• Title/Summary/Keyword: fatigue response

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Fatigue Assessment of Very Large Container Ships Considering Springing Effect Based on Stochastic Approach

  • Jung, Byoung-Hoon;Ahn, In-Gyu;Seo, Sun-Kee;Kim, Beom-Il
    • Journal of Ocean Engineering and Technology
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    • v.34 no.2
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    • pp.120-127
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    • 2020
  • Evaluation of fatigue strength considering the springing effect of very large container ships is crucial in the design stage. In this study, we established a fatigue strength evaluation method considering a linear springing component in the frequency domain. Based on a three-dimensional global model, a fluid-structure interaction analysis was performed and the modal superposition method was applied to determine the hot spot stress at the hatch corner of very large container ships. Fatigue damage was directly estimated using the stress transfer function with a linear springing response. Furthermore, we proposed a new methodology to apply the springing effect to fatigue damage using hull girder loads. Subsequently, we estimated the fatigue damage contribution due to linear springing components along the ship length. Finally, we discussed the practical application of the proposed methods.

Fatigue Life Assessment of Journal Box Attached to Bogie under Multiaxial Random Dynamic Loading (다축 Random Dynamic 하중을 받는 대차 저널박스의 피로수명평가)

  • Park, Sang-Goo;Kim, Seung-Seob;Han, Sung-Wook;Park, Geun-Su;Woo, Kwan-Je
    • Proceedings of the KSR Conference
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    • 2009.05a
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    • pp.1125-1131
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    • 2009
  • This paper presents the evaluation of fatigue life for a journal box attached to rolling stock bogie under random dynamic loading condition. Because a journal box was under random dynamic loading conditions, the fatigue life assessment due to these loads requires the analysis considering the multiaxial effect of random dynamic loading. To do this work, the finite element analysis has been conducted to calculate random dynamic response using multiaxial acceleration data. Then, the fatigue life assessment of component has been conducted using vibration fatigue analysis applying the power spectral densities of the responses obtained through the FEA The results of fatigue life assessment were compared to the damage from the strain measurement. This study shows that can be evaluated the fatigue life assessment considering real service condition about a component attached to rolling stock bogie.

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Monitoring of Fatigue Damage of Composite Laminates Using Embedded Intensity-Based Optical Fiber Sensors (광강도형 광섬유 센서를 이용한 복합재 적충판의 피로손상 감시)

  • 이동춘;이정주;서대철
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2000.11a
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    • pp.124-127
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    • 2000
  • In this study, a technique for monitoring of fatigue damage of composite laminates by measuring the stiffness change using embedded intensity-based optical fiber sensors was investigated. Firstly, the underlying measurement principle and structure of intensity-based sensors and then a simple stiffness conversion process was explained. The monitoring technique was evaluated by fatigue tests of composite laminates with an embedded intensity-based sensor. From the test results, the response of the intensity-based sensor showed good correlation with that of surface mounted extensometer. Therefore, it can be concluded that the intensity-based sensors have good potential for the monitoring of fatigue damage of composite structures under fatigue loading. In addition, it could be confirmed that the intensity-based sensors have higher resistance to fatigue than the commercial electrical strain gauge.

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A Study on an Optimal Spot-weld Layout Design for a Shock Tower Structure Considering the Fatigue Life under Random Vibration Loads (불규칙 진동하중을 받는 쇽 타워의 피로수명을 고려한 점용접 위치 최적설계)

  • Lee, Yong-Hoon;Lee, Seung-Yoon;Bae, Bok-Soo;Lee, Sang-Beom;Yim, Hong-Jae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.9
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    • pp.798-804
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    • 2011
  • In this paper, optimal spot weld layout design for a shock tower structure is presented. This design increases the fatigue life of the spot-welds thereby increasing the fatigue life of the shock tower itself. In order to predict the fatigue life, a quasi-static analysis has been conducted then a fatigue analysis was performed through the application of random vibration loads. In order to optimize the spot weld layout, the design variables that have an effect on the spot weld fatigue life were determined. A spot weld fatigue analysis was then conducted based on the experiment design. Finally, a response surface model was made using the fatigue analysis results and an optimized spot weld layout model, one that increases the fatigue life of the spot welds and thereby the fatigue life of the shock tower, was developed.

