• 한국지반공학회논문집
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• 제26권7호
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• pp.7-16
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• 2010

응력이력은 사질토 지반의 잔류 수평응력을 증가시켜 현장시험의 관입저항을 증가시킨다. 본 연구에서는 챔버에 조성된 정규 및 과압밀 시료에 대한 콘관입시험과 딜라토미터 시험을 수행하고 응력이력이 시험결과와 측정값의 상관관계에 미치는 영향을 분석하였다. 시험결과, 평균 유효응력으로 정규화된 콘선단저항은 상대밀도 및 상태정수와 높은 상관성을 보였다. 딜라토미터의 수평응력지수($K_D$)는 콘선단저항($q_c$) 뿐만 아니라, 딜라토미터 계수($E_D$) 보다도 응력이력 영향을 효과적으로 반영하였다. 수평응력지수에 반영된 응력이력의 영향을 정지토압계수인 $K_0$로 보정한 $K_D/K_0$는 상대밀도 뿐만 아니라, 상태정수, 평균 유효응력으로 정규화된 콘선단저항과 응력이력에 관계없는 높은 상관성을 보였다. 또한 평균 유효응력으로 정규화된 딜라토미터 계수($E_D/{\sigma}_m'$)와 상태정수의 관계도 응력이력에 관계없이 유일한 식으로 표현되었다.

• 한국세라믹학회지
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• 제31권5호
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• pp.543-551
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• 1994

The creep behavior and creep fracture of sintered alumina at high temperature were investigated under four point flexural test. Steady-state creep behavior was observed at low bending stress and primary creep until fracture was observed at hish bending stress. The loading history of bending stress did not affect on steady-state creep rate. Intergranular fracture was dominant for fracture of alumina at room and high temperature. However, transgranular fracture was dominant on creep of alumina under high temperature by nucleation and growth of microcracks due to residual flaws or cavities in the material.

• 기본간호학회지
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• 제23권4호
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• pp.419-429
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• 2016

Purpose: The purpose of this study was to examine the effects of a intensive clinical training program for nursing practice on the clinical competence, state anxiety, clinical practice stress in nursing students who were beginning their first clinical practice. Methods: This practice has been processed as a 'Pre-Post design with a non-equivalent control group'. The participants were 177 students in a college of nursing. The students were divided into two groups: 89 students in the experimental group and 88 students in the control group. Results: The experimental group showed significant improvement in their clinical competence scores compared to the control group. The difference between the two groups was also significant. State anxiety in the experimental group significantly decreased compared to the control group. However, scores for stress during practice were not significantly different. Conclusion: The findings in this research reveal that the program, 'Close clinical practice training for nursing students' practice entry, contributes to improving students' overall ability and performance, and reduces anxiety of nursing students as they start their first clinical practice. These findings can be utilized in helping nursing students improve the quality of their performance.

• Geomechanics and Engineering
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• 제10권3호
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• pp.325-334
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• 2016

Rock salt is a near-perfect material for gas storage repositories due to its excellent ductility and low permeability. Gas storage in rock salt layers during gas injection and gas production causes the stress redistribution surrounding the cavity. The triaxial cyclic loading and unloading tests for rock salt were performed in this paper. The elastic-plastic deformation behaviour of rock salt under cyclic loading was observed. Rock salt experienced strain hardening during the initial loading, and the irreversible deformation was large under low stress station, meanwhile the residual stress became larger along with the increase of deviatoric stress. Confining pressure had a significant effect on the unloading modulus for the variation of mechanical parameters. Based on the theory of elastic-plastic damage mechanics, the evolution of damage during cyclic loading and unloading under various confining pressure was described.

• 대한기계학회논문집
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• 제10권2호
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• pp.188-197
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• 1986

본 연구에서는 응력이 변동되는 경우 내부크랙 전파특성을 중심으로 내부크랙 전파거동을 표면크랙 전파거동과 비교 검토하였다.

• Geomechanics and Engineering
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• 제34권3호
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• pp.303-316
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• 2023

With the development and utilization of urban underground space, the artificial ground freezing technology has been widely used in the construction of underground engineering in soft soil areas. The mechanical properties of soft clay changed greatly after freezing and thawing, which affected the seismic performance of underground structures. In this paper, a series of triaxial tests were carried out to study the dynamic response of the freezing-thawing clay under the seismic load considering different dynamic stress amplitudes and different confining pressures. The reduction factor of dynamic shear stress was determined to correct the amplitude of the seismic load. The deformation development mode, the stress-strain relationship and the energy dissipation behavior of the soft clay under the seismic load were analyzed. An empirical model for predicting accumulative plastic strain was proposed and validated considering the loading times, the confining pressures and the dynamic stress amplitudes. The relevant research results can provide a theoretical reference to the seismic design of underground structures in soft clay areas.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.263-265
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• 2003

Stressed liquid crystals, SLCs, consist of a lowdensity polymer network dispersed in a nematic host. We induced stress by shearing the material. Alignment layers are not required because the liquid crystal director uniformly aligns along the direction of shear. The shearing stress also eliminates light scattering and results in sub-millisecond switching speeds, making them good candidates for video display applications.

• 한국산업융합학회 논문집
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• 제7권2호
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• pp.181-186
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• 2004

This study presents a optimization of structure, in which constraints contain the conditions of stress and serviceability, while the sequential linear programming method (SLP) is used as a rational approach. The optimum design results contained on the limit state constraints are compared with those obtained by the only stress and ministry of construction enacted standard plans. A simple slab bridge is analysed numerically for illustration of the structural optimization. It may be asserted that serviceability constraints is very important to a structure design.

• Structural Engineering and Mechanics
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• 제7권2호
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• pp.225-240
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• 1999

This paper presents a mechanistic approach to uniaxial viscoelastic constitutive modeling of asphalt concrete that accounts for damage evolution under cyclic loading conditions. An elasticviscoelastic correspondence principle in terms of pseudo variables is applied to separately evaluate viscoelasticity and time-dependent damage growth in asphalt concrete. The time-dependent damage growth in asphalt concrete is modeled by using a damage parameter based on a generalization of microcrack growth law. Internal state variables that describe the hysteretic behavior of asphalt concrete are determined. A constitutive equation in terms of stress and pseudo strain is first established for controlled-strain mode and then transformed to a controlled-stress constitutive equation by simply replacing physical stress and pseudo strain with pseudo stress and physical strain. Tensile uniaxial fatigue tests are performed under the controlled-strain mode to determine model parameters. The constitutive equations in terms of pseudo strain and pseudo stress satisfactorily predict the constitutive behavior of asphalt concrete all the way up to failure under controlled-strain and -stress modes, respectively.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.254-268
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• 2003

The explicit formulation of the J-integral and the M-integral is constructed in terms of the stress intensity factor and the higher order stress coefficients for Mode II cracks under small or large scale yielding. Furthermore, the stress intensity factor and the higher order stress coefficients as well are computed with the aid of the two-state J- and the M-integral, which is found to be accurate and efficient. It is found that the contribution from the higher order singularities to the J-integral is closely related to the configuration of the plastic zone.