• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2002.05a
• /
• pp.210-214
• /
• 2002

집중도 변화와 정신피로는 정의 방향의 평가와 부의 방향의 평가가 있으며, 작업 수행시의 집중변화와 정신피로의 평가는 정의 방향보다 부의 방향으로의 평가가 용이하다. 따라서, 저자들은 먼저 피험자에게 부가할 정신작업부하로 난이도 조정이 용이한 연산작업을 사용하여 작업수행시 가장 높은 집중을 요구하는 하나의 난이도를 선정하고 피험자에게 반복 수행시키면서 생리량과 심리량을 동시에 측정하였다. 측정된 생리량은 뇌파, 심전도, 호흡, 맥파, 말초피부온이며 심리량은 저자들이 개발한 정신피로설문지를 사용하였다. 분석결과 작업수행시 심박변화율의 전력스펙트럼 MF/(LF+HF)비가 감소하였으며, 작업이 반복됨에 따라 집중이 저하되고 정신피로가 증가하였다. 특히, 뇌파의 beta파와 호흡간격이 집중도의 변화를 말초피부온이 정신피로를 잘 반영하였다.

• Journal of the Korean Society for Railway
• /
• v.13 no.5
• /
• pp.469-475
• /
• 2010

In this paper, the structural integrity and fatigue strength for the bogie frame of Monorail being developed in domestic was evaluated. Presently, the standard of evaluation for the bogie frame of monorail was not regulated. Therefore, the evaluation of the structural integrity and fatigue strength for the bogie frame was performed on the basis of the UIC 615-4 standard. The structural integrity of the designed bogie frame was evaluated by displacement and Von-Mises stress under each load conditions. And the fatigue strength was evaluated by combined main in-service load conditions specified at UIC 615-4 standard and it was compared with result of fatigue analysis using winLIFE v3.1 with the function of batch processing. The results shows that the structural integrity and fatigue strength of the designed bogie frame was satisfied, and the fatigue analysis using batch processing was more effective than conventional fatigue analysis using combined load conditions.

• Proceedings of the KWS Conference
• /
• 2004.05a
• /
• pp.258-260
• /
• 2004

현재의 피로강도 평가법에서는 각종 실험적인 방법 및 이론적인 방법 등 여러 가지 방법으로 피로강도설계를 하고 있는 실정이다. 그리고 이러한 피로특성에 대한 정확한 평가를 위해서 대상구조물에 작용하는 하중성분과 재료 및 구조적인 특성의 상호 연관관계에 대한 연구가 지속되어지고 있다. (중략)

• Journal of Korean Society of Steel Construction
• /
• v.23 no.5
• /
• pp.569-579
• /
• 2011

Heating pipes, which are among the main equipment in district heating systems, can be classified into supply and return pipes. Because when the district heating transmission pipe, which is charged with district heating in small to medium-size cities, is under thermal stress during temperature variances in heating water, it suffers from the fatigue phenomenon caused by the thermal stress, according to the number of its service years. District heatingpipes have shown various characteristics according to the operating condition of the service connections, and the irregular temperature variance has had a bad influence on fatigue heating pipes. Therefore, in this study, a field test on laid heating pipes was performed, and the data for each region were analyzed. Also, the fatigue safety of district heating pipes was evaluated via cycle-based evaluation and stress-based evaluation.

• Journal of Aerospace System Engineering
• /
• v.14 no.spc
• /
• pp.22-30
• /
• 2020

Composite rotor blades for rotorcraft have an intrinsic vulnerability to foreign object impact from its inherent structural characteristics of insufficient strength in the thickness direction, which may easily lead to internal structure damage. Therefore, defects and strength reducing effects caused by foreign object impact should be considered in fatigue evaluation of composite blades. For this purpose, the flaw tolerant safe-life and fail-safe concepts were adopted in fatigue evaluation since 1980s, and recently those concepts have been replaced by the damage tolerance concept. In this paper, the relevant standards for fatigue evaluation are analyzed focusing on fiber reinforced composite rotor blades used in rotorcraft. In addition, fatigue evaluation procedure of composite blades considering impact damages is proposed by reviewing the practices implemented through domestic development projects.

