http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
동적 페라이트 변태에 미치는 오스테나이트 과냉도의 영향
洪承讚,林成煥,李景鍾,李經燮 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.1
Hot compression test was performed to examine the effect of degree of undercooling on dynamic ferrite transformation behavior. Austenite undercooling was controlled by cooling rate from austenitization temperature to deformation temperature. The degree of undercooling was determined as ΔT (=Ae_3 - Ar_3). Ae_3 temperature was calculated by using Thermo-Calc and Ar_3 temperature was measured by dilatometry. The fine grained ferrite was formed during 70% deformation just above Ar_3 temperature. It was observed that the average ferrite grain size was 2 ㎛ regardless of temperature. At this temperature the flow stress was decreased by ferrite formation during deformation. The amount of ferrite transformed dynamically was increased as ΔT was increased. While, the ferrite grain size was mainly influenced by the amount of deformation. It was also confirmed that the critical strain of dynamic ferrite at high cooling rate to deformation temperature was shifted to lower strain compared to that at low cooling rate with the aid of increasing undercooling.
레이저 가진 및 레이저 도플러 진동계 센싱 기반 레이저 C-scan 시스템 개발
홍승찬,이정률 제어로봇시스템학회 2014 제어로봇시스템학회 각 지부별 자료집 Vol.2014 No.12
C-scan, which is representative inspection using ultrasonic testing, shows precise result of visualizing defects in structure. However, conventional C-scanners have some drawbacks to inspect structures such as unexpected damages during contact inspection, restriction of approach on immersion technique. Recently, laser ultrasonic based nondestructive evaluation (NDE) techniques are being increasingly used. In this study, development of fully non-contact laser C-scan system using Q-switched laser (QL) and laser Doppler vibrometer (LDV) is conducted. In addition, damage visualization algorithms are developed to visualize defects that occur in various structure. Based on laser C-scan system, aluminum plate and pipe structures including artificial defects are inspected and visualized.
홍승찬,이정률,최윤실 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4
초음파 탐상 기법인 C-스캔은 결함 가시화의 아주 탁월한 결과를 제시하여 많은 관련 연구자들이 정량적인 지표로 사용한다. 하지만 기존의 C-스캐너는 침수법에 의한 접근의 제한, 접촉법에 의한 부차적인 손상 야기 등의 이유로 많은 단점이 있다. 하지만 최근에 널리 연구되고 있는 비파괴 평가 기반의 레이저 초음파는 많은 산업에 사용되고 있다. 본 연구에서는 Q-스위치 continuous wave laser(QL)와 공기 접촉식 정전 용량 트랜스듀서(C-ACT)를 사용한 완전 비접촉식의 2 차원 레이저 C-스캔 시스템을 개발하고 CFRP 시편에서 발생할 수 있는 접착박리 및 층간분리 같은 결함을 가시화를 수행하였다. 또한 결함 가시화 알고리즘 개발하고 결함 가시화 기법을 통해 CFRP 시편에 포함된 15 mm 직경의 테플론을 검사 및 가시화하였다. C-scan shows precise result of visualizing defects in structure thus many researchers have used this result as quantitative parameter. However, previous C-scanners have some disadvantages to inspect structures such as damage due to contact inspection method, restriction of approach on immersion technique and so on. Recently, laser ultrasonic based nondestructive evaluation (NDE) techniques are being increasingly used in various industries. In this study, development of fully non-contact 2 dimensional laser C-scan system using Q-switched continuous wave laser(QL) and capacitance air-coupled transducer(C-ACT) is conducted to visualize damages that occur in CFRP structure such as delamination and debonding. In addition, damage visualization algorithms are developed and 5 mm thickness CFRP plate including the artificial damage using teflon of 15 mm diameter is inspected and visualized.
모바일 펄스-에코 초음파 전파 영상화 장치를 사용한 T-50 고등훈련기 수평 안정판 현장 비파괴 평가
홍승찬,이정율,박종운 한국비파괴검사학회 2019 한국비파괴검사학회지 Vol.39 No.5
Defects and damages, such as disbond and delamination, mainly occur in composite structures, which are increasingly used in aircraft structures, and their detection is difficult. A mobile pulse-echo ultrasonic propatation imager(PE UPI) is a laser ultrasonic nondestructive inspection tool used as an in-situ nondestructive evaluation tool. The potential of mobile PE UPIs has been confirmed through a certification test of non-destructive standard specimens and F-16 Lockheed Martin standard specimens from the Korea Air Force. In this study, a mobile PE UPI was applied to the horizontal stabilizer of a T-50 advanced trainer as an in-situ non-destructive evaluation tool, and the field applicability of mobile PE UPI was proved by comparing inspection results with the conventional A-scan ultrasonic testing technique. 항공기 구조에서 사용이 증가되고 있는 복합재에서 접착 분리와 층간 분리와 같은 결함 및 손상이 주로 발생되고 있으며 탐지의 어려움이 있다. 최근에는 레이저 발생기를 사용하여 구조 표면에 초음파를 사용한 새로운 기술 레이저 비파괴 기법이 연구되고 있다. Mobile PE UPI는 현장 비파괴 평가용으로 개발된 레이저 초음파 비파괴 검사 장치로 한국 공군으로부터 비파괴 표준 시편과 F-16 록히드 마틴 표준 시편의 인증 테스트를 통과해 현장 비파괴 평가 장치로써 가능성을 확인한 바 있다. 본 논문에서는 Mobile PE UPI를 사용하여 T-50 고등훈련기 수평 안정판 현장 비파괴 평가 장치로써 적용하고 기존 A-scan 초음파 탐상 기법과 비교를 통해 검증하고 현장 적용성을 입증하였다.