• 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.

• 한국정밀공학회지
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• 제9권1호
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• pp.106-117
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• 1992

In this study, the propagation behaviour and the closure phenomena of physically small surface cracks were investigated by the techinque of the Kikukawa-unloading elastic compliance method using a back face strain gage. The surface cracks initiated and propagated from notched specimens under constant amplitude bending load. The crack shape (aspect ratio) with approximately semi-circular at the early stage was changed to semi-elliptical as the cracks grew larger. The crack depth (a) could be expressed uniquenly by the crack length (c). The dependence of the crack propagation rate on the stress ratio R was strongly related in the lower ${\Delta}K$ range. The deceleration of the surface crack propagation rate was prominent in lower R during the crack length was small. When the propagation rate was rearranged with the effective stress intensity factor range ${\Delta}$K_{eff} the dependence of the crack propagation rate on the stress ratio R was found to be diminshed. These were caused by the crack closure phenomena that was most prominent at the lower propagation rate. The mechanism of crack closure phenomena was dominated by the plasticity-induced mechanism.

• 한국진공학회지
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• 제7권s1호
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• pp.57-77
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• 1998

Heteroepitaxial $Y_2O_3$ films were grown on a Si(111) substrate by ionized cluster beam deposition(ICBD) in ultra high vacuum, and its qualities such as crystllitnity, film stress, and morphological characteristics were investigated using the various measurement methods. The crystallinity was investigated by x-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED). Interface crystallinity was also examined by Rutherford backscattering spectroscopy(RBS) channeling, transmission electron microscopy(TEM). The stress of the films was measured by RBS channeling and XRD. Surface and interface morphological characteristics were investigated by atomic force microscopy (AFM) and x-ray scattering method. Comparing the interface with the surface characteristics, we can conclude that many defects at the interface region were generated by interface reaction between the yttrium metal and SiO2 layer and by ion beam characteristic such as shallow implantation, so that they influenced the film qualities. The film quality was dominantly depended on the characteristic temperature range. In the temperature range from $500^{\circ}C$ to $600^{\circ}C$, the crystallinity was mainly improved and the surface roughness was drastically decreased. On the other hand, in the temperature range from $600^{\circ}C$ to $700^{\circ}C$, the compressive stress and film density were dominantly increased, and the island size was more decreased. Also the surface morphological shape was transformed from elliptical shape to triangular. The film stress existed dominantly at the interface region due to the defects generation.

• 대한정형도수물리치료학회지
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• 제21권2호
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• pp.53-62
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• 2015

Background: This study was to investigate the effect of 8-weeks medical exercise therapy on ankle pain, range of motion, stress symptom after traumatic injury, and depression, in a 51 years old stroke patient with right ankle joint inflammation. Method: The 8-weeks medical exercise therapy program was applied to 4 grades of Dosage 1 (1-3 weeks), Dosage 2 (4-5 weeks), Dosage 3 (6-7 weeks), and Dosage 4 (8 weeks) on right ankle joint inflammation in a female with right hemiplegia admitted to D hospital located in Gyeonggi-do. Result: The findings showed that visual analogue scale (VAS) scores improved from 8 to 0-1 scores, passive range of motion (ROM) increased to 5 degrees more than before, Korean-version impact of event scale-revised (IES-R-K) scores increased from 61 to 31 scores, and Korean-version beck depression inventory II (BDI-II-K) scores decreased from 51 to 17 scores. As such, the 8-week medical exercise therapy program may decrease the pain, increase ROM, improve stress after traumatic injury, and improve depression symptom. Conclusion: The presented evidence suggests that exercise and physical activity have beneficial effects on depression symptoms. It is possible to apply the medical exercise therapy for modulating pain experience and treating pain. Also, it may be effective methods to treat the psychological aspects of pain.

• 한국재료학회지
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• 제23권7호
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• pp.373-378
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• 2013

In order to clarify the effect of C/Ti atom ratios(${\chi}$) on the deformation behavior of $TiC_{\chi}$ at high temperature, single crystals having a wide range of ${\chi}$, from 0.56 to 0.96, were deformed by compression test in a temperature range of 1183~2273 K and in a strain rate range of $1.9{\times}10^{-4}{\sim}5.9{\times}10^{-3}s^{-1}$. Before testing, $TiC_{\chi}$ single crystals were grown by the FZ method in a He atmosphere of 0.3MPa. The concentrations of combined carbon were determined by chemical analysis and the lattice parameters by the X-ray powder diffraction technique. It was found that the high temperature deformation behavior observed is the ${\chi}$-less dependent type, including the work softening phenomenon, the critical resolved shear stress, the transition temperature where the deformation mechanism changes, the stress exponent of strain rate and activation energy for deformation. The shape of stress-strain curves of $TiC_{0.96}$, $TiC_{0.85}$ and $TiC_{0.56}$ is seen to be less dependent on ${\chi}$, the work hardening rate after the softening is slightly higher in $TiC_{0.96}$ than in $TiC_{0.85}$ and $TiC_{0.56}$. As ${\chi}$ decreases the work softening becomes less evident and the transition temperature where the work softening disappears, shifts to a lower temperature. The ${\tau}_c$ decreases monotonously with decreasing ${\chi}$ in a range of ${\chi}$ from 0.86 to 0.96. The transition temperature where the deformation mechanism changes shifts to a lower temperature as ${\chi}$ decreases. The activation energy for deformation in the low temperature region also decreased monotonously as ${\chi}$ decreased. The deformation in this temperature region is thought to be governed by the Peierls mechanism.

