Finite element analysis (FEA) was conducted to investigate the cutting process of a single-layer PET film during rotary die cutting. In a roll-to-roll system, cutting blades formed on rollers were modeled as rigid bodies, while the PET film was modeled as an elastoplastic material using a two-dimensional approach. Stress-strain behavior of the film was measured through experimental tensile testing and used as input data for FEA. Force-displacement data from vertical cutting experiments of PET film were collected to validate the FE model and compared with simulation results. Stress distribution of the film and cutting force per unit thickness during the rotary cutting process were analyzed. The cutting force and range of effective cutting angles were proportional to tip angle of the blade within a range of 25 to 60 degrees, showing a noticeable change in proportionality slope at a tip angle of 40 degrees. As the film tension increased, the cutting force in thickness direction decreased, while that in longitudinal direction remained almost constant. Errors in film feed velocity significantly affected the cutting force. When the film moved slightly slower than the reference velocity, the cutting force was minimized due to reduced contact between the film and blade surface.
Lately, due to the concentration of population in metropolitan areas, traffic congestion in the hub city has occurred, and future mobility AAM development is undergoing active progress to solve this situation. Accordingly, reducing noise pollution, which is pointed out as one of the problems of AAM, is an essential technical issue for urban operation. In this study, a duct, which is a representative aerodynamic noise reduction method, was used, and numerical analysis was performed using ANSYS FLUENT, a CFD software, according to the shape of struts in the duct. The FW-H of the transient-state LES model was used, and the steady-state analysis value was used as the initial value to save analysis time. Case 1 without strut, Case 2 with strut of an airfoil section, and Case 3 with strut of a rectangle section were designed and compared at a rotational speed of 6,000 RPM. Compared to Case 1, Case 2 and Case 3 showed improved thrust by about 7% and 2%, respectively. Compared to Case 2, Case 3 showed reduced OASPL from a minimum of 0.0793 dB to a maximum of 1.0072 dB. It was found that shapes of strut in the duct significantly affect thrust and aerodynamic noise.
Urban air mobility (UAM) is rapidly growing as a new means of transportation. As a result, noise pollution is emerging as a new technical challenge. Therefore, the sawtooth-shaped biomimetic designs were incorporated on the trailing edge of the blade to reduce flow-induced noise. The biomimetic virtual design was analyzed using the CFD software, ANSYS FLUENT V20.2. Based on the steady-state RANS flow solution, the acoustic power was calculated using the broadband noise source model to evaluate acoustic radiation. Four different cases with cutting lengths of 3.1 mm, 3.7 mm, 4.3 mm, and 4.9 mm of blades were compared with the base model at the rotational blade speed of 6,000 RPM. The maximum acoustic power level of the biomimetic blades ranged from 37.24 dB to 39.88 dB, resulting in a 10% reduction compared to the original blade (42.02 dB). The novel design affected the blade area, which inevitably reduced the slight thrust performance. However, the thrust was reduced to approximately less than 5% compared with the base blade in case 1. The biomimetic blade reduced the thrust due to its aerodynamic characteristics. However, the design of a blade with an appropriate cutting length has a greater effect in reducing noise rather than thrust.
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Propeller Modification with Groove Structure on Thrust Performance Duygu Özyurt, Hürrem Akbıyık Celal Bayar Üniversitesi Fen Bilimleri Dergisi.2025; 21(1): 27. CrossRef
A small wind power generator with Archimedes blades made of polypropylene has been developed for the effective generation of eco-friendly electronic energy. Despite the excellent structural characteristics of the higher performance of an Archimedes blade, its shape is complicated to manufacture, and presents difficulty in guaranteeing mechanical reliability in the outdoor operating environment. Especially, the UV-Light deterioration in a long-term of several years affects the mechanical properties of the polypropylene blade. To evaluate the change of strength depending on the amount of UV-Light irradiation in the outdoor environment, an accelerated UV-Light deterioration test is proposed and conducted using three types of blade materials, such as polypropylene with UV-Resistance material (C20 H25 N₃O) coated and mixed ones. Through the experimental tests, the UV resistant material coating on the blade showed the best properties for long-term exposure to UV light. Based on the test results of property changes, the Archimedes blade was analyzed using a finite element method to predict the reliability of the blade’s underused conditions. As a result of the analysis, the UV degradation resistance of Archimedes blades with UV coating improved by 2.4 times compared to the case without UV coating.
