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김옥래(Ok Rae Kim),우창기(Chang Ki Woo) 한국생산제조학회 2011 한국생산제조학회지 Vol.20 No.4
In this paper, using by rapid heating and cooling systems for injection molding and temperatures to changes. In the process of molding temperature and pressure inside the mold was found. In addition, the tensile strength of test specimens were molded, mechanical properties of injection molded parts were identified on mold temperature. Copper could withstand more tensile force than NAK. Therefore, it can be concluded that materials with high heat conductivity must be used in thin walled products.
원공결함을 갖는 SM45C 인장시험편의 강도해석과 음향방출에 관한 사례연구
우창기(Chang-Ki Woo),이장규(Zhang-Kyu Rhee) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.1
The SM45C metallic coupons have been tested under static tensile loading with acoustic emission (AE) as the load-deflection curve mainly. In this study, we used AE to detect the yielding of material and AE techniques was applied to rapidly estimate the mechanical characteristics of a material. First, coupons without an artificial defect were tested at different cross-head speed. For all cases in this analysis, yielding point of SM45C coupons did not appear definitely compared to mild steel, whereas coupons start to generate AE counts upon yielding. So all cases are normalized to know the possibility of accelerated life test of a material. And next, coupons with different from sizes of circular hole defects were tested at the same cross-head speed of 5 mm/min. Results were classified into 3 classes and analyzed by AE amplitude & signal strength as a function of time. Summarizing the specific conclusions, we need to additional research considering plate with width-ratio in order to estimate the fracture mechanism.
유효 K₁_d 산정을 위한 샬피 충격시험편의 노치형상에 관한 연구
우창기(Chang-Ki Woo),강동명(Dong-Myeong Kang),이하성(Ha-Sung Lee) 한국자동차공학회 1999 한국 자동차공학회논문집 Vol.7 No.6
This investigation evaluates effects of notch depth, fatigue precrack length and side groove in impact specimen for estimation of a valid K1d by instrumented Charpy impact test. Specimen material is 6005-T6. For notch depth 2.0mm and 2.5mm specimens or within about 2 mm fatigue precrack length with notch depth 2.0mm specimens, dynamic fracture toughness [K₁_d,(1)] obtained by crack initiation load (P_m) should be used. Dynamic fracture toughness of side grooved specimens are overestimated to that of standard impact specimen about 15%-20%. It is confirmed that the formula of dynamic fracture toughness obtained by impact absorbed energy is inappropriate for ductile materials.<br/>
원공결함을 갖는 SM45C 인장시험편의 강도해석과 음향방출에 관한 사례연구
우창기(Chang-Ki Woo),이장규(Zhang-Kyu Rhee),조대희(Dae-Hee Jo) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
This study was analyzed about load-deflection curve of SM45C metallic coupons through AE (acoustic emission) techniques mainly. Coupons that artificial defect does not exist were tested according to the speed of crosshead. First, yielding point of SM45C steel did not appear definitely compares to mild steel. So normalized all above cases to know tendency, and confirmed possibility of accelerated life test of isotropic materials. And next, coupons with differs size of circular hole defect were tested in the equal cross head speed at 5 ㎜/min. Generally AE counts appeared continually before fracture over whole unlike example of mild steel. As a result, classified 3 classes by AE amplitude & signal strength as a function of time here for signal analysis with a circular hole defect 7.5 ㎜ and analyzed. Is judged that need addition research that consider subsequentness width-ratio for searching examination of correct fracture mechanisms for this part.
원공결함을 갖는 SM45C 인장시험편의 강도해석과 음향방출에 관한 사례연구
우창기(Chang-Ki Woo),이장규(Zhang-Kyu Rhee),조대희(Dae-Hee Jo) 한국생산제조학회 2007 한국생산제조시스템학회 학술발표대회 논문집 Vol.2007 No.5
This study was analyzed about load-deflection curve of SM45C metallic coupons through AE (acoustic emission) techniques mainly. Coupons that artificial defect does not exist were tested according to the speed of crosshead. First, yielding point of SM45C steel did not appear definitely compares to mild steel. So normalized all above cases to know tendency, and confirmed possibility of accelerated life test of isotropic materials. And next, coupons with differs size of circular hole defect were tested in the equal cross head speed at 5 ㎜/min. Generally AE counts appeared continually before fracture over whole unlike example of mild steel. As a result, classified 3 classes by AE amplitude & signal strength as a function of time here for signal analysis with a circular hole defect 7.5 ㎜ and analyzed. Is judged that need addition research that consider subsequentness width-ratio for searching examination of correct fracture mechanisms for this part.
오진수,우창기,이장규,Oh, Jin-Soo,Woo, Chang-Ki,Rhee, Zhang-Kyu 한국생산제조학회 2010 한국생산제조학회지 Vol.10 No.6
In this study, DAQ and TRA modules were applied to the CFRP single specimen testing method using AE. A method for crack identification in CFRP specimens based on k-mean clustering and wavelet transform analysis are presented. Mode I on DCB under vertical loading and mode II on 3-points ENF testing under share loading have been carried out, thereafter k-mean method for clustering AE data and wavelet transition method per amplitude have been applied to investigate characteristics of interfacial fracture in CFRP composite. It was found that the fracture mechanism of Carbon/Epoxy Composite to estimate of different type of fractures such as matrix(epoxy resin) cracking, delamination and fiber breakage same as AE amplitude distribution using a AE frequency analysis. In conclusion, the presented results provide a foundation for using wavelet analysis as efficient crack detection tool. The advantage of using wavelet analysis is that local features in a displacement response signal can be identified with a desired resolution, provided that the response signal to be analyzed picks up the perturbations caused by the presence of the crack.
음향방출 신호분류에 의한 SM45C 시효처리재의 인장변형 해석
이장규(Zhang-Kyu Rhee),우창기(Chang-Ki Woo),김용배(Yong-Bae Kim) 한국생산제조학회 2009 한국생산제조시스템학회 학술발표대회 논문집 Vol.2009 No.5
This study investigates tensile deformation of the stress aging heat-treated SM45C steel which are aging temperature at 250, 300℃, aging time at 1,3 hours, and applied load at 300, 400N conditions by using acoustic emission (AE). A signal processing technology used to evaluate an AE source characterization by 2 AE measurement systems, i.e., DiSP & PCI-2 AE hardware and AEwin™ software. In this study, most suitable aging condition appeared at 250℃, 3 hours and 300N. On the other hand, in case of 250℃, 3 hours, 400N and 300℃, 3 hours, 400N conditions, yield load decreased than other conditions according to the over-aging phenomena. Especially, In case of 300℃, 3 hours and 400N condition appeared AE energy in elastic limit fairly high than non-heat treatment specimen.