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대형 풍력발전기 블레이드의 볼트체결부 응력감소를 위한 설계연구
하광태,허준,정재호 한국풍력에너지학회 2022 풍력에너지저널 Vol.13 No.4
Today, the power capacity of a wind turbine and the size of a blade is increasing to capture more wind resources, reduce the number of wind turbines on a wind farm, and reduce the cost of energy. As the blade size becomes larger, attention is being paid to the structural integrity of the blade root connection due to the heavy gravitational load effect and increased aerodynamic loads on the large blade, which could cause catastrophic failure of the blade. Therefore, the secure bolted joint connection of the blade to the hub is very important. In this paper, attention was given to the stress concentration factor (SCF) at the first thread between the M42 bolt and nut. The effect of various design parameters on the stress concentration factor was investigated, which included nut type, nut height, and reduced shank bolt. From a close design investigation of the numerical results, it turned out that the use of a reduced shank bolt resulted in the largest reduction of the stress concentration factor by 40 %, and the round nut type also reduced the SCF by 10 %, which will be beneficial to large wind turbine blades over 100 meters.
하광태,김준배 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.3
As an emerging energy transition form, many floating off shore wind turbines are expected to be located far away from the coast of Ulsan, South Korea. Due to the unintended ship’s berthing mistake which could be occurred because of the huge traffic for the installation and maintenance purpose within the wind farm, however, the spar-type substructure could be impacted by a ship collision and the residual strength of the damaged structure could be reduced. In this work, the finite element analysis of a circular tube subjected to the impact loading was performed to compute the permanent deformation after a collision in ABAQUS and the numerical results were validated with an experimental data. The validated approach was further expanded for the application to calculate the permanent damage of the spar-type substructure of 5 MW floating off shore wind turbine impacted by a ship, then a residual longitudinal strength calculation approach was implemented to evaluate the residual strength based on the relation between an increase in bending moment and the corresponding curvature. Under the collision case of a ship with 3 m/s speed to a fl oater, the evaluation showed 4.1% reduction in the residual strength, which could be used as a basis for the assessment by O&M service providers whether the damaged substructure can be safely towed to the coast or can be maintained on-site with safety.
서울 강북지역 유통 농산물의 내분비계장애 추정농약의 잔류실태(2007)
하광태,박성규,조태희,한창호,김성단,이경아,김시정,장정임,조한빈,최병현 한국식품위생안전성학회 2009 한국식품위생안전성학회지 Vol.24 No.2
This study was carried out to investigate the current status of suspected endocrine disrupting pesticides among the agricultural products in northern area of Seoul in 2007. 3,026 samples was analyzed by multiresidue method. Detected Pesticide in 11 cases were procymidone, endosulfan, chlorothalonil, chlorpyrifos, cyermethrin, fenvalerate, hexaconazole, carbendazim, pendimethalin, permethrin, parathion and exceeded 7 cases of endosulfan, procymidone, carbendazim, chlorothalonil, chlorpyrifos, cypermethrin, fenvalerate in the maximum residue limits(MRLs). Procymidone, endosulfan, chlorothalonil and chlorpyrifos comprised up to 80.5% in detected pesticides. Among the 321 cases of detected agricultural products, 287 cases(89.4%) were vegetables, 25 cases (7.8%) were fruits, Others were 9 cases(2.8%).
허광태(Kwang-Tae Hur),박후명(Hoo-Myung Park),곽재섭(Jae-Seob Kwak),하만경(Man-Kyung Ha),하경호(Kyoung-Ho Ha) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
Recently, polyurethane pre-polymer has been used widely in the social life. In this paper, evaluation of parameters for polymerization process was carried out using design of experiments. As a result, the effect of each parameter affected by viscosity and residual NCO of pre-polymer was found. Optimization of polymerization process was performed. and the these results were applied to produce casting tape having a better performance.
허광태(Kwang-Tae Hur),하만경(Man-Kyung Ha) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
This study about pre-polymerization for production of casting tape has been carried out to find good chemical composition. But, actually, different applied to pre-polymerization. So, it is necessary to perform the optimization of parameters for pre-polymerization. So, this study carried out the total of twenty-seven experiment to check the influence of the all factors. Such as water temperature of heating polymerization furnace, working time in the peak of condition, impeller rotating speed, impeller shape. And then, the result showed that impeller shape have heavily affected the NCO, and also water temperature have fairly affected the residual NCO. moreover, the prepolymer experiment took total reaction to maintain over one hear according to water and thermometry experiment of pre-polymer checked value.