• 산업경영시스템학회지
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• 제39권3호
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• pp.39-46
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• 2016

Loss of postural stability can possibly lead to slip and fall accidents in the number of workplaces and everyday life. This study was aimed to examine the effects of whole body fatigue and partially limited visual field on the ability of maintaining postural balance during quiet standing. A group of twelve healthy male subjects participated in the experiment. Before and after experiencing the whole body fatigue induced by bicycling exercises, the position coordinates of subject's center of pressure (COP) were obtained under the two levels of visual field condition (i.e., open visual field and limited visual field). Four levels of the whole body fatigue examined were rest, 300watt, 600watt, and 900watt. Position coordinates of COPs measured on a force plate were then converted into the total length of postural sway path in both the medio-lateral (ML) direction and the anterior-posterior (AP) direction. Two-way ANOVA result showed that the length of sway path in the AP direction became significantly larger as the whole body fatigue accumulated. Post-hoc test revealed statistically significant differences between rest and 900watt and between 300watt and 900watt. The significant increase of the sway length was also found when the visual field was partially obstructed by the boxes. In the ML direction, however, there was no statistically significant difference of the postural sway in both the AP and ML directions. The results imply that the ability of maintaining postural stability can be reduced significantly due to such tasks along with whole body fatigue. The postural balance can also be impaired by the limited visual field.

• 한국학교보건학회지
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• 제10권2호
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• pp.169-178
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• 1997

In order to investigate the complaint rates of subjective fatigue symptoms and study the relationship between them and body type, health awareness in middle school students, we carried out a survey of 1,209 students (654 boy students and 555 girl students) at a middle school in Taejon City by a self-recorded questionnaire. The survey was conducted in June, 1997. The results obtained were as follows: 1. Among complaints of fatigue, "feel like lying down" was the highest, followed by "feel anxious about things", "feel drowsy", "yawning a lot", "eye strain" and "whole body feels tired" in descending order. 2. In the average weighted score of fatigue complaint, dullness and sleepiness (I) was the highest, followed by a difficulty in concentration (II) and bodily projection of fatigue (III) in descending order. Fatigue seems to create mental stress rather than physical burdens. 3. In the classification of body type based on the $R\ddot{o}hrer$ index, the obesity type (145 and above) was 11.0%, standard type (110~144) was 64.7% and leptosomic type (l09 and below) was 24.3%. Comparison between both sexes revealed that the rate of obesity and leptosomic types were significantly higher in boy students than in girl students. 4. In terms body type awareness, the statistics are the following: those who consider themselves to be standard type, 44.3%, slightly obese 24.5%, leptosomic, 23.5% and obese 7.8%. However, the level of obesity awareness was significantly higher in girl students than in boy students. 5. As for health awareness, 36.5% considered themselves healthy, 5.4% generally healthy and 10.1% a little unhealthy, but the level of unhealthy awareness was higher in girl students than in boy students. 6. In the relationship between body type and health awareness, most students thought that they were obese in spite of their standard body type. Also, many students who were obese and leptosomic tended to consider themselves to be a little unhealthy. 7. The more the students were obese or felt unhealthy, the more the average weighted score of fatigue complaints was high.

• Journal of Welding and Joining
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• 제20권2호
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• pp.59-64
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• 2002

When the vehicle travels in an actual road, resistance spot weldments of the vehicle structure are exposed to complex loading state. Since the fatigue strength in resistance spot weldment of vehicle body can be determined by effect of residual stresses and loading state of driving, estimating actual loading state and considering residual stress effect are needed. In this study, Fatigue stress-fatigue life relation concerned residual stress effect was obtained by thermo elastic plastic finite element analysis. And applied loading in resistance spot weldments of vehicle body was calculated by dynamic analysis. Presumption of fatigue life was performed using proposed method

• 대한한방내과학회지
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• 제11권2호
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• pp.80-93
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• 1990

Review of Literature on Languor and fatigue. According to comparative studies of Oriental and Western medical Literature on the Languor and fatigue on causes and symptom, flowing results were obtained. 1. Common etiologies of the Languor and fatigue in Western medicine are firstly exhaustion of energy, secondly variation of control center-neurotic and body fluid control-, thirdly variation of a living body physico chemical state, forthly production of middle metabolic product, fifthly psychological instability. 2. The expression of the Languor and fatigue in Oriental medicine are consumption, dificiency of vital energy(氣虛), illness caused by overexertion and dificiency of essence of life(精虛). The caure of the Languor and fatigue are dificiency in spleen and stomach(脾胃虛弱), dificiency of both the lung and kidney(肺腎兩虛), the six excessive(六淫), irregular life and excessive mental labor. 3. The symptomes of the Languor and fatigue in western medicine are systemic feeling of fatigue, dislike of work, Dizziness, general fatigue, anorexia, painful body, nerveous prostration. anxiety and decrese of energy, and in oriental medicine dificiency of vital energy, general pain, sinking of vital energy(氣虛下階) in adequate nutrition, confusion and slow speaking.

• 한국철도학회논문집
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• 제8권4호
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• pp.348-353
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• 2005

In designing the structures of railway rolling stocks, deterministic methods associated with the concept of a safety factor have been traditionally used. The deterministic approaches based on the mean values of applied loads and material properties have been used as safety verification for the design of rolling-stock car body structures. The uncertainties in the applied loading for the high speed train and the strength of new materials in the rolling stocks require the application of probabilistic approaches to ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train passes through tunnels show reflected pressure waves for high-speed trains and they may cause a fatigue failure in vehicle bodies. Use of new material technology as body structures also introduces uncertainties in the material strength. A probabilistic approach is more adaptable in designing reliable structures when the pressure waves from the tunnels pounds and new material technology is adopted. In this paper, it is proposed that a fatigue design and assessment method based on a reliability which deals with the loading variations on a railway vehicle due to the pressure reflected in tunnels and the strength variations of material. Equation for the fatigue reliability index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating pressure loadings in a tunnel. Considered in this formulation are the pressure distribution characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer functions due to the pressure loading.

