• Title, Summary, Keyword: 피로도

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Damage Tolerance Assessment for Fatigue-Critical Locations of Wing Structure of Aged Aircraft (장기운영 항공기 주익 구조물 피로임계부위의 손상허용평가)

  • Chun, Young-Cheol;Kim, Won-Cheol;Jin, Ji-Won;Chung, Tae-Jin;Kang, Ki-Weon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.2
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    • pp.129-136
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    • 2017
  • This study aims to assess the damage tolerance of the wing structure of aged aircraft with long-term service through the fatigue crack growth analysis and tests. For the fatigue-critical locations (FCL) W2 and W4 in the wing structure, the fatigue stress spectrum was derived based on a previous study. Thereafter, a crack propagation analysis for the FCLs was conducted using the commercial software $NASGRO^{TM}$. The algorithm for the fatigue stress spectrum was verified. Fatigue crack growth tests were then performed for two types of specimens: Type #1 was extracted from the wing structure of aged aircraft, and Type #2 was made of the same material as the wing structure. By comparing the experimental results of these specimens, we assessed the damage tolerance of the wing structure of aged aircraft with service time.

Evaluating the Effects of Dry Eye Syndrome on Ocular Fatigue and Attentiveness (건성안증후군의 눈 피로도와 주의집중력에 관한 연구)

  • Hong, Kyung-Hee;Lee, Hyun-Joo;Kim, Se-Jin
    • The Korean Journal of Vision Science
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    • v.19 no.4
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    • pp.533-539
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    • 2017
  • Purpose: This study was aimed to evaluate the effects of dry eye syndrome on ocular fatigue and attentiveness. Methods: This study targeted 512 subjects who did not have an abnormal visual function, did not wear contact lens, had corrective eyesight over 0.8, and were between 19 and 83 year olds (mean age of 40.27 years). General characteristics (i.e., sex, age, drinking, and smoking status), dry eye syndrome, the score of a survey on ocular fatigue, and sub-factors of attentiveness were tested and analyzed. Results: Among the subjects, 312 were women and the mean age of them was 40.27 years. The number of drinkers was 260 and there were more drinkers than non-drinkers. There were 438 non-smokers, which was more than smokers. Dry eye syndrome showed positive correlations with age, sex, smoking, drinking, and eye fatigue. Attentiveness showed significant differences with BET, NAR, OET, and RED, which were sub-factors, had significant effects on dry eye syndrome. Conclusion: People with dry eye syndrome showed lower attentiveness than those who without it and higher dry eye syndrome increased ocular fatigue.

Effect of Working Hours on Fatigue and Fatigue Induced Factor in Private Guard and Security (민간 경호.경비원들의 근무시간이 피로에 미치는 영향)

  • Park, Suk;Jung, Suk-Hyun;Choi, Moo-Young
    • Korean Security Journal
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    • no.17
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    • pp.131-141
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    • 2008
  • The porpuse of present study was to examine the effects of working time on fatigue and fatigue induced factor in private guard and security. The munber of private guard on which this study has been conducted in 200, who work at large conmpanies, medium or small companies and the like as located in Seoul and kyonggi. In this study blood lactate, phosphorus and ammonia were measred to see the level of fatigue. There was significant difference in blood lactate, phosphorus ammonia and fatigue between working hours(P<0.05). in view of the results of this study, it can be thought that fatigue is more affected by working hours In summary, these results are interpreted to mean that 1) fatigue levels and blood fatigue induced factor (lactate, phosphorus, ammonia) increase due to a rise in working hours.

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Thickness Effects on the Fatigue Strength of Butt Welded Specimens using SM520C-TMC Steel (SM520C-TMC 강재의 피로강도에 대한 두께효과)

  • Kim, Kyoung Nam;Jung, In Su;Hwang, Nak Yeon;Jung, Kyoung Sup
    • Journal of Korean Society of Steel Construction
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    • v.16 no.6
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    • pp.847-855
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    • 2004
  • The criterion or specification on fatigue design has been generally based on fatigue strength curve derived by tests on specimens with varying thickness (10-30mm). Making the plate thicker, however, also decreases fatigue strength. It has been noted from the test results and the results of the analysis by fracture mechanics that the effect of thickness cannot be bypassed. From the several fatigue strength curves of specimen tests, modification of fatigue strength on plate thickness has been proposed. In this study, fatigue tests on SM520C-TMC were carried out, and the effects of thickness were evaluated. Finally, in consideration of the thickness, the modification of fatigue strength was derived. Comparing the results of this paper with those of previous studies, an outline of the behavior obtained is similar to previous ones, but the rate of decrease is smaller.

