• 터널과지하공간
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• 제1권2호
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• pp.218-228
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• 1991

Natural stress measurements have been made at two sites at the depth of 280m from surface by means of stress relief overcoring methods using three directonal deformation gage. Attempts have been made to determine the state of natural stress in the rock and provide useful basic data to investigate the stress distribution and the determination of yield zone around powerhouse cavern. The magnitude and the direction of the miximum principal stress obstained from in-situ stress measurements is -96.1kgf/$\textrm{cm}^2$ and N38$^{\circ}$W, N35$^{\circ}$W respectively. Vertical stresses are in approximately agreement with the theoretical value. The ratio of measured to theoretical stresses are 85% at two sites. The ratio of average horizontal to vertical stresses(k=($\sigma$h)ave/$\sigma$v is 1.07.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.493-496
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• 2008

The residual stress generated in the boron steel blank formed via hot press forming process was predicted by JMatPro, a material property modeler, and Abaqus. The numerical predictions were compared by the experimental measurements obtained by the instrumented indentation. Both the predicted and measured principal stresses monitored at the outer surface of central bending position were qualitatively in good agreement. It was concluded that the residual stresses generated from hot forming process is not negligible as it has been generally assumed, although the spring back deformation is quite small. This should be specially considered from the part design stage since the tensile nature of the residual stress exhibited on the surface may lead to the stress corrosion cracking.

• 한국지반공학회지:지반
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• 제12권3호
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• pp.5-16
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• 1996

실리카질 모래에 대한 많은 시험결과로부터 삼축압축시첩과 평면변형시험간의 강도관계를 밀도와 파괴시 유효평균주응력의 함수로 표현하였다. 또한 파괴시 평균주응력과 축차응력간의 응력비가 내부마찰각의 함수로 잘 규정되었으며 그 비는 내부마찰각의 증가에 따라 감소하였다. 또한 중간주응력을 최대주응력과 최소주응력으로써 표현하였으며 이론적인 파괴면의 각도와 평면변형시험에서 관찰된 파괴면의 각도가 비교적 잘 일치함이 확인되었다.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1982-1989
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• 2004

In photoelasticity, the directions of principal stresses are given by isoclinic fringe patterns. In this study, photoelastic theory is represented by Jones calculus and the photoelastic 8-step phase shifting method is described. A feasibility study using computer simulation is done to get isoclinics from photoelastic fringes of a circular disk under diametral compression. Fringe patterns of the disk are generated from the stress-optic law. The magnitudes of isoclinics obtained from the fringe patterns of computer simulation and experiment are compared with those of theory. The results are close between them. Then, the 8-step phase shifting method is applied to get distributions of isoclinics along the specified lines of a cuved beam plate under tensile load. Experimental results obtained from the phase shifting method were compared with those of finite element analysis (ANSYS). It is confirmed that measurement of isoclinic distributions is possible by use of photoelasitc phase shifting method.

• 한국농공학회지
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• 제37권2호
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• pp.64-72
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• 1995

A series of cubical triaxial tests with three independent principal stresses was per- formed on Baekma river sand( # 40~100). It was found that the major principal strain at failure remained approximately constant for b values larger than about 0.3 for both the drained and undrained condition, and thereafter increased as b value decreased. The test results showed that the direction of the strain increment at failure form acute angles with the failure surfaces for both the drained and undrained condition. The results were thus not in agreement with the normality condition from classic plasticity theory. Howev- er, it was found that the projections of the plastic strain increment vectors on the octahe- dral plane were perpendicular to the failure surface in that plane. Failure strength in terms of effective stress anlaysis was greatly influenced by the variation of intermediate principal stress and so was failure criterion. The effective stress failure surfaces for both the drained and undrained condition were estimated quite well by use of Lade's failure criterion.

• Structural Engineering and Mechanics
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• 제28권4호
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• pp.411-442
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• 2008

Ground motions in near source region of large crustal earthquakes are significantly affected by rupture directivity and tectonic fling. These effects are the strongest at longer periods and they can have a significant impact on Engineering Structures. In this paper, it is aimed to determine near-fault ground motion effects on the nonlinear response of dams including dam-reservoir-foundation interaction. Four different types of dam, which are gravity, arch, concrete faced rockfill and clay core rockfill dams, are selected to investigate the near-fault ground motion effects on dam responses. The behavior of reservoir is taken into account by using Lagrangian approach. Strong ground motion records of Duzce (1999), Northridge (1994) and Erzincan (1992) earthquakes are selected for the analyses. Displacements, maximum and minimum principal stresses are determined by using the finite element method. The displacements and principal stresses obtained from the four different dam types subjected to these nearfault strong-ground motions are compared with each other. It is seen from the results that near-fault ground motions have different impacts on the dam types.

