• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.759-764
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• 2010

In this study, from the comparison of the results obtained by 3 dimensional dynamic analyses using the inverse-calculated properties and those by calculating using the real earthquake records, the inverse calculation method for obtaining the dynamic properties of rockfill materials was verified. The fundamental frequency of the dam was determined by analyzing the response spectrum of observed records. By repeated dynamic analyses for various shear moduli of rockfill material, the shear moduli in the rockfill zone that satisfy the relationship between the fundamental frequency obtained by analysis of the observed records and that by numerical analyses were determined. Using the determined shear moduli, the 3 dimensional dynamic analyses for the dam were carried out and the result were compared with the real response characteristics on the crest of the dam.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.84-90
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• 2001

The electro-reheoligical(ER) effect refers to the abrupt change in viscosity in certain suspensions on application of an electric field. This paper presents experimental results on material properties of an ER fluids subjected to electrical fatigues. As a first step, two types of EF fluids are made of arabic gum and methyl cellulose(MC) choosing 25% of parti-cle weight-concentration. Following the construction of test mechanism for electrical durability of ER fluid, the dynamic yield shear stress and current density of the ER fluids are experimentally distilled as a function of electric field. The yield shear stress of operated ER fluids are distilled and compared with those of unused ER fluids.

• Structural Engineering and Mechanics
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• v.18 no.6
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• pp.759-768
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• 2004

The torsion of a penny-shaped crack in a transversely isotropic strip is investigated in this paper. The shear moduli are functionally graded in such a way that the mathematics is tractable. Hankel transform is used to reduce the problem to solving a Fredholm integral equation. The crack tip stress field is obtained by taking the asymptotic behavior of Bessel function into account. The effects of material property parameters and geometry criterion on the stress intensity factor are investigated. Numerical results show that increasing the shear moduli's gradient and/or increasing the shear modulus in a direction perpendicular to the crack surface can suppress crack initiation and growth, and that the stress intensity factor varies little with the increasing of the strip's height.

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.133-139
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• 2007

Low density polyethylene nanocomposites were prepared by melt intercalating maleic anhydride grafted polyethylene and montmorillonite clay. It has been found that maleic anhydride has promoted strong interactions between polyethylene and montmorillonite, leading to the homogeneous dispersion of clay layers. Rheological experiments revealed that prepared nanocomposites exhibited shear thinning behaviour. Polyethylene nanocomposites exhibited an increase in steady shear viscosities compared to virgin polyethylene owing to strong polymer clay interactions. The tensile strength of nanocomposites was improved but elongation at break decreased considerably. Also, barrier properties improved significantly with montmorillonite content.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1371-1374
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• 2007

The velocity auto-correlation (VAC) function of liquid argon in the Green-Kubo formula decays quickly within 5 ps to give a well-defined diffusion coefficient because the velocity is the property of each individual particle, whereas the stress (SAC) and heat-flux auto-correlation (HFAC) functions for shear viscosity and thermal conductivity have non-decaying, long-time tails because the stress and heat-flux appear as system properties. This problem can be overcome through N (number of particles)-fold improvement in the statistical accuracy, by considering the stress and the heat-flux of the system as properties of each particle and by deriving new Green-Kubo formulas for shear viscosity and thermal conductivity. The results obtained for the transport coefficients of liquid argon obtained are discussed.

• Advances in materials Research
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• v.9 no.1
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• pp.33-48
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• 2020

With the use of differential quadrature method (DQM), forced vibrations and resonance frequency analysis of functionally graded (FG) nano-size beams rested on elastic substrate have been studied utilizing a shear deformation refined beam theory which contains shear deformations influence needless of any correction coefficient. The nano-size beam is exposed to uniformly-type dynamical loads having partial length. The two parameters elastic substrate is consist of linear springs as well as shear coefficient. Gradation of each material property for nano-size beam has been defined in the context of Mori-Tanaka scheme. Governing equations for embedded refined FG nano-size beams exposed to dynamical load have been achieved by utilizing Eringen's nonlocal differential law and Hamilton's rule. Derived equations have solved via DQM based on simply supported-simply supported edge condition. It will be shown that forced vibrations properties and resonance frequency of embedded FG nano-size beam are prominently affected by material gradation, nonlocal field, substrate coefficients and load factors.

• Steel and Composite Structures
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• v.51 no.2
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• pp.103-116
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• 2024

Based on the consistent couple stress theory (CCST), we develop a unified formulation for analyzing the static bending and free vibration behaviors of functionally graded (FG) microscale beams (MBs). The strong forms of the CCST-based Euler-Bernoulli, Timoshenko, and Reddy beam theories, as well as the CCST-based sinusoidal, exponential, and hyperbolic shear deformation beam theories, can be obtained by assigning some specific shape functions of the shear deformations varying through the thickness direction of the FGMBs in the unified formulation. The above theories are thus included as special cases of the unified CCST. A comparative study between the results obtained using a variety of CCST-based beam theories and those obtained using their modified couple stress theory-based counterparts is carried out. The impacts of some essential factors on the deformation, stress, and natural frequency parameters of the FGMBs are examined, including the material length-scale parameter, the aspect ratio, and the material-property gradient index.

• Proceedings of the KACD Conference
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• 2002.11a
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• pp.669-669
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• 2002

No Abstract, See Full Text

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.153-154
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• 2011

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.31-38
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• 2020

Controlled Low Strength Material (CLSM) has high fluidity and self-compaction characteristics. CLSM is mainly used for backfilling the excavated road. Early-age properties of CLSM should be characterized for fast restoration of the road. In this study, shear wave monitoring and Vicat needle test are performed to investigate the early-age properties of CLSM depending on the setting time. CLSM consists of CSA cement, fly ash, silt and sand, accelerator, and water. Five fly ashes with different chemical properties are used for CLSM samples. The penetration of CLSM along setting time is obtained through the Vicat needle test. A pair of bender elements are placed in a mold for shear wave measurement, and the change in shear waves with the setting time is monitored. The experimental results show that, regardless of the type of fly ash, the penetration depth decreases and the shear wave velocity increases with the setting time. Depending on the type of fly ash, initial and final times and shear wave velocity change. After testing, the correlation between penetration and shear wave velocity is obtained with high coefficient of determination. The shear wave measurement technique using the bender element can be used to identify early-age properties.