• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.669-672
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• 1999

In this paper, we studied the properties of small-size disk-type ultrasonic motor using travelling wave for the application to the precise control robotic joint motor and fabricated it. The diameter of the ultrasonic motor fabricated was 13mm. Also, the piezoelectric vibrator was constructed by piezoelectric ceramic and elastic material. The piezoelectric ceramic was composed to PZ-PT-PMN which was shown the high electromechanical stability under high vibration level and stainless steel was used as the elastic material in which configuration was disk-type. To conform the capability of application to robotic motor, we measured the change of rotational speed according to applied voltage and applied frequency. As the results, the small-size disk-type ultrasonic motor was able to fabricate, and the revolution speed was 350 (rpm) when input voltage was 55 (Vrms) and applied frequency 160.4 IkHz] under pre-load.

• 구강회복응용과학지
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• 제25권1호
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• pp.31-40
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• 2009

고무인상재의 유변학적 특성은 높은 정확성을 가진 인상체의 채득에 중요한 역할을 한다. 그러나 국산 고무인상재의 유변학적 특성에 관한 연구가 거의 이루어지지 않았다. 이 연구는 국산 및 수입 고무 인상재의 유변학적 특성을 측정, 연구함으로써 임상적 과정에서 정확성 높은 인상채득에 도움이 되고자 함이다. 시판중인 Type 3 점성을 가진 6종의 고무인상재의 유변학적 특징을 측정하였다. 2종의 국산 폴리비닐실록산, 3종의 수입 폴리비닐실록산, 1종의 폴리이써, 1종의 폴리썰파이드에 대하여 plate 대 plate 형의 rotational rheometer인 HAAKE RHEOSTRESS $1^{(R)}$ 이용하여 Mixing 후 900초간 G′, Loss tangent 값을 측정하였다. 각 제품 당 3회씩 측정 후 통계분석하였다. 국산 PVS, 수입 PVS, Polyether, Polysulfide 모두 G′의 S자형 증가와, Loss tangent 값의 S자형 감소를 보였다. 경화 후 G′ 값의 최대치는 Polyether였으며, 최소치는 Polysulfide였다. Loss tangent의 초기값은 폴리이써 인상재에서 가장 높았으며 국산 폴리비닐실록산 인상재에서 가장 낮았다. 같은 점조도를 가진 국산 PVS 와 수입 PVS의 G′ 값은 유의한 차이가 없었으나, 초기 Loss tangent 값에서 유의한 차이가 나타났다.

• Structural Engineering and Mechanics
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• 제57권4호
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• pp.617-639
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• 2016

In this work, an analytical formulation based on both hyperbolic shear deformation theory and stress function, is presented to study the nonlinear post-buckling response of symmetric functionally graded plates supported by elastic foundations and subjected to in-plane compressive, thermal and thermo-mechanical loads. Elastic properties of material are based on sigmoid power law and varying across the thickness of the plate (S-FGM). In the present formulation, Von Karman nonlinearity and initial geometrical imperfection of plate are also taken into account. By utilizing Galerkin procedure, closed-form expressions of buckling loads and post-buckling equilibrium paths for simply supported plates are obtained. The effects of different parameters such as material and geometrical characteristics, temperature, boundary conditions, foundation stiffness and imperfection on the mechanical and thermal buckling and post-buckling loading capacity of the S-FGM plates are investigated.

• Advances in concrete construction
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• 제15권2호
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• pp.115-126
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• 2023

This paper investigates creep analysis of a plate made of Al-SiC functionally graded material using Mendelson's method of successive elastic solution. All mechanical and thermal material properties, except Poisson's ratio, are assumed to be variable along the thickness direction based on the volume fraction of reinforcement and thickness. First, the basic relations of the plate are derived using the Love-Kirchhoff plate theory. The solution of governing equations yields an elastic solution to start creep analysis. The creep behavior is demonstrated through Norton's equation based on Pandey's experimental results extracted for Al-SiC functionally graded material. A linear variation is assumed for temperature distribution along the thickness direction. The creep strain, as well as the thermal strain, are included in the governing equations derived from classical plate theory for mechanical strain. A successive elastic solution based on Mendelson's method is employed to derive the history of stresses, strains, and displacements over a long time. History of stresses and deformations are obtained over a long time to predict damage to the plate because of various loadings, and material composition along the thickness and planar directions.

