• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.129-138
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• 2000

Composites are finding increasing use in a wide variety of engineering applications due to their outstanding mechanical properties. A number of studies have focused on the development of new materials as well as the response of composite structures to static and dynamic loads by assuming the external driving forces to be deterministic. However, there ate many situations in practice where the exciting forces vary randomly. In this work, the nonlinear response of laminated composite plates excited by stochastic loading is studied by the finite element method. Classical, first-order and third-order shear theories for plates are used in the finite element formulation. Since most composites exhibit significant nonlinearity in the shear stress-strain law, this is included in the present analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.882-887
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• 2003

This paper presented a design and control of a new RGO(reciprocating gait orthosis)and its simulation. The new RGO was distinguished from the other one by which had a very light-weight and a new RGO(reciprocating gait orthosis) system. The vibration evaluation of the hip joint system on the new RGO(reciprocating gait orthosis)was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 ㎐. The gait of the new RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the new RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties, we made the hip joint system of FEM and the hip joint system by 1-axis and 3-axis Accelerometers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.253-253
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• 2008

Recently, high performance microelectronic devices are designed in multi-layer structure in order to make dense wiring of metal conductors in compact size. For making dense wiring of metal conductors, we investigated CTE and peel strength of dielectric materials for next generation PCB. It is an object of this research to develop an epoxy resin composition for an interlayer insulating material exhibiting low CTE and high peel strengnth and making an insulating layer thinner.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.4
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• pp.220-228
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• 2002

The cool-down performance after soaking is very important in an automotive air-conditioning system and is considered as a key design variable. Therefore, transient characteristics of each system component are essential to the preliminary design as well as steady-state performance. The objective of this study is to develop a computer simulation model and ostinato theoretically the transient performance of an automotive air-conditioning system. To do that, the mathematical modelling of each component, such as compressor, condenser, receiver/drier, expansion valve, and evaporator, is presented first of all. The basic balance equations about mass and energy are used in modelling. For detailed calculation, condenser and evaporator are divided into many sub-sections. Each sub-section is an elemental volume for modelling. In models of expansion valve and compressor, dynamic behaviors are not considered in this analysis, but the quasisteady state ones are just considered, such as the relation between mass flow rate and pressure drop in expansion device, polytropic process in compressor, etc. Also it is assumed that there are no heat loss and no pressure drop in discharge, liquid, and suction lines. The developed simulation model is validated by comparing with the laboratory test data of an automotive air-conditioning system. The overall time-tracing properties of each component agreed well with those of test data in this case.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.133-139
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• 2019

The utilizations of ceramics in the modern industries are increasing due to the desirable combinations of electrical, mechanical and physical properties found in ceramics. Ceramic materials are brittle, hard, strong in compression, weak in shearing and tension which is prone to affect the defects such as scratch, crack and breakage during the machining. Generally, the defects of the ceramic machining are generated from the structural vibrations of the machine. In this study, the dynamic characteristics of a machining center for ceramic machining were investigated to analyze the structural vibrations for the improved stability. Frequency response test and computer simulation have been conducted for the analysis and the design improvement. The improved design is suggested to suppress vibrations for the higher stability of the machine and further to reduce vibrations. And the result shows that simple design alterations without any change of major parts of the machine can reduce the vibration of the machine effectively.

• Computational Structural Engineering
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• v.10 no.2
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• pp.149-160
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• 1997

Mechanical structures are composed of substructures connected by joints and boundary elements. While the finite element representation of plain substructures is well developed and reliable, joints have a lot of uncertainties in being accurately modelled and affect dynamic behavior of a total system. In order to improve the accuracy of a finite element model, a new method is proposed, in which reduced finite element model is combined with a system identification technique. After substructures except joints are modelled with finite element method and joint properties are represented by parameter states, non-linear state equation is derived in which parameter states are multiplied by physical states such as displacements and velocities. So the joint parameter identification is transformed into non-linear state estimation problem. The methods are tested and discussed numerically and the feasibility for physical application has been demonstrated through two example structures.

