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백동천(Dong-Cheon Baek),박태상(Tae-Sang Park),이순복(Soon-bok Lee),이낙규(Nag-Kyu Lee),최태훈(Tae-Hoon Choi),나경환(Kyoung-Hoan Na) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Nickel thin film is one of the most important materials used in micromachined structure. To measure the mechanical properties of electropated nickel thin film, two techniques are adopted and compared quantitatively with. One is nano-indentation test to measure the elastic modulus. The other is tensile test to measure no only elastic modulus but also yield strength and plastic deformation, ultimate strength. To perform the tensile test, apparatus was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.
백동천(Dong-Cheon Baek),박종원(Jong-Won Park) 대한기계학회 2016 大韓機械學會論文集A Vol.40 No.8
실제 사용되는 기계 구조물의 수명 예측은 공정산포, 미래의 하중조건, 손상 모델의 불완전성 등으로 인하여 실험실에서 얻은 결과와 차이를 보일 수 밖에 없다. 본 연구에서는 이러한 불확실성이 내포된 기계 구조물의 피로파괴를 사전에 예지하기 위해 이중센서를 개발하고, 상온에서 단축 피로 하중을 받는 구조물에 적용하여 실증하였다. 이중 센서는 피로하중을 받는 대상 구조물보다 약간 더 큰 응력이 인가되도록 고안된 감지 구조물에 변형률 게이지를 부착한 형태이며, 균열이 센서자체에 먼저 발생함으로써 피로파괴를 예지하며, 쌍으로 제작된 감지부의 변형률 차를 이용하여 변동하중 하에서도 정상상태와 고장상태를 구분이 가능하다. Because of the inherent uncertainties caused by the manufacturing process variations, future loading conditions, and incomplete damage models, the lifetimes of mechanical structures under field conditions are significantly different from the results obtained in the laboratories. In this study, a dual sensor was developed to prognosticate the fatigue failure of structures under these uncertain conditions, and its effectiveness was demonstrated on a rectangular columnar structure under repeated uni-axial loading. The dual sensor is a slightly weaker structure embedded in the target structure, so that failure occurs in the sensor earlier than in the target structure. From the signal differences in the strain gauges in the embedded dual sensor, it is possible to differentiate between the normal status and warning status, even under variable loads.
세탁기 조립체 가속수명시험평가를 위한 부품 강제열화 기법 개발
백동천(Dong-Cheon Baek),장무성(Mu-Seong Chang),박종원(Jong-Won Park) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
The washing machine manufacturers assess the reliability in assembly level to assure the lifetime of their products. Passing the criteria in the accelerated life testing in assembled washing machine, however, does not mean that all submodules or components meet the target. Its because the accelerating factors differ from each other. For example, the components having low accelerating factor are not stressed enough while the critical components do when they are tested all together in an accelerated manner. In this paper, an artificial degradation method in parts level was proposed for accelerated life testing of the assembly. The hardness of the door gasket was measured as a degradation index along with high-temperature aging, and then artificial degradation condition was determined. This treatment on rubber components before assembling is expected to enable the tailored degradation, consequently, improves the effectiveness of the assembly-level reliability assessment.
백동천(Dong-Cheon Baek),이순복(Soon-Bok Lee),강보식(Bo-Sik Kang),김형의(Hyoung-Eui Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The model for accelerated life testing of hydraulic hose was proposed based on failure mechanisms. Flexing effects on the impulse testing of hydraulic hose were estimated as the equivalent pressure with respect to proposed model.
백동천(Dong-Cheon Baek),김성열(Sung-Yeol Kim),이순복(Soon-Bok Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Thin copper films were sputtered on 12.7-㎛-thick polyimide(Kapton) substrate. They were tested in a micro tensile tester in which the strain is measured by dual microscope, optical pattern matching system. To obtain the properties of the film, the properties of the substrate are subtracted from the overall measurement. The Young's modulus of the copper film is derived assuming that the effect from the difference in the Poisson's ratio between the two layers is negligible. The stress and strain of etallic film on soft polymer substrate were checked by analytic solution and FEA(finite element analysis) to verify the similarity between tensile testing of thin film on substrate and that of free standing thin film.