• Computers and Concrete
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• 제7권2호
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• pp.191-202
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• 2010

A laboratory investigation was conducted to characterize the constitutive property behavior of Cor-Tuf, an ultra-high-performance composite concrete. Mechanical property tests (hydrostatic compression, unconfined compression (UC), triaxial compression (TXC), unconfined direct pull (DP), uniaxial strain, and uniaxial-strain-load/constant-volumetric-strain tests) were performed on specimens prepared from concrete mixtures with and without steel fibers. From the UC and TXC test results, compression failure surfaces were developed for both sets of specimens. Both failure surfaces exhibited a continuous increase in maximum principal stress difference with increasing confining stress. The DP tests results determined the unconfined tensile strengths of the two mixtures. The tensile strength of each mixture was less than the generally assumed tensile strength for conventional strength concrete, which is 10 percent of the unconfined compressive strength. Both concretes behaved similarly, but Cor-Tuf with steel fibers exhibited slightly greater strength with increased confining pressure, and Cor-Tuf without steel fibers displayed slightly greater compressibility.

• Structural Engineering and Mechanics
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• 제70권1호
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• pp.113-123
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• 2019

In the classical stability investigation of rectangular plates the classical thin plate theory (CPT) is often employed, so omitting the transverse shear deformation effect. It seems quite clear that this procedure is not totally appropriate for the investigation of moderately thick plates, so that in the following the first shear deformation theory proposed by Meksi et al. (2015), that permits to consider the transverse shear deformation influences, is used for the stability investigation of simply supported isotropic rectangular plates subjected to uni-axial and bi-axial compression loading. The obtained results are compared with those of CPT and, for rectangular plates under uniaxial compression, a novel direct formula, similar to the conventional Bryan's expression, is found for the Euler stability stress. The accuracy of the present model is also ascertained by comparing it, with model proposed by Piscopo (2010).

• 대한금속재료학회지
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• 제49권7호
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• pp.515-521
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• 2011

Small punch creep testing has received attention due to the convenience of using smaller specimens than those of conventional uniaxial creep tests, which enables creep testing on developing or currently operational components. However, precedent studies have shown that it is necessary to consider friction between the punch and specimen when computing uniaxial equivalent stress from a finite element model. In this study, small punch creep behaviors of AISI 316L stainless steel, which is widely used in high temperature-high pressure machineries, have been compared for the two different ceramic balls such as $Si_3N_4$ and $Al_2O_3$. The optimal range of the friction coefficient is 0.4~0.5 at $650^{\circ}C$ for the best fit between experimental and simulation data of AISI 316 L stainless steel. The higher the friction coefficient, the longer the creep rupture time is. Therefore, the type of ceramic ball used must be specified for standardization of small punch creep testing.

• 한국지반공학회논문집
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• 제22권10호
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• pp.139-150
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• 2006

울산분지 퇴적암을 대상으로 Schmidt hammer 타격시험을 시행하여 일축 압축강도, 압열 인장강도, 탄성계수, 흡수율 및 간극율과의 상호 관계를 구명하였다. 기 연구된 결과는 여러 암종이 혼합된 결과로 실용적 적용에 어려움이 있어 지질학적 생성배경의 차이로 인한 원인을 배제하고 실용적 적용에 유용하도록 울산분지 퇴적암만을 대상으로 하여 연구를 시행하였다. Schmidt 햄머 반발지수와 각 실험결과상호간에 높은 상관성이 있으며 본 연구 결과 값으로 상호 교차검정을 한 결과도 만족할 수 있는 결과가 도출되었다.