Research on the automation of many types of construction equipment, including motor graders, is being actively conducted. In a motor grader cabin, the operator has difficulty observing the working environment because of a constructed field of view. Thus, workers rely on their experience and senses. Further, the working environment of the blade must be observed, and a control algorithm should be created to enable autonomous operation. In this study, a blade rotation control strategy considering the soil distribution was proposed. First, a co-simulation environment was constructed using RecurDyn for multibody dynamics analysis and EDEM for discrete element method simulation, and simulations were performed to determine the correlation between soil distribution and the blade rotation angle. Work quality and blade load were analyzed according to the simulation results. The optimal blade rotation angle according to soil distribution was obtained to develop the strategy for autonomous flattening and scattering work. The proposed control strategy was implemented in a 1/4 full-scale motor grader experimental setup. An experiment to evaluate work quality was conducted to validate the effectiveness of the proposed methods. The experimental results indicated that the proposed strategy effectively performed scattering work.
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In the gas turbine, the clearance between the blade tip of the rotor and the inside of the stationary casing varies depending on the rotation of the rotor and the heat output of the combustor. Accordingly, the assembly clearance is determined, and the leakage of the gas occurs because of the gap during operation, affecting the efficiency of the system. Thus, designers use a variety of techniques to optimize this clearance, a typical method that reduces the relative variation of the clearance using heating and cooling mechanisms. In this study, we developed a method to control the blade tip clearance through the axial movement of the inclined blade without using heating and cooling mechanisms. Recently, we designed an advanced blade tip clearance control system that can control multi-step, not on-off control, to apply to large gas turbines developed by Doosan. The designed system is hydraulic and can be used with a maximum thrust of 100 tons, and the desired displacement can be moved in multiple stages as required. We have completed the reliability verification of the entire lifecycle level and applied it to the newly developed gas turbine.
The purpose of this study was to investigate the flow characteristics and cooling performance for the heavy turbine blade with different shapes. Research was focused on the numerical study on forced convective heat transfer coefficients for three different blades with base, tip, and hole. Thus, selected local locations for various temperature distributions were shown in the flow domain. Final temperature on the local surface of blades was compared with three different blades. According to the results of velocity and temperature distributions in the fluid domain, the blade with holes had the best convective cooling performance with higher 13-16% average heat transfer coefficient than the other two blades. Apparent vortex at the tip of tip and hole blade caused the stable temperature drop. According to the calculations of local convective heat transfer coefficient between blade surface and atmosphere in the blade, approximately 18% of heat transfer coefficient at hole was higher than the base blade and 7% at hole blade was higher than the base blade. Lowest cooling performance existed at the center position of all three blades.
The blade cylinder root is a key component connecting the blade and pitch bearing of a wind turbine and is 20% of the blade’s manufacturing cost. Blade cylinder roots are manufactured using the open die forging method with steel alloy. However the blade cylinder root for 750 KW class wind turbine is manufactured using AA5083 cast material to reduce weight. The purpose of this study is to develop a hot open die forging method, through experiment and FEA, using AA5083 material manufactured by continuous casting. The forging process was designed using the mandrel forging method. Hot compression tests were conducted to obtain flow stress of cast microstructure at different temperatures and strain rates. Control parameters of each forging process were analyzed/compared to predict adaptability of the mandrel forging process. High productivity, good internal quality, shapes, and dimension were verified by prototypes manufactured by the proposed forging process.
The purpose of this review paper is to highlight recent efforts and achievements to realize high productivity of micro/nano structure fabrication processes and feasible applications. Due to development in micro/nano fabrication processes, demands on micro/nano related applications are increasing rapidly in various fields. To meet requirements, fabrication process must have high production yield and be automated. Also, fabricated micro/nano structures are expressed on large area substrate. So, it is timely and appropriate to move forward to a new epoch by researching more robust and high throughput fabrication methods, large area fabrication techniques, and new applications. In this review paper, we present a series of recent achievements to overcome some of the limitations in productivity and product size of current fabrication processes, such as photolithography and imprinting lithography. For potential applications, transparent metal electrode, large size optical film, bus wire for narrow bezel, and water collecting surface, are briefly described to expand the application field from the well-known.
