• 한국지반신소재학회논문집
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• 제10권3호
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• pp.9-18
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• 2011

본 논문은 연약지반에 모래말뚝의 설치심도를 달리하여 타설함으로써 모래의 사용량을 절약하기 위한 개량형식에 착안한 모래말뚝 설치지반의 전단특성에 대하여 연구하였다. 모래말뚝은 연약지반 깊이에 따라 설치심도 및 말뚝의 직경을 달리하고 또한 모래말뚝을 토목섬유 기능을 갖는 연성재료로 감싸 보강한 시료와 그렇지 않은 시료로 나누어 압밀비배수 삼축압축시험을 수행하였다. 그 결과 모래말뚝의 직경과 설치심도가 증가할수록 그리고 연성재료로 보강한 시료가 전단강도와 응력비등에 있어서 더 큰 증가를 보였으며 그중 내부마찰각 보다 점착력 요소의 증가가 더 두드러진 증가를 보였다.

• 한국정밀공학회지
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• 제16권6호
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• pp.183-189
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• 1999

A numerical analysis was performed to predict flow curves and dynamic recrystallization behaviors of Al-5wt%Mg alloy on the basis of results of hot compression tests. The hot compression tests were carred out in the ranges of 350 ~ 500 ${^\circ}C$ and 5 ${\times}{10^-3}$ ~ 3 ${\times}{10^0}$/sec to obtain the Zener-Hollomon parameter Z. The modelling equation for flow stress was a function of strain, strain rate, temperature. The influence of these variables was quantifield using the Zener-Hollomon parameter. In the modelling equation, the effects of strain hardening and dynamic recrystallization were taken into consideration. Therefore, the modelling stress-strain curves of Al-5wt%Mg alloy were in good agreement with experimental results. Finally, the dynamic recrystallization kinetics were illustrated through the inspection of microstructure after deformation.

• 한국소음진동공학회논문집
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• 제13권2호
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• pp.132-143
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• 2003

Viscoelastic components for vibration isolation or shock absorption in automobiles, machines and buildings are often subject to a high level of static deformation. From the dynamic design point of view, it is requisite to predict dynamic complex stiffness of viscoelastic components accurately and efficiently. To this end, a systematic procedure for complex modulus measurement of the viscoelastic material under large static deformation is often required in the industrial fields. In this paper, dynamic test conditions and procedures for the viscoelastic material under small oscillatory load superimposed on large static deformation are discussed. Various standard test methods are investigated in order to select an adequate test methodology. The influence of fixed boundary condition in the compression tests upon complex stiffness are investigated and an effective correction technique is proposed. Then the uniaxial tension and compression tests are performed and its results are compared with analysis results from conventional constitutive models.

• 대한의용생체공학회:의공학회지
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• 제41권1호
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• pp.14-21
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• 2020

Recently, porous additive manufactured(AM) cages have been introduced to provide more desirable stiffness and may be beneficial to bone ingrowth. They are designed to attempt to reduce the subsidence problem of traditional titanium cage and to get osseointegrative property that PEEK doesn't have. This study was performed to evaluate the mechanical performance of newly developed lumbar porous AM cages. Three types of mechanical tests were performed in accordance with the ASTM standards: Static compression, compression-shear, and subsidence tests. The porous AM cages with 60% porosity showed similar device stiffness and strength as the various products submitted to FDA 510(k), and their wider contact area improved the subsidence test results by about 50%. In conclusion, the porous AM cages developed in this study were considered mechanically safe and could be an alternative to solid PEEK cages.

• 한국지반공학회지:지반
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• 제11권2호
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• pp.107-120
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• 1995

섬유혼합 보강토는 흙과 섬유의 마찰력에 의해 유발되는 섬유의 인장력을 이용하여 흙의 역학적 특성을 개선시킨 새로운 형태의 보강토이다. 일반적으로 섬유혼한 보강토의 공학적 특성은 흙의 단위 중량, 입자크기, 입도분포와 섬유의 길이, 인장강도, 혼합률 등에 영향을 받는 것으로 알려져 있다. 본 연구에서는 국내에서 많이 발생하는 건설잔토 종류별로 섬유의 형태, 직경 및 길이, 섬유 혼합률, 시멘트 홉합률, 양생기간 등을 변화시켜가며 섬유혼합 보강토의 다짐특성, 전단특성 및 투수특성 등을 고찰하고, 이를 토대로 섬유혼합 보강토의 공학적 특성에 미치는 섬유 보강 효과를 규명하였다. 또한, 실험에 사용된 흙과 섬유에 대한 최적의 섬유길이와 섬유혼합률의 범위에 대한 평가를 수행하였다.