• Restorative Dentistry and Endodontics
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• 제45권3호
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• pp.37.1-37.8
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• 2020

Objectives: This study aims to compare the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium (NiTi) rotary files at body temperature. Materials and Methods: In total, 80 VDW.ROTATE (25/0.04), TruNatomy (26/0.04), 2Shape (25/0.04), and HyFlex CM (25/0.04) NiTi rotary files (n = 20 in each group) were subjected to static cyclic fatigue testing at body temperature (37℃) in stainless-steel artificial canals prepared according to the size and taper of the instruments until fracture occurred. The number of cycles to fracture (NCF) was calculated, and the lengths of the fractured fragments were measured. The data were statistically analyzed using a 1-way analysis of variance and post hoc Tamhane tests at the 5% significance level (p < 0.05). Results: There were significant differences in the cyclic fatigue resistance among the groups (p < 0.05), with the highest to lowest NCF values of the files as follows: VDW.ROTATE, HyFlex CM, 2Shape, and TruNatomy. There was no significant difference in the lengths of the fractured fragments among the groups. The scanning electron microscope images of the files revealed typical characteristics of fracture due to cyclic fatigue. Conclusions: The VDW.ROTATE files had the highest cyclic fatigue resistance, and the TruNatomy and 2Shape files had the lowest cyclic fatigue resistance in artificial canals at body temperature.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.143-150
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• 1998

The evaluation of joint fatigue strength of light weight materials for electrical vehicle body has been performed through single lap joint tests with the design parameters such as joint style, adherend, bonding overlap length and bonding thickness. Fatigue strength was evaluated through 5-Hz, tension-tension, load controlled test with the stress ratio zero value. It is experimentally observed that fatigue strength of joint increases for the increase of overlap length. The combinations of Al-Al and Al-FRP adherends show that fatigue strength of joint is hardly changed for the increase of bonding thickness, but FRP-FRP adherend specimen shows that fatigue strength of joint increases after decreases for the increase of bonding thickness. Al-Al adherend specimen has much higher fatigue length than Al-FRP and FRP-FRP adherend specimens. Riveting at adgesive bonded joint gives little effect on fatigue strength.

• 한국해양공학회지
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• 제11권3호
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• pp.20-28
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• 1997

The fatigue crack propagation properties and fatigue life of two kinds of Al body panel for automobile were examined experimentally by using the plate specimen and the single spot welding specimen. The fatigue limit of spot welding specimens was lower than that of a plate specimen. The fatigue limit was similar in two kinds of spot welding specimen. The shape and size of crack propagation were observed and measured on beach mark of fracture surface. The crack propagation of surface crack specimen showed almost same tendency to that of a thick plate as almost semi-elliptical. In spot welding specimen, the fatigue crack occurred in inside surface of nugget area was almost semi-elliptical. The crack growth rate can be explained using equation of stress intensity factors.

• 한국생산제조학회지
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• 제19권1호
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• pp.71-79
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• 2010

One of methods that accomplish fuel-efficient vehicle is to reduce the overall vehicle weight by using aluminum structure typically for cross members, rails and panels in body and chassis. For aluminum structures, the use of Self Piercing Rivet(SPR) is a relatively new joining technique in automotive manufacture. To predict SPR fatigue life, fatigue behavior of SPR connections needs to be investigated experimentally and numerically. Tests and simulations on lap-shear specimen with various material combinations are performed to obtain the joining strength and the fatigue life of SPR connections. A Finite element model of the SPR specimen is developed by using a FEMFAT SPR pre-processor. The fatigue lives of SPR specimens with the curvature are predicted using a FEMFAT 4.4e based on the liner finite element analysis.

• 산업경영시스템학회지
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• 제41권2호
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• pp.16-23
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• 2018

Postural instability can increase the likelihood of hazardous slip and fall accidents in workplaces. The present study intended to extend understanding of the effect of abnormal neck posture on postural control during quiet standing. The effect of body fatigue on the postural control was also of primary concern. Twelve healthy undergraduate students volunteered to participate in the experiment. Standing on a force platform with the neck neutral, flexed, extended, or rotated, subjects' center of pressures (COP) were measured under the two levels of body fatigue. For the fatigue condition, Subjects exercised in a treadmill to meet the predetermined level of body fatigue. Analyzing the position coordinates of COPs, the length of postural sway path was assessed in both medio-lateral (ML) axis and anterior-posterior (AP) axis. Results showed that, in AP direction, neck extension or rotation significantly increased the sway length as compared with neck neutral. Neck extension led to greater sway length compared to neck rotation. Neck flexion did not differ from neck neutral. The sway length in the AP direction also became significantly larger as the body fatigue accumulated after treadmill exercise. In ML direction, as compared to neutral posture, the neck extension, flexion, or rotation did not significantly affect the length of postural sway path. However, the sway length seemed to increase marginally with the neck extended during the fatigued condition. This study demonstrates that abnormal neck posture may interfere with postural control during standing. The ability to maintain postural stability decreases significantly with the neck extended or rotated. Body fatigue leads to postural instability further.