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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.
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.