• Title/Summary/Keyword: fatigue design

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Effects of Aroma Inhalation on Fatigue and Sleep Quality of Postpartum Mothers

  • Lee, Sung-Hee
    • Women's Health Nursing
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    • v.10 no.3
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    • pp.235-243
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    • 2004
  • Purpose: The purpose of this study was to measure the effects of aroma inhalation on fatigue and quality of sleep of postpartum mothers. Method: The study design was a non-equivalent control group pre-post design. 51 Postpartum mothers were assigned either to a control group or to an experimental group that was exposed to aromas through inhalation for 6 days. Subjects in the experimental group were instructed to wear a necklace filled with Lavender and Eucalyptus oil from 2:00 PM to 8:00 PM every day. Fatigue was measured using the Rhoten Fatigue Scale. Sleep duration, night arousal frequency and sleep satisfaction were used to assess the quality of sleep. Result: There was a significant difference in the score of fatigue following the treatment between the experimental and control groups (t=-2.79 p=.00). However, there was no significant difference in sleep duration, frequency of night arousal and sleep satisfaction following aroma inhalation between two groups. Conclusion: This intervention appears to be effective in reducing the fatigue in postpartum mothers.

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Study on aircraft fatigue life substantiation method (항공기 피로수명 입증방법 연구)

  • Kim, Sung Joon;Kim, Tae-Uk
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.24 no.1
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    • pp.41-46
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    • 2016
  • This paper reviews and summarizes overall fatigue substantiation method of aircraft. The fatigue substantiation method has been studied using the related regulation and examples of industry application. And the comparisons of fatigue substantiation procedure between safe-life and damage tolerance design have been performed. Fatigue substantiation methods have wide variability depend on design methodology and type of aircraft such as fixed wing and rotorcraft. In this study, fatigue substantiation methodologies have been reviewed using analysis and test methods.

Fatigue Life Prediction of Suspension Knuckle by CAE Technology (CAE 기법을 이용한 서스펜션 너클의 피로수명 평가)

  • Kim, Y.J.;Suh, M.W.;Suh, S.M.;Suh, J.H.;Kim, J.J.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.3 no.2
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    • pp.112-121
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    • 1995
  • Various CAE technologies are used in automobile industries for the purpose of design and analysis. In this paper, a fatigue life evaluation system FLEVA based on the local strain approach is developed and the system is applied for the fatigue strength design of the suspension knuckle, an automobile component. Various steps such as material test, finite element analysis and cumulative fatigue damage analysis of the suspension knuckle were taken. The usefulness of the approach was verified by the fatigue test on the suspension knuckle.

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Fatigue experiment of stud welded on steel plate for a new bridge deck system

  • Ahn, Jin-Hee;Kim, Sang-Hyo;Jeong, Youn-Ju
    • Steel and Composite Structures
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    • v.7 no.5
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    • pp.391-404
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    • 2007
  • This paper presents push-out tests of stud shear connectors to examine their fatigue behavior for developing a new composite bridge deck system. The fifteen push-out specimens of D16 mm stud welded on 9 mm steel plate were fabricated according to Eurocode-4, and a series of fatigue endurance test and residual strength test were performed. Additionally, the stiffness and strength variations by cyclic loading were compared. The push-out test, when the stiffness reduction ratio of the specimens was 0.95 under cyclic load, resulted in the failure of the studs. The stiffness variation of the push-out specimens additionally showed that the application of cyclic loads reduced the residual strength. The fatigue strength of the shear connectors were compared with the design values specified in the Eurocode-4, ASSHTO LRFD and JSSC codes. The comparison result showed that the fatigue endurance of the specimens satisfies the design values of these codes.

Fatigue Design and Fatigue Strength Evaluation of Bogie Frame (대차프레임의 피로설계 및 피로강도 평가)

  • 이상록;이학주;한승우;김정엽;차정환;강재윤;박찬경
    • Proceedings of the KSR Conference
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    • 2000.05a
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    • pp.234-241
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    • 2000
  • Stress analysis of the bogie frame by using the finite element method has been performed for the various loading conditions according to the results of vehicle dynamics analysis. Multiaxial fatigue analysis methods such as signed von Mises method, and typical critical plane theories were reviewed, and margin of safety for fatigue is defined. Multiaxial fatigue analysis program to predict the margin of safety of bogie frame under non-proportional loading conditions has been developed by using a commercial command language. Fatigue analysis of bogie frame under multiaxial loading was performed through this program and finite element analysis result. The procedure developed in this study is considered to be useful for the fatigue strength analysis in preliminary design stage of railway components under multiaxial loading condition.

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Patterns and Characteristics of Fatigue Failure in Cruciform Fillet Weld Joint (십자형 필릿 용접부에서의 피로파괴 형상과 특성)

  • Lee, Yong-Bok;Chung, Joon-Ki;Park, Sang-Heup
    • Journal of Welding and Joining
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    • v.29 no.4
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    • pp.67-72
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    • 2011
  • The proportion of the welding in the production process of machinery, buildings and marine structures is increasing and the joining are mainly conducted by butt and fillet weld. In the case of fillet weld, the shape of structures is complicated depending on the constraint on the geometry of the structures, therefore, the full penetration is mostly difficult. Accordingly, it is necessary to establish safe and economical criteria of design of the structures through the strength based on the penetration state of the fillet weld. Patterns of fatigue failure in cruciform fillet weld jont appear in the form of the root, toe and mixed failure. In the case of toe and mixed failure, the fatigue strength is higher than root failure. Therefore, we have to make the enough depth of penetration or perform the welding work through improving the fatigue strength of cruciform joints in welded structures. So it is necessary to optimize the penetrated depth in the range of the possible mixed failure and find the way in the cost-effective design to lessen the amount of the welding work.