• 한국지반공학회논문집
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• 제15권3호
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• pp.17-25
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• 1999

인천 해안지역을 중심으로 송도 신도시 개발과 인천 국제공항 공사는 공유수면을 대규모로 매립하여 지반을 조성하고 있다. 현재까지 막대한 양의 준설토를 매립에 사용한 결과로 양질의 매립토 확보에 상당한 어려움을 겪고 있는 실정이다. 이러한 현실성을 고려하여 소다회를 생산하고 부산물로 발생되는 폐석회를 화강풍화토와 혼합하여 매립재로 활용할 수 있는 방법에 대하여 연구를 수행하였다. 환경 실험을 통하여 화학적 성분, pH, 중금속함량 등을 측정하여 환경적 영향에 대하여 검토를 수행하였다. 또한 혼합비에 따른 다짐시험, 일축압축강도시험, X-ray 회절분석시험 등을 수행하여 강도증가 및 매립재로서의 활용가능성을 검토하였다. 상기의 연구결과 폐석회를 화강풍화토에 무게중량으로 20%를 혼합하면 양호한 매립재로 활용이 가능하며, 환경적 영향도 국내 관련기준법을 만족함을 알 수 있다.

• 한국지반공학회지:지반
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• 제13권1호
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• pp.159-168
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• 1997

보강재의 방향, 표면거칠기 그리고 점토의 함수비가 보강점토의 응력-변형률 거동 및 파괴거동에 미치는 영향을 조사하기 위하여 강으로 보강된 점토를 대상으로 일축압축시험을 실시하였다. 시험결과 보강점토 강도의 증가 또는 감소는 보강재의 방향과 점토의 함수비에 영향을 받고 있는 것으로 나타났다. 보강재 설치방향에 따른 점토의 강도저하는 점토와 보강재의 경계면 끝에서 발생된 균열과 관련이 있는 것으로 판단된다. 파괴역학 이론을 적용하여 보강점토의 파괴 거동에 대한 이론적인 고찰을 하였으며 시험 결과를 이론적인 예측결과와 비교하였다. 폐합된 균열이 내재된 물질의 파괴기준을 적용하여 예측한 균열진행 방향은 시험으로부터 측정된 값과 비교적 잘 일치되었다.

• 한국재료학회지
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• 제31권3호
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• pp.172-180
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• 2021

In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 ㎛ below the surface of the base material; however, when the depth exceeds 100 ㎛, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.

• Geomechanics and Engineering
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• 제30권5호
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• pp.471-478
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• 2022

Creep of soils has a significant impact on mechanical properties. The one-dimensional consolidation creep test, thermal analysis test, scanning electron microscope (SEM) test, and mercury compression test were performed on Guilin red clay to study the changes in bound water and microstructure during the creep process of Guilin red clay. According to the results of the tests, only free and weakly bound water is discharged during the creep of Guilin red clay. When the consolidation pressure p is in the 12.5-400.0 kPa range, it is primarily the discharge of free water; when the consolidation pressure p is in the 800.0-1600.0 kPa range, the weakly bound water is converted to free water and discharged. After consolidation creep, the microstructure of soil changes from granular overhead contact structure to flat sheet-like stacking structure, with a decrease in the number of large and medium pores, an increase in the number of small and micro pores, and a decrease in the fractal dimension of pores. The creep process of red clay is the discharge of weakly bound water as well as the compression of large pores into small pores and the transition of soil particles from loose to dense.

• Geomechanics and Engineering
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• 제30권5호
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• pp.437-448
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• 2022

Alluvial soil is challenging to work with due to its high compressibility. Thus, consolidation settlement of this type of soil should be accurately estimated. Accurate estimation of the consolidation settlement of alluvial soil requires accurate prediction of compressibility parameters. Geotechnical engineers usually use empirical correlations to estimate these compressibility parameters. However, no attempts have been made to develop correlations to estimate compressibility parameters of alluvial soil. Thus, this paper aims to develop new models to predict the compression and recompression indices (Cc and Cr) of alluvial soils. As part of the study, geotechnical laboratory tests have been conducted on large number of undisturbed samples of local alluvial soil. The obtained results from these tests in addition to available results from the literature from different parts in the world have been compiled to form the database of this study. This database is then employed to examine the accuracy of the available empirical correlations of the compressibility parameters and to develop the new models to estimate the compressibility parameters using the nonlinear regression analysis. The accuracy of the new models has been accessed using mean absolute error, root mean square error, mean, percentage of predictions with error range of ±20%, percentage of predictions with error range of ±30%, and coefficient of determination. It was found that the new models outperform the available correlations. Thus, these models can be used by geotechnical engineers with more confidence to predict Cc and Cr.