• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.427-433
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• 2005

Railway wheelset is the most essential part which undergoes severe cyclic loadings. In recent years, there has been increasing need for insuring the safety of running as the speed of the railway vehicles is getting higher. So it is required on the assessment of fatigue characteristics of the wheelset to consider plastic deformation which might be probable in the severe loading condition. In this study, total-strain controlled low cycle fatigue(LCF) test were performed to observe the LCF behaviors of the railway wheels and axles using companion specimens method. From the experimental results, the cyclic mechanical properties have been evaluated and total strain amplitude versus life relationship have been derived using the empirical Coffin-Manson law.

• 한국구조물진단유지관리공학회 논문집
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• 제11권3호
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• pp.105-115
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• 2007

리모델링의 증가로 보수보강에 대하여 많은 관심을 갖게 되었다. 탄소섬유시트의 사용은 철근콘크리트 구조의 강성을 증가시키기 위하여 많이 쓰이고 있다. 따라서 새로운 보강방법으로 외부 부착에 의한 강성이 증가된 RC구조의 휨거동을 알아보기 위하여 실험과 분석 연구를 수행하였다. 또한 본 연구는 실험에 의한 피로하중을 받도록 한 FRP패널 보강방법에 대하여 살펴보는데 그 목적이 있다.

• 한국안전학회지
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• 제7권2호
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• pp.47-56
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• 1992

The retardation effect of fatigue crack propagation after cyclic overloading seems to be affected by strain hardening exponent. Namely, for the material with high values of n, the delay effect is found to be severe. We proposed a modified crack retardation equation which may apply the retardation of fatigue crack growth after a cyclic overloading, as (da/dN)'$_{cyc}$=($\mu$n＋λ)B $\Delta$ $K^{q}$ /[(1－ $R_{eff}$) $K_{cf}$ －$\Delta$K]. where, $R_{eff}$ is effective stress ratio [＝( $K_{min}$－K, os)/( $K_{max}$－ $K_{res}$)] The constants $\mu$＝－0.5 and λ＝0.6, and the values are found to be identical for materials such as aluminum (A 1060), steel (SS 34), brass ( $B_{s}$ SIB) and stainless steel (SUS 304) used in this investigation. (SUS 304) used in this investigation.ation.n.n.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2006년도 학술발표대회 논문집
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• pp.357-361
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• 2006

Fatigue fracture behavior of a hybrid joint part with bolting was evaluated in comparison to the case of static fracture. Hybrid joint part specimens for bending test were made with layers of CFRP and aluminum honeycomb. Characteristic fracture behaviors of those specimens were obviously different under static and cyclic loads. Static bending load showed the shear deformation at the honeycomb core, whereas cyclic bending load caused the delamination between CFRP skin layers and honeycomb core. Experimental results obtained by static and fatigue tests were considered in modifications of design parameters of the hybrid joint.

• 한국안전학회지
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• 제8권1호
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• pp.71-79
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• 1993

The welding implementation used widely in the industrial field is gradually increasing due to weight reduction. unlimited material thickness. simplified structure design. and 1 manufacturing time and cost reduction. The most significant factor that influences the fatigue crack growth rate is the residual stress generated during the welding process. Many researchers have studied the effect of the residual stress on crack growth behavior. Through a fatigue test in a various-thickness welded specimen. redistributed residual stress is measured as the crack is developed. Then. by superposing the measured residual stress on the K value obtained by the finite element method.

• 한국안전학회지
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• 제10권2호
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• pp.17-23
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• 1995

Though the magnitude is decreasing, the compressive residual stress is always distributed during fatigue crack growth near the crack tip. This means that the residual stress is released during fatigue crack growth due to the alternative load. ${\Delta}K_{IV}$ is modified by using the initial residual stress and the redistributed residual stress in uniform and various thickness welded specimens. The former is denoted by ${\Delta}K_{IV.eff.i}$ and the latter is denoted by ${\Delta}K_{IV.eff.i}$. ${\Delta}K_{IV.eff.i}$ gives more accurate relations in da/dN vs. ${\Delta}K_{IV}$ curve, however the difference is very small.

• 한국산업융합학회 논문집
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• 제22권6호
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• pp.649-655
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• 2019

Fracture behaviors of SCM435 high strength bolt have been studied including macroscopic and microscopic fracture observation, Energy Dispersive X-ray Spectroscopy, Vickers hardness test and applied stress evaluation. cracks (ratchet marks) were generated by the repetitive loads acting on the bolts, initial stress of bolt and the stress concentration. The applied stress was found to be slightly higher than the fatigue limit of the material. The initial stress of bolt must be removed, and the mold temperature during the process must be maintained by room temperature. Bolts are recommended to be peened to improve fatigue limit.

