• 한국도로학회:학술대회논문집
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• 2009.11a
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• pp.531-534
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• 2009

• Composites Research
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• v.34 no.2
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• pp.77-81
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• 2021

Due to the high specific strength and stiffness of the composite materials, the composite materials have been extensively used in various industries. In particular, carbon fiber reinforced composites are widely used in many mechanical structures. In addition, since carbon fiber reinforced composites have anisotropic properties, to understand the fatigue behavior of composites with different fiber orientation is very important for the efficient structural design. Therefore, in this paper, the effect fiber orientation on the fatigue life of composite materials was experimentally evaluated. For this purpose, tensile and fatigue tests were performed on the off-axis specimens (0°, 10°, 30°, 45°, 60°, 90°) of the composite materials. As a result of the fatigue tests, the fatigue strength of the composites decreased significantly as the fatigue strength slightly deviated from 0 degrees. On the other hand, the more deviated, the less decreased. This is because the role of supporting the load of fibers decreased as the stacking angle increased. In addition, the fatigue behavior was analyzed by introducing a fatigue strength ratio (Ψ) that eliminates the fiber orientation dependence of the off-axis fatigue behaviors on the unidirectional composites. The off-axis fatigue S-N lines can be reduced to a single line regardless of the fiber orientation by using the fatigue strength ratio (Ψ). Using the fatigue Ψ-N line, it is possible to extract back to any off-axis fatigue S-N lines of the composites with different fiber orientations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.260-268
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• 2016

The objective of this study was to investigate the relationship among the variables and effects of depression and physical activity on fatigue in the elderly with chronic disease. A descriptive research design was employed in this study. In total, 500 elderly patients diagnosed with chronic disease were selected from 3 medical centers for the study. The measurements were used to examine their general characteristics, fatigue, depression, and physical activity. To analyze the data, statistical analyses, including ANOVA, t-test, Scheffe's test, Pearson's correlation coefficient, and hierarchical regression analysis, were conducted for the analysis of the data. The results indicated that the age, gender, and educational level in the first step model explained 6% of the effect on fatigue among the elderly with chronic disease. In addition, depression and physical activity in the second step model explained 16% of the effect on fatigue. These findings demonstrate the significance of (considering) depression and physical activity related to care plans when developing health-programs for decreasing fatigue and planning intervention strategies.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.483-491
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• 2010

In this paper, ${\Delta}J$-integral is used to analyze fatigue crack growth of viscoelastic material. Using analytical integral value, the J-integral is calculated. So, reduction of calculation time and increase of accuracy are made possible. The stress intensity factor is calculated using the finite element method code. In difference with existed fatigue crack analysis using ${\Delta}K$, we were successfully able to analyze various load amplitude and the fatigue crack of load cycle only with two fatigue crack growth parameters and creep compliance. The analysis gives N-${\alpha}$ curve for simulation of crack growth, and the curve almost corresponds with test results.

• Journal of agricultural medicine and community health
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• v.33 no.1
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• pp.11-26
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• 2008

Objectives: We evaluated the level of psychosocial stresses and fatigue symptoms among clerical public officers and its related factors.Methods: The self-administered questionaires were performed, during the period between Dec. 5th, 2005 Metropolitan City. The survey items included subjects' socio-demographic and job-related characteristics, health-related behavior, degree of job demand, job autonomy, social support in work, type A behavior pattern, locus of control, sense of self-esteem, psychosocial distress and degree of fatigue.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.546-553
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• 2007

The objective of the present paper is to evaluate the effect of the evolution of contact surface profile by fretting wear on the contact stress distribution and fatigue crack initiation site of press-fitted shaft by means of an analytical method based on experimental data. A finite element analysis was performed to analyze the stress states of press-fitted shaft, considering the worn contact surface profiles of shaft. The evolutions of contact stress as wearing of contact surface were analyzed by finite element analysis and fatigue crack nucleation sites were evaluated by fretting fatigue damage parameter (FFDP) md multiaxial fatigue criteria. It is found that the stress concentration of a contact edge in press-fitted sha손 decreases rapidly at the initial stage of total fatigue life, and its location shifts from the contact edge to the inside due to fretting wear as increasing of fatigue cycles. Thus the transition of crack nucleation position in press-fitted shaft is mainly caused by stress change of a contact edge due to the evolution of contact surface profile by fretting wear. Therefore, it is suggested that the nucleation of multiple cracks on fretted surface of press fits is strongly related to the evolution of surface profile at the initial stage of total fatigue life.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.499-505
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• 2007