• 한국항공우주학회지
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• 제39권7호
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• pp.612-617
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• 2011

동합금 Elbrodur-NIB 재질에 대해 평균응력을 포함한 응력제어시험을 수행하였으며, 그 결과 라체팅 거동에 응력진폭, 평균응력, 응력속도가 어떠한 영향을 주는지에 대해 시험을 통해 알 수 있었다. 라체팅 변형률은 같은 평균응력에서 응력진폭이 증가할수록, 또한 같은 응력진폭에서 평균응력이 증가함에 따라 같이 증가하는 것을 볼 수 있었다. 그러나, 응력속도가 증가함에 따라 라체팅 변형률은 감소하는 것을 알 수 있었다. $10^2-10^5$ 영역에서 3가지 평균응력을 포함한 피로수명예측모델을 검토하였으며, 그 결과 Smith-Watson-Topper가 제안한 모델과 Walker가 제안한 모델이 매우 신뢰성 있는 결과를 보여주었다.

• 대한기계학회논문집
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• 제11권6호
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• pp.884-894
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• 1987

본 연구에서는 적합재료의 경계면 균열에 대한 응력세기계수를 경계요소법의 다중영역법과 이중절점기법을 이용하여 산출하고자 한다.

• 콘크리트학회논문집
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• 제17권5호
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• pp.843-852
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• 2005

Presently, test results and stress-strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than $2.0\%$, are scarce. This paper presents test results loaded in axial direction for square reinforced concrete columns confined by various volumetric ratio lateral ties including low-volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type, and tie volumetric ratio. Local strains measured using strain gages bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was efficiently improved by changing tie arrangement type from Type-A to Type-B. A method to compute the stress in lateral ties at the concrete peak strength and a new stress-strain model for the confined concrete are proposed. Over a wide range of confinement parameters, the model shows good agreement with stress-strain relationships established experimentally.

• 대한기계학회논문집
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• 제4권3호
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• pp.113-118
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• 1980

Stresses were calculated for finite-width orthotropic laminates with a circular hole and remote uniaxial loading using a two-dimensional finite-element analysis with both uniform stress and uniform displacement boundary conditions. Five different laminates were analyzed: quasi-isotropic [0.deg./.+-.45.deg./90.deg.].$\_$s/, 0.deg., 90.deg., [0.deg./90.deg.]$\_$s/, and [.+-.45.deg.]$\_$s/, Computed results are presented for selected combinations of hole diameter-sheet-width ratio d/w and length-to width ratio L/w. For small L/w values, the stress-concentration factors K$\_$tn/ were significantly different for the uniform stress and uniform displacement boundary conditions. Typically, for the uniform stress conditions, the K$\_$tn/ values were much larger than for the infinite-strip reference conditions; however, for the uniform displacement conditon, they were only slighty smaller than for this reference. The results for long strips are also presented as width-correction factor. For d/w.leg.33, these width-correction factors are nearly equal for all five laminates.

• Structural Engineering and Mechanics
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• 제34권3호
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• pp.377-390
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• 2010

This paper studies fracture initiation direction of two parallel non-coplanar cracks of equal length. Using the dislocation pile-up modelling, singular integral equations for two parallel cracks subjected to mixed-mode loading are derived and the crack-tip field including singular and non-singular terms is obtained. The kinking angle is determined by using the maximum hoop stress criterion, or the ${\sigma}_{\theta}$-criterion. Results are presented for simple uniaxial tension and biaxial loading. The biaxiality ratio has a noticeable influence on crack growth direction. For the case of biaxial tension, when neglecting the T-stress the crack branching angle is overestimated for small crack inclination angles relative to the largest applied principal stress direction, and underestimated for large crack inclination angles.

• 대한기계학회논문집A
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• 제24권3호
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• pp.560-566
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• 2000

Many researchers have dealt with the problems of fracture mechanics. Generally, these researches are concerned with crack in isotropic material without other micro defects. Actual structure, however, may contain micro defects as well as crack in manufacture processing or operation. If it contains mi defects near a crack, some different characteristics will be appear in fracture behaviors of the crack. This study examines the effect of the micro defect on stress intensity factor of center slant crack rectangular plate subjected to uniform uniaxial tensile stress. In this study, boundary element method(BEM) is used for analysis in stress intensity factor(SIF).