• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.819-829
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• 2008

Fatigue cracking occurs over long time period because dynamic strength of slab continuously decreases by vehicle loading repetitively applied to the concrete pavement. To more accurately predict the fatigue life of the concrete pavement, the stress due to environmental loading should be considered prior to calculating the stress due to the vehicle loading because the stress due to temperature and moisture distribution always exists within the slab. Accordingly, a new fatigue model considering the environmental loading was developed in this research by evaluating factors of existing fatigue models most widely used and by making data points from the models. The applicability of the new model was evaluated by performing a fatigue analysis on the general concrete pavement structure using local climatic and traffic conditions in Korea. It was concluded that the top-down cracking due to the tensile stress at top of the slab is dominant cause of the fatigue failure than the bottom-up cracking occurred at bottom of the slab. More advanced fatigue analysis considering vehicle speed is expected by developing this study.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.19-30
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• 2017

Austenitic Stainless Steels (ASSs) are widely used as structural materials in the pressurized water reactors (PWRs) because of their superior mechanical properties and corrosion resistance. However, it is well known that ASSs are susceptible to the environmental assisted cracking (EAC) such as environmental assisted fatigue (EAF) during the long term operation. There have been extensive tests and researches to understand the extent and the mechanisms of environmental effects. In this paper, the world-wide EAF test results of ASSs are introduced including those of Korean test programs. The suggested EAF mechanisms of ASSs are also discussed. Finally, the areas of further research to resolve the issue of EAF are suggested.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.86-86
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• 2003

주편은 1차 냉각 지역인 수냉 몰드를 통과한 후, 2차 냉각 지역에서 guide roll, pinch roll 그리고 driven roll등에 의해 반복적인 압축하중을 받고 있으며, roll과 roll사이에서는 철정압에 의한 주편 bulging 현상이 발생하고 주편의 표면은 인장응력을 받게 된다. 특히 연속주조 중 주편의 변형기구가 단순 탄소성 변형 이 아닌 creep에 의한 변형임을 고려할 때, 2차 냉각 지역에서 주편의 표면은 전술한 압축 및 인장변형 이 반복되는 저주기 고온 피로 환경을 거침을 알 수 있다. 본 연구에서는 탄소함량에 따른 주편의 bulging시의 크랙 발생에 미치는 저주기 고온 피로의 효과를 조사하였다. 또한, 용체화 처리 온도에서 시험 온도까지의 냉각 속도의 영향을 조사하기 위하여 1$^{\circ}C$/s 및 1$0^{\circ}C$/s로 냉각 속도를 변화시켜 열간 연성 곡선을 작성하였다. 본 연구에서 얻어진 결과는 다음과 같다. 저탄소강의 경우는 저주기 피로의 영향이 관찰되지 않았으며, 중탄소강의 경우, 저온에서는 저주기 피로로 인해 열간 연성이 증가하였으나, 고온에서는 변형유기 페라이트의 생성으로 인해 열간 연성 이 감소하였다. 고탄소강의 경우는 저주기 피로로 인하여 열간 연성이 모든 온도 구간에서 증가하였다. 또한 용체화 처리후 시험 온도까지의 냉각 속도가 감소함에 따라 열간 연성이 증가하였는데, 이는 입 계 석출물의 조대화로 인해 열간 연성이 증가하는 것으로 판단된다.

• Journal of Ocean Engineering and Technology
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• v.4 no.2
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• pp.59-72
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• 1990

본 논문은 해양 구조물에 대한 확률적 기법을 이용한 스펙트럴 피로해석 방법에 대하여 기술하고 있다. 환경조건 특히 파도 및 관련된 해상상태, 파도 스펙트럼에 대하여 조사하였다. 각종 공식을 이용한 응력 집중계수와 유한요소법을 이용한 응력 집중계수 산출 방법 및 피로수명에 대한 그 영향에 대하여 연구하고, S-N선도의 선택과 해상상태의 간략화 문제등에 관해서도 다루었다. 마지막으로 스펙트럴 피로해석 기법을 응용한 실제 피로해석 사례 연구를 통하여 본 방법의 유용성을 입증하였다.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.64-64
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• 2018

