• 한국자동차공학회논문집
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• 제12권4호
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• pp.181-190
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• 2004

The interest of the fatigue life of rubber components such as engine mounts is increasing according to the extension of warranty period of the automotive components. Automotive engine mounts get damaged due to thermal and mechanical loadings. This paper discusses a fatigue life prediction of the 3-dimensional dumbbell specimens for natural rubber compound considering the effects of maximum strain and heat aging temperature. Displacement controlled fatigue life tests were performed using specimens with different levels of maximum strain and various hardness. The basic mechanical properties test and the fatigue test of aged rubber specimen under normal and elevated temperature were executed. A procedure to predicted the fatigue life of vulcanized natural rubber material based on the maximum strain method was proposed, and then this curve was in good agreement with fatigue test data less than 200% error range.

• 대한기계학회논문집A
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• 제30권11호
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• pp.1417-1424
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• 2006

In order to evaluate variation of fatigue life of mechanical components including engineering plastics, it is important to estimate probabilistic strain-life curves to accurately define the variation of fatigue characteristics. This paper intends to provide new assessment of P-$\varepsilon$-N (probabilistic strain-life curves) for considering the variation of fatigue characteristics in polyacetal. The fatigue strain controlled tests were conducted under constant 50% humidity and room temperature condition by a universal testing machine at strain ratio, R=0. A practical procedure is introduced to evaluate probabilistic strain-life curves. Three probabilistic distributions were used for generating P-$\varepsilon$-N curves such as normal, 2-parameter and 3-parameter Weibull. In this study, 3-parameter Weibull distribution was found to be most appropriate among assumed distributions when the probability distributions of the fatigue characteristic were examined using chi-square and Kolmogorov-Smirnov test. The more appropriate P-$\varepsilon$-N curves for these materials are generated by the proposed method considering 3-parameter Weibull distribution.

• 대한기계학회논문집A
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• 제29권11호
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• pp.1472-1479
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• 2005

Multiple surface crack distributed randomly along a weld toe influences strongly on the fatigue crack propagation life of welded joint. It is investigated by using statistical approaches based on series of systematic experiments. From the statistical results, initial crack numbers and its locations follow the normal distribution, and the probability of initial crack depths and lengths can be described well by tile Weibull distribution. These characteristics are used to calculate the fatigue crack propagation life, in which the mechanisms of mutual interaction and coalescence of the multiple cracks are considered as well as the Mk-factors obtained from a parametric study on the crack depths and lengths. The automatic calculation is achieved by the NESUSS, where the parameters such as the number, location and size of the cracks are all treated as random variables. The random variables are dealt through the Monte-Carlo simulation with sampling random numbers of 2,000. The simulation results show that the multiple cracks lead to much shorter crack propagation life compared with those in single crack situation. The sum of the simulation and tile fatigue crack initiation life derived by the notch strain approach agrees well with the experiments.

• 한국운동역학회지
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• 제23권1호
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• pp.63-76
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• 2013

The purpose of this study was to investigate the effects of knee joint muscle fatigue and overweight on the angular displacement and moments of the lower limb joints during landing. Written informed consent forms, which were approved by the human subject research and review committee at Dong-A University, were provided to all subjects. The subjects who participated in this study were divided into 2 groups: a normal weight group and an overweight group, consisting of 15 young women each. The knee joint muscle fatigue during landing was found to increase the dynamic stability by minimizing the movements of the coronal and horizontal planes and maintaining a more neutral position to protect the knee. The effect of body weight during landing was better in the normal weight group than in the overweight group, with the lower limbs performing their shock-absorbing function in an efficient manner through increased sagittal movement. Therefore, accumulated fatigue of knee joint muscles or overweight may be highly correlated with the increase in the incidence of injury during landing after jumping, descending stairs, and downhill walking.

• 대한후두음성언어의학회지
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• 제27권2호
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• pp.91-94
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• 2016

Voice is a physical phenomenon, generated by vocal fold and expiratory airflow. Dysphonia should come from abnormal vocal fold and airflow. Occassionally larynx looks normal in show, but it is actually not. There should be undetected structural or functional abnormalities. So when ENT doctors face dysphonia patients who looks normal larynx, should make a diagnosis through close observation. In this review article we present some dysphonia diseases which looks normal larynx. For example vocal fatigue, vocal fold paresis, posterior glottic diastasis, muscle tension dysphonia and psychogenic dysphonia.

