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전은채,제태진,이응숙,박은숙,이재령,최환진,장성환,최상규 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
A new concept, ‘hybrid LED package system (HLP system)’, is proposed as a simpler LED manufacturing process that unifies two steps of the process, the package step and the module step. Moreover, the HLP system can increase optical efficiency by virtue of its integrated optical pattern. A square pyramidal pattern was selected as the basic shape of the pattern of the HLP system. Four shape parameters of the HLP system were selected for optimizing the system. Nine cases of optical simulations organized according to the Taguchi method were performed using LightTools, and the optimum values of the parameters were determined by an SN ratio analysis. Using the optimum values, 28% higher illuminance and 32% higher luminance were predicted simultaneosly compared to the values without the integrated optical pattern. The optimum square pyramidal pattern was machined on a metal mold using an ultra-fine planer and a 90 degree angle diamond tool which would be used as a mold for manufacturing the optimized integrated optical pattern of the HLP system. The exact shape of the square pyramidal pattern with a height of 25 μm and a 90 degree angle was obtained. This study verified that the micro machined mold for manufacturing an optimized integrated optical pattern could be machined accurately, and finally the HLP system with the integrated optical pattern had higher uniform and brighter light distribution.
압입하중-변위곡선의 정량적 해석을 통한 가공경화지수의 평가
全銀埰,安政勳,權東一 대한금속재료학회 2001 대한금속·재료학회지 Vol.39 No.12
Continuous indentation test with ball indenter has been studied for years because of its convenience and simpleness. Especially, the test is expected to supersede tensile test. Among tensile properties work-hardening exponents of various steels were evaluated by the test. We newly defined true stress and true strain with contact depth and indentation load. Finite element analysis shows that the contact depth is affected by elastic deflection and pile-up/sink-in. Therefore, the contact depth was calculated with taken both elastic deflection and pile-up/sink-in into account. The work-hardening exponents derived in this study show good agreement to those from tensile test.
전은채,박주승,권동일 대한금속재료학회 2002 대한금속·재료학회지 Vol.41 No.2
The continuous indentation test, which measures indentation depth with applied load, has been used to evaluate the tensile properties whose accuracy can vary depending on such experimental conditions as maximum depth ratio, indenter radius, number of unloadings and unloading ratio. In this study, Taguchi method, one of the designs of experiment, was applied to quantify the effects of the experimental conditions effectively. Using a signal-to-noise ratio calculated from the error in the indentation tensile properties, the optimum values of the experimental conditions were presented. The indentation tensile properties from the load-depth curves with the optimum conditions showed better accuracy than those with existing conditions.