• Journal of Welding and Joining
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• 제9권1호
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• pp.40-47
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• 1991

The most fatigue tests carried out under the either stress or strain control, but machines and structures had taken variable stress. This variable stress was treated as statistics based on p-type distributions. In this paper, the cumulative fatigue damage of SM45C round bar specimens having a center hole resulting from block loading with p-distributions in rotating bending conditions, is presented. The value of p was changed in the range from 0.25 to 1; 0.25, 0.5, 0.75, 1. The following conclusions were obtained through the constant stress amplitude experiments and the block loading experiments. (1) In constant loading test, fatigue life was affected by cyclic rate. From experimental data, N$_{f}$ (100cpm)/N$_{f}$(3000cpm)equal to 0.56. (2) In case of the cyclic rate 100cpm and 3000cpm, at the high stress amplitude level the crack propagation life N$_{*}$f is longer than the low stress amplitude level. (3) Miner's hypothesis may be valid for p=0.75 and prediction of fatigue life by Haibach's method agree with experimental data well for the case p=0.5, while the modified Miner's method agree with experimental data well for the case p=0.25.5.

• 한국해양공학회지
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• 제12권1호
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• pp.32-38
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• 1998

This paper is to investigate of microhardness, adhesive strength, tensile strength, and fatigue strength of ceramic sprayed steel. Rotary bending fatigue tests have been conducted at room temperature in air and 3% NaCl solution using specimens of carbon steel(S45C) with sprayed coating layers of Ni-4.5% Al(under coating) and $TiO_2$ (top coating). The microhardness has been improved at $800^{\circ}C$ heat treatment and 150mm spraying distance. Tensile strength of the sprayed steel is dependent on the substrate strength. The fatigue strength of the sprayed steel is larger than that of substrate due to blasting and constraint surface of plastic deformation effect. In low stress level, the corrosion fatigue strength of the sprayed steel were lower than that of fatigue strength in air by corrosion.

• 대한기계학회논문집A
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• 제22권1호
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• pp.142-147
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• 1998

Rotary bending fatigue tests were carried out on the nitrided titanium in order to investigate the effect of nitriding layer on fatigue limit. Main results obtained are as follows. (1) The fatigue limit of nitrided pure titanium is remarkably reduced because of enlargement of grain size at high heat treating temperature and high stress field created from the elastic interaction in the compound layer. (2) Further test using specimen which was removed nitrified layer gradually, were also conducted and it was found that by removing the compound layer the fatigue limit recovered as the level of basic material and rather increased by coming of a diffusion layer. Therefore it is concluded that the surface compound layer generated by nitriding treatment reduced the fatigue limit but diffusion layer increased it.

• 한국재난정보학회 논문집
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• 제6권2호
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• pp.119-130
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• 2010

In designing a railroad bridge, the fatigue is one of the main factors to be considered for ensuring safe operation. Especially, for a new type of a structural member, which has not been adopted to railroad bridges, the fatigue performance should be checked. In this paper, the fatigue characteristics of an IT girder are examined. The IT girder is a new type of a prestressed concrete girder which has two prestressed H-beams in the top of the girder to give the girder additional sectional capacity. To obtain the fatigue performance, a 10m IT girder specimen is designed, and a repeated load test is performed by applying the load cyclically two million times. The magnitude of the repeated load is determined considering the stress level under the service condition. During the test, static load tests are performed to identify the stiffness degradation. The fatigue performance of the girder is checked according to the Japanese and the CEB-FIB design codes. The fatigue test result shows that the IT girder satisfies both design codes.

• 지역사회간호학회지
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• 제22권4호
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• pp.458-464
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• 2011

Purpose: The purpose of this study was to investigate the effect of cardiopulmonary symptoms and sleep on fatigue in pneumoconiosis patients. Methods: Self-administered questionnaires were given to 211 neumoconiosis patients during the period from May 12 to May 20, 2010. Results: The mean score of fatigue was as high as 6.7. The level of fatigue depended on the subjects' leisure activity and complication. Fatigue was significantly correlated with cardiopulmonary symptoms and sleep. The influential factors affecting fatigue were cardiopulmonary symptoms, complication, sleep and leisure activity, which explained about 46.5% of the variance. Conclusion: The results of this study indicate that nursing interventions are needed to reduce fatigue and to improve cardiopulmonary symptoms and insomnia in pneumoconiosis patients.

