(1-x)$NdAlO_3$-$xCaTiO_3$세라믹스의 결정구조와 마이크로파 유전특성 연구

우창수,김민한,남산,최창학,이확주,박현민,Woo, Chang-Soo,Kim, Min-Han,Nahm, Sahn,Choi, Chang-Hack,Lee, Hwack-Joo,Park, Hyun-Min 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.12

(1-x)NdAlO$_3$-xCaTiO$_3$세라믹스의 결정구조와 마이크로파 유전특성을 조사하였다. 시편의 결정구조는 조성에 따라서 변화하였는데, 그 결정구조는 x$\leq$0.1일 때는 능면정(rhombohedral) 구조를, 0.3$\leq$x$\leq$0.7에서는 정방정 (tetragonal) 구조를 그리고, x$\geq$0.7일 때 다시 사방정 (orthorhombic) 구조로 바뀌었다. 또한 (1-x)NdAlO$_3$-xCaTiO$_3$세라믹스에서 이차상의 두 종류가 발견되었다. x$\leq$0.5인 시편에서는 Nd$_4$Al$_2$O$_{9}$상이, x$\geq$0.7인 시편에서는 Al-rich상이 발견되었다. x가 증가함에 따라, 유전율 ($\varepsilon$$_{r}$)과 공진주파수의 온도계수 ($ au$$_{f}$ )가 증가하였고, Q$\times$f 값은 x의 증가에 따라 증가하며, x=0.5일 때 최대값을 얻었다. 그리고 0.3NdAlO$_3$-0.7CaTiO$_3$에서 Q$\times$f=46,000, $\varepsilon$$_{r}$=45 그리고 $\tau$$_{f}$ =-1.5 ppm/$^{\circ}C$의 우수한 마이크로파 유전특성을 얻을 수 있었다.

자동차용 방진고무부품 통합설계시스템 개발

우창수(Changsu Woo),김완두(Wandoo Kim),김영길(Younggil Kim),신외기(Waegi Shin),이성훈(Seonghoon Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. Recently, the design, analysis and evaluation technology was required to achieve the high quality, fidelity, reliability of rubber products. However, rubber manufacturing companies of our country have uesd the method of trial and error and experience in the process of a compound mixing, manufacturing and improvement of rubber properties. The objectives of this study are to establish the test methods of rubber material and to make the database of rubber material properties and to evaluate the performance of rubber components and to construct the prediction system of fatigue life. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test.

연구논문 : 열 노화에 따른 NBR과 EPDM 가황물의 물성변화 및 노화수명 예측

우창수 ( C. S. Woo ),최성신 ( S. S. Choi ) 한국고무학회 2005 엘라스토머 및 콤포지트 Vol.40 No.2

실험에 의한 방진고무의 동특성 고찰

우창수(C. S. Woo),김완두(W. D. Kim),김기세(K. S. Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5

Rubber materials with excellent damping property are widely applied for vibration isolators. The<br/> dynamic characteristics of the rubber materials for vibration isolators were investigated. Dynamic test<br/> for rubber material with 5 different hardness were performed. In dynamic tests for test specimen,<br/> non-resonance method, was used to obtain the dynamic storage modulus and loss factor and the effect<br/> of dynamic vibration frequency, strain amplitude and temperature were investigated.

실험에 의한 방진고무의 동특성에 관한 연구

우창수 ( C. S. Woo ),김완두 ( W. D. Kim ),김기세 ( K. S. Kim ),권재도 ( J. D. Kwon ) 한국고무학회 2002 엘라스토머 및 콤포지트 Vol.37 No.3

우수한 신장성과 탄성복원 능력으로 여러 산업분야에 방진, 제진, 충격흡수 및 완충재료로 널리 사용되고 있는 고무재료에 대하여 주파수, 변형률 진폭 및 온도변화가 동특성에 미치는 영향을 실험을 통하여 검토하였다. 동특성 시험은 5종류의 경도에 대하여 인장·압축시험과 전단시험용의 천연고무 시험 편으로 비 공진법으로 수행하였다. 시험결과, 경도가 높을수록 동적 특성 값들이 크게 나타났으며 저장탄성계수와 손실계수는 주파수가 증가할수록 서서히 증가하였으며 변형률 진폭이 커질수록 감소하였다. 또한, 온도 특성은 -50℃ 영역에서 저장탄성계수가 급격히 상승하며 손실계수가 최대로 나타나는 전이역임을 알 수 있었다. Rubber materials with excellent damping property are widely applied for vibration isolators. The dynamic characteristics of the rubber materials for vibration isolators were investigated. Dynamic tests for rubber materials with five different hardness were performed. In dynamic tests for test specimen, non-resonance method was used to obtain the dynamic storage modulus and loss factor. Moreover, the effect of dynamic vibration frequency, strain amplitude and temperature were investigated. As results, the storage modulus and loss factor genearlly increase when the hardness and frequency increase, and the glass transition temperature is -50℃ by a large change in modulus and loss factor

철도차량용 원추형 고무스프링 특성 및 피로수명 평가

우창수(Chang-Su Woo),박현성(Hyun-Sung Park) 한국철도학회 2016 한국철도학회 학술발표대회논문집 Vol.2016 No.5

본 연구에서는 철도차량 1차 현가장치에 사용되는 원추형 고무스프링에 대해 유한요소해석과 특성시험을 수행하여 수직방향, 길이방향, 횡 방향의 강성을 예측하고 평가하였다. 또한, 설계 초기 단계에서 짧은 기간에 고무부품의 피로수명을 예측할 수 있는 방법을 개발하여 원추형 고무스프링에 대한 피로수명을 평가한 결과, 실제 피로시험을 통해 얻어진 피로수명과 예측수명이 비교적 정확하게 예측됨을 확인하였다. Conical rubber springs are used in primary suspensions for railway vehicle. Conical rubber spring have function which reduce vibration and noise, support load carried in operation of railway vehicle. Prediction and evaluation of characteristics and fatigue lifetime are very important in design procedure to assure the safety and reliability of the rubber spring. The computer simulation using the nonlinear finite element analysis program executed to predict and evaluate the load and displacement for the conical rubber spring. The non-linear properties of rubber which are described as strain energy functions are important parameters. Also, fatigue lifetime prediction methodology of vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter of maximum Green-Lagrange strains appearing at the critical location determined from fatigue test. Predicted useful lifetime of the conical rubber spring showed a fairly good agreement with the experimental fatigue lifetime.