• 터널과지하공간
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• 제15권6호
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• pp.391-399
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• 2005

본 연구에서는 횡등방성 암반에서 이방성 정도에 따른 응력 차와 3차원 주응력 하의 터널방향, 이방성 정도에 따른 터널 단면에서의 2차원 응력 차를 이론적으로 구하였다. 구해진 응력상황 하의 터널에 대하여 $FLAC^{2D}$를 이용하여 이방성 고려여부에 따른 천단, 측벽, 바닥의 응력 차를 비교${\cdot}$검토하였다. 그 결과 이방성을 무시할 경우 응력 조건에 무관하게 주응력의 크기와 방향이 다르게 나타나며, 이방성 정도가 커질수록 응력차가 증가함을 알 수 있다. 이방성의 방향에 따라 응력 차가 달리 나타나며, 특히 이방성의 방향이 x축으로부터 시계반대방향으로 $45^{\circ}$와 $135^{\circ}$에서 가장 큰 응력 차가 발생함을 확인하였다.

• 대한토목학회논문집
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• 제11권1호
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• pp.153-166
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• 1991

모래(표준사(標準砂))의 응력(應力)-변형거동(變形擧動)에 관계되는 중간주응력(中間主應力)의 영향을 조사(調査)하기 위하여 삼주응력제어시험(三主應力制御試驗)을 응력경로(應力經路) 별(別)로 실시(實施)하였다. 시험과정(試驗課程)에 의하면 모래의 전단강도(剪斷強度)는 응력경로(應力經路)의 변화(變化)에 따라 다르게 나타나고 있다. 즉 내부마찰각(內部摩擦角)은 응력경로(應力經路)를 나타내는 Habib의 응력변수(應力變數) b값에 따라, b값이 0에서 0268의 범위(範圍)에서 크게 증가(增加)하고, b=0268~0.682의 범위(範圍)에서 거의 비슷하여, b=0.682~1.0의 범위(範圍)에서 약간 감소(減少)하지만 삼축신장상태(三軸伸張狀態)의 내부마찰각(內部摩擦角)은 삼축압축상태(三軸壓縮狀態)의 것보다 크게 나타난다. 이러한 응력변수(應力變數)의 변화(變化)에 따른 내부마찰각(內部摩擦角)의 변화(變化)는 공시체(供試體)의 밀도(密度)와 구속압(拘束壓)의 변화(變化)에 관계하지 않고 동일(同一)한 경향(傾向)을 나타내었다. 따라서 모래의 전단강도(剪斷強度)는 중간주응력(中間主應力)의 영향을 크게 받고 있음을 알 수 있다. 결과적(結果的)으로 본(本) 연구(硏究)에서 조사(調査)된 모래의 전단강도(剪斷強度)에 미치는 중간주응력(中間主應力)의 영향을 기존(旣存)의 연구(硏究)와 비교하여 보면 Lade Duncan 및 Matsuoda Nakai의 연구결과(硏究結果)와 비슷한 경향(傾向)을 나타내었으며 대략 이들의 파괴규준(破壞規準)사이에 있음을 알 수 있었다.

• 대한조선학회지
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• 제3권1호
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• pp.19-24
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• 1966

The maximum shear stress distribution in a stiffening flat attached to a plat undergoing a single tensile force has been investigated by photoelastic method. In the experiments a photoelastic model, as shown in Fig. 1, has been studied in the fields of a polariscope, as shown in Fig. 2. Fig. 3 shows the isoclinics and Fig. 4 and 5 are stress trajectories of the principal stresses and maximum shear stresses, respectively. Fig. 6 is the isochromatics in light field. The maximum shear stress at each point in the stiffener were determined from the isochromatics in both of light field of light field and dark field. Then the maximum shear stresses were divided by the average shear stress in the model, to obtain the ratio ${\tau}max/{\tau}av$ at each point. Finaly the variations of the ratio ${\tau}max/{\tau}av$ along the horizontal and vertical lines in the stiffener have been plotted, as shown in Fig. 7 and 8. The conclusions reached in this investigation are as follows: (1) The shear stresses transmitted to the stiffener through the juncture are concentrated on the end portions. (2) The maximum shear stress at the ends of the stiffener reaches to about 4 times of average shear stress. (3) The irregularities in the stress distribution are restricted in the end portions of the stiffener.

• 대한치과보철학회지
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• 제27권2호
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• pp.79-100
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• 1989

The Purpose of this study was to investigate material differences in stress transmission among various artificial teeth and denture base materials. For this study, a two-dimensional finite element model and a two-dimensional photoelastic model of a mandible with complete denture were made. A resin tooth and a porcelain tooth were used as artificial teeth, and a resin base, a metal lined base, and a soft-liner lined base were used as denture bases. An occlusal load was applied and principal stresses generated in the supporting tissues were compared. To test the impact stress transmission, strain gauge attached to the denture base specimens made of the different materials were made in thick and thin groups. Voltage outputs from hitting the specimen with a steel ball were compared. The results were as follows : 1. In FEM, increasing the mucosal thickness reduced the maximum principal stresses in the supporting tissues, but altering the tooth materials and the base materials induced no difference in the stresses. 2. In photoelastic model study, no difference in fringe order among the specimens were observed, but the thick mucosa group and the soft-liner lined group revealed a more uniform distribution of the load. 3. In strain measuring, the impact force transmission was highest in the soft-liner lined group, and was the lowest in the metal lined group(p<0.01). 4. In the thin group using the resin base, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the thick group. In the soft-liner lined group, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the metal lined group. 5. The thick group showed lower impact stress transmission than the thin group(p<0.01).