• Title/Summary/Keyword: Fatigue

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Study on Fatigue Damage Model and Multi-Stress Level Fatigue Life Prediction of Composite Materials (II) -Fatigue Damage Model using Reference Modulus- (복합재료의 피로손상 모형 및 다응력 수위 피로수명 예측 연구 (II) - 참고계수를 이용한 피로 손상 모형 -)

  • 이창수;황운봉;한경섭
    • Composites Research
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    • v.12 no.2
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    • pp.62-69
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    • 1999
  • During fatigue loading of composite materials, damage accumulation can be monitored by measuring their material properties. In this study, fatigue modulus is used as the damage index. Fatigue life of composite materials may be predicted analytically using damage models which are based on fatigue modulus and resultant strain. Damage models are propesed as funtions of applied stress level, number of fatigue cycle and fatigue life. The predicted life was comparable to the experimental result obtained using E-glass fiber reinforced epoxy resin materials and pultruded glass fiber reinforce polyester composites under two-stress level fatigue loading.

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Fatigue performance assessment of welded joints using the infrared thermography

  • Fan, J.L.;Guo, X.L.;Wu, C.W.
    • Structural Engineering and Mechanics
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    • v.44 no.4
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    • pp.417-429
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    • 2012
  • Taking the superficial temperature increment as the major fatigue damage indicator, the infrared thermography was used to predict fatigue parameters (fatigue strength and S-N curve) of welded joints subjected to fatigue loading with a high mean stress, showing good predictions. The fatigue damage status, related to safety evaluation, was tightly correlated with the temperature field evolution of the hot-spot zone on the specimen surface. An energetic damage model, based on the energy accumulation, was developed to evaluate the residual fatigue life of the welded specimens undergoing cyclic loading, and a good agreement was presented. It is concluded that the infrared thermography can not only well predict the fatigue behavior of welded joints, but also can play an important role in health detection of structures subjected to mechanical loading.

A Study on Corrosion Fatigue Characteristics Based on Welding Methods of Structural Steel (구조용강의 용접방법에 따른 부식피로특성 연구)

  • Park, Keyoung-Dong;Ryu, Hyoung-Ju
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.5 no.3
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    • pp.58-64
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    • 2006
  • The security of stability for fractures of all sorts of parts and structure has become a first subject these days. We have need to organize fatigue characteristics of weldment because fatigue break out suddenly without a change of shape. In this study, we execute the fatigue test according to different of the welding method at the same materials. It was investigated about a fatigue limit according to welding methods of SMAW, FCAW and SAW at normal temperature and a frequency of 10Hz. The important results of the experimental study on fatigue characteristics of weldment are as follows: The fatigue limit of welding methods became low in the order of SMAW, FCAW, SAW.

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Fatigue Life Evaluation of the Plastic Gear (플라스틱 기어의 피로수명 평가 및 수명 예측)

  • Chong Tae Hyong;Kang Sung Kyu;Ha Young Wook
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2005.05a
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    • pp.239-245
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    • 2005
  • Through the fatigue test of plastic gears using polyacetal polymer, this research aims at providing basic data for not only specifying operation conditions of plastic gears, but also designing dimensions of plastic gears with giving fatigue life and the estimated equation of fatigue life of plastic gears. That is, from the fatigue life curves, the estimated equation of fatigue life of plastic gears is taken out. For the estimated equation of fatigue life of plastic gears, this research provides two test methods; one is preserving non-limited temperature of tooth flank, the other is preserving limited temperature of tooth flank. As results, how the temperature of tooth flank affects the fatigue life is shown. In addition, based on the endurance limit, the essential factors of the unit load and K-factor are determined, which are needed in the design of gear by bending strength and surface durability.

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Fatigue and Its Related Factors in Korean Patients on Hemodialysis

  • Kim Hye-Ryoung;Son Gwi-Ryung
    • Journal of Korean Academy of Nursing
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    • v.35 no.4
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    • pp.701-708
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    • 2005
  • Purpose. This study examined the characteristics of fatigue and the relationship between fatigue and its related factors in Korean patients on hemodialysis. Methods. A cross-sectional correlational study was conducted with 104 patients on hemodialysis in Seoul, Korea. Finding. Of a total of 104 subjects, eighty-one ($77.9\%$) complained of fatigue. Fatigue severity was measured by the self-rating Visual Analogue Scale-Fatigue (VAS-F) with a mean score of 36.5 (SD = 17.49, range 2 - 81). The mean duration of fatigue was 3.8 hours (SD = 5.3, range 0 - 24). Depression was most significantly correlated with fatigue (beta = .43, p<.00), with interdialytic weight gain (beta = .25, p<.05) being the second most significant correlate. Conclusion. This study shows that nursing interventions for patients who experience fatigue while on hemodialysis should be focused on both psychological problems, such as depression, as well as on physiological problems, such as interdialytic weight gain.

An Experimental Study on the Safety of Glass Fiber Reinforced Plastic Pipes under Fatigue Load (피로하중을 받는 유리섬유 보강 플라스틱관의 안전성에 관한 연구)

  • 채원규
    • Journal of the Korean Society of Safety
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    • v.11 no.3
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    • pp.154-159
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    • 1996
  • In this thesis, a series of loading tests are conducted in order to investigate the fracture safety of GFRP(Glass Fiber Reinforced Plastics) pipes under fatigue load which are widely used in the developed countries becauses of their natural of anticorrosion and lightweight etc. . Fatigue test is performed by changing number of laminates and loading cycles to examine the flexural strains, the ductility and the fatigue strength for two million repeated loading cycles. From the fatigue test results, it was found that the larger the laminates of GFRP pipes is, the larger the stiffness of GFRP pipes under the fatigue load increases. This phenomenon is true until the fatigue failure. According to the S-N curve drawn by the regression analysis on the fatigue test results, the fatigue strength of percent of the static ultimate strength increases by increasing the laminates of GFRP pipes. The fatigue strength with two million repeated leading cycles in GFRP pipes with the laminates of GFRP pipes varing 15, 25, 35 shows about 75%, 80%, 84% on the static ultimate strength, respectively.