• 연구논문집
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• 통권23호
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• pp.45-56
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• 1993

In order to acquire more comprehensive understanding of textile composites, the processing-microstructure-performance relationships for a variety of material systems, reinforcing schemes and processing technologies should be established. In this paper, emphasis is placed on the integrated analysis of three-dimensional (3-D) 2-step braided composites. The analysis includes the geometric model of unit cells, identification of key process parameters and processing windows due to limiting geometries of yarn jamming, and prediction of elastic constants of the composite. The coordinate transformation and averaging of stiffness and compliance constants are utilized in the prediction of elastic constants. Since there are several types of unit cells in the thickness and width directions of the composites, characterization of mechanical properties is based upon the macro-cell, which occupies the entire cross-section and the unit pitch length of the sample. The performance map demonstrates that a wide range of elastic properties can be achieved by varying the geometric and process parameters.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.319-322
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• 2004

In this paper, we studied on the thermal conductivity and a mechanical property of the elastic epoxy. According to industrial development, insulation materials have various properties. They are solid, liquid, gas state, there are various type. Epoxy, a kind of insulation material, demand of not only high hardness but also elastic property. When the electric current flows into the conductor and the place where the heat occurs, this heat becomes the cause which shortens the life of the electrical appliance. Therefore, for the heat occurred transmit quickly, thermal conductivity of the insulation material is highly demanded. We studied on the thermal conductivity of elastic epoxy on the high voltage. In this result, thermal conductivity confirmed that it followed thermal property of mixed epoxy and addictives. Hardness is decreased when addictives increased.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1950-1957
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• 2004

Analysis for structures composed of materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. In order to evaluate the effective properties, a unit cell is defined and loaded somehow, and its response is investigated. The imposed loading, however, should accord to the status of unit cells immersed in the macroscopic structure to secure the accuracy of the properties. In this study, mathematical description for the periodicity of the displacement field is derived and its direct implementation into FE models of unit cell is attempted. Conventional finite element code needs no modification, and only the boundary of unit cell should be constrained in a way that the periodicity is preserved. The proposed method is applicable to skew arrayed in-homogeneity problems. Homogenized in-plane elastic properties are evaluated for a few representative cases and the accuracy is examined.

• Structural Engineering and Mechanics
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• 제77권5호
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• pp.651-659
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• 2021

In this study, a new constitutive model has been developed to predict the elastic behavior of plain weave textile composites, using the finite element (FE) method. The geometric conditions and basic assumptions of this model are based on the basics of a continuum theory developed for the plane curved composites. In this model, the mechanical properties of the weave region and pure matrix region is calculated separately and then imported for the FE analysis. This new constitutive model is used to implement the mechanical properties of weave region in the representative volume element (RVE). The constitutive relations are implemented as user-material subroutine code (UMAT) in ABAQUS® FE software. The results of FE analysis have been compared with experimental results and other data available in the literature. These comparisons confirmed the capability of the presented model for the prediction of effective elastic properties of plain weave fabric composites.

• Elastomers and Composites
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• 제58권3호
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• pp.142-151
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• 2023

In this study, we investigate the thermal and mechanical properties of composites comprising ethylene propylene diene monomer (EPDM) and polybutadiene (PB) obtained using carbon black (CB) as a reinforcing and compatibilizing filler. Owing to the significance of elastomeric materials in various industrial applications, blending of EPDM and PB has emerged as a strategic method to optimize the material properties for specific applications. This study offers insights into the blend composition, its microstructure, and the resulting macroscopic behaviors, focusing on the synergetic effects of composite materials. Furthermore, this study delves into curing and rheological behaviors, crosslink densities, and mechanical, thermal, and elastic properties of the elastomeric composites. Through systematic exploration, we believe that this study will be beneficial to material scientists and engineers working on developing advanced elastomeric composites.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.460-463
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• 2003

In this paper, we present the properties of water absorption of elastic epoxy for high voltage. The ratio of water absorption shows linearly increase according to ${\sqrt}t$ till 66 hours. And rigid epoxy is 0.053 [%], elastic epoxy at addictives 35 [phr] is 0.309 and it at addictives 70 [phr] is 0.44 [%]. The reason where absorption of elastic epoxy is high is because of micro void. It can be confirmed by SEM analysis. Dieletric constant increased linearly by addictives' concentration and tans is also increased by addictives' concentration.