• Journal of Digital Contents Society
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• v.16 no.2
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• pp.235-244
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• 2015

This study proposes a leaf modeling method that uses feature-based warping for efficient generation of various digital leaves. The proposed method uses warping method, one of image processing application techniques that can control various shapes of leaves in an easy, intuitive way, and generate natural patterns of veins efficiently. First, information on approximated contour is detected from a leaf blade image to identify the shape of a blade. Based on this, control line is automatically calculated to be used for feature-based warping. Then, control line-based warping is conducted to modify forms of leaf blade images in an intuitive way, automatically generating leaves of various shapes. And natural vein patterns are generated by applying a contour-based venation growth algorithm from contour information of the modified leaf blade images. This study performs experiments to verify whether various shape of leaves that comprise plants can be efficiently generated using a sample binary image of a blade. Also, we demonstrate that express the natural growth of leaves by applying warping to the growth of the leaf blade.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.201-208
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• 2009

Recently, the wind energy has been widely used as a renewable energy resource due to lack and environmental issues of the mostly used fossil fuel. This work is to develop a 500W class small wind turbine blade which will be applicable to relatively low speed region like Korea and for the domestic use. For this blade a high efficiency wind turbine blade was designed with the proposing aerodynamic design procedure, and a light and low cost composite structure blade was designed considering fatigue life. Structural analyses including load case study, stress, deformation, buckling and vibration analysis were performed using the Finite Element Method. The fatigue life was estimated using the load spectrum analysis and the Miner rule. In order to evaluate the designed blade, the structural and aerodynamic performance tests were carried out, and the test results were compared with the analysis results.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.105-118
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• 2023

The present work is an attempt to develop a simple and accurate finite element formulation for the assessment of thermal shock/thermally induced vibrations in pretwisted and tapered functionally graded material thin (FGM) blades obtained from Voigt and local representative volume elements (LRVE) homogenization models, based on neutral surface approach. The neutral surface of the FGM blade does not coincide with its mid-surface. A finite element model (FEM) is developed using first-order shear deformation theory (FSDT) and the FGM turbine blade is modelled according to the shallow shell theory. The top and the bottom layers of the FGM blade are made of pure ceramic and pure metal, respectively and temperature-dependent material properties are functionally graded in the thickness direction, the position of the neutral surface also depends on the temperature. The material properties are estimated according to two different homogenization models viz., Voigt or LRVE. The top layer of the FGM blade is subjected to high temperature and the bottom surface is either thermally insulated or kept at room temperature. The solution of the nonlinear profile of the temperature in the thickness direction is obtained from the Fourier law of heat conduction in the unsteady state. The results obtained from the present FEM are compared with the benchmark examples. Next, the effect of angle of twist, intensity of thermal shock, variable chord and span and volume fraction index on the transient response due to thermal shock obtained from the two homogenization models viz., Voigt and LRVE scheme is investigated. It is shown that there can be a significant difference in the transient response calculated by the two homogenization models for a particular set of material and geometric parameters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.63-68
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• 2017

This study determines the selection of an appropriate jig material for the blade edge of the medical sapphire knife. The physical properties of the jig material affects the edge shape and chipping phenomenon in machining of the medical sapphire knife. If a grinding wheel is used, brittle workpieces such as sapphire are easily damaged by the propagation of cracks because the grinding force significantly increases. It is important to constantly maintain the grinding force in the grinding process of the brittle materials. The grinding force can be kept constantly by inducing the elastic deformation of the Jig material because the elastic deformation of brittle work-piece is negligibly low. The chipping phenomenon may be reduced by selecting the proper Jig material. Aluminum, copper, stainless steels and carbon steel were used as Jig materials. The experiment was conducted using a cast iron grinding wheel, which was installed on a conventional grinding machine with the ELID grinding system. The thickness and width of the chipping area were measured using an optical microscope and FE-SEM to analyze the shape of the blade edge. According to the experiment result, the chipping phenomenon decreased, and the sharp edge was formed when the jig materials with low elastic modulus were used.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.4
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• pp.550-556
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• 2021