• 한국전문물리치료학회지
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• 제7권1호
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• pp.79-90
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• 2000

Participants of this 1998 survey included 100 physical therapists working in hospitals located in Andong City. 77.7% of the participants were in their twenties and 20.2% in their forties. 46.4% of the participants were 3rd year students at a junior college, and 1.0% were college graduates. 67.6% of the participants had less than 5 years experience and 1.0% 16 years experience in their field. 59.6% of the participants were married. Regarding questions about occupational satisfaction, many of the participants replied "normal" for the first and third questions, and few answered "very much". Most of the participants answered "normal" for all the questions concerning their work environment with few replying "very much". With regards to awareness of the physical signs of fatigue, "occasionally, yes" were the most frequent answers. Regarding awareness of the psychological signs of fatigue, the similar proportions of participants answered "occasionally, yes" as that for "feeling nothing". Similarly, with regard to awareness of the neuro-sensitive signs of fatigue, there was a similar ratio of participants answering "occasionally, yes" and "feel nothing". It can be concluded that there are many causes of fatigue amongst physical therapists. Improvements in daily nutrition, mental health and general well-being are important in tackling these problems. It appears that fatigue amongst physical therapists may be cumulative and due to prolonged working hours To promote better daily functioning and early recovery from fatigue, appropriate assignments of working and resting hours are necessary. They would also benefit the prevention of symptomatic problems in the waist and shoulder.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.161-166
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• 1992

In this paper, the effect of compressive strength on the fatigue behavior of plain concrete was studied. The fatigue behavior of plain concrete in uniaxial compression is somewhat affected by the compressive strength of the concrete. Concrete cylindrical specimens(100$\times$200mm) with compressive strength of 265kg/$\textrm{cm}^2$, 530kg/$\textrm{cm}^2$ , 860kg/$\textrm{cm}^2$ and 1053kg/$\textrm{cm}^2$ were tested and analyzed on the fatigue strength, In addition to fatigue strength, the deformation characteristics of the concrete subjected to fatigue loading was investigated. The fatigue strength was decreased for the high-strength concrete. The deformation studies indicated that the irrecoverable strain in normal strength concrete is greater than that in high strength concrete.

• 산업기술연구
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• 제18권
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• pp.203-208
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• 1998

Fatigue tests were performed to examine the 4 parameter method for specimens prepared by various heat treatment which resulted in different mechanical properties. Obtained main results are as follows. (1) Samples treated by austempering did not show the expected improvement of fatigue limit although hardness and strength increased. This is attributed to the fact that defect sensitivities of materials increase as increasing of hardness and tensile strength, it is also shown that the graphites acting as stress concentration place become larger by austempering heat treatment than by normal annealing. (2) It is very reasonable to predict the fatigue limit of ductile irons with 4 parameter method based on ${\sigma}_{TS}$, $H_v$, ${\Delta}K_{th}$ and ${\sqrt{area}}_{max}$. (3) The half-austempering treatment appeared to be more useful than the full-austempering method to improve the fatigue limit in the spheroidal graphite cast iron with multi defective material.

• 한국융합학회논문지
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• 제12권8호
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• pp.369-379
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• 2021

본 연구는 임신성 당뇨병 임부와 정상 임산부의 스트레스, 우울, 피로 및 수면의 질을 비교하기 위한 서술적 조사연구이다. 연구대상은 연령, 임신주수, 출산 횟수가 일치하는 임신성 당뇨병 임부 49명과 정상 임부 51명이었다. 자료수집은 구조화된 설문지, 숫자 척도, Canopy9 RSA(IEMBIO, Gangwondo, Korea)장비를 사용하여 측정하였다. 자료 분석은 SPSS for window version 24.0을 이용하여 빈도, 백분율, 평균과 표준편차 Independent two sample t-test, Fisher's exact test, x²-test로 분석하였다. 본 연구 결과 임신성 당뇨병 임부는 임신 전 체중(t=3.698, p<.001)이 높고 임신 중 스트레스(t=4.505, p<.001), 우울(t=4.564, p<.001), 피로(t=3.709, p<.001)가 높았기 때문에 임신 전 체중 관리가 중요하며, 임신성 당뇨병 임산부의 스트레스, 피로, 우울을 완화하는 간호가 필요하다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.690-693
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• 2005

In this paper, probabilistic distribution of fatigue life of chassis component is determined statistically by applying the design of experiments and the Pearson system. To construct $p-\varepsilon-N$ curve, the case that fatigue data are random variables is attempted. Probabilistic density function(p.d.f) for fatigue life is obtained by design of experiment and using this p.d.f fatigue reliability about any aimed fatigue life can be calculated. Lower control arm and rear torsion bar of chassis component are selected as examples for analysis. Component load histories, which are obtained by multi-body dynamic simulation for Belsian load history, are used. Finite element analysis are performed using commercial software MSC Nastran and fatigue analysis are performed using FE Fatigue. When strain-life curve itself is random variable, probability density function of fatigue life has very little difference from log-normal distribution. And the case of fatigue data are random variables, probability density functions are approximated to Beta distribution. Each p.d.f is verified by Monte-Carlo simulation.