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GA를 이용한 레이저 용접 공정변수 최적화에 대한 연구
윤태종(Tae Jong Yun),오원빈(Won Bin Oh),이보람(Bo Ram Lee),이충우(Chong Woo Lee),나현호(Hyeon Ho Na),최주석(Ju Seok Choi),김일수(Ill Soo Kim) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.4
LNG(liguefied natural gas)는 여타의 화석연료에 비해 환경 부담이 작은 청정에너지의 장점 때문에 그 사용량은 세계적으로 증가하는 추세이며, 저장탱크, 파이프라인, 수송용 LNG 선박의 수요가 크게 증가하고 있다. 현재 LNG 탱크선의 30~40%가 곡선으로 이루어져 있는 LNG 탱크선에 대한 맞대기의 용접 한계를 극복하기 위한 용접부 형상 및 용접법의 변화가 필요하다. 본 연구에서는 맞대기 용접의 한계를 극복하고 고품질의 용접부 품질을 위해 필렛 형상의 레이저 용접을 수행하였으며, 필렛 용접부의 용입 형상에 대한 데이터를 활용하여 용접공정변수의 최적화를 최종목표로 하였다. 용접 공정변수의 최적화를 위해 유전자 알고리즘의 목적함수 및 제한함수를 선정하였다. 또한 GA를 이용하여 최적의 파이버 레이저 필렛 용접 공정변수를 도출하였으며, 알고리즘의 오차 분석을 통해 알고리즘의 신뢰성을 확보하였다. The use of liquified natural gas (LNG) is increasing globally because of its advantages as a clean source of energy with lower environmental burden compared to other fossil fuels. The demand for storage tanks, pipelines, and LNG transportation vessels is increasing significantly. About 30~40% of the current LNG tankers are curved and hence require butt welding. To overcome the limitations of butt welding, it is necessary to change the weld shape and welding method. In this study, fillet-shaped laser welding was performed to overcome the limitations of butt welding and to achieve high-quality welds. The ultimate goal was to optimize the welding process parameters by utilizing data on the penetration shape of the fillet weld. For optimization of welding process variables, the objective and limiting functions of the genetic algorithms were selected. In addition, the optimal fiber laser fillet welding process parameters were derived using the genetic algorithm, and the reliability of the algorithm was secured through error analysis of the algorithm.
다중 반응표면분석법을 이용한 980MPa급 GA강판의 저항 점 용접조건 최적화
최상규(Sang-Gyu Choi),황인성(Insung Hwang),강문진(Munjin Kang),현승균(Soongkeun Hyun),김영민(Young-Min Kim) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.4
In this study, the welding quality prediction model with high reliability was developed for the 980 MPa grade TRIP steel with minimum conditions in resistance spot welding process using response surface methodology. The welding time and welding current were selected as the important parameters. The welding quality was predicted by deriving four parameters including tensile shear strength, nugget size, expulsion, and button fracture. The experiment was carried out by using the central composite design. Then, the regression equation derived using the result data was analyzed and the effect of the independent variable on the objective function was analyzed by ANOVA. The welding time had a very small effect on tensile shear strength and nugget, but welding current had a dominant effect on the two properties. Also, the reliability of the derived regression model equation is verified by R correlation coefficient and experiments.
차체용 1.2GPa급 합금화아연도금 TRIP강의 용접성에 미치는 Weldbond 공정의 효과
이종대(Jong-Dae Lee),이혜림(Hye-Rim Lee),김목순(Mok-Soon Kim),서종덕(Jong-Deok Seo),김준기(Jun-Ki Kim) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.6
Galvannealed(GA) steels are now generally used in car body manufacturing for corrosion resistance. In this study, the weldability and joint mechanical behavior of a newly developed 1.2GPa grade GA ultra high strength TRIP(transformation induced plasticity) steel was investigated for three joining processes, such as adhesive bonding, resistance spot welding and weldbonding. Under both shear and peel stress conditions, the failure mode of the adhesive joints were the mixture of the adhesive cohesive failure, adhesive interface failure and coating layer failure. It means that the adhesion strength of GA coating onto the base metal was similar to that of adhesive bonding onto the GA coating. Under the shear stress condition, the weldbonding exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel because the strength of adhesive bond overwhelmed that of the resistance spot weld. Under the peel stress condition, the weldbonding also exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel by inducing the tear fracture mode rather than the partial plug fracture mode.
