• Journal of Industrial Technology
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• v.21 no.B
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• pp.213-222
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• 2001

In the study, the fatigue strength improvement and mechanism have been estimated by the Spot-Heating treatment on welded bead toes. For this, web-gusset specimens were made without residual stresses and the others with residual stresses imposed by Spot-Heating. The 4-point bending tests were performed in order to estimate the effect of spot-heating on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue test, fatigue strength of As-Welded specimen for non load-carrying fillet welded joints subjected to pure bending has satisfied the grade of fatigue prescribed in specifications of korea, AASHTO and JSSC. As compare with As-Welded specimen and Spot-Heating specimen have increased about 20% for the fatigue strength at $7.7{\times}10^6$ cycles. The Spot-Heating by reformation of the residual stress on welded bead toes has greatly affected the fatigue crack propagation life, but has slightly affected the fatigue crack initiation life.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.80-89
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• 1996

Fatigue life of a notched shaft was evaluated in order to estimate the durability and integrity of the notched shaft in design stage. Cumulative fatigue dama- ge analysis was performed using local strain approach based on the assumption that the fatigue life of a notched component is approximately same as that of a smooth specimen is subjected to the same strain at the notched component. In this paper, shafts with different notch root radius of 1, 2㎜ resulting in different values of stress concentration factors were tested under||rotating bending fatigue loading condition. Theoretical stress concentration factor for each notch type was calculated using finite element method. Fatigue life prediction program, FALIPS, written in C language was developed using the strain-life curve, and the local strain approach integrating Neuber's rule, cyclic stress-strain, and hysteresis loop equations. The fatigue life evaluated using the fatigue notch factor obtained from the experimentally determined fatigue strength showed very large scattering with nonconservatism, but the fatigue notch factors derived from the stress concentration factors and Peterson's equation reduced the considerablely accurate fatigue life evaluation within a factor of three.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.30-34
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• 2007

Structural integrity of railway vehicles should last for a long period against various and continuous fatigue loadings, and the carbody structures of railway vehicle are manufactured by applying multiform welding types for each material. Since the most of cracks are occurred and proceeded at the vicinity of welding area during the lifetime of carbody structure, the fatigue strength evaluation for welding area of carbody structure should have been carried out. Rotem Company has evaluated lifetime and fatigue strength of carbody structure according to the fatigue analysis based on the international standard and/or inner-official regulation. This study introduces the fatigue analysis method that we have evaluated and calculated the damages for the welding areas of carbody structure under various fatigue loading conditions using cumulative fatigue damage rule(Miner's rule) to verify whether the cumulative damage does exceed unity. This study contains the fatigue test of specimens to derive stress-life relations(S-N curve), sub-modeling analysis and the calculation of cumulative damages under fatigue loading. The fatigue analysis verifies the welding area shall be capable of withstanding under fatigue loading, identifies how critical area shall be selected and presents the principles to be used for design verification.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.76-82
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• 2002

In this study, the rotary bending fatigue test was carried out with low carbon steel(SM25C). The specimens were heat-treated in order to change the grain size, and investigated items are fatigue limit, small crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction according to the different grain size. The summarized result are as follows ; Fatigue limit of the smooth specimen was dependent upon the grain size. The fatigue crack initiation of the small grain size specimen was delayed more than that of the large grain size specimen. And the small cracks of small grain size specimen were distributed in the narrow region of the main crack circumference contrary to the large grain size specimen. The main crack was grown along the grain boundary having co-alliance with small cracks. The experiment material has quantitatively disclosed the possibility of fatigue life prediction because the fatigue crack propagation behavior is dependent upon the grain size.

• Journal of Korean Academy of Nursing
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• v.29 no.4
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• pp.755-765
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• 1999

Most people experience fatigue at some point in their lives, and they say the word ‘fatigue’ in their ordinary conversational speech. The ordinary word is used as a military or engineering term and has been studied in various different disciplines, such as ergonomics, physiology, psychology, medicine, and nursing. In spite of its widespread uses, however, fatigue has not been well defined. The term of fatigue Is thus often used with different meanings and is applied in diverse contexts that had led to a confusion of ideas. In people with cancer, fatigue is reported as a major distress. Despite the importance of fatigue in cancer patients, the phenomena of fatigue is poorly understood. Therefore, the purpose of the present study is to analyze the concept of fatigue in people with cancer. The process for the concept analysis was guided by Walker and Avant's conceptual analysis methodology. The identified attributes of fatigue in the present study were subjective feeling, lack of energy, sustenance, and multidimensions. The antecedents were cancer treatment and economic status. The consequences were decreased daily, vocational, leisure, and social activities, uncertainty, and difficulties in adjustment. Symptoms (pain, anorexia, and insomnia) and emotional disturbance were not clear whether they are antecedents or consequences. However, they are related with cancer related fatigue. Even though still in the beginning stage, instruments measuring cancer related fatigue have been developed by some nursing investigators.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.316-321
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• 2000

