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와전류센서를 이용한 펜슬가공시 볼엔드밀의 가공궤적 해석
윤경석,왕덕현 경남대학교 신소재연구소 1997 論文集 Vol.9 No.-
펜슬가공시 절삭조건을 변화시켰을 경우 발생하는 공구변형 특성을 머시닝센터의 주축부에 설치한 와전류센서로 측정하여 최빈도(median)필터를 거쳐 해석하였다. 펜슬가공중 코너에서 이송속도를 줄이는 것이 공구변형을 감소시키는데 효과적인 것으로 나타났다. 공구변형을 하향절삭에서 절삭력이 작게 작용하기 때문에 상향절삭보다 하향절삭에서 줄일 수 있었으며, 금형제작에서 펜슬가공할 때 하향절삭으로 상방향 경사면가공을 하였을 경우 가장 양호한 가공상태를 얻을 수 있었다. Tool deflection of ball-end mill in pencil cutting for free-form surface according to cutting condition was measured by eddy-current sensor attached to the spindle of machining center, and analyzed by median filter. The best way to minimize the tool deflection in corner when pencil cutting is to decrease feedrate during cutting. Tool deflection was decreased for down-cutting rather than up-cutting due to the smaller cutting force. The method of upward ramp cutting with down-cutting represents the optimum machining strategy for pencil cutting in the die and mould making industry.
윤경석,이장용,김태호,유덕만,서동완,홍성권,홍영택 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4
Densely sulfonated polyketones (sPK-m) based on poly(p-phenylene)s were successfully synthesized through Ni(0)-catalyzed cross coupling reaction for polymer electrolyte membrane fuel cell (PEMFC) application. sPK-m membranes exhibited proton conductivities comparable to or better than that of Nafion 212 in the hydrate state. sPK-12.5 and sPK-15 membranes showed outstanding PEM fuel cell performance at 80 ℃ under 100% RH. In particular, sPK-15 membranes exhibited very high current density (around 1300 mA/cm2 at 0.6 V). Among the synthesized polymers, sPK-12.5 showed reasonable dimensional change and morphological property. Furthermore, proton conductivity and cell performance comparable to those of Nafion 212 membrane were obtained.