강구조물 용접이음부 외부결함의 자동검출 알고리즘

서원찬,이동욱,Seo, Won Chan,Lee, Dong Uk 한국강구조학회 1999 韓國鋼構造學會 論文集 Vol.11 No.1

본 논문에서는 강구조물의 제작 및 시공에서 용접이음부의 고품질을 확보하기 위하여 강구조물 용접이음부 외부결함의 자동검출에 관한 화상처리 알고리즘을 개발한다. 개발 알고리즘은 광학계의 적절한 배치에 의해 얻어지는 4매의 입력화상을 이용하여 기존의 기법에서 검출할 수 없었던 용접이음부 외부결함을 검출할 수 있음을 보인다. 용접 외부결함이 존재하는 시험편을 제작하고 실험을 통하여 개발 알고리즘의 유용성을 확인하였다. 또한 검출된 용접외부결함의 분류 결과를 육안검사 결과와 비교하였다. The aim of this study is to construct a machine vision monitoring system for an automatic visual inspection of weld joint in steel structure. An image processing algorithm for a visual weld defects detection on weld bead is developed using the intensity image. An optic system for getting four intensity images was set as a fixed camera position and four different illumination directions. The input images were thresholded and segmented after a suitable preprocessing and the features of each region were defined and calculated. The features were used in the detection and the classification of the visual weld defects. It is confirmed that the developed algorithm can detect weld defects that could not be detected by previously developed techniques. The recognized results were evaluated and compared to expert inspectors' results.

NOAA/AVHRR SST 자료를 이용한 한반도 주변해역에서의 수온과 어장변화특성 연구

서원찬,윤홍주,Seo, Won-Chan,Yoon, Hong-Joo 한국정보통신학회 2008 한국정보통신학회논문지 Vol.12 No.12

최근 대두 되고 있는 지구 온난화 및 기후 변화와 관련해서 수온이 해양 생태계에 미치는 영향을 알기 위하여 한반도 주변 해역을 중심으로 $1988{\sim}2000$년까지 NOAA SST자료를 활용하여 어류 회류의 변동성에 대하여 조사하였다. 위성자료를 분석해 본 결과 우리나라는 전반적으로 온난화 경향이 나타나고 있다. 연근해의 수온상승과 비교해 볼 때, 오징어, 멸치, 정어리, 꽁치 등 회유성 어종의 분포해역이 점차 북상하고 있는 것으로 나타났다. 또한 난류성 어종인 오징어와 멸치의 어획량은 증가한 반면, 한류성 어종인 꽁치와 정어리는 감소하는 경향을 보였다. 그러나 어황에 영향을 미치는 요인에는 수온뿐만 아니라 염분 및 오염도 등 여러 가지 요소가 존재하기 때문에 수온상승으로 인해 생기는 어황의 변화라고 단정 짓기는 어렵다. 따라서 금후 기후 변동과 연근해 어황 변화에 대해서도 계속적인 연구가 필요하다. It was studied to the displacement and the amount of catch for migratory fishes with NOAA/AVHRR SST(Sea Surface Temperature) from 1988 to 2000 in the Korean Seas. The analyzed results from SST data showed generally the oceanic warming trend in the Korean Seas. On the increasement of SST, the distributed areas of migratory fishes which living in the warm waters were displaced gradually to the northward directions(high latitude) and then the amount of catch was increased during this studied periods against to migratory fishes which living in the cold waters.

특징점의 수를 제약조건으로 하는 선도형의 특징점 검출 기법

서원찬(Seo Won Chan) 한국정보처리학회 1997 정보처리학회논문지 Vol.4 No.9

An algorithm for detecting dominant points on a digital contour is proposed. The algorithm detects the dominant points from the given contour with the given number of points as a constraint condition, on the basis of the principle of the top-down approach. The dominant points are detected by minimizing the object function that presents the similarity between the given contour and the approximated polygon drawn by connecting the dominant points of candidate. The penalty multiplier method is applied to minimize the augmented Lagrangean function which is made by adding the penalty of the constraint condition to the object function. on the minimization, a local searching method by the partial problem division is considered, and it is clarified that the reasonable solution is obtained by the method. The proposed algorithm has a merit that the dominant points can be detected exactly and stably even for the digital contour composed of multiple-scale features and similar contours, because it detects them on considering the property of a whole figure of the given contour. It is confirmed that the proposed algorithm is more excellent than other previously proposed algorithms by the comparison and the evaluation through the experiment on using typical digital curves.

영상 처리 기법을 위한 병렬화 네트워크 시스템의 구성

서원찬(Won-Chan Seo),조강현(Kang-Hyun Jo),김우열(Woo-Yeol Kim) 제어로봇시스템학회 2000 제어·로봇·시스템학회 논문지 Vol.6 No.6

고강도강 용접금속 저온균열 발생에 미치는 확산성수소량 및 경도의 영향

서원찬(Won-Chan Seo),방국수(Kook-Soo Bang) 한국해양공학회 2012 韓國海洋工學會誌 Vol.26 No.2

The effects of the diffusible hydrogen content and hardness on the cold cracking in high strength weld metal were investigated. The diffusible hydrogen contents were influenced by welding parameters such as the voltage and contact tip-to-work distance (CTWD). The diffusible hydrogen content increased with an increase in voltage. However, it was decreased with an increase in CTWD. CTWD also influenced the weld metal hardness,especially when the wire used had a higher strength than the base metal. This showed that weld metal hardness had a more powerful effect on weld metal cold cracking than the diffusible hydrogen content in this experiment.

