• 한국안전학회지
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• 제13권3호
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• pp.60-66
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• 1998

ABS sensor ring has been manufactured by P/M method using 400 series ferrite stainless steel. The results are as following: It is supposedly sufficient to use for control computer due to good experimental results of magnetic characteristics. Compared with sensor ring made by iron, 400 series ferrite stainless steel has shown a good corrosion resistance without an addition surface treatment. Thus the decreasing production process has been obtained. As a result of hardness and tensile test, 400 series ferrite stainless steel shown a good endurance when it is combined to C/V joint, and has a good hardness properties endurable to sand and pebble impact.

• 한국정밀공학회지
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• 제20권3호
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• pp.149-156
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• 2003

The estimation of fatigue limit for the component with complicated shape is difficult than of standard fatigue specimen, due to complex test equipment. So, we substitute maximum principle stress from FEM results for fatigue limit diagram made by standard fatigue specimen. Then we can estimate endurance safety of component with high trust. The static stress analysis, the nonlinear contact stress analysis and the model analysis for turbine blade is performed by ANSYS ver. 5.6. the comparison of maximum static stress around hole with maximum contact stress between pun and hole can make the cause of fracture for turbine blade clear. The difference of fatigue limit between fatigue test by standard specimen and in-service mechanical components is due to surface roughness and machining condition etc. In in-service mechanical components, Goodman diagram has to consider surface roughness for failure analysis. To find fracture mechanism of torison-mounted blade in nuclear plant. This study performs the static stress, the nonlinear contact stress and the modal analysis on torison-mounted blade with finite element method and makes the estimation for safety of turbine blade.

• 산업경영시스템학회지
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• 제41권4호
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• pp.213-219
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• 2018

Mechanical components are to be produced with accurate dimensions in order to function properly in assemblies of a machine. Once designs of mechanical components are created, designers examine the designs by adopting many known experimental methods. A primary test method includes stress and strain evaluation of structural parts. In addition, fatigue test and vibration analysis are an important test method for mechanical components. Real experiments at a laboratory are established when products are manufactured. Since design changes should be done before producing the designs in factories, rapid modifications for new designs are required in production industries. FEM simulation is a proper choice for a design evaluation with speed at a detail stage in design process. This research focuses modeling and mechanical simulation of a mechanical component in order to ensure structural safety. In this paper, a universal joint, being used in driving axels of vehicles, is studied as a target component. A design model is created and tested in some ways by using commercial software of FEM. The designed component is being twisted to transmit heavy power and thus, torsional stress should be under strengths of the component's material. The next is fatigue analysis to convince fatigue cycles to be within the endurance limit of the material. Another test is a vibration analysis for rotational components. This research draws final conclusions from these test analyses and recommends whether the designed model is under safety condition in terms of mechanical structure.

• 한국기계가공학회지
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• 제18권6호
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• pp.9-18
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• 2019

This study derives load characteristics and analyzes the safety of plowshares operating in dry fields. We mounted a three-blade, reversible plow on a 23.7 kW tractor and measured the plow's tractive force as well as the torque from the engine output shaft on the rear axle under various working speeds (L4, M1, M2, M3). We chose a Korean test site of Seomyeon, Chuncheon with sandy soil texture, as determined using the USDA method. We constructed the load spectrum for torque and tractive force using measured data and derived the fatigue life of the plowshare from a stress-cycle (S-N) curve of the plow material. Our results show that the M3 gear maximizes the driving shaft torque loads and, applying the tractive force load spectrum, creates a cumulative damage sum of $4.14{\times}10^{-5}$. Considering sampling time, we estimate a fatigue life of 805 hours while using the M3 gear. When using the other working speeds, however, all of the stress levels fell within the endurance limits and, therefore, our model predicts infinite plowshare lifetimes. For this analysis, we used a yield strength of 1,079 MPa for the plowshare and static safety factors, analyzed using the maximum stress, between 6.83 and 8.63 under each working speed.

• Structural Engineering and Mechanics
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• 제70권1호
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• pp.33-41
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• 2019

The influence of two parameters on fatigue damage predictions of a variably loaded cantilever beam has been examined. The first parameter is the geometry of the cantilever beam and the weld connecting it to a rear panel. Variables of the geometry examined here include the cantilever length, the weld width on the critical cross-section and the angle of the critical cross-section. The second parameter is the safety factor, as set out by the Eurocode 3 standard. An analytical approach has been used to calculate the stresses at the critical cross-section and standard rainflow counting has been used for the extraction of the load cycles from the load history. The results here suggest that a change in the width and angle of the critical cross-section has a non-linear impact on the fatigue damage. The results also show that the angle of the critical cross-section has the biggest influence on the fatigue damage and can cause the weld to withstand fatigue better. The second parameter, the safety factor, is shown to have a significant effect on the fatigue damage calculation, whereby a slight increase in the endurance safety factor can cause the calculated fatigue damage to increase considerably.

• 한국안전학회지
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• 제30권6호
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• pp.102-109
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• 2015

In this study, on the basis of the results of the field survey and the theoretical consideration for Korean Standard Specification for concrete durability and maintenance, the following conclusions are derived. From the survey, the prediction equation of carbonation depth for the southwest region in Korea is experimentally proposed, $y_p=5.865{\sqrt{t}}$, which predicts about 60mm of the carbonation depth for the concrete structures of 100 years, a 1st class of target endurance period, under a combined deterioration environment like a marine environment. Considering that the marginal value for a carbonation depth limitation under very severely marine environment is 25mm, in accordance with the Specification, it is found that the predicting carbonation depth for the concrete cover depths, 100mm and 60mm are 63mm and 29.4mm, respectively. In conclusion, according to the equation and the Specification, it is strongly required that the reinforced concrete structures with the cover depth under 100mm have to make a protection from combined deterioration factors by any methods like a surface coating, an increment of cover depth or an application of a special concrete.