• 한국재난정보학회 논문집
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• 제6권1호
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• pp.140-152
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• 2010

In designing a railroad bridge, the fatigue is one of the main factors to be considered for ensuring safe operation. Especially, for a new type of a structural member, which has not been adopted to railroad bridges, the fatigue performance should be checked. In this paper, the fatigue characteristics of an IT girder are examined. The IT girder is a new type of a prestressed concrete girder which has two prestressed H-beams in the top of the girder to give the girder additional sectional capacity. To obtain the fatigue performance, a 10m IT girder specimen is designed, and a repeated load test is performed by applying the load cyclically two million times. The magnitude of the repeated load is determined considering the stress level under the service condition. During the test, static load tests are performed to identify the stiffness degradation. The fatigue performance of the girder is checked according to the Japanese and the CEB-FIB design codes. The fatigue test result shows that the IT girder satisfies both design codes.

• 산업경영시스템학회지
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• 제35권2호
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• pp.30-36
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• 2012

This study is aimed to show that an asymmetric load in the frontal plane leads to an increase in low back loading and fatigue in comparison with a symmetric load when workers lift an external weight by investigating previous studies and verifying the phenomenon with an experiment. Ten male subjects are required to lift and hold an given external load at 70cm height during 50sec, then the EMG amplitude and median frequency on bilateral low back muscle groups (Longissimus, Iliocostalis, and Multifidus) are recorded and analyzed. Independent variables are two-level load weight (13kg, 20kg) and three-level LCG (Center, 6.5cm to the right, and 13cm to the right), and dependent variables are EMG amplitude average, difference, and Fatigue Index (FI). Results show that load weight increases significantly amplitude average and FI, but LCG does significantly amplitude difference and FI significantly (P-value < 0.05). Also the correlation coefficient between amplitude difference and FI is over 0.99. These implies that trunk loading should be explained by not EMG amplitude but muscle fatigue aspect since the association between an external load and amplitude is linear, but the relationship between an external load and median frequency as muscle fatigue index is almost exponential.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.101-107
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• 1996

In this study, the wedge splitting test (WST) specimens with various strength levels were tested to investigate the fatigue crack growth behavior of concrete. Selected test variables were concrete compressive strength with 2 levels (28 MPa, 60 MPa, 100 MPa) and maximum fatigue loading with 2 levels (75%, 85%). Fatigue testing was preceded by fracture energy test and the crack growth was measured by means of the compliance calibration method, 60 WST specimens were cast for the fatigue test, and 6 companion cylinders ($\phi$100${\times}$ 200 mm) for each batch. In fatigue test, the frequency of loading cycle was 1 Hz, and the minimum fatigue loading level was 5~10 % of ultimate monotonic loading. On the basis of the experimental results, a fracture mechanics-based empirical relationships for fatigue crack growth rate (da/dN-$\Delta$KI relationships) were presented. In addition, the effect of initial notch depth on the fracture energy and the validity of compliance calibration technique for the WST were shown.

• 산업기술연구
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• 제26권A호
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• pp.69-73
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• 2006

Mach peening treatment is one of the various kinds of techniques to improve the fatigue properties. The mach peening process gives high-level work hardening and compressive residual stress near the surface layer, improving the fatigue strength. In addition, this treatment reduces slip bands that initiate the fatigue cracks near the surface. During impingement, a plastic indentation surrounded by a plastic zone is formed. Mach peening treatment characteristic is less energy consumption and is an environmental friendly processing methods that is not accompanied by pollution. It is machining process that can prevent fatigue fracture beforehand in structure using already as well as process of production. The test results showed that fatigue crack propagation delay appeared by drilling type 43%, mach peening type 110%.

• Journal of the Optical Society of Korea
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• 제19권1호
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• pp.38-44
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• 2015

Three-dimensional (3D) crosstalk is one of the main causes of visual fatigue and needs to be suppressed. The 3D crosstalk can be categorized into two different kinds according to its appearance-additive 3D crosstalk and subtractive 3D crosstalk. In this paper, we analyze the influence of different kinds of 3D crosstalk to the perceived level of visual fatigue in order to suppress the perceived 3D crosstalk effectively.