• Earthquakes and Structures
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• v.2 no.1
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• pp.43-64
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• 2011

One-dimensional rod theory is very effective as a simplified analytical approach to large scale or complicated structures such as high-rise buildings, in preliminary design stages. It replaces an original structure by a one-dimensional rod which has an equivalent stiffness in terms of global properties. The mechanical behavior of structures composed of distinct constituents of different stiffness such as coupled walls with opening is significantly governed by the local variation of stiffness. Furthermore, in structures with setback the distribution of the longitudinal stress behaves remarkable nonlinear behavior in the transverse-wise. So, the author proposed the two-dimensional rod theory as an extended version of the rod theory which accounts for the two-dimensional local variation of structural stiffness; viz, variation in the transverse direction as well as longitudinal stiffness distribution. This paper proposes how to deal with the two-dimensional rod theory for structures with setback. Validity of the proposed theory is confirmed by comparison with numerical results of computational tools in the cases of static, free vibration and forced vibration problems for various structures. The transverse-wise nonlinear distribution of the longitudinal stress due to the existence of setback is clarified to originate from the long distance from setback.

• Macromolecular Research
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• v.14 no.3
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• pp.261-266
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• 2006

Blends of silicone rubber (VMQ) and liquid crystalline polymer (LCP) were prepared using a melt blending technique in the presence and absence of glass fiber and coupling agents. The effect of glass fiber and coupling agents on the thermal, dynamic mechanical, morphological pro-perties and cure characteristics of VMQ/LCP blends were studied. The vinyl silane coupling agent showed a significant effect on the above mentioned properties of VMQ/LCP blends by reacting at the interface between VMQ and LCP. The viscosity of the VMQ/LCP blends decreased with the addition of a coupling agent. A substantial improvement in storage modulus of VMQ/LCP blends was observed in the presence of glass fiber and coupling agents. However, as a coupling agent vinyl silane proved to be better than amine for the VMQ/LCP-glass-containing blends. The thermal stability of the pure silicone rubber was higher than those of the blends. This high thermal stability of silicone rubber was attributed to the Si-O-Si bonds. However, the thermal stability of the blends decreased further in the presence of a coupling agent, possibly due to a decrease in blend crystallinity.

• Elastomers and Composites
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• v.55 no.3
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• pp.167-175
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• 2020

Various studies have been conducted to improve silica dispersion of silica filled tire tread compounds; among them, silica wet masterbatch (WMB) technology is known to be suitable for manufacturing silica filled compounds that have high silica content and high dispersibility. Till now, the WMB study is focused on the natural rubber (NR) or emulsion styrene-butadiene rubber (ESBR) that does not have a silica-affinity functional group, and a study of NR or ESBR having a silica-affinity functional group is still not well known. Unlike the dry masterbatch technology, the WMB technology can solve the problems associated with the high Mooney viscosity when applied to silica-friendly rubber. However, a coagulant suitable for each functional group has not yet been determined. Therefore, in this study, different coagulant applied silica WMB was prepared by applying calcium chloride, sulfuric acid, acetic acid, and propionic acid by using a carboxyl group functionalized reversible addition fragmentation chain transfer ESBR. The evaluation of the WMB compounds revealed that the calcium chloride added WMB compound showed excellent silica dispersion, abrasion resistance, and rolling resistance.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.56-64
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• 2016

It is generally accepted that the surface quality of wafer edge is mostly damaged by the vibrations of the edge grinding machine. The surface quality of wafer edge is supposed to be the most dominant factor of the cracks, scratches, burrs and chips on the edge surfaces, which are the main defects of the wafers. In this study, the structure of a wafer edge grinder has been investigated through the frequency response experiment and the computer simulation to find ways to suppress the vibrations from the structure. The main reasons of the structural vibrations were analyzed. And further the design alterations were deduced from the results of the experiment and the simulation, and applied to the machine to check the effects of those alterations and to eventually improve the structural stability. The result shows that the machine can have much improved stability with relatively simple design changes.