• Steel and Composite Structures
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• 제34권5호
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• pp.657-670
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• 2020

In this paper, vibration analysis of functionally graded nanoshell is studied based on the sinusoidal higher-order shear and normal deformation theory to account thickness stretching effect. To account size-dependency, Eringen nonlocal elasticity theory is used. For more accurate modeling the problem and corresponding numerical results, sinusoidal higher-order shear and normal deformation theory including out of plane normal strain is employed in this paper. The radial displacement is decomposed into three terms to show variation along the thickness direction. Governing differential equations of motion are derived using Hamilton's principle. It is assumed that the cylindrical shell is made of an arbitrary composition of metal and ceramic in which the local material properties are measured based on power law distribution. To justify trueness and necessity of this work, a comprehensive comparison with some lower order and lower dimension works and also some 3D works is presented. After presentation of comparative study, full numerical results are presented in terms of significant parameters of the problem such as small scale parameter, length to radius ratio, thickness to radius ratio, and number of modes.

• Structural Engineering and Mechanics
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• 제66권5호
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• pp.665-676
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• 2018

In this study, a four-node quadrilateral partial mixed plate element with low degrees of freedom (dofs) is developed for static and free vibration analysis of functionally graded material (FGM) plates rested on Winkler-Pasternak elastic foundations. The formulation of the presented finite element model is based on a parametrized mixed variational principle which is developed recently by the first author. The presented finite element model considers the effects of shear deformations and normal flexibility of the FGM plates without using any shear correction factor. It also fulfills the boundary conditions of the transverse shear and normal stresses on the top and bottom surfaces of the plate. Beside these capabilities, the number of unknown field variables of the plate is only six. The presented partial mixed finite element model has been validated through comparison with the results of the three-dimensional (3D) theory of elasticity and the results obtained from the classical and high-order plate theories available in the open literature.

• Journal of Mechanical Science and Technology
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• 제15권10호
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• pp.1386-1397
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• 2001

In this paper, the plane elasticity equations are used to investigate the in-plane normal (mode I) and shear (mode II) behavior of a crack perpendicular to and terminating at the interface in bonded media with a graded interfacial zone. The interfacial Bone is treated as a nonhomogeneous interlayer with the continuously varying elastic modulus between the two dissimilar, homogeneous semi-infinite constituents. For each of the individual loading modes, based on the Fourier integral transform technique, a singular integral equation with a Cauchy kernel is derived in a separate but parallel manner. In the numerical results, the values of corresponding modes of stress intensity factors are illustrated for various combinations of material and geometric parameters of the bonded media in conjunction with the effect of the material nonhomogeneity within the graded interfacial zone.

• Structural Engineering and Mechanics
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• 제74권4호
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• pp.471-479
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• 2020

This paper aims to study the effect of the elastic nonlocality on the transient waves in a two-dimensional thermoelastic medium influenced by thermal loading due to the laser pulse. The bounding plane surface is heated by a non-Gaussian laser beam. The problem is discussed under the Eringen's nonlocal elasticity model and the Green-Naghdi (G-N) theory with and without energy dissipation. The normal mode analysis method is used to get the exact expressions for the physical quantities which illustrated graphically by comparison and discussion. The effects of nonlocality and different values of time on the displacement, the stresses, and the temperature were made numerically. All the computed results obtained have been depicted graphically and explained.

• 한국농공학회지
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• 제42권1호
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• pp.92-98
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• 2000

This study is performed to evaluate the elastic properties of rice straw ash concrete using reices straw ash, cement, natural sand, gravel, and superplasticizer. The following conclusions are drawn ; The ultrasonic pulse velicity is in the range of 4,084 ~4,336m/s , which has showed about the same compared to that of the normla cement concrete. The highest ultrasonic pulse velocity is showed by 5 % rice straw ash filled rice straw ash concrete. The dynamic and static modulus of elasticity is in the range of 294 $\times$10$^3$ ~347 $\times$ 10$^3$ and 266 $\times$10$^3$~328 $\times$10$^3$kgf/㎤ , respectively. It is showed about the same compared to that of the normal cement concrete. The Poisson's number of rice straw ash concrete is less than that of the normal cement concrete.

• 한국농공학회지
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• 제42권1호
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• pp.99-104
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• 2000

This study is performed to evaluate the physical and mechanical properties of pine needle ash (PNA) concrete. Materials used for this experiment are PNA, normal portland cement, natural fine and coarse aggregate. Test results show that the unit weights of PNA concrete are decreased 1 % ∼3% and the highest strength is achieved by 5% PNA filled PNA concrete. Compresive strength increased by 5% , tensile strength by 20% and bending strength by 15% as compared with those of the normla cement concrete , respectively. The highest ultrasonic pulse velicity and dynamic mudulus of elasticity are acheved by 5% PNA filled PNA concrete, which are similar to those of the normal cement concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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• pp.37-44
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• 1998

The objective of this study is development of high strength lightweight concrete and application or structural use. For this, mix proportions for each strength level were selected from lab tests, and adapted to producing ready-mixed concrete in batcher plant. It was very important to prewet the lightweight aggregates sufficiently for producibility and also workability. Splitting tensile strength of high-strength lightweight concrete produced has lower values than that of normal weight concrete, but modulus of rupture and modulus of elasticity are not less than normal weight concrete. The strength reduction factor ($\lambda$) for sand-lightweight concrete make higher than 0.85 present in structures using high-strength lightweight concrete. And it was showed that not parabola distribution but triangular distribution of stress in compression zone.

• 산업기술연구
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• 제33권A호
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• pp.109-116
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• 2013

In this study the compressive strength data were collected from ready­mix concrete plants, and the analysis result showed that when using A­D test the concrete of 24MPa is suitable than that of 21MPa for normal distribution. The prediction formula for average compressive strength were proposed to $f_{cu}=f_{ck}+4(MPa)$. When comparing the proposed equations and existing relationship, the estimation variations of elastic modulus and creep modulus were not significant. The proposed equation confirmed that there was no effect to the influence function for modulus of elasticity and creep. Therefore, it was concluded that the proposed equation could replace the exiting interaction formula.

• 한국농공학회지
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• 제41권5호
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• pp.99-103
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• 1999

This study examines the stress-strain and acid-resistance of pine needle ash (PNA) concrete. Materials used for this experiment are PNA , normal portland cement, natural fine and coarse aggregate. Test results show that the highest static modulus of elasticity are achieved by 5 % PNA filled PNA concrete. Acid-resistance of PNA concrete is increased with increase of the content of PNA. It is 1.29 times of the normal cement concrete for 5 % PNA filled PNA concrete and 2.57 times fo r15% PNA filled PNA concrete, based on the elased days for 25% mass loss of original mass immersed in the 5% H2SO4 solution. Accordingly, PNA concrete will greatly improve the properties of concrete.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.324-329
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• 1999

This study is performed to evaluate an elastic properties of rice straw ash concrete . The following conclusions are drawn ; The ultrasonic pulse velocity is in the range of 4.084 ∼4.336㎧, which has showed abuot the same compared to that of the normal cement concrete. The highest ultrasonic pulse velocity is showed by 5% rice straw ash filled reice straw ash concrete. The dynamic and static modulus of elasticity i sin the range of 294 ${\times}$103 ∼ 347 ${\times}$103 and 266${\times}$ 103 ∼347${\times}$ 103 kgf/$\textrm{cm}^2$ , respectively. It is showed about the same compared to that of the normla cement concrete. The poisson's number of rice straw ash concrete is less than that of the normal cement concrete . The stress-strain curve of concrete which is contained rice straw ash within 10% appear slowly and over 10% appear almost straightly.