로브곡선을 이용한 자동차용 신강재의 저항 점 용접성 평가 기술 개발
김태형,이동옥,이세헌,Kim, Tae-Hyung,Lee, Dong-Ock,Rhee, Se-Hun 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.4
The resistance spot welding is one of the most commonly used welding process for joining the sheet metal in automotive manufacturing process due to higher deposition rates and higher economy achieved. Control variables in the resistance spot welding for achieving high quality are welding current, welding force and welding time. Generally at the manufacturing scene, welding current Vs welding time lobe diagram is used to estimate weldability because controlling welding force is not practical due to economical reasons. However new automotive steel plates have been developed to make lightweight automobiles and to improve resistance against rusting. Also the weldability of these steel plates are worst than the existing steel plates because of changing bare metal and surface plating effect. In consequence of above mentioned reasons, it is necessary to use welding force to present the lobe diagram. In this study, we obtained the welding force Vs welding current lobe diagram for commonly used GA steel plate and found that the second order repression model of tensile shear strength was useful in reducing the number of experiments, and the indentation, and thickness change during welding were used as a response to estimate quantitatively expulsion.
Comparative Investigation Into Field Performance of Steel Bridge Deck Asphalt Overlay Systems
Xiaoyang Jia,Baoshan Huang,Shangjiang Chen,Dawei Shi 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.7
The steel bridge deck overlay provides a smooth surface for riding and protects the deck from influence of traffic and environment factors. The presence of distress on overlay may compromise the serviceability of a bridge. A better understanding of distress is indispensable for designers to make improvements on asphalt overlay to extend the service life. A field investigation into performance of two bridge deck asphalt overlay systems was conducted. The overlay system included an epoxy asphalt overlay and a composite asphalt overlay consisting of Stone-Matrix-Asphalt (SMA) and Gussasphalt (GA). The field investigation was conducted to evaluate the difference in performance between two systems. Chemical analyses were performed on core samples from each bridge to further investigate the distress mechanism of each system. Results indicated that the two overlay systems generally exhibited similar field performance. Each bridge developed different distress, mainly due to the poor bonding between layers or between overlay and steel deck.
Hashem Jahangir,Danial Rezazadeh Eidgahee,Mohammad Reza Esfahani 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.6
Composite materials are effective in forming externally bonded reinforcements which find applications related to existing structures repair, attributed to their high strength-to-weight ratio and ease of installation. Among various composites, fibre reinforced polymers (FRP) have somewhat been largely accepted as a commonly utilized composite for such purposes. It is only recently that steel fibres have been considered as additional members of the FRP fibre family, intuitively termed as steel reinforced polymer (SRP). Owing to its low cost and permissibility of fibre bending at sharp corners, SRP is rapidly becoming a viable contender to other FRP systems. This paper investigates the bond behaviour of SRP-concrete joints with different bonded lengths (50, 75, 100, 150 and 300 mm) and widths (15, 30, 40, 50, and 75 mm) using single-lap shear tests. The experimental specimens contain SRP strips with a fixed density of steel fibres (0.472 cords/mm) bonded to the face of concrete prisms. The load responses were obtained and compared in terms of corresponding load and slip boundaries of the constant region and the peak loads. The failure modes of SRP composites are discussed, and the range of effective bonded length is evaluated herein. In the end, a new analytical model was proposed to estimate the SRP-concrete bond strength using a genetic algorithm, which outperforms 22 existing FRP-concrete bond strength models.
Aissa Laouissi,Mohammed Mossaab Blaoui,Hammoudi Abderazek,Mourad Nouioua,Ali Bouchoucha 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12
The main purpose of the present investigation is to achieve an optimization of the heat treatment process along with improvingthe mechanical properties of Medium-carbon steel C45 illustrated by the tensile strength (Ts), the hardness (HV) andthe elongation (A). This is performed through varying three necessary factors represented by the quench temperature, theholding time and the cooling medium (air, oil and acid solution). An experimental design illustrated by the performance of27 ( ]] ><![CDATA[33 ) tests was adopted for the planning of the experiments. The Response Surfaces Methodology (RSM),the Neural Networks Approach (ANN) and the Genetic Algorithm (GA) were selected for the modeling and optimization ofthe heat treatment process. Analysis of Variance (ANOVA) results show the cooling medium to have the greatest influenceon the mechanical properties of C45 steel with contributions of 47.34% to 74.3%. The experimental results demonstratethat heating at a temperature of T = 800 ◦C for 30 minutes and then performing a quenching in the acid solution gives largevalues of both Ts and HV, and achieves Ts = 1060MPa and HV = 825.