• Advances in nano research
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• 제17권3호
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• pp.275-284
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• 2024

In this article, a nonlocal stress-strain elasticity theory on the vibration analysis of Timoshenko sandwich beam theory with symmetric and asymmetric distributions of porous core and functionally graded material facesheets is introduced. According to nonlocal elasticity Eringen's theory (nonlocal stress elasticity theory), the stress at a reference point in the body is dependent not only on the strain state at that point, but also on the strain state at all of the points throughout the body; while, according to a new nonlocal strain elasticity theory, the strain at a reference point in the body is dependent not only on the stress state at that point, but also on the stress state at all of the points throughout the body. Also, with combinations of two concepts, the nonlocal stress-strain elasticity theory is defined that can be actual at micro/nano scales. It is concluded that the natural frequency decreases with an increase in the nonlocal stress parameter; while, this effect is vice versa for nonlocal strain elasticity, because the stiffness of Timoshenko sandwich beam decreases with increasing of the nonlocal stress parameter; in which, the nonlocal strain parameter leads to increase the stiffness of structures at micro/nano scale. It is seen that the natural frequency by considering both nonlocal stress parameter and nonlocal strain parameter is higher than the nonlocal stress parameter only and lower for a nonlocal strain parameter only.

• Journal of Magnetics
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• 제16권3호
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• pp.197-200
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• 2011

Using the full potential linearized augmented plane wave (FLAPW) method, the influences of uniform and tetragonal strains on the magnetic state have been explored for chemically ordered bulk $L1_2$ $FePt_3$. The ordered state displays antiferromagnetic $Q_1$ (AFM-$Q_1$) state but it transitions into antiferromagnetic $Q_2$ (AFM-$Q_2$) state at about 10% uniform strain. The ferromagnetic (FM) state is observed at 11% uniform strain. For tetragonal strain, it is also seen that the transition from AFM-$Q_1$ to AFM-$Q_2$ depends on the strength and direction of the applied strain. The FM state does not appear in this case. Magnetocrystalline anisotropy (MCA) calculations for tetragonal distortion reveal that the spin reorientation transition occurs. In addition, we find that the direction of magnetization and the magnitude of magnetic anisotropy energy strongly depend on the c/a ratio.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2002년도 제9회 학술 발표회 프로그램과 논문초록
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• pp.30-30
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• 2002

The native forms of common globular proteins are in their most stable state but the native forms of plasma serpins (serine protease inhibitors) show high-energy state interactions. The high-energy state strain of a ${\alpha}$$_1$-antitrypsin, a prototype serpin, is distributed throughout the whole molecule, but the strain that regulates the function directly appears to be localized in the region where the reactive site loop is inserted during complex formation with a target protease.(omitted)

• 한국농공학회지
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• 제41권2호
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• pp.70-79
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• 1999

The lower ground of structure, in which the strip loads, such as earth dams and embankments , are signiificantly working on , is required to be interpreted as a state of plane strain where the strain of intermediated principal stress direction is put '0' . The plane strain state is frquently observed in actural soil engineering case. For those case, drained stress-strain and strength behavior of Iksan weathered granite soil prepared in cubical specimens with cross-anisotropic fabric was studied by conventional triaxial compression, plane strain and cubial triaxial tests with independent control of the three principal stress. All specimens were loaded under conditions of principl stress directions fixed and aligned with the directions of the material axes. As a result of research , when a ground condition is analyzed under plane strain state, the shear strength obtained from the conventional triaxial compression test can be understimated.

• Structural Engineering and Mechanics
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• 제44권6호
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• pp.801-814
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• 2012

The strain rate effects on the interaction between a Mode I matrix crack and an inclined elliptic matrix-inclusion interface under dynamic tensile loadings were investigated numerically, and the results are in agreement with previous experimental data. It is found, for a given material system, that there are the first and the second critical strain rates, by which three kinds of the subsequent crack growth patterns can be classified in turn with the increasing strain rate, namely, the crack deflection, the double crack mode and the perpendicular crack penetration. Moreover, such a crack deflection/penetration behavior is found to be dependent on the relative interfacial strength, the inclined angle and the inclusion size. In addition, it is shown that the so-called strain rate effect on the dynamic strength of granule composites can be induced directly from the structural dynamic response of materials, not be entirely an intrinsic material property.