The major effective of this study is to investigate the fatigue effects of rail pad on High Speed Railway with concrete slab track system. It analyzed the mechanical behaviors of HSR concrete slab track with applying rail pad stiffness based on fatigue effect (hardening and increasing stiffness) on the 3-dimensional FE analysis and laboratory test for static & dynamic characteristics. As a result, the hardening of rail pad due to fatigue loading condition are negative effect for the static & dynamic response of concrete stab track which is before act on fatigue effect. The analytical and experimental study are carried out to investigate rail pad on fatigue effected increase vertical acceleration and stress and decrease suitable deflection on slab track. And rail pad based on fatigue effect induced dynamic maximum stresses, the increase of damage of slab track is predicted by adopting fatigue effected rail pad. after due consideration. The servicing HSR concrete slab track with resilient track system has need of the reasonable determination after due consideration fatigue effect of rail pad stiffness which could be reducing the effect of static and dynamic behavior that degradation phenomenon of structure by an unusual response characteristic and a drop durability.

• The Journal of the Korea Contents Association
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• v.21 no.9
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• pp.684-695
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• 2021

The purpose of this study was to identify the influence of compassion fatigue, compassion satisfaction and nursing organizational culture on burnout in integrated nursing care units nurses. The participants were 170 nurses working in integrated nursing care units of three general hospitals located in Seoul and Gyeonggi-do. Data were analyzed using independent t-test, ANOVA, Scheffé, Pearson's correlation and stepwise multiple regression analysis. Burnout was significantly different according to turnover intention, job satisfaction, health status. Burnout showed a positive correlation with compassion fatigue and a negative correlation with compassion satisfaction and relation oriented culture. Regression analysis revealed that compassion fatigue, compassion satisfaction, relation oriented culture and age were significant variables affecting the burnout, and the lower the age, the higher the burnout. Therefore, strategies to decrease compassion fatigue and to enhance compassion satisfaction and positive aspects of relation oriented culture for lower age nurses group are needed.

• Journal of Convergence for Information Technology
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• v.9 no.9
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• pp.258-268
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• 2019

The purpose of this study was to investigate the effects of stress factors on fatigue and depression of aesthetician. The subjects of this study were 133 Aesthetician in Busan Metropolitan City. Analysis was done by frequency analysis, t-test, one-way ANOVA and regression analysis. The results of this study are as follows. First, the aesthetician showed an average 2.57 of job stress. Second, the aesthetician showed an average 2.45 of socio-psychological stress. Third, the aesthetician showed an average fatigue(4.16) and depression(1.54). Therefore, in order to reduce the duties and socio-psychological stress of the aesthetician, fatigue and depression are reduced through regularization of the employees, adjustment of legal working hours, and establishment of similar paying system. Finally, it is necessary to lower the turnover rate of the aesthetician and increase the job satisfaction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.1-13
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• 2008

The web of a horizontally curved plate girder bridge is, in general, subject to not only longitudinal flexural in-plane stress but also out-of-plane bending stress. Therefore, the induced stresses in the fillet welded joints at the intersection of the web and flange plates in the curved plate girder bridge can be considerably high, and the welded joints of gusset plates connecting the main girder to the floor beams or sway bracings can be subject to much more severe situation than those in the ordinary straight plate girder bridge. In order to investigate the cause of fatigue crack occurred in a curved girder bridge that has been served in about 23 years, in this study, field load tests have been performed to obtain the stress characteristics at the welded joint under the real traffic flow. Using the test results, we have investigated the causes of the occurrence of various fatigue cracks and have estimated the fatigue lives for the cracks. In addition, the characteristics of structural behavior at welded joint of the curved girder bridge have been examined by comparing the FE analysis and the field test result.