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Numerical Analysis Model for Fatigue Life Prediction of Welded Structures (용접구조물의 피로수명예측을 위한 수치해석모델)

  • Lee, Chi-Seung;Lee, Jae-Myung
    • Journal of Welding and Joining
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    • v.27 no.6
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    • pp.49-54
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    • 2009
  • In this study, the numerical analysis model for fatigue life prediction of welded structures are presented. In order to evaluate the structural degradation of welded structures due to fatigue loading, continuum damage mechanics approach is applied. Damage evolution equation of welded structures under arbitrary fatigue loading is constructed as a unified plasticity-damage theory. Moreover, by integration of damage evolution equation regarding to stress amplitude and number of cycles, the simplified fatigue life prediction model is derived. The proposed model is compared with fatigue test results of T-joint welded structures to obtain its validation and usefulness. It is confirmed that the predicted fatigue life of T-joint welded structures are coincided well with the fatigue test results.

An Evaluation of Bending Fatigue Strength for Cold Forged Bevel Gear (냉간단조 베벨기어의 굽힘피로강도 평가)

  • 김재훈;사정우;김덕회;이상연
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.1
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    • pp.61-67
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    • 2000
  • Gears are the most commonly used parts in automotive and industrial applications. One of most common modes of gear failures is tooth breakage, which is usually produced by the bending fatigue failure. It is important to manufacture the gears which can withstand the applied stresses in view of safety and economic requirement. This paper deals with bending fatigue strength for cold forged bevel gear. Especially, to compare fatigue characteristics for manufacturing processes difference, bending fatigue tests of bevel gears made by three different processes respectively. Results indicate that the fatigue strength of bevel gear is improved by cold forging process. Intergranular fracture is found on fatigue fracture surface, and dimples are observed on final fracture surface. The fatigue failure cannot be considered as a deterministic quantity, but must be characterized statistically. This study proposes a method to estimate bending fatigue lift of the bevel gear using the probability-load-life and Weibull analysis.

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Reliability analysis on fatigue Strength for Certification of Aircraft Composite Structures

  • Choi, Cheong Ho;Lee, Doo Jin;Jo, Jae Hyun;Bae, Sung Hwan;Lee, Myung Jik;Lee, Jong Ho
    • Journal of Aerospace System Engineering
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    • v.15 no.2
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    • pp.16-25
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    • 2021
  • Reliability of fatigue strength on Aircraft Composites(GFRP) Structures was assessed in this paper. Fatigue strength of GFRP was used through the existing fatigue test data with Monte Carlo method. The Sa-Nf curve of composites fatigue strength was assumed as normal distribution and reliability was analyzed using SSIT model. Fatigue stress was designed IAW ASTM F3114-15 with special safety factor of Ssf=1.2~2.0. Reliability was calculated by analytic method and FORM. Sensitivity for the effect of mean and standard deviation of fatigue strength as well as fatigue stability was evaluated. This result can be usefully applied to reliability and fatigue design for composite structures of light weight aircraft.

Speculation of the Correlationship between Public Health Practice, Consumption and Fatigue in Patients who Complain Fatigue (피로를 주소로 내원한 환자의 생활섭생, 허손 및 피로의 상관성에 대한 고찰)

  • Kim, Se-Hoon;Lee, Jang-Hoon;Lee, Seung-Bo;Choi, Mi-Young;Kim, Young-Chul;Woo, Hong-Jung
    • The Journal of Internal Korean Medicine
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    • v.29 no.1
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    • pp.219-230
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    • 2008
  • Objectives : Consumption is a chronic wasting disease, in oriental medicine concept. Fatigue is a common symptom experienced by many people who have consumption. However, there has been little study about the relationship between consumption and fatigue in the Oriental medicine. For this reason, we attempted to investigate the present status of fatigue of outpatients, and its relation with consumption index, public health practice index, Chalder fatigue scale and Subjective Symptoms of Fatigue Test. Methods : The subjects were 149 outpatients who complain fatigue between Nov. 1, 2006 and Oct. 31, 2007. We measured degree of consumption by consumption index. We measured degree of fatigue by Chalder fatigue scale and Subjective Symptoms of Fatigue Test. Public health practice were investigated by "Breslow's 7 health practice". Results : Studies have shown that a group who disregard public health practices have higher numerical value, in part of $q\grave{i}-x\bar{u}$, $xu\grave{e}-x\bar{u}$, and Physical symptoms than a group more concerned with public health practice. A group who has fatigue for a period over 6 months are more likely to be $q\grave{i}-x\bar{u}$, $y\bar{i}n-x\bar{u}$, Chalder fatigue scale, neuro-sensory symptoms than a group fatigued for less than 6 months. Among the subjects, 81 (55.5%) were considered as 'fatigue patients' by the Chalder scale. Chalder fatigue scale, according to the Subjective Symptoms of Fatigue Test, consumption also, The more increase of Subjective symptoms of fatigue test, the more of consumption scale. Conclusions : This study has shown that there is a link between consumption and fatigue. Moreover, oriental medicine's consumption is more concrete than fatigue scale, so consumption index will have wide application to the study of fatigue.

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