• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.225-231
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• 2003

A new three-dimensional thin shell element for a structure containing an integrated distributed piezoelectric sensor and actuator is Proposed. The assumed strain formulation and the bubble function are introduced to improve the performance of the shell element. A finite element formulation gives a general tool that can predict the static or dynamic responses of the shell with piezoelectric sensor/actuator. The verification through the calculation of the static response for the piezoelectric bimorph beam shows that the results agree with those from the theoretical analysis very well. Dynamic response of a shell shows that the reduction of vibration is possible with the introduction of the piezoelectric shell sensor and actuator. However. the curvature of sensor/actuator is an obstacle for application, since the flexible PVDF is not strong enough and the PZT with curvature should be made specially.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2078-2086
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• 1996

This paper introduces two three-dimensional eight-node hexagonal elements obtained by using multivariable variational mehtod. Both of them are based on the modified hellinger-reissner principle to employ incompatible displacements and assumed stresses of assumed strains. The internal functions of element are introduced to as element formulation through two different methods : the first one uses the functions determined directly from the element boundary condition of the incompatible displacements ; while the second, being a kind of B-bar mehtod, employs the modification technique of strain-displacement matrix to pass the patch test. The elements are evaluated on the selective problems of bending and material incompressibility with regular and distorted meshes. The results show that the new elements perform with good accuracy in both of deformation and stress calculation and they are insensitive to distorted geometry of element.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.272-282
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• 2000

Based on numerical reduced minimization theory, new anisoparametric 3-node elements for out-of-plane curved beam are developed. The elements are designed to be free from spurious constraints. In this paper, the effect of the Jacobian upon numerical solution is analyzed and predicted through reduced minimization analysis of anisoparametric 3-node elements with different Jacobian assumption. The prediction is verified by numerical tests for circular and spiral out-of-plane deformable curved beam models. This paper proposes two kinds of 3-node elements with 7-DOF; one element employs 2-point integration for all strains, and the other element uses 3-point integration with a constant Jacobian within element for calculation of shear strain.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.143-146
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• 2001

The evolution of dynamic recrystallization (DRX) was studied with torsion test for AISI 304 stainless steel in the temperature range of $900-1000^{\circ}C$ and strain rate range of 0.05-5/sec. The evolution of DRX was investigated with microstructural analysis and change of flow stress curve slope. The investigation of serrated grain boundaries using electron back scattered diffraction (EBSD) analysis indicated that the nucleated new DRX grain size was similar to the size of bulging part. Before the steady state, the dynamically recrystallizing grains do not remain a constant size and gradually grow to the size of fully DRX grain at steady state. The calculation of grain size was based on $X_{DRX}$ and the assumption, which the nucleated DRX grains are growing to the steady state, continuously. It was found that the calculated results agreed with the microstructure of the alloy.

• Computers and Concrete
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• v.9 no.5
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• pp.357-374
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• 2012

The aim of this paper is to develop a procedure able to calculate the long-term stress and strain patterns in modern prestressed composite structures which are largely influenced by creep and shrinkage and whose final static configuration is the result of many phases of loading and restraints conditions. The introduction of equivalent moduli, depending on the viscous and elastic features of materials, can guarantee a significant simplification of the problem presented above. The proposed calculation model has been used to design the "Quattroquercie Viaduct" located on the highway "A3" Salerno-Reggio Calabria, Italy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.914-917
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• 2001

Single-shot laser damage of thin Cr films on glass substrates has been studied to understand the cracking and peeling-off mechanism. A numerical model is developed for the calculation of transient heat transfer and thermal stresses in Cr films during excimer laser irradiation and cooling, the transient temperature, and the stress-strain fields are analyzed by using a three-dimensional finite-element model of heat flow. According to the numerical analysis for the experimentally determined cracking and peeling-off conditions, cracking is found to be the result of the tensile brittle fracture due to the excessive thermal stresses formed during the cooling process, while peeling-off is found to be the combined result of films bulging from the softened glass surface at higher temperature and the tensile brittle fracture during the cooling process.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.181-183
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• 2011

This study was carried out about construction management plan to reduce water leakage of underground parking lot in the apartment housing. To minimize effect of upper working load, installation position of jack support and paving with rubble on the top of underground parking lot were studied. By calculation shrinkage strain of underground parking lot scale, water leakage risk in design of level difference was studied. In this study, the basic data about construction management was provided to reduce water leakage of underground parking lot in the apartment housing.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.339-345
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• 1998

The creep of concrete structures caused by variable stresses is mostly calculated by step-by-step method based on the superposition of creep function. Although most practical application is carried out by this linear assumption, significant deviations between predictions and experiments have been observed when unloading takes place, that is, stress is reduced. The recovery is overestimated. The main purpose of this study is to present the application method of the creep analysis model which is expressed with both creep function and creep recovery function to concrete structures where is expressed with both creep function and creep recovery function to concrete structures where increase or decrease of stress is repeated . To apply two function method to time analysis of concrete structures, this study presents the calculation method of creep strain increment for stress variation. Then, this paper executes the time analysis for an example using suggested method, and compares theses results with the previous analysis values and experimental results.

• Journal of Ocean Engineering and Technology
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• v.16 no.4
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• pp.32-36
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• 2002

In this paper, a numerical methodology for health monitoring of weldment was proposed using finite element method coupled with continuum damage mechanics. The welding-induced residual stress distribution of T-joint weldment was calculated using a commercial finite element package SYSWELD+. The distribution of latent damage was evaluated from the stress and strain components taken as the output of a finite element calculation. Numerical examples were given to demonstrate the usefulness of this so-called "post-processing approach" in the case of welding-induced damage assessment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.486-494
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• 1995

This paper introduces two kinds of new four-node quadrilateral axisymmetric elements with independently-assumed strains. They are formulated by the modified Hellinger-Reissner principle so as to employ incompatible displacements and assumed strains. In one of the present elements, the strains from incompatible displacements are corrected to pass the constant strain patch test. The other contains incompatible functions that are obtained from the element boundary condition. The elements are evaluated on the several problems of bending and material incompressibility with regular and distorted meshes. The results show that the new element performs excellently in deformation and stress calculation.