• 한국해양공학회지
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• 제16권5호
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• pp.80-87
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• 2002

In this study, CT specimens were prepared from spring steel(SUP9) which was used in suspension of automobile for room temperature and low temperature service. We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{\circ}C$, ­3$0^{\circ}C$, ­5$0^{\circ}C$, ­7$0^{\circ}C$ and ­10$0^{\circ}C$ in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range ΔKth in the early stage of fatigue crack growth (Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It is assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.58-64
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• 2004

The purpose of this study is to predict the behavior of fatigue crack propagation as one of fracture mechanics on the compressive residual stress. We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, and -10$0^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. There is a difference between shot peened specimen and unpeened specimen. Fatigue crack growth rate of shot peened specimen was lower than that of unpeened specimen. Shot peening is improve the resistance of crack growth by fatigue that make a compressive residual stress on surface. That is the constrained force about plasticity deformation was strengthened by resultant stress, which resulted from plasticity deformation and compressive residual stress in the process of fatigue crack propagation. Temperature goes down, fatigue crack growth rate decreased.

• 대한가정학회지
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• 제36권6호
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• pp.13-26
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• 1998

This study investigated first, socio-economic, residential characteristics, and values for future life among low-income family wives. Second, the relationship of these characteristics to the wives' stress was examined. The subjects were 249 mothers of urban low-income families whose children attended one of 20 daycare centers located in poor residential areas. The instruments included Social Network Scale, Home Stress Scale, and Occupation Stress Scale. Data were analyzed by means, standard deviations, frequencies, paired t-tests, and the stepwise multiple regressions. We found that a majority of the mothers and their husbands had high school educational status and simple labor or sales/service work status. They lived in rental houses or apartments. Their families of origin were a major source of emotional supports. Insufficient income for non-employed wives, long work hours and lack of free time for employed wives were a major stress. Levels of the wives' home-related job-related stress were negatively related to their own and their hudsbands' work status.

• 대한의용생체공학회:의공학회지
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• 제13권3호
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• pp.253-262
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• 1992

The wall shear stress in the vicinity of end-to end anastomoses under steady flow condi- tions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experi- mental measurements were in good agreement lith numerical results except In flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compli- ance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia (ANFH) in end-to-end anastomoses.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.353-358
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• 2004

We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{circ}C$, $-60^{circ}C$, $-80^{circ}C$, and $-100^{circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. And there is a difference between shot peened specimen and unpeened specimen. The purpose of this study is to predict the behavior of fatigue crack propagation as one of fracture mechanics on the compressive residual stress. Fatigue crack growth rate of shot peened metal was lower than that of unpeened metal. The compressive residual stress made an impact on tension and compression of the plasticity deformation in fatigue crack plasticity zone. That is. the constrained force about plasticity deformation was strengthened by resultant stress, which resulted from plasticity deformation and compressive residual stress in the process of fatigue crack propagation.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1209-1216
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• 2006

An AZ31 magnesium alloy was tested at constant temperatures ranging from 423 to 473 K (0.46 to 0.51 Tm) under constant stresses. All of the creep curves exhibited two types depending on stress levels. At low stress (${\sigma}/ G < 4 {\times}10^{-3}$), the creep curve was typical of class A (Alloy type) behavior. However, at high stresses (${\sigma}/ G > 4 {\times}10^{-3}$), the creep curve was typical of class M (Metal type) behavior. At low stress level, the stress exponent for the steady-state creep rate was of 3.5 and the true activation energy for creep was 101 kJ/mole which is close to that for solute diffusion. It indicates that the dominant deformation mechanism was glide-controlled dislocation creep. At low stress level where n=3.5, the present results are in good agreement with the prediction of Fridel model.

• 설비공학논문집
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• 제15권11호
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• pp.895-901
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• 2003

Direct numerical simulation database of an axial turbulent boundary layer is used to compute frequency and wave number spectra of the wall shear-stress fluctuations in a low-Reynolds number axial turbulent boundary layer. One-dimensional and two-dimensional power spectra of flow variables are calculated and compared. At low wave numbers and frequencies, the power of streamwise shear stress is larger than that of spanwise shear stress, while the powers of both stresses are almost the same at high wave numbers and frequencies. The frequency/streamwise wave number spectra of the wall flow variables show that large-scale fluctuations to the ms value is largest for the streamwise shear stress, while that of small-scale fluctuations to the rms value is largest for pressure. In the two-point auto-correlations, negative correlation occurs in streamwise separations for pressure and spanwise shear stress, and in spanwise correlation for both shear stresses.

• 전자공학회논문지
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• 제50권8호
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• pp.285-291
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• 2013

본 논문은 금속 산화물 반도체의 산화막 두께, 채널 폭과 길이에 따른 실리콘 산화막의 신뢰성 특성을 연구하였다. 스트레스전류와 전이전류는 스트레스 전압에 의하여 발생된다. 스트레스 유기 누설전류는 스트레스 전압 인가 동안과 인가 후의 실리콘 산화막에 나타난다. 이때 저레벨 스트레스 전압에 의한 저레벨 누설전류는 저전압 인가 동안과 인가 후의 얇은 실리콘 산화막에서 발생한다. 저레벨 누설전류는 각각 스트레스 바이어스 조건에 따라 스트레스전류와 전이전류를 측정하였다. 스트레스 채널전류는 일정한 게이트 전압이 인가동안 측정하였고 전이 채널전류는 일정한 게이트 전압을 인가한 후에 측정하였다. 본 연구는 소자의 구동 동작 신뢰성을 위하여 저레벨 스트레스 바이어스 전압에 의한 스트레스 전류와 전이전류가 발생되어 이러한 저레벨 누설전류를 조사하였다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 춘계학술대회 논문집
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• pp.146-151
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• 2001

Low temperature fatigue crack propagation ratio and characteristics of the pressure structural steel which is used for the low temperature pressure vessels. Fatigue crack properties was studied at room temperature of $25^{\circ}C$ and low temperature ranges $-60^{\circ}C,\; -80^{\circ}C \;and\; -100^{\circ}C$ with stress ratio of R=0.05, 0.1, 0.3 in the logarithmic relationship between the fatigue crack propagation rate (da/dN) and stress intensity factor $\DeltaK$, in low temperature case the relationship was extend to the range of low crack propagation rate. The fractured specimens were examined by SEM tested. That results showed specimen failed at low temperature exhibit the quasi-cleavage fracture formation, however, considerable ductility proceed final fracture.

• 터널과지하공간
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• 제13권3호
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• pp.169-179
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• 2003

암석의 절리면 전단강도의 이방성을 연구하기 위하여 인공절리면을 형성한 시편에 대한 실험을 실시하고 그 결과를 분석하였다. 즉 낮은 수직응력 상태에서 전단 방향에 따른 전단강도, 전단강성 및 마찰각을 구하기 위한 실험을 실시하였다 그 결과 낮은 수직응력하에서 전단 강도 및 강성은 전단 방향에 따라 이방성을 보이며, 특히 수직응력 2.45 MPa미만에서 뚜렷하였다. 그리고 수직응력이 증가할수록 절리면의 이방성 효과는 감소하였다. 따라서 낮은 수직응력 하에서 전단강도 및 강성값을 보다 정확히 구하기 위해서 Barton의 식에 전단방향을 고려한 보정함수 F(a)를 반영하여 새로이 수정식을 제안한다.