전동차용 세브론 고무스프링 특성 및 사용수명 평가

우창수(Woo, Chang-Su),박현성(Park, Hyun Sung),강문채(Kang, Mun-Chae) 한국도시철도학회 2013 한국도시철도학회논문집 Vol.1 No.2

전동차량의 1차 현가장치로 사용되는 세브론 고무스프링의 특성과 사용수명을 예측하고 평가하는 기술은 안전성과 신뢰성을 확보하기 위해 매우 중요하다 하겠다. 변형률 에너지함수로 정의되는 고무소재의 비선형 물성은 세브론 고무스프링의 해석과 설계에 중요한 변수로 단축인장, 등 이축인장 및 순수전단시험을 통해 결정하였으며, 전산해석을 통해 세브론 고무스프링의 특성을 예측하고 평가하였다. 또한, 유한요소 해석과 피로시험을 통해 취약부위에서의 최대 그린-라그랑지 변형률을 이용하여 가황고무 소재의 사용수명 예측방법을 제안하였다. 제안된 방법에 의해 예측된 세브론 고무스프링의 사용수명은 피로시험을 통해 얻어진 수명과 잘 일치함을 알 수 있었다. Chevron rubber springs is used in primary suspension system for electric locomotives. Characteristics and useful lifetime prediction and evaluation of chevron rubber spring were very important in design procedure to assure the safety and reliability. Non-linear properties of rubber material which are described as strain energy function was important parameter to design and analysis of chevron rubber spring. These are determined by mechanical tests which are uni-axial tension, equi-biaxial tension and pure shear test. The computer simulation was execute to predict and evaluate the characteristics for chevron rubber spring. Also, Useful lifetime prediction methodology of vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter of maximum Green-Lagrange strains appearing at the critical location determined from fatigue test. Predicted useful lifetime of the chevron rubber spring showed a fairly good agreement with the experimental useful lifetime.

고무부품의 피로수명 예측 및 평가

우창수(Changsu Woo),김완두(Wandoo Kim),권재도(Jaedo Kwon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Fatigue life prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from the fatigue tests. Nonlinear finite element analysis of the 3-D dumbbell specimen of natural rubber was performed based on a hyperelastic material model determined from the tension, compression and shear tests. The Green-Lagrange strain at the critical location determined from the FEA was used for evaluating the fatigue damage parameter of natural rubber. Fatigue tests were formed using the 3-D dumbbell specimens with different levels of maximum strain and various hardness. Fatigue life curves can be effectively represented by a following single function using the Green-Lagrange strain. Predicted fatigue lives of the rubber component agreed fairly well the experimental fatigue lives.

철도차량 완충기 패드용 고무소재 수명예측

우창수(Woo Chang-Su),박현성(Park Hyun-Sung),박동철(Park Dong-Chul) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-

Coupling rubber pad are important components in railway vehicles. It can be used for reduce shock, vibration and noise. Simple tension, equi-biaxial tension and pure shear test were performed to acquire the coefficient of rubber material which were Mooney-Rivlin and Ogden model. The finite element analysis was executed to evaluate the behavior of deformation and stress distribution by using the commercial finite element analysis code. Useful life evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, useful life prediction of rubber pad for railway vehicle were experimentally investigated. Accelerated heat-aging test for rubber material were carried. Compression set results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot.

자동차 칵핏 모듈용 플라스틱 소재의 열화 동특성 평가

우창수(Chang Su Woo),박현성(Hyun Sung Park),조진호(Jin Ho Jo),김지훈(Ji Hoon Kim),최주호(Ju Ho Choi),김영국(Yeoung Kuk Kim) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.12

플라스틱 소재는 온도, 습도 및 자외선 등 다양한 환경의 영향으로 인해 기계적 물성변화가 심하기 때문에 체결부의 견고함이 느슨해지고 형태의 변형에 의해 부품간의 마찰 등을 유발하여 잡음이 발생하게 된다. 따라서, 본 논문에서는 자동차 칵핏 모듈에 사용되는 다양한 플라스틱 소재에 대해 온도변화에 따른 동 특성시험을 통해 유리전이온도, 저장탄성계수, 손실계수 등을 측정하여 상온 및 열화조건에 따른 물성변화를 파악하였다. 시험결과, 온도가 높을수록 저장탄성계수는 감소하고 손실계수는 증가하는 경향을 나타내었다. Engineering plastics are used in instrument panels, interior trim, and other vehicle applications, and the thermomechanical behaviors of plastic materials are strongly influenced by many environmental factors such as temperature, sunlight, and rain. As the material properties change, the mechanical parts create unexpected noise. In this study, the dynamic mechanical property changes of plastics used in automobiles are measured to investigate the temperature effects. Viscoelastic properties such as the glass transition temperature and storage modulus and loss factor under temperature and frequency sweeps were measured. The data were compared with the original ones before aging to analyze the behavior changes. It was found that as the temperature increased, the storage modulus decreased and the loss factor increased slightly.