• 한국구조물진단유지관리공학회 논문집
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• 제4권4호
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• pp.171-180
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• 2000

This study aims to present a more reasonable control value than the exiting one by comparing and analyzing control values and field instrumentation values of the whole excavation depth of the four case sites using geometric averaging as a statistical method. The range of the study is confined to three things: (1) the axial force of the braced excavation walls among a variety of items prescribed in the control values by stress deformation of walls and adjacent structures; (2) by approximation of the allowable and design value; (3) and by safety factor. As a res it is desirable to revise "(Long term allowable stress + Short term allowable stress)/2 ~ Short term allowable stress," presented in the present control values by stress deformation of walls and adjacent structures, to "(Long term allowable stress + Short term allowable stress)/5 ~ (Short term allowable stress)/3." The result also shows that since there is a difference of about 3.5%, it is not necessary to revise 70, 90, and 100 percent of LEVEL I, II, and III, prescribed in the control values by the allowable and design value approximation. In addition, modifying the control value by the safety factor, now 1.07, is unnecessary, although it varies little difference from the present value.

• 한국재료학회지
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• 제24권11호
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• pp.625-631
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• 2014

To investigate the deformation properties of TiC-(5-20) mol% Mo solid solution single crystals at high temperature by compression testing, single crystals of various compositions were grown by the radio frequency floating zone technique and were deformed by compression at temperature from 1250K to 2270K at strain rates from $5.1{\times}10^{-5}$ to $5.9{\times}10^{-3}/s$. The plastic flow property of solid solution single crystals was found to be clearly different among a three-temperature range (low, intermediate and high temperature ranges) whose boundaries were dependent on the strain rate. From the observed property, we conclude that the deformation in the low temperature range is controlled by the Peierls mechanism, in the intermediate temperature range by the dynamic strain aging and in the high temperature range by the solute atmosphere dragging mechanism. The work softening tends to become less evident with an increasing experimental temperature and with a decreasing strain rate. The temperature and strain rate dependence of the critical resolved shear stress is the strongest in the high temperature range. The curves are divided into three parts with different slopes by a transition temperature. The critical resolved shear stress (${\tau}_{0.2}$) at the high temperature range showed that Mo content dependence of ${\tau}_{0.2}$ with temperature and the dependence is very marked at lower temperature. In the higher temperature range, ${\tau}_{0.2}$ increases monotonously with an increasing Mo content.

• 대한기계학회논문집
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• 제11권6호
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• pp.953-962
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• 1987

본 연구에서는 국산 구조용강의 SM 45C 와 SUS 304 재를 최고 강도치가 나타 나는 압접조건하에서 압접하여 우재료의 용착금속부, 열영향부, 각 모재부 소정의 장 소에 미소원공을 가공한 시험편을 토대로 피로크랙의 발생 및 전파거동을 응력 레벨의 고저를 고려하여 고찰하였다.

• 지역사회간호학회지
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• 제26권3호
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• pp.221-229
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• 2015

Purpose: The purpose of this study was to investigate factors influencing depression among mothers-in-law in multicultural families. Methods: For this study, 159 participants from multicultural families were recruited through administrative units of the B. & U. Metropolitan City and G. Province. Data related to acculturation stress, resilience, and depression were collected from April to August 2014 and analyzed through t-test, one-way ANOVA, Pearson correlation coefficients, and regression analysis with the SPSS/WIN 22.0 for Windows program. Results: The participants had a moderate level of acculturation stress ($2.43{\pm}0.75$: range 1~5) and resilience ($4.74{\pm}1.14$: range 1~7). About 58% of the participants had depression. The results of stepwise multiple regression analysis indicated that mothers-in-law's depression was affected by resilience (${\beta}=-1.17$, p<.001), acculturation stress (${\beta}=0.85$, p=.026), perceived economic level (${\beta}=-0.83$, p=.016), difficulty in physical activity (${\beta}=-0.62$, p=.027), relationship satisfaction (${\beta}=-0.51$, p=.035), and education level (${\beta}=-0.48$, p=.033). The explanatory power of these factors was 35%. Conclusion: The findings indicated the need to lower the level of depression by enhancing resilience and reducing acculturation stress among mothers-in-law in multicultural families. Future research to reduce depression among mothers-in-law in multicultural families should consider how to enhance resilience and reduce acculturation stress.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.311-324
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• 2015

The purpose of this study was to investigate experimentally the fatigue performance of reinforced concrete (RC) beams with hot-rolled ribbed fine-grained steel bars of yielding strength 500MPa (HRBF500). Three rectangular and three T-section RC beams with HRBF500 bars were constructed and tested under static and constant-amplitude cyclic loading. Prior to the application of repeated loading, all beams were initially cracked under static loading. The major test variables were the steel ratio, cross-sectional shape and stress range. The stress evolution of HRBF500 bars, the information about crack growth and the deflection developments of test beams were presented and analyzed. Rapid increases in deflections and tension steel stress occured in the early stages of fatigue loading, and were followed by a relatively stable period. Test results indicate that, the concrete beams reinforced with appropriate amount of HRBF500 bars can survive 2.5 million cycles of constant-amplitude cyclic loading with no apparent signs of damage, on condition that the initial extreme tensile stress in HRBF500 steel bars was controlled less than 150 MPa. It was also found that, the initial extreme tension steel stress, stress range, and steel ratio were the main factors that affected the fatigue properties of RC beams with HRBF500 bars, whose effects on fatigue properties were fully discussed in this paper, while the cross-sectional shape had no significant influence in fatigue properties. The results provide important guidance for the fatigue design of concrete beams reinforced with HRBF500 steel bars.