• Journal of the KSME
• /
• v.31 no.4
• /
• pp.356-363
• /
• 1991

선형 탄성 유한요소 응력해석과 평균응력 효과를 고려한 저주기 피로실험으로부터 결정된 피로 특성, 그리고 국부변형률 방법을 종합하여 외경에 흠이 존재하는 자긴가공된 두꺼운 압력 용기의 피로수명이 평가되었다. 직사각형의 매우 날카로운 흠에서의 응력집중계수는 타원형 홈에서의 응력집중계수의 약 두배의 값이 얻어졌으며, 고강도 압력용기강인 ASTM A723의 저주기 피 로거동에 대한 평균응력 영향은 Morrow 및 SWT 파라메타를 이용하여 충분히 고려되었다. 균열발생이 예상되는 위험한 부분인 홈의 뿌리부분에서의 국부적인 응력, 변형률이 계산되었으며 예측된 피로수명은 실험적으로 얻어진 수명과 비교했을 때 2에서 4배의 오차를 보이면서 일치 하는 결과를 얻었다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.2
• /
• pp.139-145
• /
• 2010

Bending fatigue of aluminium alloy was characterized by acoustic nonlinearity of narrow band laser-generated surface wave. The higher harmonic components generated intrinsically by arrayed line laser beam were analyzed theoretically and acoustic nonlinearity was measured successfully on the surface of fatigue damaged aluminium 6061 alloy. The acoustic nonlinearity increased as a function of fatigue cycles and has close relation with damage level. Consequently, the nonlinear acoustic technique of laser-generated surface wave could be potential to characterize surface damages subjected to fatigue.

• Magazine of the Korea Concrete Institute
• /
• v.9 no.5
• /
• pp.177-187
• /
• 1997

철근 콘크리트 구조부재는 철근과 콘크리트로 구성된 합성부재이므로, 철근콘크리트 구조부재의 피로강도는 철근과 콘크리트 고유의 피로특성에 따라 변화하게 된다. 철근자체의 피로특성은 철근의 정적강도 특성과 상이함으로, 실험을 통하여 규명할 필요가 있다. 본 논문에서는 대표적인 국내 2개사에서 생산되는 철근에 대하여 직접인장 피로실험을 실시하여 이들의 피로특성을 규명하였으며, 철근콘크리트 휨부재 내부의 철근 피로특성과 철근만의 직접인장 피로특성의 비교 분석으로부터 직접인장 피로실험만으로 철근콘크리트 휨부재의 피로특성을 평가할 수 있음을 밝혔다. 또한 반복하중을 받는 철근콘크리트 부재의 피로점토를 위한 기준을 제시하였다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1319-1327
• /
• 1994

Since fatigue cracks in rail can be the source of fractures and subsequent derailments, quantitative evaluation of the fatigue behavior and fracture properities due to the analysis results of laboratory test are drawn on the basis for predicting fatigue life and making a decision of safe inspection interval. Charpy V-notch and fracture toughness behavior were evaluated from the results of Charpy impact test. Fatigue test was performed by using CT type specimen under constant amplitude loading, and finally the effects of the following parameters; crack orientation, temperature, and stress ratio, on the fatigue crack growth behavior were studied.

• Journal of the Korea Convergence Society
• /
• v.10 no.8
• /
• pp.21-26
• /
• 2019

This paper proposes a fatigue recognition method using the C4.5 algorithm. Based on domestic and international studies on fatigue evaluation, we have completed the fatigue self - assessment scale in combination with lifestyle and cultural characteristics of Chinese people. The scales used in the text were applied to 58 sub items and were used to assess the type and extent of fatigue. These items fall into four categories that measure physical fatigue, mental fatigue, personal habits, and fatigue outcomes. The purpose of this study is to analyze the leading causes of fatigue formation and to recognize the degree of fatigue, thereby increasing the personal interest in fatigue and reducing the risk of cerebrovascular disease due to excessive fatigue. The recognition rate of the fatigue recognition system using the C4.5 algorithm was 85% on average, confirming the usefulness of this proposal.