• Tribology and Lubricants
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• 제20권1호
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• pp.7-13
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• 2004

High strength steels are widely used as tribo-materials in the field. Previous study revealed that for mild steel, the states of strain on the worn surface measured by X-ray diffraction has a good relationship with the state of wear. The objective of this study is to identify the relationship between the state of strain on the worn surface and the state of wear in high strength steels. Sliding wear tests were carried out using several hardened steels. X-ray diffraction tests were conducted to analyze the state of strain on the worn surface during wear. The experimental results indicated that the state of strain on worn surface in the hardened steel shows the same tendency as in the mild steel. It is clear that change of half value width on the worn surface as a function of sliding speeds is broadly similar in shape to wear characteristics curve and its magnitude has a good relationship with the wear rate at two different wear modes in the hardened steel.

• 한국지반공학회논문집
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• 제19권1호
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• pp.77-92
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• 2003

사질토에서의 한계상태정수 결정시 근본적인 물리적 과정들과 고유적 인 한계성들을 파악하기 위하여 일련의 표준삼축시험을 실시하였다. 시험결과에 의하면, 주어진 흙에 대하여 한계상태마찰각은 배수조건에 상관없이 일정한 반면에, e-log p＇공간상에서의 한계상태선은 주로 표준삼축시험에서 충분치 못하게 도달하는 변형률과 비배수시험에서의 변형률 국지화효과 때문에 배수조건에 따라 다른 결과를 보였다. 실내시험을 통하여 한계상태정수를 산정하는 최선의 방법은 균일하고 느슨하게 성형된 시료를 배수조건하에서 전단하는 것으로 나타났다. 더불어 배수시험에서 다일러턴 시효과나 변형률 국지화효과를 피할 수 있는 시험을 계획하기 위한 참고상태정수를 제시하였다.

• 한국정밀공학회지
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• 제2권2호
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• pp.31-42
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• 1985

The metal flow and the strain distribution is investigated for the steady state and non-steady state bulk deformation processes by using an improved visioplasticity method which includes the effective smoothing scheme. The comparison of various smoothing schemes leads to the selection of the five- point least square smoothing method which is employed to reduce the measurement errors. As a steady state forming process experiments are carried out for axisy- mmetric forward extrusion through conical and curved dies of various area reduc- tions using Aluminum and steel billets. Axisymmetric backward extrusion is chosen for a nonsteady state forming process. In axisymmetric forward extrusion the results from visioplasticity show that the curved die of a fourth-order polynomial renders more uniform distribution of strain rates and strains. Higher reduction leads to greater strain rates at the outer side of the billet. The visioplastic observation for axisymmetric backward extrusion as a non-steady state deformation process shows the concentration of higher strain at the inner wall of the extruded product. The visioplastic results in forward extrusion are in agreement with the computed results by the finite element method. It is thus shown that the visio- plasticity combined with a smoothing technique is an effective method to determine the pattern and the distribution of strain rates and strains.

• KCI Concrete Journal
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• 제12권2호
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• pp.55-72
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• 2000

This paper proposes a mechanical model to describe the load-deformation responses of the reinforced concrete plate members under service load state. An Analytical method is introduced on the basis of the rotating crack model which considers equilibrium, compatibility conditions, load-strain relationship of cracked member, and constitutive law for materials. The tension stiffening effect in reinforced concrete structures is taken into account by the average tensile stress-strain relationship from the load-strain relationship for the cracked member and the constitutive law for material. The strain compatibility is used to find out the crack direction because the crack direction is an unknown variable in the equilibrium and compatibility conditions. The proposed theory is verified by the numerous experimental data such as the crack direction, moment-steel strain relationship, moment-crack width relationship. The present paper can provide some basis for the provision of the definition of serviceability for plate structures of which reinforcements are deviated from the principal stresses, because the present code defines the serviceability by the deflection, crack control, vibration and fatigue basically for the skeletal members. The proposed theory is applicable to predict the service load state behavior of a variety of reinforced concrete plate structures such as skew slab bridges, the deck of skew girder bridges.

• 터널과지하공간
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• 제20권2호
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• pp.119-124
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• 2010

암석의 인장강도에 미치는 변형률 속도 및 수분포화의 영향을 파악하기 위하여 건조상태 및 포화상태 3종류의 암석에 대해서 여러 가지 변형률 속도에서의 홉킨슨효과를 이용한 인장파괴실험을 실시하였다. 실험결과 건조상태뿐만 아니라 포화상태에서도 변형률 속도가 증가할수록 암석의 인장강도는 증가하였다. 특히, 건조 상태에 있어서 암석의 동적인장강도는 암석의 종류와는 상관없이 변형률 속도의 약 1/3승에 비례하는 경향을 나타내었다. 또한, 수분포화의 영향으로 공극률이 높은 사암과 응회암은 건조상태와 비교하여 인장강도가 감소하였으나, 공극률이 0.49%로 낮은 화강암은 건조상태와 포화상태와의 사이에 유의한 차이는 없었다.