• 기본간호학회지
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• 제6권3호
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• pp.477-492
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• 1999

The disease patterns among the Korean was shifted from acute and infectious diseases to chronic diseases. According to the these disease patterns trends, people have concerned about the health promotion and health behaviors. Pender's(1996) revised health promotion model(HPM) is consist of three categories; Individual characteristics and experiences, Behavior-specific cognitions and affect, behavioral outcome. Of these categories, individual characteristics and experiences, this category of variables is considered to be of biological, psychological and socio-cultural personal factors, especially, individual fatigue. Futhermore. these variables constitute a critical core for nursing intervention, as they are subject to modification through nursing actions. But there is no few the research of the relationship between the fatigue and health promotion. Therefore, the purpose of this study is to investigate the correlation between the fatigue and health promoting life style among a rural college students. Additionally, this descriptive correlational study identified the relation of demographic factors and fatigue, health promoting life style. From June 20 to 26, 1998, a convenience sample of 270 college students completed the questionnaire of the fatigue and health promoting life style profile which were developed by the Yoshitake(1978) and Walker, et al.(1987), respectively. The descriptive correlational statistics, mean, t-test, ANONA, Pearson correlation coefficient were used to analyze the data gathered with SAS pc+ program. The results were as it follows: 1. The average fatigue score of the subjects was $64.93{\pm}12.89$. Fatigue scores by subcategory were physical symptoms($23.5{\pm}4.87$). psychological symptoms($22.11{\pm}4.66$) and neuro-sensory symptoms($19.32{\pm}5.14$). With the respect to the demographic characteristics of the subjects, there were statistically significant differences between the demographic factors and fatigue, especially, sex(t==3.69 p<0.01), major(t=-2.89 p<0.01). the experience of family illness(t=2.76 p<0.01). 2. The average health promoting life style item score of the subjects was $2.33{\pm}0.33$. In the subcategories, the highest degree of performance was self-actualization(2.94), following interpersonal support(2.81). stress management(2.33), exercise(2.20), nutrition(2.10), and the lowest degree was health responsibility(1.73). There were the significant differences on the learning of health education(t=2.00 p<0.01). religion(F=3.01, p<0.05), circle activity(t=2.07, p<0.05), nutrition control(t=5.25, p<0.01) of demographical factors with the health promoting life style. 3. The correlation between the fatigue and health promoting life style made statistically no significance(r=-0.09731, p>0.05). But there was negative significant relationship between health promoting life style and psychological symptom as a fatigue subcategory(r=-0.15721, p<0.05). The self-actualization showed negative significant correlation with all fatigue subcategory. The health responsibility showed significant relationship with total fatigue(r=0.13050. p<0.05). For further research, it suggests to replicate the correlational and causal study between the fatigue and the health promoting life style using the another fatigue scale which is able to measure the subjective and objective fatigue degree. And it needs to develop the nursing intervention program for maintaining and promoting the health behavior as well as for decreasing the college students's fatigue.

• 여성건강간호학회지
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• 제7권4호
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• pp.447-460
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• 2001

The purpose of this study were to identify a relationship between symptom of health and fatigue-regulation behavior in middle-aged women. The subjects were 241 women living in Seoul and near the city, ranging in ages of 30-59(mean= 42.1 years) being interviewed during the month of Oct. to Dec., 2000. The following questionnaires were utilized in this study: a self reported symptom of health and a fatigue-regulation behavior scale originated from Kwon(1997). The analysis for the data was done by SAS program, t-test, ANOVA, and Pearson correlation. The results of this study were as follows 1. Total mean scores of health status were shown 29.1, physical symptom 17.9 and psychological symptom 11.2. According to symptom of body system were higher in muscular-skeletal sympom 5.5, neurologic symptom 3.5, and digestive symptom 2.7. 2. The mean scores of symptom of health were significantly different in duraion of marriage, status of menstruation, perceived fatigue, perceived cause of fatigue, perceived help of family, hours of sleep. Physical symptom was significantly different in years of educational, status of menstruation, perceived fatigue, perceived cause of fatigue, perceived help of family, hours of sleep. Psychological symptom was significantly different in parity, whether or not having past illness, perceived fatigue. 3. The neurologic symptom was significantly different in years of education, status of menstruation, perceived fatigue, time to rest The respiratory symptom was significantly different in years of education, status of menstruation and hours of physical exercise. The muscular-skeletal symptom was significantly different duration of marriage, status of menstruation, BMI. perceived fatigue, perceived cause of fatigue, perceived help of family. The cardiovascular symptom was significantly different in whether or not having religion, number of children, duration of marriage, number of pregnancy & abortion, parity, status of menstruation, BMI. The digestive symptom was significantly different in whether or not having religion and the number of children. The urologic symptom was significantly different in whether or not having job, type of family, status of menstruation, BMI, perceived fatigue, perceived cause of fatigue, perceived help of family. The score of fatigue was significantly different in number of pregnancy. 4. There were significantly positive relationships in the area of symptom on health, especially fatigue was significantly positive relationships in score of symptom of health, physical symptom and psychological symptom. 5. They choose fatigue-regulation behavior physical rest, method of diversion, management of stress, enough sleep, and psychological rest in order. In the near future, it is required that further studies investigate socio-environmental factors related to symptoms of health and develop programs motivating fatigue-regulation behaviors actively.

• 대한기계학회논문집A
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• 제26권2호
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• pp.374-379
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• 2002

Corrosion fatigue tests were carried out to clarify the influence of acid fog as environmental factor on the fatigue strength of SM55C using rotary bending fatigue tester. The fatigue strength of acid fog specimen extremely decreased about 80% compared to that of distilled water specimen. In acid fog environment, a number of cracks commenced at corrosion pit and coalesced with the adjacent cracks during they propagate, and they formed a single non-propagating circumferential crack under the endurance stress of N=5$\times$10$\^$7/ cycles. Also, the depth of the crack is smaller than that of normal fatigue crack, so the crack has a veil small aspect ratio. The reason of this peculiar crack growth characteristics is that the crack opening-closure behaviors are hindered by corrosion products on the surface crack faces, and hence it is thinkable that the strong corrosion action like anodic dissolution for crack growth in depth direction is weaker compared with surface, resulting from faint pumping action of crack during loading-shedding processes.