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Design of Transparent Conductive Oxides with Metal Patterning Techniques Hyeji Kim, Junghyun Lee, Younggwang Lee, Minwoo Hong, Dohyun Kim, Inpyo Lee, Chanhyuk Choi, Joondong Kim Journal of the Korean Solar Energy Society.2024; 44(5): 33. CrossRef
Fabrication of Nanopatterned Metal Mold based on Zirconia Nanoparticle and its Application into Thermal Replication of Thermoplastic Materials Selim Park, Kyoung Chan Min, Sowon Jang, Yujin Ha, Wook-Bae Kim Journal of the Korean Society for Precision Engineering.2022; 39(7): 501. CrossRef
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This paper examines the stability of the blades that convert the wind kinetic energy into the mechanical energy among the small wind power-generation systems, and proposes the design improvement for blades with a higher rigidity and a lighter weight than the conventional blades. The composite-specimen tensile test and static-load test are conducted to verify the reliability. To design the lightweight blade with the high stiffness, the displacement and the safety factor of the blade composed of the composite material are calculated from the structural-analysis results, and the optimal dimensional and material designs are performed. The optimal design parameters are selected by the shear-web lamination angle and the lamination thickness. The objective function is selected by the safety factor and the weight. For the optimum material design, the GFRP is converted into the CFRP. In this paper, the structural improvement is performed by optimizing the dimensional and material designs, the blade stiffness and weight are redesigned and compared with those of the designed blades, and the structural stability of the redesigned blades is also examined.
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The Suitability of Substructures of the Offshore Wind Power Complex Dae Kyung Kim, Dong Soon Kang, Jong Hak Lim, Young Il Byun, Chul Ki Song Journal of the Korean Society for Precision Engineering.2022; 39(4): 299. CrossRef
Evaluation of Structural Integrity for Lifting-and-Lowering-Type Drone Station Using Fluid-Structure Interaction Analysis Sang Ho Kim, Jae Youl Lee, Sung-Ho Hong, Jehun Hahm, Kap-Ho Seo, Jin-Ho Suh, Young Sik Joung, Se Hoon Jeung Journal of the Korean Society for Precision Engineering.2021; 38(11): 841. CrossRef
We have designed the structural shapes of a spiral blade and the frame to be used in an Archimedes wind-power system with the objective of increasing its mechanical strength. A conical roll-bending forming process was introduced to fabricate a metallic spiral blade, based on an incremental stepwise approach. From this process, the complicated spiral blade was constructed, and it could be applied to the wind-power mill. We proposed a few structural design concepts for improvement of the mechanical strength of the blade and frame. Fixing rods between the blades increased the natural frequency of the blades three-fold, compared to the original model with no rods. Also, the strength of the frame was increased by introducing edge-flanges with a height greater than 20 mm. This study will be helpful to industrial engineers interested in the structural design of a wind-power system in understanding the structural design process.
A gas turbine is a power plant unit that converts thermal energy into rotational energy by rotating a blade using hightemperature and high-pressure combustion gas. A gas turbine blade is directly exposed to a high-temperature flame. Various studies have aimed to improve the durability of the blade in harsh conditions. One proposes coating the blade with a thermal barrier to protect it from the flame, using a ceramic material with better thermal insulation. Another proposes using internal cooling, by creating an air flow path inside the blade to lower its temperature. Because both these techniques create a thermal gradient in the cross section of the blade, they amplify the difference in thermal expansion, thereby producing thermal stress in the blade and the thermal barrier coating. This study investigates the internal cooling effect on thermal gradient fatigue by using finite element analysis.
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An interaction integral method for calculating heat flux intensity factor with the XFEM Huachao Deng, Bo Yan, Honghong Su, Xiaomin Zhang, Xin Lv International Journal of Thermal Sciences.2019; 136: 379. CrossRef
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