The role of fatigue on the surface damage of 5% chrome cold milling work roll is evaluated. Uniaxial and torsional fatigue tests are carried out, and the baseline data for fatigue life evaluation are established. An appropriate multiaxial fatigue parameter is developed from the fatigue data. Fatigue tests are also performed under compressive mean stresses, and a mean stress model is formulated. A computer program is developed to assess the interaction of fatigue and grinding of the roll. The fatigue damage is computed for selected servicing conditions. It is found that the fatigue damage can be an important issue when the effect of mean stress is ignored, however the fatigue damage is negligibly small when the effect of mean stress including the residual stresses currently used is fully accounted. The result indicates that spalling due to the growth of thermal shock cracks is more important than fatigue damage in roll surface failure.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.84-92
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• 1998

On this study, the variations of hardness and microstructure were observed at he spot-welded part of 5182 alminum alloy sheets with thickness of 1.2 mm. The hardness of spot-welded part of aluminum alloy indicated the lowest value at nugget center. Also, the position where fatigue crack exists was investigated by surveying microstructure of the spot-welded sections. Mean load-deformation diagrams were obtained from static tensile test. Fracture was occurred completely within 5 mm after transforming elastic into plastic area. Fatigue test was stopped when the specimens of fatigue test had the final displacement of 0.2mm and measured fatigue bending angle and crack length. This study utilized them, investigated the relations between fatigue bending angle and fatigue crack length and made a estimation of the fatigue fracture life of resistance spot welded part of 5182 aluminum alloy sheet. The relative equation o fatigue crack length and fatigue failure life can be represented by {TEX}$L_{C}${/TEX}=α{TEX}$N_{f}^ {β}${/TEX}.

• The Journal of Korean Physical Therapy
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• v.26 no.6
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• pp.425-429
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• 2014

Purpose: The first purpose of this study was to evaluate whether hand muscle fatigue alters sensorimotor control of the hand in healthy subjects, using hand position sense. The second objective was to assess the repositioning variables during a 7.5-min period after the fatigue protocol. Methods: Participants performed a repeated handgrip movement to induce the fatigue condition as fast as possible, until they could no longer continue. Recordings were performed before (pre-fatigue) and after the completion of the fatigue exercises (immediately: post-fatigue, after a 2.5 min recovery, after a 5 min recovery and after a 7.5 min recovery). Results: The joint reposition test of the MP joint in the post-fatigue condition showed higher reposition errors than the prefatigue condition (p<0.05). Additionally, there was a significant difference in recovery of joint reposition errors after fatiguing exercises of the hand muscle, among groups (p<0.05). Conclusion: The fatigue of the hand muscles affected joint position sense by an alteration of somatosensory and proprioceptive information. Nonetheless, the effect of hand muscle fatigue was short-lived, since joint reposition errors decreased to post-fatigue values after 7.5 min of recovery.

• Steel and Composite Structures
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• v.33 no.3
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• pp.433-444
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• 2019

Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High-Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.

• The Journal of Korean Medicine
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• v.21 no.4
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• pp.55-63
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• 2000

Objectives : Fatigue is a common symptom experienced by everyone. Nevertheless, clinicians have a tendency of ignoring it since fatigue itself is not considered a distinct disease. Actually, some limited research about chronic fatigue syndrome has been made within the country, but in reality, the probability of getting this syndrome is still considered very low due to the strict diagnosis standard. Therefore, there are tremendous numbers of patients who do not get enough attention from clinicians for their fatigue symptoms only because technically they do not belong to the syndrome. Therefore, a basic statistical database must be compiled and patient management programs must be developed. To accomplish this, we conducted this study by measuring degree of fatigue, clinical characteristics and processes of Oriental medical treatment of fatigue patients. Methods : The objects of this study were selected from the new patients who entered the tonification Clinic in Kynnghee Oriental Medical Center between August 11, 2000 and October 7, 2000. Their main complaint was fatigue and they did not suffer from any physical or mental problem either historically or at the time of the study. The objects were divided into two groups based on duration of fatigue; fatigue under 6 months is considered as acute fatigue and fatigue for longer than 6 months is chronic fatigue. The prepared survey sheet for measuring fatigue degree was distributed to the patients with their consent. The patients were divided again into three subgroups : the fIrst group went through 1st test and constitution test after tonification clinic; the second one went into constitution test skipping Ist measuring test; the third one went into only tonification clinic with neither 1st measuring test nor constitution test. Results : The total number of object patients was 47 and 80% of them were considered as 'fatigue patients' by the Chalder scale. Among all patients, 29.5% requested treatment for chronic fatigue, which is over 6 months. The average of scale II for all patients was 14.8, which indicates moderate fatigue. The averages of scale II-1, II-2, II-3 were respectively 7.5, 5.9, and 3.7 so the most common complaint was physical fatigue. When compared scale II based on occupations, student group scored 6.9 and office man group scored 8.5 in scale II-1, physical fatigue, but it was not significant. Conclusions : Numerous number of patients have come to Oriental medical centers or hospitals in Korea. Therefore, deeper statistical research and follow-up-monitoring are reqnired in the Oriental medical academic world. In this study, among all patients who entered the tonification Clinic in Kyunghee Oriental Medical Center, 29.5% requested treatment for chronic fatigue, which is over 6 months. This kind of statistical report is the first time trial in the Oriental medical academy world. Through these steps, more objective treatment can be made and standards of prognosis assessment can be established.tablished.