Research Trends on Compassion Fatigue in Korea Nurses (간호사의 공감피로에 관한 국내연구동향)

  • Cho, Ho Jin;Jung, Myun Sook
    • Journal of muscle and joint health
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    • v.21 no.3
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    • pp.255-264
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    • 2014
  • Purpose: The purpose of the study were to analyze the research trends of compassion fatigue in Korea nurses and to suggest future research directions. Methods: For this study, RISS, KISTI, KISS, National Assembly Library databases were searched using the key words 'compassion fatigue', 'secondary traumatic stress', 'professional quality of life' that contains compassion fatigue as a sub-element, and 'nurses' for this study. A total of 124 articles published in June 2014 were searched and analyzed 19 articles for the final analysis. Results: The most frequently used study design was descriptive (N=17, 89.5%). High compassion fatigue was reported in this study. Factors affecting compassion fatigue were personal factors (e.g., age, health state, and sleep hours), work-related factors (e.g., experience with traumatized patients), and psychological factors (e.g., job stress, anxiety, excessive empathy, social support, and coping strategy). Finally, Consequence factors of compassion fatigue was reported burnout, silencing response and turnover intention. Conclusion: There was a few studies on compassion fatigue. Further research on compassion fatigue needs to use a variety of study designs instruments suitable for Korean nurses, and to develop management programs on compassion fatigue in nurses.

Analysis of Differences in Indoor Environment and Fatigue Response According to Ventilation in Lecture Hall (대형강의실의 환기여부에 따른 실내환경과 피로감 반응의 차이분석)

  • Oh, Ye-Seul;Hwang, Jin-A;Choi, Yoon-Jung
    • Korean Journal of Human Ecology
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    • v.19 no.2
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    • pp.417-428
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    • 2010
  • The purpose of this study was to analyze differences of the indoor environment and student's fatigue response according to ventilation in university lecture hall. The experiments consisted of measuring the indoor environmental parameters and a survey of student's responses. The experiments were in the lecture hall that the actual lecture was conducted in on the $25^{th}$ of May 2009 (not opening windows and door- A) and the $1^{st}$ of June 2009 (opening windows and door- B). The experimental variable was ventilation by opening the windows and door, and the controlled conditions were indoor temperature by air conditioner, volume of the microphone and VTR, lighting conditions and teaching method. The results are as follows: 1) The indoor temperature was maintained in controlling A, B but the $CO_2$ and relative humidity of A (average 3579ppm, 62.6%) was higher than B (average 1697ppm, 48.1%). 2) There were differences in the student's subjective responses and student's fatigue responses between A and B. 3) Therefore, it was found that ventilation by opening the windows and door was a valid way to improve the relative humidity and to reduce $CO_2$ in the lecture hall.

Response Surface Approximation for Fatigue Life Prediction and Its Application to Multi-Criteria Optimization With a Priori Preference Information (피로수명예측을 위한 반응표면근사화와 순위선호정보를 가진 다기준최적설계에의 응용)

  • Baek, Seok-Heum;Cho, Seok-Swoo;Joo, Won-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.2
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    • pp.114-126
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    • 2009
  • In this paper, a versatile multi-criteria optimization concept for fatigue life prediction is introduced. Multi-criteria decision making in engineering design refers to obtaining a preferred optimal solution in the context of conflicting design objectives. Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a response surface model, the compromise decision support problem, which is a multi-objective formulation based on goal programming. Examples illustrate the concepts and demonstrate their applicability.

Effects of the Nuegra from Male Silkworm Extract on Enhancement of the Masculine Function and Activation of Overall Physical Function