Shape Optimization Considering Fatigue Life of Pulley in Power-Steering Pulley (파워스티어링 오일펌프용 풀리의 피로수명을 고려한 형상최적화)

  • Shim, Hee-Jin;Kim, Jung-Kyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.9 s.252
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    • pp.1041-1048
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    • 2006
  • The pulley is one of core mechanical elements in the power steering system for vehicles. The pulley operates under both the compressive loading and the torque. Therefore, to assure the safety of the power steering system, it is very important to investigate the durability and the optimization of the pulley. In this study, the applied stress distribution of the pulley under high tension and torsion loads was obtained by using finite element analysis. Based on these results the fatigue life of the pulley with the variation of the fatigue strength was evaluated by a durability analysis simulator. The results at 50% and 1% for the failure probability were compared with respect to the fatigue life. In addition to the optimum design for the fatigue life is obtained by the response surface method. The response function utilizes the function of the life and weight factors. Within range for design life condition the minimization of the weight, one of the formulation, is obtained by the optimal design. Moreover the optimum design by considering its durability and validity is verified by the durability test.

An Experimental Study of fatigue Strength of Welded Structures Using Structural Stress and Hot Spot Stress (구조응력 및 핫스팟응력을 이용한 피로수명 평가에 관한 실험적 연구)

  • Kang, Sung-Won;Kim, Myung-Hyn;Kim, Seok-Hun;Ha, Woo-Il
    • Journal of the Society of Naval Architects of Korea
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    • v.42 no.2 s.140
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    • pp.129-135
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    • 2005
  • At present, fatigue design of welded structures is primarily based on a nominal stress or hot spot stress approach with a series of classified weld S-N curves. Although well accepted by major industries, the nominal stress based fatigue design approach is cumbersome in terms of securing a series of S-N curves corresponding to each class of joint types and loading modes. The hot spot stress based fatigue design has a difficulty of finding a proper stress through the global model, the midium size model, and the detail model of ship structure. Also, it is difficult to link proper displacements within three different mesh size models. Recently, the structural stress is proposed as a mesh-size insensitive structural stress definition that gives a stress state at weld toe with relatively large mesh size. However, this method requires an experimental validation in obtaining the fatigue strength of weldments. Therefore, in this study, a series of experiment is performed for various sizes of weldments.

FATIGUE DESIGN FORSUS30IL SPOT-WELDED MULTI-LAP JOINTS SUBJECTED TO TENSILE SHEAR LOAD

  • Na, T.H.m;Jung, W.S.;Bae, D.H;I.S.Shon
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.121-126
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    • 2002
  • The railroad cars or the commercial vehicles are generally manufactured by the spot welding. Among various kinds of spot welded lap joints, multi-lap joints are one of popular joints in manufacturing their body structures. But, fatigue strength of these joints are lower than that of base metal due to high stress concentration at the nugget edge of the spot weld and are known to considerably be influenced by welding conditions as well as the mechanical and geometrical factors. Thus, it is necessary to establish a reasonable and systematic fatigue design criterion for spot welded multi-lap joints. In this paper, the $\Delta$P-N$_{f}$ curves has been rearranged in the $\Delta$$\sigma$-N$_{f}$ relation with the maximum stress at the nugget edge of spot welded multi-lap joints subjected to tensile shear load. Consequently, the fatigue data were evaluated in terms of fracture mechanics by plotting on the $\Delta$OP-N$_{f}$ curves. From the results obtained, both of them have been revealed to be applicable to fatigue design of spot welded multi-lap joints. However, the fracture mechanical approach is found to be more effective than the maximum stress approach in the range on N$_{f}$$\geq$2x10$^{5}$ . .

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Assessment and Recommendation of Fatigue Design Codes for Stud Shear Connectors in Composite Bridge (강합성 교량 스터드 전단연결재의 피로 설계식 평가 및 제안)

  • Lee, Kyoung-Chan;Yoon, Ki-Yong
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.5
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    • pp.15-21
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    • 2009
  • The design of the stud shear connector of a bridge structure is mostly controlled by the fatigue resistance not by the strength, if it is followed by AASHTO LRFD Bridge Design Specification. This fatigue design code in AASHTO LRFD is based on the research work done by Slutter and Fisher in 1966. These tests seemingly underestimated the fatigue resistance of connectors because of the inherent eccentricity of the one-face test setup which results additional tension forces to the stud. In addition, the stress ranges were not plotted in the log scale, because it was not known at that time that the fatigue resistance of the welded steel structures has a linear relationship of log scales of stress range and number of loading cycles. This study evaluates the test data produced by the Slutter and Fischer, and plot the data on the proper manner. The fatigue push-out test data produced recently by many other researches all around the world are gathered and analyzed, furthermore a design curve is recommended.