activity program. More than half (60%) of the subjects preferred walking, 80.6% preferred more than 30 minutes of exercise, and 57.1% wanted to engage in physical activity three times a week and preferred home-based activities. Perceived barriers included fatigue, lack of strength and pain. Conclusion: It is necessary to consider intensity, personal preferences, and patient-perceived barriers when developing physical activity programs for breast cancer survivors.

• Elastomers and Composites
• /
• 제49권4호
• /
• pp.293-304
• /
• 2014

고무 공기 스프링(rubber air spring)은 자동차, 철도차량 등 수송기기의 서스펜션 장치로 사용되고 있다. 고무 공기 스프링은 고무 에어백의 압축과 팽창을 통한 탄성효과로 스프링의 역할을 한다. 고무 공기 스프링의 주요 구성요소 중 하나가 고무 슬리브(rubber sleeve)이다. 고무 슬리브는 주요 구성성분인 클로로프렌 고무와 나일론 6 코드 간의 접착이 매우 중요하다. 본 연구에서는 첨가제의 영향을 고려한 고무 슬리브의 최적 배합조성과 조건을 찾기 위해 다양한 물성시험을 하였다. 또한, 보강섬유의 최적 배향을 선정하기 위해 유한요소해석법을 이용한 수치해석을 수행하였다. 고무 공기 스프링을 제조하여 실제 차량에 장착하여 기초물성과 피로수명 및 기밀성을 시험하였다.

• 기본간호학회지
• /
• 제7권1호
• /
• pp.122-136
• /
• 2000

Stroke patient needs rehabilitation after receiving an acute treatment in a hospital. When stroke patient gets involved in an early discharge program, home care nurse plays a pivotal role to make them to gain a full strength and to come back to his/her prior life before he/she is sick. In spite of the importance of home care nursing intervention protocol for home care nurses to perform home care nursing autonomously, home care nursing intervention protocol for stroke patient is rarely developed. Therefore this study was conducted to develop home care nursing protocol that is applicable for stroke patients in home care nursing area. 41 home care nursing charts for stroke patients registered in home care nursing agencies from December 1st 1994 to August 31st 1999 at Y hospitals in Seoul and Won-Ju city were analyzed. 44 home care nurses who were having over three years' experience on stroke patients were participated in this study as a user validity validation group. The results of this study are as follows. 1. 28 nursing diagnoses were selected on the basis of evaluation of nursing diagnoses of stroke patients presented in a previous literature and case studies on home care nursing. 2. 17 nursing diagnoses were classified through the frequency analysis of home care nursing charts for 41 stroke patients who had received home care nursing. The order of sequence was like these: impaired skin integrity, risk for infection, nutritional deficit, impaired physical mobility, constipation, knowledge deficit, ineffective airway clearance, anxiety in family members, risk for aspiration, self care deficit, altered urinary elimination, ineffective individual coping, social isolation, risk for injury, self-esteem disturbance, impaired verbal communication, fatigue of family caregiver. 3. Based on validation on expert and user validities, 44 nursing interventions which were above ICV=.80 were chosen. 4. Nursing intervention protocols which showed above ICV=.90 were developed and were like these; pressure ulcer care, position change, preventive care for circulatory dysfunction, tube care : catheter, vital sign monitor, constipation/impaction management, artificial airway management, suction of airway secretion, environmental management : safety, and fall prevention.