• 한국콘텐츠학회논문지
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• 제14권8호
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• pp.266-276
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• 2014

본 연구는 사과, 배 작목 농업인을 위해 개발한 근골격계질환 예방운동프로그램이 농업인의 신체적 능력 및 삶의 질에 미치는 영향을 알아보고자 하였다. 근골격계 자각증상(NIOSH 기준1)이 있는 농업인 25명을 대상으로 2011년 4월 7일부터 7월 1일까지 12주간 예방운동프로그램을 실시하였다. 그 결과 과수재배 농업인들을 위해 실시한 근골격계질환 예방운동프로그램은 농업인들의 신체적인 능력(상지지구력, 하지지구력, 평형성, 민첩성)을 향상시키고 삶의 질을 개선하는 데 효과적이었다. 또한 삶의 질은 요통장애지수, 심리사회적 스트레스와도 유의한 상관성을 보였다. 향후 연구에서는 농작업의 특성을 고려한 운동프로그램의 개발 및 적용을 위해 다양한 연구가 시도되기를 기대한다.

• 국제물리치료학회지
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• 제2권1호
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• pp.214-221
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• 2011

The purpose of this study is to investigate and reveal the effects that the complex exercise training consisting of aerobic exercise and strength training(sit up, push up) that everyone can easily practice regardless of a time and a place in order to manage practically the physical strength of the aged affects the difference on their body composition and the change of physical fitness level. Looking into the change of body composition of an experimental group, the weight of 2.5kg was reduced after applying complex training for 12 weeks and the body fat mass of 2.65kg was reduced. Also, the abdominal fat of 0.13% was decreased and the muscle mass of 1.56kg was increased. For the change factors of physical fitness, cardiovascular endurance, muscular strength, muscular endurance, balance and flexibility excluding agility showed significant improvement after applying complex exercise training. The improvement of health fitness of the aged under this study was significantly effective to improve specified body functions which had been lowered by aging and insufficient physical activities. So, it is regarded that their health fitness is the important factor to improve the activity competence required for daily life and to lead healthy living by the improved activity competence. Henceforth, it needs to study more the complex composition of several sports, exercise intensity and the frequency based on the previous researches and studies. In addition, it needs to develop the complex exercise training in accordance with various characteristics such as a sex of the aged, an age, a physical fitness level, environment, a disease and the program in consideration of the efficacy and safety during training.

• 한국산학기술학회논문지
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• 제21권12호
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• pp.612-618
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• 2020

최근에 외부 유리창 청소에 대한 수요는 증가하고 있으나, 이 청소는 매우 위험한 인력 의존형 작업이다. 또한 청결을 중시하는 업장에서 원하는 빈도로 자주 청소하는 것도 용이하지 않다. 따라서 이 작업을 자동화 할 필요가 있다. 본 연구에서는 특정 유리창에 부착하여, 그 유리창을 지속적으로 청소하는 장치의 개념을 제시하고, 이 장치의 경제적 타당성을 분석하였다. 분석 결과, 장비의 예상 제작비 1천만 원 수준이나, 투자 가능비용은 내구연한 5년 기준으로 최소 9.8백만 원, 내구연한 10년 기준으로 최소 103백만 원 수준이었다. 따라서 장비비 보다 예상 절감액이 충분히 커서, 경제적 타당성이 있는 것으로 평가 되었다. 본 연구에서는 정량적 지표만으로 분석하여, 안전성 향상에 의한 노무자 안전 사고 감소, 생산성 향상, 공기 단축, 품질 향상 등으로 인한 원가 절감 기대 값은 고려되지 않았다는 한계가 있다. 따라서 향후 고려되지 않은 기대 값을 추가하여 자동화 장비에 의한 원가절감 효과를 산출하면 경제성이 보다 정확하게 산정될 것으로 예상된다.

• 한국조경학회지
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• 제24권1호
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• pp.1-14
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• 1996

The purpose of this study was an analysis of the elementary school child's attitude and dangerous factors of play apparatuses n elementary schools. The results were summarized as follows; 1. 53.0% of the reply child thought that play apparatuses were dangerous, and 41.0% of the total reply had experienced accidents by apparatuses, the child under 10 had experienced the accidents manytimes. 2. The types of injuries most frequently occurred are falls from play apparatuses, and part of the body most frequently injured parts of the body are arms and legs. 3. The danger of fall in play apparatuses that is over 3M amounted 19.6%, it asked safety of bottom materials. 4. Destructed play apparatuses reached up to 20.0%, and rusted or decomposed apparatuses reached to 28.4%. 5. The distance of each apparatus were very close ; it was within 0.3~1.5M, which was 24.9%, it was very dangerous factor. 6. The most frequent hazards of educational play apparatuses are ; - inappropriate size of apparatuses(height, gap, thick etc.)- inappropriate shape and finished state(bad welding and cutting, projection part etc.)- unsuitable use of bottom material in playground and safety color.- insufficient use zone.-inappropriate maintenance and inspection(endurance passage, erosin of iron-ware and wooden ware, projection of foundation concrete)