• 대한토목학회논문집
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• 제33권1호
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• pp.81-92
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• 2013

HSB를 적용한 플레이트거더의 압축플랜지 국부좌굴을 고려한 극한휨강도를 비선형 유한요소해석으로 분석하였다. 압축플랜지의 비탄성 국부좌굴 또는 소성항복이 휨강도를 지배하는 압축플랜지 세장비를 갖도록 해석대상 강거더를 선정하였다. HSB600 및 HSB800 강재로 제작된 균질단면 강거더와 HSB800 강재와 SM570-TMC 강재를 함께 적용한 하이브리드 단면을 고려하였으며, 일반강재와의 비교를 위하여 SM490-TMC 강거더에 대한 해석도 수행하였다. 비선형 유한요소해석 시에는 플랜지와 복부판을 쉘요소로 강재는 탄소성-변형경화 재료로 모델링하였으며, 초기변형과 단면의 잔류응력을 고려하였다. 비선형 유한요소해석 결과와 기존 문헌의 실험결과를 비교하여 유한요소 해석결과를 검증하였으며, 초기변형과 잔류응력이 극한휨강도에 미치는 영향을 분석하였다. 총 60개 해석대상 강거더의 휨극한강도를 유한요소해석으로 구하고, 도로교설계기준, AASHTO LRFD와 Eurocode 3의 설계규정으로 구한 휨강도와 비교하여 이들 규정의 HSB 강거더에 대한 적용성을 검토하였다.

• Journal of Welding and Joining
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• 제35권1호
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• pp.61-67
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• 2017

Recent studies on the fatigue assessment of high strength steel weld based on the fracture mechanics have frequently raised the problems related to the conservatism in the fatigue crack growth rate specified in the relevant design code. The purpose of this study is to evaluate the effect of the fatigue crack growth parameter on the fatigue life for the low carbon steel weld. In order to do it, the fatigue tests with the constant stress ratio were performed to evaluate the fatigue crack growth rate in the butt weld of SM490. And the fatigue crack growth parameters of the weld were evaluated in accordance with ASTM E647. From the comparative fatigue assessment results, it was found that the fatigue crack growth rate specified in the relevant design code was too conservative to estimate the residual fatigue life of welded structure. So, in order to get the more reliable results, it was recommended that the fatigue life estimation based on the fracture mechanics be performed with the fatigue crack growth parameter specified by test.

• 한국생산제조학회지
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• 제22권1호
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• pp.22-28
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• 2013

Robotic GMA (Gas Metal Arc) welding process is one of widely acceptable metal joining process. The heat and mass inputs are coupled and transferred by the weld arc to the molten weld pool and by the molten metal that is being transferred to the weld pool. The amount and distribution of the input energy are basically controlled by the obvious and careful choices of welding process parameters in order to accomplish the optimal bead geometry and the desired quality of the weldment. To make effective use of automated and robotic GMA welding, it is imperative to predict online faults for bead geometry and welding quality with respect to welding parameters, applicable to all welding positions and covering a wide range of material thickness. MD (Mahalanobis Distance) technique was employed for investigating and modeling the GMA welding process and significance test techniques were applied for the interpretation of the experimental data. To successfully accomplish this objective, two sets of experiment were performed with different welding parameters; the welded samples from SM 490A steel flats. First, a set of weldments without any faults were generated in a number of repeated sessions in order to be used as references. The experimental results of current and voltage waveforms were used to predict the magnitude of bead geometry and welding quality, and to establish the relationships between weld process parameters and online welding faults. Statistical models developed from experimental results which can be used to quantify the welding quality with respect to process parameters in order to achieve the desired bead geometry based on weld quality criteria.