Fatigue Evaluation Method for 3D Video based on Characteristics of Depth Map (깊이 영상의 시공간적 특성 분석을 통한 3차원 영상의 피로도 측정)

  • Choi, Jae-Seob;Kim, Dong-Hyun;Sohn, Kwang-Hoon
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • pp.77-80
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    • 2009
  • 3차원 영상 처리 기술과 3차원 디스플레이의 발전은 3차원 영상 시장의 빠른 발전을 가져왔고 차세대 방송 기술로 큰 관심을 받고 있다. 하지만 3차원 영상은 시청할 때 눈의 피로, 어지럼증과 같은 현상이 일어날 수 있으며, 왜곡된 3차원 영상이 인체에 해로운 영향을 미칠 수도 있다. 이는 3차원 영상 산업의 활성화를 위해서 가장 시급히 해결되어야 할 문제이다. 현재 3차원 디스플레이는 스테레오 방식과 함께 1view 1depth 다시점 방식이 개발되었다. 특히 1view 1depth 다시점 디스플레이에서 깊이 영상의 공간적/시간적으로 복잡한 정도는 피로감을 일으키는 주요 요소이며 이는 1view 1depth 영상을 통해 직접 연구할 수 있다. 본 논문에서는 1view 1depth 디스플레이에서 주관적인 피로도와 큰 상관도를 가지는 깊이 영상의 특성 측정 방법을 제안한다. 1view 1depth 디스플레이에서 view 영상은 양호한 화질을 가정하였으며 피로감에 큰 영향을 미치는 깊이 영상 정보만 사용하여 공간적, 시간적인 특성을 분석한다. 공간적 복잡도는 각 프레임에 대하여 깊이 영상 내 화소 값의 분산 값을 취하여 공간적으로 깊이 값의 분포와 구조의 복잡한 정도를 측정하고, 시간적 복잡도는 연속적인 프레임에 대하여 동일한 화소위치에서 화소 값 차이의 분산 값을 사용한다. 또한 공간적/시간적 평균값의 측정하여 피로감에 영향을 주는 요인으로 사용하였다. 결과적으로 측정한 값들을 바탕으로 주관적인 피로도 평가와 유사성을 가지도록 모델링하여 3차원 영상의 피로도를 예측한다.

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Applicability of Hammer-Peening Treatment for Fatigue Life Improvement of Fatigue Damaged Weld Joints (피로손상된 용접이음의 피로수명 향상을 위한 햄머피닝 처리법의 적용)

  • Kim, In Tae;Park, Min Ho;Cheung, Jin Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.3
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    • pp.48-55
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    • 2013
  • In this study, fatigue tests were performed on longitudinal out-of-plane gusset fillet welded joints and transverse non-load-carrying cruciform rib fillet welded joints, and then applicability of hammer-peening treatment on improvement of fatigue life for fatigue damaged weld joints were investigated. Fatigue tests were carried out on three types of gusset and rib welded specimens: as-welded specimens, post-weld hammer peened specimens and hammer peened specimens at 50% of as-welded specimen's fatigue life. Before and after hammer peening treatment, the geometry of weld toes and surface stresses near weld toes were measured. As a result of hammer peening treatment, compressive residual stresses of 30-83MPa were introduced near weld toes of the gusset and rib welded joints, and 130% increase in fatigue life and fatigue limit of the welded joints could be realized by hammer peening treatment at 50% fatigue life of as-welded conditions.

