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레이저 계측시스템에 의한 복합재료 구조물의 실제결함 검출
정성균(Seong Kyun Cheong),김태형(Tae Hyung Kim),김경석(Koung Suk Kim),강영준(Young June Kang) 한국복합재료학회 2002 Composites research Vol.15 No.5
본 연구에서는 레이저 계측시스템을 이용하여 복합재료 구조물의 실제결함을 검출하였다. 다양한 하중을 적용하여 충격에 의한 복합재료 적층판의 층간분리, 하니컴 구조에서의 접착분리, 복합재료 적층판의 자유단 층간분리, 그리고 접착조인트 구조의 접착부위 접착분리와 같은 네 종류의 시험편을 제작하였고 ESPI 와 전단 간섭계의 레이저 계측시스템으로부터 결함을 검출하였다. 열하중 방법을 통하여 시험편의 표면에 변형을 쉽게 일으켜 결함을 검출하였다. 실험결과 복합재료 구조물의 실제결함을 ESPI와 전단 간섭계로부터 쉽게 검출하였으며 더 나아가 ESPI와 전단 간섭계로부터 다양한 종류의 복합재료 구조물의 결함을 검출하는데 있어서 유용하게 이용될 것으로 사료된다. Real defects in composite structures were detected by using laser measuring system. four types of real defects, that is, impact-induced delamination in a composite laminate, debond in a honeycomb structure, free-edge delamintion in a composite laminate and debond in an adhesive joint, were made by applying several types of loads to the specimens. Laser measuring system such as ESPI and shearography technique were used to tetect those defects. Thermal loading method, which can easily induce the surface deformation of specimen, was used to detect the defects. Experimental results show that the defect in composite structures could be easily detected by ESPI and shearography technique. Moreover, it shows that ESPI and shearography technique could be usefully applied to the detection of defects in various kinds of composite structures.
부식환경하에서 Al 7075-T6의 피로수명에 미치는 쇼트피닝의 효과에 관한 연구
정성균(Seong-Kyun Cheong),남지헌(Ji-Hun Nam),구대림(Dae-Lim Kou),노승남(Seung-Nam Ro) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.2
부식은 기계류나 금속 부품의 성능과 수명을 저해하는 가장 큰 요인으로 작용하고 있다. 이 논문에서는 쇼트피닝이 부식환경하에서 Al 7075-T6의 피로수명에 미치는 쇼트피닝의 효과를 연구하였다. 쇼트피닝한 시험편의 피로한도는 약 52% 증가하는 것으로 나타났으며, 금속재 부품의 피로수명을 크게 연장시키는 것으로 보인다. 쇼트피닝을 한 시험편과 쇼트피닝 하지 않은 시험편을 1주에서 1년까지 비교 시험한 결과 부식은 피로강도를 현격히 감소시켰다. 쇼트피닝을 하였을 경우에는 부식에 의해 6개월 까지는 피로강도 및 피로 수명이 감소하지 않은 것으로 나타났다. 따라서 쇼트피닝 가공이 금속재료의 수명에 대한 부식의 영향을 크게 감소시키는 효과가 있음을 알 수 있다. Corrosion highly affects the lifetime and performance of machinery metallic components. The effects of shot peening on the fatigue life of Al 7075-T6 under corrosive environment are investigated in this paper. Experimental results show that the fatigue limit of shot peened specimen increases about 52%. That means the fatigue life of metallic components is highly extended by shot peening. The corrosion greatly reduces the fatigue strength depending on the corrosive condition from one week up to one year. In case of shot peened specimen, the corrosion does not reduce the fatigue strength and fatigue life up to six months. It means that the shot peening has superior effectiveness to reduce the influence of corrosion to the metallic materials.
권경배,정성균,Kwon, Kyoung-Bae,Cheong, Seong Kyun 한국안전학회 2017 한국안전학회지 Vol.32 No.5
Bicycles are very popular sporting goods in these days. Thus, the durability of bicycles is very important for the safety of bicyclists. It is well known that a bicycle frame is a major component which is essential to the safety and performance of a complete bicycle. In this study, the durability of bicycle frames were experimentally investigated under the fatigue load. Eighty bicycle frames with different types and materials were prepared and tested according to EN standards. Three kinds of fatigue loads, that is, pedalling, vertical and horizontal fatigue load, which occur constantly during riding a bicycle, were applied to the bicycle frames. The experimental results show that the horizontal fatigue load was the severest mode to pass EN standard. The pass ratio of horizontal fatigue load test was 45.2%, while the pass ratio of vertical fatigue load test was 100%. Most of cracks were found at the right side of bottom bracket shell and at the intersection area between head tube and down tube. It seems that the experimental results can be applied to improve the safety and performance of a bicycle frame.
Sn-xAg-0.5Cu 무연 솔더의 파손특성에 관한 실험적 연구
정종설,이용성,신기훈,정성균,김종형,장동영,Jeong, Jong-Seol,Lee, Yong-Sung,Shin, Ki-Hoon,Cheong, Seong-Kyun,Kim, Jong-Hyeong,Jang, Dong-Young 한국생산제조학회 2009 한국생산제조학회지 Vol.25 No.1
This paper presents an experimental study on the failure characteristics of SnAgCu lead-free solder balls. To estimate the effect of Ag, three types of SnAgCu balls are first prepared by varying the weight percent of Ag(1.0, 3.0, 4.0 wt%) and then analyzed by reliability tests such as thermal shock, high speed ball shear, and drop tests. Thermal shock test reveals that the higher the weight percent of Ag is, the longer the fatigue lift becomes. To the contrary, high speed ball-shear test and drop test show that the shear strength and the fracture toughness of solder balls are inversely proportional to the weight percent of Ag, respectively, Reasons for these observations will be further investigated In the future work.