• Journal of Ocean Engineering and Technology
• /
• v.17 no.2
• /
• pp.54-59
• /
• 2003

The characteristics of the parameters for the probability distribution of fatigue crack growth life, using the non-Gaussian random process simulation method is investigated. In this paper, the material resistance to fatigue crack growth is treated as a spatial random process, which varies randomly on the crack surface. Using the previous experimental data, the crack length equals the number of cycle curves that are simulated. The results are obtained for constant stress intensity factor range conditions with stress ratios of R=0.2, three specimen thickness of 6, 12 and 18mm, and the four stress intensity level. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Wiubull,, showing a slight dependence on specimen thickness and stress intensity level. The shape parameter, $\alpha$, does not show the dependency of thickness and stress intensity level, but the scale parameter, $\beta$, and location parameter, ${\gamma}$, are decreased by increasing the specimen thickness and stress intensity level. The slope for the stress intensity level is larger than the specimen thickness.

• Women's Health Nursing
• /
• v.11 no.2
• /
• pp.163-168
• /
• 2005

Purpose: This study was to identify the relationship between fatigue and sleep disturbance in adult women so as to provide basic data for developing a women's health promotion program and nursing intervention. Method: A convenience sample of 184 women who visited a Well-baby clinic at P city Maternal child center during October in 2004 was obtained. Data was collected by self-administered questionnaires. Results: The Subjects' mean age was 36.87 years and 70% were employed and had more education than high school. The mean level of fatigue was 56.65, mean sleeping hours were 6.54, and time until falling asleep was 17.58 minutes. Scores of fatigue differed by subject's age, level of education, and menstruation status. In addition, sleeping hours differed by age, occupation status, and income level. There were significant low levels of correlation between fatigue and sleeping hours (r=-.16) and getting up too early (r=-.15). Conclusion: This study concludes that fatigue and sleeping patterns have a significant relationship.

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.181-183
• /
• 2007

Experimental analysis was carried out to understand the fatigue phenomena of different thickness stainless steel overlap joining structure by Nd:YAG laser welding. The fatigue life was obtained through fatigue tests with the various levels of applied load. The fatigue life is related with the parameters such as gap condition and penetration depth through experiment. As the results, tensile and fatigue strength were proportional in heat input level and bead width was identified the major factor for joining strength. Also the fatigue life were decreased depend on gap condition, it was more affected at the low load level.

• Journal of Korean Society of Steel Construction
• /
• v.15 no.2
• /
• pp.137-145
• /
• 2003

In this study, direct tensile fatigue tests of the PS bar were performed in terms of diameter, minimum stress level, and maximum stress level. In the static test, the stress - strain curve and ultimate streng th of the PS bar were determined. Results of the fatigue test indicate that the diameter of the PS bar was not influenced by fatigue life. Minimum stress also had quite an influence on the fatigue of the PS bar. Thus, the fatigue characteristic equation was proposed in terms of stress range and minimum stress through statistical process. Strains on specimen that loaded direct tension were measured in the fatigue test, with the secant modulus of elasticity calculated from measured strains. The strain development consisted of three different stages, i.e., rapid increases during the initial fatigue life, uniform increases during the middle stage, and rapid increases until failure. The secant modulus of elasticity decreased during the fatigue life with increasing strain. However, stress level seemed to have no influence on the secant modulus of elasticity.

• Journal of the Ergonomics Society of Korea
• /
• v.32 no.1
• /
• pp.139-144
• /
• 2013

Objective: The current study investigated a non-obtrusive measure for detecting physical fatigue based on the analysis of formant frequencies of human voice. Background: Fatigue has been considered as a main cause in industrial and traffic accidents. Therefore, it is critical to detect worker's fatigue for accident prevention. Method: After running exercises on a treadmill, participants were instructed to read a sentence and their voices were recorded under four different physical fatigue levels. Korean vowels of "아", "어", "오", "우", and "이" from the voice recorded were then used to collect formant 1 frequencies. Results: Results of separate ANOVAs showed a significant main effect of physical fatigue on formant 1 frequency of "아", "어", and "이". Furthermore, post-hoc comparisons revealed that formant 1 frequency of "아" was most sensitive to physical fatigue level employed in this experiment. Conclusion: Formant 1 frequencies of some vowels significantly decrease as the physical fatigue level increases. Application: Potential application of this study includes the development of a measure of physical fatigue state that is free from sensor attachment and requires little preparation.

• Journal of Korean Academy of Nursing
• /
• v.36 no.7
• /
• pp.1224-1231
• /
• 2006

Purpose: This study was conducted to identify comprehensive predictors of fatigue in cancer patients. Methods: One hundred ten cancer patients visiting in-patient or out-patient clinics of a university hospital located in Incheon participated in this study. Results: The hematologic indicators (WBC and Hemoglobin) were significant fo. explaining fatigue. The psychological factors of fatigue were statistically significant. Both anxiety and depression, included as psychological factors, were significant in explaining fatigue in cancer patients. The influence of physical factors on fatigue was also statistically significant. Among the variables included as physical factors, pain, nausea/vomiting/anorexia, and sleep disturbance were significant whereas, dyspnea was not significant. The influence of the daily activity factor on fatigue was statistically significant. Among the variables included as daily activity factors, regular exercise or not and the usual activity level were significant in explaining fatigue of cancer patients, while the level of rest was not statistically significant. Conclusions: From the study results fatigue of cancer patients appeared to be influenced by multidimensional factors, such as physiological, physical, psychological, and activity related factors.

