• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.315-322
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• 2003

Cyclic simple shear tests were performed to find out the effect of preshear on dynamic strength of the sandy soil. Tests were performed for the specimens with 40% and 60% of relative density, under three different effective vertical stress of 50, 100 and 200kPa. For 50 and 100kPa, preshear ratios 0.00, 0.08, 0.12 and 0.16 were given, respectively, For low and high relative densities, two different results are shown in dynamic tests. Under the dense conditions, the maximum shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) and the cyclic shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) causing a certain shear strain increase with augmenting preshear ratio(${\alpha}$). However, the maximum shear stress ratio and the cyclic shear stress ratio increase or decrease with increasing preshear ratio under the loose conditions. Correction factor(K$\_$${\alpha}$/) for preshear increases at an early stage and then decreases with increasing preshear ratio at loose condition and increase with increasing preshear ratio at dense condition. Correction factor (K$\_$${\alpha}$,Max/) for preshear increases with the increasing preshear ratio irrespective of relative density, and the value of has same behavior as K$\_$${\alpha}$/.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.921-926
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• 2001

In this paper the biaxial failure criteria and stress-strain response for plain concrete are studied under uniaxial and biaxial stress(compression-compression, compression-tension, and tension-tension combined stress). The concrete specimens of a square plate type are used for uniaxial and biaxial loading. The experimental data indicate that the strength of concrete under biaxial compression, f2/fl=-l/-1, is 17 percent larger than under uniaxial compression and the poisson's ratio of concrete is 0.1745. On the base of the results, a biaxial failure envelope for plain concrete that the uniaxial strength is 398kgf/$cm^{2}$ are developed. The biaxial failure behaviors for three biaxial loading areas are also plotted respectively. In addition, the characteristics of stress-strain response under biaxial compression are compared and verified with the experimental and analytical results.

• 한국지반공학회지:지반
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• 제9권4호
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• pp.83-92
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• 1993

세 주응력을 서로 독립적으로 조절할 수 있는 입방체형삼축시험기를 이용하여 모래에 대한 일련의 배수삼축시험이 실시되었다. 실험결과 모래의 응력 -변형률거동과 강도는 중간주응력의 크기에 따라 각기 다른 특성을 보이는 것으로 나타났다. 우선 최소주응력이 일정한 상태에서 중간 주응력이 증가함에 따라 파괴시의 축변형률 e1은 감소하는 경향이 있으며 체적팽창현상은 증가 하는 것으로 나타나고 있다. 그리고 내부마찰각은 축차응력비 b가 증가함에 따라 증가하다 b가 1 부근에 접근하면서 약간 감소하는 경향을 보이고 있다. 한편 Mohrfoulomb규준은 모래의 파괴 강도를 과소산정하는 경향을 보이고 있으나 Lade의 파괴규준은 시험치와 좋은 일치를 보이고 있다.

• Journal of Magnetics
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• 제16권3호
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• pp.294-299
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• 2011

Nd-Fe-B high performance magnets were prepared by die-upset forging. The effects of the deformation parameters on magnetic properties and flow stress were studied. Deformation temperatures in the range of $600{\sim}900^{\circ}C$ enable to achieve an effective anisotropy and temperature $800^{\circ}C$ proves to be suitable for deformation of Nd-Fe-B magnets. The amount of c-axis alignment along the press direction seems to depend on the amount of deformation and a saturation behavior is shown at deformation ratio of 75%. Magnetic properties are also related to strain rate, and maximum energy product is attained at an optimum strain rate of ${\varphi}=1{\times}10^{-2}s^{-1}$. By analyzing the relationship of stress and strain at different deformation temperature during die-upset forging process, deformation behavior of Nd-Fe-B magnets was studied and parameters for describing plastic deformation were obtained. Nd-rich boundary liquid phase, which is additionally decreasing the flow stress during deformation, is supposed to play the role of diffusion path and enhance the diffusion rate.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.163-170
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• 1999

Although the bulge forming technique is currently employed in commercial superplastic forming processes, the uniaxial tensile test is still the most commonly used method for the evaluation of the superplasticity of materials due to its simplicity in testing. However, the results obtained from the uniaxial tensile test can not be applied in analyzing the characteristics of the real parts formed in multi-axial stress state. In this paper, using the tensile test specimen obtained from the square cup manufactured by superplastic forming, tensile strength and elongation have been investigated according to the strain and cavity volume fraction. From the result of experiment, tensile strength and elongation are decreased according to the strain and cavity in Al-6%Cu-0.4%Zr alloy. On condition of uniaxial stress, cavity volume fraction is increased on linear according to the increasement of thickness strain. However, on condition of biaxial stress there are critical point( E t=1.5-1.6) that the slope, the ratio of cavity volume fraction and strain, have been changed. Therefore, cavity volume fraction is different with respect to stress condition, although the same strain.