B 첨가 620℃급 터빈 케이싱용 고Cr 페라이트계 주강의 용접성에 미치는 탄소함량의 영향

서원찬(WON-CHAN SEO),방국수(KOOK-SOO BANG),지병하(BYUNG-HA CHI) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.6

Effectsof carbon content on the weldability of B-containing 620℃ grade high Cr ferritic cast steele were investigated. Cast steel with lower carbon content of 0.07% showed lower HAZ hardness because of the formation of lower carbon martensite in HAZ. It also showed less solidification cracking susceptibility in weld metal because of the formation of delta ferrite. However, hot ductility showed no difference between cast steels with lower and higher carbon contents. Cast steel with lower carbon content showed greater HAZ softening after PWHT in the region heated between AC1 and AC3 because of its higher base metal hardness.

다층용접한 슈퍼 듀플렉스 스테인리스강 용접금속의 조직 및 충격인성

서원찬(Won-chan Seo),박찬(Chan Park),방국수(Kook-soo Bang) 한국해양공학회 2012 韓國海洋工學會誌 Vol.26 No.6

The effects of reheating during welding on the microstructure and impact toughness of weld metal in 25% Cr super duplex stainless steels were investigated. Using different heat inputs, weld metals with different reheated regions were obtained. This showed that, depending on the reheating temperature, the microstructure in the reheated region was quite different from that of the as-deposited microstructure. When reheated into the y+α temperature range, fine intragranular austenite was formed in the as-deposited columnar structure. However, when reheated above the a solvus temperature range, most of the columnar structure disappeared and fine equiaxed austenite and ferrite were formed. Because of the larger amount of fine austenite in the reheated region, a higher impact toughness was obtained in the weld metal with a higher amount of reheated region.

Fe-XAl-0.1Y(X =5, 10, 14 wt.%) 합금의 고온 산화거동

이병우,서원찬,박찬,Lee, Byung-Woo,Seo, Won-Chan,Park, Chan 한국재료학회 2003 한국재료학회지 Vol.13 No.12

The oxidation behaviour of Fe-XAl-0.1Y(X= 5, 10, 14 wt.%) alloys were investigated at 1073, 1173 and 1273 K in oxygen/ nitrogen gas atmosphere for 1∼24 hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.1Y alloys followed the parabolic rate law. Oxidation rates of 10Al and 14Al alloys were ten times lower than that of 5Al alloys. This is attributed to the formations of protective $A1_2$$O_3$oxides on the surface of 10Al and 14Al alloys. The oxidation product scales of the 5Al alloy showed that thick iron oxide scales($Fe_2$$O_3$, $Fe_3$$O_4$) containing porosities formed during early stages of oxidation. With continued oxidation, aluminum oxide was formed at the alloy/scale interface.

강상판(鋼床版) U형(形) 트라프리브 단차용접(段差熔接)이음부(部)의 피로강도(疲勞强度)에 관(關)한 연구(硏究)

이동욱,서원찬,Lee, Dong Uk,Seo, Won Chan 한국강구조학회 1996 韓國鋼構造學會 論文集 Vol.8 No.3

With the adoption of welded joints rather than bolted joints, we investigate the fatigue strength and the fatigue crack initiation of U-type trough rib and welded specimen with misalignment in a steel deck plate. The stress concentration factor of welded specimens with a misalignment is also verified by a finite element method. The main conclusions obtained from this study are as follows Experimental results of full-scaled U-type trough rib models have indicated that fatigue life depends on misalignments of welded joints in steel deck plate ; The more misalignments are, the less the fatigue life is. It has also shown that fatigue crack propagates from the welded root to the bead surface. We have also obtained the same results from both the fatigue test of welded specimens with a misalignment and the stress analysis of a finite element method.

교량 피로설계의 동시재하계수에 관한 연구

이동욱,서원찬,최재원,Lee, Dong Uk,Seo, Won Chan,Choi, Jae Won 한국강구조학회 2000 韓國鋼構造學會 論文集 Vol.12 No.2

Since vehicles become large and heavy and traffic volume is increased rapidly, many fatigue damages have been reported in bridge members. In order to prevent fatigue damages of bridge members and maintain safety it is essential to perform rational fatigue check. Only one vehicle is loaded on a bridge deck for the fatigue design. But in reality it is seldom that only one vehicle passes on a bridge deck. Usually more than two vehicles are passing on a bridge deck simultaneously. Therefore, it is necessary to consider the influence of simultaneous loading for a rational fatigue design. In this study, the influence of simultaneous loading is investigated by performing stress variation analysis due to vehicle load on the basis of linear superposition method and Monte-Carlo simulation of traffic flow, and then calculating the measure of fatigue damages. 교량에 통행하는 차량의 대형화와 통행교통량의 급격한 증가로 인하여 교량부재에서 피로손상이 많이 보고되고 있다. 교량부재의 피로손상을 방지하고, 안전을 유지하기 위해서 합리적인 피로조사를 실시하여야 한다. 교량의 피로설계에서는 차량 1대만 재하 시키는 방법을 채택하고 있으나, 실제 교량의 상부에 차량이 1대만 통과하는 일은 거의 없다. 통상 교량의 상부에는 복수의 차량이 동시에 재하되므로 합리적인 피로설계를 위해서는 동시재하의 영향을 고려하여야 한다. 본 논문에서는 도로교를 통행하는 차륜하중에 대해 선형중첩법과 교통류의 몬테카를로 시뮬레이션에 의한 변동응력해석을 실시하고, 피로 손상도를 구함으로써 통행차량의 차축하중에 대한 동시재하의 영향에 대해 연구하였다.