• Journal of Society of Preventive Korean Medicine
• /
• v.19 no.2
• /
• pp.67-74
• /
• 2015

Objective : The aim of this study was to investigate fatigue-related factors including socio-demographic variables and life styles among workers in the automobile manufacturing industry. Method : The subjects were 22,937 individuals who had received health examination by Korean Medical doctors and responded to questionnaires for 8 months from March to November in 2011. The fatigue index was measured by heart rate variability (HRV) in an automobile manufacturing industry. A multivariate analysis with SPSS version 19.0 was used to examine the relationship between fatigue and other factors including ages, smoke consumption, drinking frequency, exercise frequency, occupational category, conjugal condition. Results : In comparison between normal and very bad level of fatigue, factors of ages, smoking, drinking, and exercise showed significant difference(p<0.05). In addition, when normal and bad fatigue were compared, ages, smoking, exercise also produced significant difference(p<0.05). Furthermore, in normal and good level of fatigue comparison, occupation and smoking yielded significant difference(p<0.05). Finally, in other comparisons between normal and very good fatigue, exercise, smoking and occupation revealed significant difference(p<0.05). Conclusion : The results of this study suggest that age increase affects fatigue negatively, whereas exercise and drinking of once or twice per a week can have positive correlations.

• Korean Journal of Adult Nursing
• /
• v.15 no.4
• /
• pp.617-627
• /
• 2003

Purpose: The purpose of this study is to investigate fatigue and its related factors in cancer patients receiving radiotherapy. Method: The subjects of this study consisted of 98 patients receiving radiotherapy. Subjects were recruited from C University Hospital radiation oncology unit located in Gwangju from March to May, 2001. Questionnaire and medical records were used for data collection. The obtained data was analyzed using SAS program that included descriptive statistics, t-test, ANOVA, Post-hoc test(Fisher's LSD) and Pearson's correlation coefficients. Result: The fatigue perceived by the subjects was middle level ($5.59{\pm}1.59$) and 72.4% of them reported greater than 5 points. The subjects in no religion, low income, and spouse caregiver groups experienced the higher fatigue than another groups, respectively. The subjects in nasopharyngeal cancer, head & neck radiation site, and analgesics medication groups did, experience fatigue as well. The fatigue not only positively correlated with symptom distress, disruption of usual activity, sleep dissatisfaction, and mood state, but also negatively with less family support. Conclusion: Cancer patients receiving radiotherapy experience the middle level of fatigue and it correlates with the multi-dimensional factors. However, further research is needed to identify the changes in fatigue over the radiotherapy period through longitudinal design and to develop nursing intervention for fatigue decrease.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.2 s.31
• /
• pp.159-169
• /
• 1997

Recently, due to the increasing overloaded heavy vehicles and traffic volumes fatigue failures of steel highway bridges frequently occur. Therefore, it is important to decide rational fatigue design procedure which can reflect lifetime cumulative fatigue damage reasonably. In this study, cumulative fatigue damages are simulated for various bridge systems and traffic conditions. The AASHTO LRFD fatigue design procedure is reviewed and the current fatigue design loading format, in which a single representative truck is loaded regardless of bridge width, is found to yield inconsistent safety level. Improved loading format with rational design load level for fatigue design is suggested.

• Korean Journal of Adult Nursing
• /
• v.20 no.3
• /
• pp.443-451
• /
• 2008

Purpose: This study is to examine how dementia day care service affects fatigue, depression and life satisfaction of caregiver. Methods: The study was conducted using a convenient sampling method from 6 Dementia Day Care Center in Incheon. Thirty nine primary caregivers answered the questionnaires. Pre-test was done before demented elders start using the dementia day care center and post-test was done five months after. Data were analyzed by using descriptive statistics and paired t-test. Results: There was a significant difference in caregivers' fatigue level after using dementia day care service(t=2.188, p=.035). Results of subcategories were as follows; There was a significant difference in caregivers' physical fatigue level(t=2.270, p=.029) and psychological fatigue level(t=2.277, p=.029) after using dementia day care service. However, there was not significant difference in caregivers' neurological fatigue level(t=1.312, p=.197). There was a significant difference in caregivers' depression level(t=3.066, p=.004) and life satisfaction(t=-2.131, p=.040) after using dementia day care service. Conclusion: The results indicated that dementia day care service is helpful for family with demented elders. Therefore it is necessary to expand dementia day care center in terms of its size and numbers in order to support increasing number of demented elders and their families.