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.105-110
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• 1999

여러 종류의 작업장은 생산공정상의 필요나 일기변화에 따가 온습조건에 많은 차이가 있으며, 인체에 불리한 열환경조건이 조성되는 경우가 있다. 일반적으로 열피로(heat stress)와 열장애(heat strain)는 근로자의 안전과 보건을 평가하는데 필요하며, 열피로는 열적영향을 발생시키는 원인을 말하고, 열장애는 열에 의해 발생되는 결과로서 생리적인 부하를 의미하게 된다. 신체내부에서 발생되는 열은 열피로의 한가지 형태이고, 따라서 이것을 측정하는 것은 아주 본질적인 사항이다. (중략)

• Science of Emotion and Sensibility
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• v.12 no.2
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• pp.169-180
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• 2009

The present study have investigated the effect of the characteristics of stereoscopic images and viewing environment on visual fatigue. We manipulated the speed of stereo images with motion-in-depth and viewing distance, which were used as representative variables of the characteristics of stereo image and viewing environment, respectively. Visual fatigue was evaluated with use of a subjective questionnaire which is consisting of 5 different and independent factors: "Eye pain", "Visual stress," "Nauseousness", "Body stiffness", and "Blurriness". In general, when viewing time increased from 10 minutes to 20 and 40 minutes, observers felt severe visual fatigue. Among other factors, only the factor score of "Nauseousness" was significantly increased as the speed of object moving in depth became faster. When viewing distance was increased, the score of "Blurriness" was decreased. These results suggest that different kind of the visual fatigue might be induced depending on characteristics of the stereo images and viewing environment.

• Proceedings of KOSOMES biannual meeting
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• 2004.11a
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• pp.49-56
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• 2004

It has been estimated that up to $80\%$ of all marine accidents have human elements as a cause. t of these, human elements of crew fatigue is main causes of marine accident. Crew fatigue involves sleep, schedule. workload. off-time. alcohol health and stress. With a ship handling simulator, the effect of alcohol on ship operational performance is studied for each 0.05 and $0.08g\%$ blood alcohol concentrations. A main effect for alcohol was found indicating that ship operational performance was significantly impaired by this alcohol relative to performance in the non-alcohol condition. The results of this research can be applied to minimize marine accidents as basic data.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.84-94
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• 1993

This paper deals with the fatigue properties of chopped strand glass mat/polyester composite to understand the effect of water absorption on fatigue behavior of GFRP. The fatigue crack in the both no water and a water absorption materials initiated at the initial of cycle. Thereafter, it was divided with two regions that one decreased with the crack extension and the other increased with the crack extension. The absorption of distilled water degrades the bond strength between fiber and matrix, there, by the tendency of fiber pull-out is increased in perpendicular to crack growth deirection and the debonding of fibers increased to the place which is parallel to crack growth direction. Therefore, the reduction of fatigue strength was caused by these factors.

• Korean Security Journal
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• no.60
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• pp.283-302
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• 2019

This study was conducted to provide the basic data for improving the working environment and welfare level of the security guard by identifying the primary effects of stress response on fatigue with emotional labor and identifying the adjustment effects with coping strategy. The data were collected from 214 security personnel using questionnaire and the statistical tests of correlation, heavy return analysis and hierarchical return analysis using the SPSS 18.0 statistics program were used to reach the conclusion that: First, it has been shown that the emotional labor of a security guard affects fatigue Second, the effects of emotional labor on fatigue of a security guard have been shown to have the effect of coping strategy. Based on the above studies, it was concluded that the emotional labor of a security guard was affected by fatigue and could be controlled by a stress coping strategy. Therefore, it is believed that there is a need to seek an autonomous corporate culture based on the organization's performance by changing the management system for employees at the organizational level so that security guards can use an active way of coping.