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링압축시험에서 역해석을 이용한 유동응력과 마찰상수 결정법
최영,김호관,조해용,김병민,최재찬,Choi, Y.,Kim, H.K.,Cho, H.Y.,Kim, B.M.,Choi, J.C. 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
An inverse analysis been applied to obtain the flow stress of the material. In this method, a ring-shaped specimen is compressed between two flat tools. This procedure employs, as the object function of inverse analysis, the balance of measured loads and reaction forces calculated by using rigid-plastic finite element method. The balance is explicit scalar function of flow stress which is a function of some unknown constants. For minimizing the balance, Newton-Raphon scheme is used. The friction factor, m, between flat tools and the specimen is determined by using friction area-divided method. The proposed method allows an accurate identification by avoiding the usual assumptions made in order to convert experimental measures into stress-strain relation. In this paper, the proposed method is numerically tested. A commercial pure aluminum was selected, as an example, to apply the method and the results are compared with stress-strain relation obtained by experiments.
프레넬 렌즈 성형에서 tip radius가 광학 성능에 미치는 영향
심종명(Jongmyeong Shim),김호관(Hokwan Kim),김중억(Joongeok Kim),명호(Ho Myung),김명연(Myungyon Kim),강신일(Shinill Kang) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
This paper describes the effect of tip radius on optical performance for fabricating Fresnel lens. We firstly designed Fresnel lens for uniform light distribution by backward design method and energy compensation method. To verify the effect of tip radius, simulation was conducted varying lens tip radius. Designed Fresnel lenses were replicated by UV imprinting and injection molding process using metal mold fabricated by direct machining. Lens profile fabricated by each process and optical performance with each fabricated lens were measured. We compared the results with simulation data, and analyzed the effect of tip radius.