• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.259-262
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• 1998

PbTi $O_3$ family ceramics can be used for the piezoelectric transformer using thickness extensional vibration mode because it is a material with the large anisotropy between electromechanical coupling factors $k_{t}$ and $k_{p}$. However, PbTi $O_3$ family ceramics have a difficult poling condition on account of its large anisotrophy. In this study, the structural and piezoelectric properties of (P $b_{0.76}$ $Ca_{0.24}$)[ $Ti_{0.96}$(M $n_{1}$3/S $b_{2/3}$)$_{0.04}$] $O_3$ system ceramics were investigated as a function of poling voltage in order to find the best poling condition.ion.n.n.ion.n.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.3
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• pp.142-148
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• 2002

Considerable progress has been made in organic photorefractive materials, since the first observation of photorefractive phenomena from organic materials. Within recent years, a large number of organic photorefractive materials, especially amorphous materials, have been developed based on polymeric composites, fully functional polymers and the multi-functional chromophore approach. Among these organic photorefractive materials, some of them containing carbazole components as a charge transporting function have been demonstrated to exhibit high performance photorefractive effects. The carbazole building blocks with charge transporting function or multifunctions play a very important role in photorefraction. In this paper, it confirmed that acceptor-substituted carbazoles show the multifunctionality both of photoconductivity and electro-optic(EO) activity and photorefractive materials newly can be developed with acceptor-substituted carbazoles.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.365-372
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• 2006

A new meshfree formulation is developed for material discontinuity problems. A local interfacial jump function which is defined as hyperplane function is embedded in the meshless approximation and the approximation accurately models functions with jumps in the displacement and the derivative fields. Diffuse derivative technique copes with difficulty due to complexity of derivative computation of meshfree approximation. Collocation method with diffuse derivative accelerates computing speed for numerical solution. By solving inclusion and composite material problems, the robustness and effectiveness of the method are verified.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.309-314
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• 2000

Rubber is used as a primary suspension component in a vehicle or a mechanical structure. The aim of this study is to establish a procedure for measuring the material properties of rubber and to analyze the differences of material properties of virgin rubber and heat aged rubber. The effect of mechanical conditioning was shown and included in the procedures of tensile. compression. simple shear. and pure shear tests. In addition. using engine oil was recommended for compression test in order not to have barrelling. Moreover, based on the material properties of vil·gin rubber and heat aged rubber. equations of C10 and IRHD were proposed as a function of heat aging temperature and time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.1
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• pp.43-53
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• 2008

Surface edge crack in transversely isotropic piezoelectric material is analyzed. The concentrated antiplane mechanical and inplane electrical loadings are applied to an arbitrary point of the surface, where the impermeable crack boundary condition is imposed. Using Mellin transform the problem is formulated, from which Wiener-Hopf equations are derived. By solving the equations the solution is obtained in a closed form. Mechanical and electric intensity factors and energy release rate are obtained and discussed. This problem could be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2165-2171
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• 1997

The analysis model is the infinite power law creep material containing the rigid inclusion with crack shape. The present analysis is performed using the complex pseudo-stress function method. The strain rate intensity factor is developed as new fracture mechanics parameter which represents the stress and strain rate distribution near a crack tip in power law creep material. The strain rate intensity factor is developed in terms of Kolosoff stress functions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.162-166
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• 1996

This paper presents a position control of ultra-precision machine tool post using piezoelectric material. A stack-type piezoelectric actuator Is employed in a hinge-type tool holder. An assumed linear transfer function of the practical nonlinear plant is established through the comparison of transfer functions and step responses in the experiments and the simulations. Several types of feedforward/feedback controllers are designed via computer simulations using the assumed linear transfer function. The position tracking control experiments are undertaken to show the control efficiency of each controller.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.186-191
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• 2001

A crack with electrically impermeable surfaces in an electrostrictive material subjected to uniform electric loading is analysed. The effect of electric yielding on stress intensity factor is investigated by using a small scale yielding model and a strip yield zone model. Complete forms of electric fields and elastic fields are derived by using complex function theory. The electrical yield zone shapes for two models are different each other. The two models, however, predict similar yield zone sizes under the small scale yielding conditions. It is found that the influence of electric yielding on the stress intensity factor is insensitive to the modeling of the electrical yield zone shape.

• Smart Structures and Systems
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• v.6 no.8
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• pp.889-903
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• 2010

Idea of using piezoelectric materials with flexible structures made of rubber-like materials is quite novel. In this study a non-linear finite element model based on updated Lagrangian (UL) approach has been developed for dynamic response and its control of rubber-elastic material with surface-bonded PVDF patches/layers. A compressible stain energy density function has been used for the modeling of the rubber component. The results obtained are compared with available analytical solutions and other published results in some cases. Some results are reported as new results which will be useful for future references since the number of published results is not sufficient.

• Journal of the Korean Society for Railway
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• v.6 no.3
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• pp.194-202
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• 2003

To make railway carbody light in weight has advantages at some aspects of both manufacturing and maintenance. Recently, railway carbodys of steel structure have been lightened their weight by using aluminum extrusion plate. for the additional lightening of railway carbody, an optimal design which maintains proper strength and minimizes weight must be achieved. Optimization which is used with finite element analysis for aluminum extrusion plate has the disadvantage of consuming much time. In this paper, the method of equivalent material property which is available to FEA code is established using the method of equivalent stiffness. This method for plate is expanded into the method for railway carbody structure with plates and shells. An objective function is established for maximum stiffness of unit aluminum extrusion plate using established method of equivalent material property. We performed an multi-objective optimization using the penalty function method. As a result, recommendable shapes and sizes of unit extrusion plate for under-frame of high speed train is presented.