The Impact of Functional and Emotional Factors on User Satisfaction and Commitment toward Mobile Messenger Service: Investigating the Mediating Effects of Intimacy and Fatigue (기능적·정서적 요인이 모바일 메신저 서비스에 대한 사용자 만족과 몰입에 미치는 영향: 친밀감과 피로도의 매개효과를 중심으로)

  • Lee, Ae Ri;Park, Yong Wan;Park, Yujin
    • The Journal of Society for e-Business Studies
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    • v.21 no.1
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    • pp.33-63
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    • 2016
  • The diffusion of smartphone has make people engaged in communication with mobile messenger in everyday life. To understand the rapid growth of mobile messenger usage, this study investigates the unique features of mobile messenger services as communication media. Based on the media synchronicity theory and literature about online communication, we identify the functional and emotional features of mobile messenger. In particular, this study demonstrates that functional and emotional features of mobile messenger would influence intimacy and fatigue. Also, intimacy and fatigue, as mediating variables, have an impact on user satisfaction and commitment toward mobile messenger service. The results of this study provide practical implications for mobile messenger providers and users which attempt to facilitate positive effect such as intimacy among users and reduce negative effect such as fatigue on mobile messenger communication.

Accelerated Life Prediction for STS301L Gas Welded Joint (I) - Fillet Type - (STS301L 가스용접 이음재의 가속수명예측 (I) - Fillet Type -)

  • Baek, Seung-Yeb
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.4
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    • pp.467-474
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    • 2010
  • Stainless steel sheets are widely used as the structural material for railroad cars and commercial vehicles. Structures made of stainless steel sheets are commonly fabricated by gas welding, For the fatigue design of gas welded joints such as fillet joints, it is necessary to obtain design information of the stress distribution at the weldment as well as the fatigue strength of the gas-welded joints. Further, the influence of the geometrical parameters of gas-welded joints on stress distribution and fatigue strength must be evaluated. in this study, ${\Delta}P-N_f$ curves were obtained by fatigue tests. and, the ${\Delta}P-N_f$ curves were rearranged on the basis of the ${\Delta}{\sigma}-N_f$ relation for the hot-spot stresses at the gas-welded joints. These results, were used for conducting an accelerated life test(ALT) From the experiment results, an acceleration model was derived and factors were estimated. The objective is to obtain the information required for the analysis of the fatigue lifetime of fillet welded joints and for data analysis by the statistic reliability method to save time and cost and to develop optimum accelerated life prediction plans.

An Experimental Study on Fatigue Crack Growth Characteristics of Welded High-Strength Steels (용접구조용 고강도강재의 피로균열성장특성에 관한 실험적 연구)

  • Hong, Sung Wook;Kyung, Kab Soo;Nam, Wang Hyun;Jung, Young Hwa
    • Journal of Korean Society of Steel Construction
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    • v.14 no.6
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    • pp.773-782
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    • 2002
  • In this study, a series of fatigue tests are performed in order to estimate quantitatively the characteristics of fatigue crack growth rate according to the base metal, heat affected zone(HAZ) and weld metal, and the welding method and grade of strength of object steels, and the influence on fatigue crack growth rate according to the direction of welded line for high strength steels of SM570, POSTEN60, and POSTEN80 steels. From the fatigue test results, the retardations of fatigue crack growth rate are remarkable in case that the direction of notch is parallel to welded line than in case that the direction of notch is perpendicular to welded line because of compresive residual stress in weld metal & HAZ. And the characteristics of fatigue crack growth rate according to welding method are that the dispersion of fatigue crack growth rate in case of FCAW method is smaller than that of SAW method. Also, it knows that the fatigue crack growth rate converges in high stress intensity factor range. Meanwhile, fatigue safety is guaranteed sufficiently in the object steels because the fatigue crack growth rate in the range of fatigue crack propagation has a similar tendency to the test results & existing results.

A Study on the Optimum Shot Peening Condition for Al7075-T6 (AL7075-T6의 최적 쇼트피닝 조건에 관한 연구)

  • Jeong,Seong-Gyun;Kim,Tae-Hyeong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.7
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    • pp.63-68
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    • 2003
  • Shot peening process is most often used to improve the fatigue properties of metal parts, In order to achieve an optimum, repeatable, and reliable fatigue enhancement from the shot peening process, the important shot peening parameters must be optimized, In this paper, the optimum peening intensity(Almen intensity) condition is investigated by experiment. Rotary bending fatigue test has been adopted to investigate the effects of optimum peening on the fatigue characteristics, Experimental results show that the fatigue strength and fatigue life has been tremendously increased by optimum-peening treatment. However, the fatigue strength and fatigue life has been decreased by under or over peening.