• Computers and Concrete
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• 제24권5호
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• pp.445-452
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• 2019

In this paper, dynamic stress, strain and deflection analysis of concrete pipes conveying nanoparticles-water under the seismic load are studied. The pipe is buried in the soil which is modeled by spring and damper elements. The Navier-Stokes equation is used for obtaining the force induced by the fluid and the mixture rule is utilized for considering the effect of nanoparticles. Based on refined two variables shear deformation theory of shells, the pipe is simulated and the equations of motion are derived based on energy method. The Galerkin and Newmark methods are utilized for calculating the dynamic stress, strain and deflection of the concrete pipe. The influences of internal fluid, nanoparticles volume percent, soil medium and damping of it as well as length to diameter ratio of the pipe are shown on the dynamic stress, strain and displacement of the pipe. The results show that with enhancing the nanoparticles volume percent, the dynamic stress, strain and deflection decrease.

• 대한토목학회논문집
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• 제30권3A호
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• pp.265-275
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• 2010

콘크리트 충전형 합성부재와 콘크리트 피복형 합성부재는 압축하중 상태에서 강재에 의한 콘크리트의 구속효과와 콘크리트에 의한 강재의 국부좌굴에 대한 보강효과를 기대할 수 있는 압축부재이다. 기존의 연구결과를 바탕으로 RC, CFT, CET 압축부재에 대한 응력-변형률 관계와 하중-변위 관계를 철근비와 강재비에 따라 해석하였다. 이후 도출된 해석결과를 실험결과와 비교한 후, 구속효과가 하중과 변위에 미치는 영향을 평가하여 기존의 응력-변형률 관계를 수정하였다. 또한 국외 각국의 설계기준의 설계강도와 비교하여 수정된 응력-변형률 관계 제안식을 검토하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.651-656
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• 2000

The strain compatibility analysis shows that the influential parameters of loading type, reinforcing ratio, and span-depth ratio affect on the tendon stress in unbonded prestresses concrete member significantly. However, existing test results did not comply exactly with the analytical results. In consequence, the present study was planned to examine the parameters in order to complete Moon/Lim's design equation. The test variables with 12 specimens were loading type, reinforcing ratio, and span-depth ratio. As results, the effect of influential parameters were examined throughly and Moon/Lim's design equation was proven to be accurate.

• 전자공학회논문지T
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• 제35T권1호
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• pp.75-81
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• 1998

본 논문은 장방형 다이아프램 형상과 단일형 피에조저항 전단응력 스트레인 게이지 와의 관계를 해석하여 최적의 전단응력 압력센서를 설계하기 위한 것이다. 다이아프램상의 전단응력을 시뮬레이션 하기 위하여 유한요소법 분석 프로그램 ANSYS 5.1를 사용하였다. 시뮬레이션 결과는 다이아프램 형상비가 3일때 스트레인 게이지의 위치는 중앙에서, 크기는 전체 장방형 다이아프램 크기의 8%를 점유할때 온도에 안정적이고, 최대 감도를 가진다는 것을 조사하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권1호
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• pp.54-62
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• 2019

본 논문에서는 압축파괴에너지를 이용하여 고강도 구속콘크리트에 대한 응력-변형률 모델을 제안하였다. 참고문헌[5]에서 저자가 실시한 압축실험에는 변형률 게이지를 부착한 아크릴 막대를 실험체의 중앙부에 매립하여 압축부재의 국부 변형률 측정을 시도하였다. 이 아크릴 막대를 이용한 국부 변형률 측정은 매우 효과적인 것으로 나타났다. 압축파괴영역길이는 아크릴 막대로부터 측정된 국부 변형률 분포에 기초하여 정의되었다. 구체적으로, 구속콘크리트의 국소파괴영역길이는 압축강도 발현시의 변형률 ${\varepsilon}_{cc}$의 2배 이상 변형률이 증가하는 영역으로 정의하였다. 또한, 동일한 횡구속압을 받는 압축부재에 흡수된 에너지양은 부재의 형상이나 크기에 관계없이 일정하다는 가정에서 압축 파괴에너지를 도입한 구속콘크리트의 응력-변형률 관계를 제안하였다. 본 연구에서 제안된 모델은 본 연구의 실험결과뿐만 아니라 타 연구자들의 실험결과를 대체적으로 잘 예측하는 것으로 나타났다.