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CFRP 판재의 비파괴 평가를 위한 비접촉식 초음파 평가 기법
최상우(S. W. Choi),서경철(K. C. Seo),이준현(J. H. Lee),변준형(J. H. Byun),조윤호(Y. H. Cho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Fiber reinforced plastic materials should be inspected in fabrication process in order to enhance quality by preventing defects such as delamination and void. Generally, ultrasonic technique is used to evaluate CFRP. In conventional ultrasonic techniques, transducer should be contacted on FRP through couplant during evaluation in service and after fabrication. However, non-contact measuring technique should be developed to apply ultrasonic testing technique in fabrication process. In this study, laser-generated ultrasonic technique was applied for non-contacting generation of guided wave in CFRP plate. Velocities of laser-generated guided wave were evaluated for various fiber orientation. In addition, air-coupled transducer was used for non-contacting receiving guided wave of selected mode.
급냉응고/분말야금법으로 제조한 Al-Fe-V-Si-Ti-W 합금의 고온크립거동
김인수,김낙준,남수우,위당문,오승철,최상우 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.11
The elevated temperature creep properties and microstructural stability of RS/PM Al-10Fe-1.3V-2Si-1Ti-1W(wt.%) alloy have been investigated. The alloy showed high stress exponent of 12 to 18 and activation energy of 237 to 808 kJ/㏖, which was strongly dependent on the temperature and stress. The unusual creep behavior of the dispersion strengthened alloys cannot be described satisfactorily by current creep laws, Recently, Ro¨sler and Arzt proposed a new model assuming thermally activated dislocation detachment from dispersoids exerting an attractive force. In the present study, experimental evidence was achieved for the presence of attractive interaction between the dislocation and the dispersoids using TEM observations. The creep behavior of the alloy was analyzed using the model proposed by Ro¨sler and Arzt, and the experimental data were consistent with the prediction based on the model. It has been confirmed that the high temperature deformation of the alloy was dominated by the dislocation creep at the temperature range of 400 to 480℃, but the diffusional creep at the interface between powders also contributed to the deformation above 430℃.