  • Kim, D. C.;Kim, Y. W.;Park, M. S.;J. K. Suh;Lee, D. S.;Lee, S. H.;B. H. Chun;Y. K. Jun
    • International Journal of Industrial Entomology and Biomaterials
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    • v.5 no.1
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    • pp.109-122
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    • 2002
  • The purpose of this investigation is to evaluate the effects of the Nuegra on enhancement of the masculine and physical activities in general through measuring changes of the testosterone, FSH and subjective symptoms like fatigue, insomnia, urinary stream, muscular weakness, libido and erectile dysfunction. Total 168 male subjects were enrolled from 12 urology, internal medicine clinics and general practitioner, During the 6-week investigational period, 2 capsules of Nuegra were given to the subjects right after meal for 4 weeks, and 1 capsule of Nuegra was added each time in subjects with no or minimal effect. Testoster-one and FSH levels were measured at first visit and last visit, for evaluating masculine activities. To avoid bias and standardize the test results, only one clinic was assigned as a central lab, and all blood samples were transferred. General information and subjective symptoms were evaluated at first visit and at 2 weeks interval, week 2, 4 and 6 using VAS (Visual Analogue Scale). The mean age of the subjects were 51.8${\pm}$8.2 years old (range: 36.1-82.1). Based on the subjects who were tested on testosterone and FSH levels at day l and week 6, the means were 4.4${\pm}$1.4 nmol/L (range: 2.6-7.7), 8.6${\pm}$9.6 mIU/mL (range: 0.3-40.4), respectively at day 1. At week 6, the results were 4.9 ${\pm}$1.6 (2.6-8.9 range), 9.4${\pm}$13.1 (1.0-53.9 range), respectively. Marginally significant difference between pre-dose and post-dose was present. Statistically significant differences were revealed in general assessment for subjective symptoms, fatigue, insomnia, erectile dysfunction, etc. In fatigue, response rates were 39.6, 65.4 and 76.4% at week 2, 4 and 6, respectively (P < 0.0001). Response vates for erectile dysfunction were 13.4, 41.2 and 72.7% at week 2, 4, and 6 (P < 0.0001), respectively, Response rates for libido were 13.6, 51.6 and 73.5% at week 2, 4, and 6 (P < 0.0001), respectively. For urinary stream response rates were 26.9, 44.7 and 66.8% at week 2, 4, and 6 (P < 0.0001), respectively. VAS for muscular weakness did not show significant results that response rates were 40, 60 and 80% at week 2, 4, and 6 from 8.2 (P = 0.24), respectively. Response rates for insomnia were 50, 60, 100% at week 2, 4, and 6 (P < 0.0001), respectively. The results shows that Nuegra tends to enhance masculine activities including libido, erectile dysfunction and urinary stream and also effective for improving general conditions especially insomnia, muscular weakness and fatigue. In conclusion, this investigation has demonstrated that Nuegra does not only have tendency to increase masculine activities through increased secretion of the testosterone and FSH but also improve general conditions such as erectile dysfunction, libido, fatigue and muscular power.

Fatigue Life Prediction of Fiber-Reinforced Composite Materials having Nonlinear Stress/Strain Behavior (비선형 변형 거동을 갖는 섬유강화 복합재료의 피로수명 예측)

  • 이창수;황운봉
    • Composites Research
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    • v.12 no.4
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    • pp.1-7
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    • 1999
  • Fatigue life prediction of matrix dominated composite laminates, which have a nonlinear stress/strain response, was studied analytically and experimentally. A stress function describing the relation of initial fatigue modulus and elastic modulus was used in order to consider the material nonlinearty. New modified fatigue life prediction equation was suggested based on the fatigue modulus and reference modulus concept as a function of applied stress. The prediction was verified by torsional fatigue test using crossply carbon/epoxy laminate tubes. It was shown that the proposed equation has wide applicability and good agreement with experimental data.

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Ultimate and fatigue response of shear dominated full-scale pretensioned concrete box girders

  • Saiidi, M. Saiid;Bush, Anita
    • Structural Engineering and Mechanics
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    • v.23 no.4
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    • pp.353-367
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    • 2006
  • Two full-scale, precast, pretensioned box girders were subjected to shear-dominated loading, one under monotonic loads to failure and the other subjected to one-half million cycles of fatigue loads followed by monotonic ultimate loads. The number of cycles was selected to allow for comparison with previous research. The fatigue loads were applied in combination with occasional overloads. In the present study, fatigue loading reduced the shear capacity by only six percent compared to the capacity under monotonic loading. However, previous research on flexure-dominated girders subjected to the same number of repeated loads showed that fatigue loading changed the mode of failure from flexure to shear/flexure and the girder capacity dropped by 14 percent. The comparison of the measured data with calculated shear capacity from five different theoretical methods showed that the ACI code method, the compression field theory, and the modified compression field theory led to reasonable estimates of the shear strength. The truss model led to an overly conservative estimate of the capacity.