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유원효,김정관,손지희,문중식,권성일,박정웅 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
구조물 조립시 용접중 불균일한 온도분포 및 열응력이 발생하고 용접후에는 비선형 소성변형으로 인하여 용접잔류응력이 필연적으로 발생하는데, 이중 용접중심부의 인장잔류응력은 균열 전파력을 증가시켜 피로강도를 감소시키며 취성파괴에 대한 구조물의 저항력을 감소시킨다. 그러므로 용접구조물의 역학적인 지표로서, 용접잔류응력이 구조물의 파괴거동에 미치는 영향을 정확히 파악하는 것은 용접구조물의 파괴해석에 있어서 매우 중요하다. 따라서 본 연구에서는 용접강도별 고강도 극후판 YP460MPa급(100t) 강재를 적용하여, 고유변형도 기법을 활용하여 FCA 용접재료 강도매칭에 따른 잔류응력분포가 역학적 거동(소성변형율 분포 및 인성)에 미치는 영향에 대해 고찰하였으며, 이때 얻어진 잔류응력이 피로성능과 균열성장 속도에 미치는 상관성을 확인하였다.
An experimental study on fatigue performance of cryogenic metallic materials for IMO type B tank
이진성,유원효,유창혁,김경수,김유일 대한조선학회 2013 International Journal of Naval Architecture and Oc Vol.5 No.4
Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue,fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low (-100oC) and cryogenic (-163 oC) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.
변동하중하의 잔류응력을 고려한 십자형 용접부의 잔존 수명 예측에 관한 연구
김성훈,김경수,이장현,유창혁,유원효,유미지,Kim, Sung-Hoon,Kim, Kyung-Su,Lee, Jang-Hyun,Yoo, Chang-Hyuk,You, Won-Hyo,Yoo, Mi-Ji 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.2
This paper deals with the crack propagation life assessment of T-joint welded structure where typical fatigue cracks have been frequently initiated when the marine vessels experience the storm load. Welding residual stresses are calculated to investigate its effects on the fatigue life. Thereafter the residual stress distribution was applied to the AFGROW life prediction program, which incorporated the loading, the welding residual stress, and the geometric shape of the structure. The fatigue tests of the T-joint welded specimen under storm loading show the beach mark clearly generated on the fractured section of the weldment. The crack propagation life estimated based on the beach mark is compared with that of AFGROW to validate the life prediction. Based on the results, the evaluation method of the remaining fatigue life for T-joint fillet weldment of marine vessel's cargo hold with random load or storm load was established.