• 접착 및 계면
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• 제15권1호
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• pp.9-13
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• 2014

본 연구는 폴리프로필렌/마이카 복합재료의 고상압출에 의한 배향에 따른 기계적 물성의 변화에 관한 연구이다. 마이카 함량이 증가할수록 복합재료의 비중이 증가하였다. 하지만 고상압출에 따른 배향에 의해 복합재료의 비중은 미세공극의 발생으로 말미암아 비중은 배향 전에 비해 현저히 감소하는 것으로 나타났다. 이러한 미세공극의 존재는 복합재료의 인장 및 굴곡물성에 큰 영향을 미치는 것으로 나타났다. 고상압출 여부에 관계없이 마이카 함량이 10 wt%일 때 최대 굴곡 물성이 관찰되었다.

• 접착 및 계면
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• 제14권4호
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• pp.175-182
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• 2013

본 논문에서는 고상압출된 폴리프로필렌/탄산칼슘 복합재료의 배향 전후의 비중, 열적 및 기계적 물성의 변화에 대해 연구하였다. 본 연구를 위해 두 가지 다른 크기를 갖는 탄산칼슘 충진제(OM-1 및 OM-10)를 폴리프로필렌에 첨가하여 폴리프로필렌/탄산칼슘 복합재료를 제조하였다. 충진제의 함량이 증가할수록 복합재료의 비중이 증가하였는데, 배향된 복합재료의 비중은 배향되지 않은 복합 재료에 비해 작은 것으로 나타났으며 이는 배향에 따라 발생된 미세공극으로 기인한 것이다. 배향 시 발생하는 이 미세공극은 복합재료의 인장 및 굴곡 물성에 큰 영향을 미치는 것으로 밝혀졌다. 굴곡강도 및 굴곡 탄성률에 미치는 배향의 영향은 충진제의 입자 크기에 상관없이 충진제의 함량의 영향보다 더 강한 것으로 나타났다.

• 한국표면공학회지
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• 제42권5호
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• pp.232-239
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• 2009

This study presented the effect of membrane thickness on hydrogen permeability. Microvoids on the surface of the membrane should not exist for the exact values of hydrogen permeability. Pd-Cu-Ni hydrogen alloy membranes were fabricated by Ni powder sintering, substrate plasma pretreatment, sputtering and Cu reflow process. And this leaded to void-free surface and dense film of Pd-Cu-Ni hydrogen alloy membrane. Hydrogen permeation test showed that hydrogen permeability increased from 2.7 to $15.2ml/cm^2{\cdot}min{\cdot}atm^{0.5}$ as membrane thickness decreased from 12 to $4{\mu}m$. This represented the similar trend as a hydrogen permeability of pure palladium membrane based on solution-diffusion mechanism.

• 소성∙가공
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• 제3권1호
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• pp.120-132
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• 1994

Strip drawing of strain-hardening, viscoplastic materials with damage is analyzed by a rigid plastic finite element method. A process model is formulated using two state variables, one for strain hardening from slip dominated plastic distortion and the other for damage from growth of microvoids. Application of the model to aluminum strip drawing is given via implementation in a consistent penalty finite element formulation. The predicted density changes as a result of void growth are compared to those from experiments reported in the literature. The effects of drawing conditions such as drawing speed and die angle on the mechanical property chages are studied.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.71-79
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• 1994

Strip drawing of strain-hardening, viscoplastic materials with damage is analyzed by a rigid plastic finite element method. A process model is formulated using two state variables, one for strain hardening from slip dominated plastic distortion and the other for damage from growth of microvoids. Application of the model to steady state drawing is given via implementation in a consistent penalty finite element formulation. The predicted density changes as a result of void growth are compared to those from experiments reported in the literature. The effects of drawing conditions such as drawing speed and die angle on the mechanical property changes are studied.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.125-126
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• 2006

We show that thermal rearrangement of glassy polymers below the thermal degradation temperature can create unexpected and large microvoids in the membranes, leading to unexpected high gas permeability with high gas selectivity. These current polymer membranes display unexpected gas permeation-separation performance. There are above the upper-bound for conventional polymer membranes for several gas pairs. In the present study, molecular simulation, BET sorption, positron annihilation lifetime spectroscopy (PALS), and gas separation experiments were performed to characterize the unusual structure-property relationship of these rigid glassy polymer membranes.

• 동력기계공학회지
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• 제9권1호
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• pp.57-63
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• 2005

In the calendar and the advertising catalog, the surface is usually coated by coating polypropylene film. The delamination failure of coating film depends on surface roughness and quality of the substrate paper. In this paper, the mechanisms of delamination failure between the coating film and the paper is investigated by using the root cause analysis as one of techniques of reliability evaluation. The papers used in failure analysis are three kind products made by two domestic and one foreign companies. It found that the main causes of delamination failure between the coating film and the paper were the creation of microvoids caused by shape of filler and their growth caused by contraction of paper.

• 한국표면공학회지
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• 제36권4호
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• pp.347-355
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• 2003

Roughening of metal surfaces frequently enhances the adhesion strength of metals to polymers by mechanical interlocking. When a failure occurs at a roughened metal/polymer interface, the failure prone to be cohesive. In a previous work, an adhesion study on a roughened metal (oxidized copper-based leadframe)/polymer (Epoxy Molding Compound, EMC) interface was carried out, and the correlation between adhesion strength and failure path was investigated. In the present work, an attempt to interpret the failure path was made under the assumption that microvoids are formed in the EMC as well as near the roots of the CuO needles during compression-molding process. A simple adhesion model developed from the theory of fiber reinforcement of composite materials was introduced to explain the adhesion behavior of the oxidized copper-based leadframe/EMC interface and failure path. It is believed that this adhesion model can be used to explain the adhesion behavior of other similarly roughened metal/polymer interfaces.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.199-208
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• 2005

In the calendar and the advertising catalog, the surface Is usually coated by coating polypropylene film. The delamination failure of coating film depends on surface roughness and quality of the substrate paper. In this paper, the mechanisms of delamination failure between the coating film and the paper is investigated by using the root cause analysis as one of techniques of reliability evaluation. The papers used in failure analysis are three kind products made by two domestic and one foreign companies. It found that the main causes of delamination failure between the coating film and the paper were the creation of microvoids caused by shape of filler and their growth caused by contraction of paper.

• 소성∙가공
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• 제12권1호
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• pp.60-65
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• 2003

HIP diffusion bonding of Ni-based superalloys, cast Mar-M247 (MM247) and Udimet 720 (U720) powder, was experimentally and numerically studied. Subsolvus HIP treatment was optimized by investigating the variations of high temperature tensile properties of HIP-bonded specimens with powder size, HIP'ing time, etc. While the tensile strength at high temperatures showed no detectable changes, the tensile elongation and reduction in area were slightly increased as the powder size decreased from -140 mesh to -270 mesh. While as-HIP'ed U720 showed a high tensile strength comparable to that of lorded U720 alloy, the HIP diffusion-bonded specimen showed a strength lower than the forged U720 alloy and the cast MM247 alloy The increase of HIP'ing tune from 2 hours to 3 hours resulted in a rapid risc of tensile strength and elongation due to the disappearence of microvoids in the cast MM247. FEM simulation for HIP process was conducted by applying the McMeeking micromechanical model, which uses power-law creep model as constitutive equations. ABAQUS user subroutine CREEP with an implemented microscopic model was used for the simulation. Numerical simulation was shown to be essential for the near-net shape manufacturing as well as the HIP process optimization.