• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.130-143
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• 1993

Engineering ceramics have some excellent properties as the material for the mechanical components. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper, experiments are carried out to obtain the effect of "In-process dressing" to grind the Engineering ceramics with high efficiency. To save running time for dressing process and obtain restraint effect of diamond grain wear, "In-process dressing" system using WA stick type honing stone is proposed. Representative Engineering ceramics, such as AI$_{2}$O$_{3}$, Si$_{3}$N$_{4}$, are ground with diamond wheel. Also bending strength test is carried out to check upward tendancy of mecahnical properties as the result of machining defact restraint through the grinding machining method using "In-process dressing" process. Some results obtained in this study provide useful information to attain the high efficiency grinding and the high mechanical properties of Engineering ceramics.rties of Engineering ceramics.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.178-189
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• 1993

Engineering ceramics have some excellent properties as the material for the mechanical components. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper experiments are carried out to obtain the effect of "In-process dressing" to grind the Engineering ceramics with high efficiency. To save running time for dressing process and obtain restraint effect of diamond grain wear, "In-process dressing" system usint WA stick type honing stone is proposed. Representative High Strength Engineering ceramics A1$_{2}$O$_{3}$ and Si$_{3}$N$_{4}$are ground with diamond wheel. Also bending strengrh test is carried out to check upward tendancy of mecahnical properties as the result of machining defact restraint through the grinding maching method using "In-process dressing" process. Some results obtained in this study provide useful information to attain the high efficency grinding and the high mechanical properties of Engineering ceramics.rties of Engineering ceramics.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.23-36
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• 1990

The various composite materials have been developed with the development of high strength material and the increasement of composite material usage. Therefore many researchers have studied about the stress analysis and the fracture mechanics for composite materials through the experiment or the theory. Among the experimental methods, the photoelastic experiments have been used for the stress analysis of the isotropic structures or the anisotropic structures. To analyze the stresses in the orthotropic material with photoelastic experiment, the basic physical properties ( $E_{L}$, $E_{T}$, $G_{LT}$ , .nu.$_{LT}$ ) and the basic stress fringe values ( $f_{L}$, $f_{T}$, $f_{LT}$ )are needed, therefore the relationships between the basic physical properties and the stress fringe values were derived in this paper. When the stress fringe value is very large, it was assured by the experiment that the relationships are established both in the room temperature and in the high temperature (T = 130.deg. C). Therefore the basic physical properties can be obtained from the relationships by measuring stress fringe values instead of measuring the basic physical properties.rties.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.239-245
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• 2000

In this paper, the fundamental properties of diffractive optical element were investigated. Also, this work deals with theoretical approaches for achromatization in DOE's optical system based on thin lens theory. It is found that achromatization could be satisfied by one hybrid lens only, which is composed of a diffractive and a refractive element. In order to have compact optical system, we used the tele-photo type lens composed of a positive and a negative power elements instead of retro-focus lens. From the Gaussian brackets and Seidel aberration theory, the initial design was numerically obtained. The aberration properties of an initial design was aplanat and flat field. In order to correct the chromatic aberrations, refractive and diffractive elements were used on front element. This hybrid lens is also useful for correction of higher order aberrations. Compared to conventional design composed of refractive lenses only, this approach dramatically improved the compactness of the optical system. Finally, residual aberration balancing results in a lens with focal length of 3.89 mm and overall length of 5.19 mm, which has enough performance over an f-number of 4.0. Also, it is expected to fulfill all the requirements of a digital still camera lens. This optical system is superior to the current refractive lens system in the number of elements, weight, and aberration properties. rties.

• Journal of the Korean Wood Science and Technology
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• v.31 no.5
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• pp.96-103
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• 2003

This study was conducted to evaluate the tensile properties of metal plate connector for the domestic major softwoods, such as Korean red pine, Korean white pine, and Japanese larch. The maximum tensile load of Korean red pine was 3,612kgf in AA type, it was 1.2 and 1.7 times higher load than that of Japanese larch and Korean white pine. In EA type, it was 2,704kgf, and 1.1 and 1.5 times higher than the loads of Japanese larch and Korean white pine. The failure modes of metal plate connector were metal plate withdrawal, plate tensile failure, and wood shear block failure. The failure mode of Korean red pine connector was tensile failure of plate, that is reason of the high tensile load resistance for metal plate connections in Korean red pine. The mechanical properties of metal plate connector could be predicted by the Foschi model parameter. In the initial stage, the Korean red pine connector was stiffer than the other species. The design values for metal plate connector per tooth was 25, 22, and 15kgf for Korean red pine, Japanese larch, and Korean white pine in AA type and 19, 17, and 13kgf in EA type.