The scissor-type rope cutter is the most widely used amongst all kinds of commercially available rope cutters in Korea. In this study, we performed finite element analysis on the scissor-type rope cutter. We determined the structure of the cutter that would ensure its stable operation in various situations involving rope entanglement, and verified its effectiveness by testing it in the lab and in an actual ship. These investigations revealed that when the propeller shaft was not rotated by rope entanglement, the constant torque generated by the engine resulted in the torsion of the rope cutter and maximum deformation in the lower blade, which was not restricted by finite element analysis. With increasing blade thickness, the maximum values of deformation and equivalent stress decreased, resulting in a rise in the safety factor. At the constant blade thickness, the effect of the torque variations on the maximum equivalent stress and the maximum deformation is independent of the position of the external force of the rope cutter and decreases in direct proportion. The results of this study confirmed that the rope-cutter structure determined by analysis could lead to a hassle-free removal of ropes and fishing nets under all conditions and environments.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.20-26
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• 2014

It is essential to consider the effect of blade deformation in order to design a better tidal stream turbine being operated in off-design condition. Flow load causes deformation on the blade, and the deformation affects the turbine performance. In the present study, CFD analysis procedures were developed to predict open water performance of horizontal axis tidal stream turbine (HATST). The developed procedures were verified by comparing the results with existing experimental results. Fluid-structure interaction (FSI) analysis method, based on the verified CFD procedure, have been carried out to estimate the turbine performance for a turbine with flexible composite blades, and then the results were compared with those for rigid blades.

• Composites Research
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• v.22 no.1
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• pp.22-31
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• 2009

Recently the wind energy has been alternatively used as a renewable energy resource instead of the mostly used fossil fuel due to its lack and environmental issues. This work is to propose a structural design and analysis procedure for development of the 500W class small wind turbine system which will be applicable to relatively low speed region like Korea and for the domestic use. The wind turbine blade was performed structural analysis including stress, deformation, buckling, vibration and fatigue. In addition, the blade should be safe from the impact damage due to FOD(Foreign Object Damage) including the bird strike. MSC.Dytran was used in order to analyze the bird strike penomena on the blade, and the applied method Arbitrary Lagrangian-Eulerian was evaluated by comparison with the previous study results. Finally, the structural test was carried out and its test results were compared with the estimated results for evaluation of the designed structure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.354-357
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• 2005

When Ti-6Al-4V is used in long steam turbine blades, the main issues are how to improve the fatigue strength as a problem of internal quality and how to forge the thinnest possible blades as problem of dimensional precision. To assure an excellent fatigue strength, it is important to make the two phase fine and equiaxial structure by providing enough plastic deformation in the two phase$(\alpha\;phase/\beta\;phase)$ temperature region. Accordingly, it needs to predict that forging temperature, preform design and forging velocity in forging process. To achieve this end, the two steps forging process was suggested to forge the thin and twisted blades with a precision hammer considering die forces and metal flow. Two steps forging process consists of the flattening forging process and finishing forging process. Process in forging of a 1016mm long steam turbine blade is designed by the finite element method. This study attempts to derive systematic design procedures for process design in the forging. Forging parameters was analyzed in two-dimensional plane-strain simulation and two steps forging process carried out in three-dimensional simulation. Consequently, optimal forging process parameters of long steam turbine blades in Ti-6Al-4V with a high dimensional precision are selected in the hammer die forging.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.2
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• pp.212-224
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• 2018

The characteristics of the relationship between the evolution of propeller trailing vortex wake and skew angle are numerically examined based on four different five-blade David Taylor Model Basin (DTMB) model propellers with different skew angles. Numerical simulations are based on Reynolds-averaged Naviere-Stokes (RANS) equations combined with SST $k-{\omega}$ turbulence model. Results show that the contraction of propeller trailing vortex wake can be restrained by increasing skew angle and loading conditions, and root vortices fade away when the propeller skew angle increases. With the increase of the propeller's skew angle, the deformation of the hub vortex and destabilization of the tip vortices are weakening gradually because the blade-to-blade interaction becomes weaker. The transition trailing vortex wake from stability to instability is restrained when the skew increases. Furthermore, analyses of tip vortice trajectories show that the increasing skew can reduce the difference in trailing vortex wake contraction under different loading conditions.

• Journal of computational fluids engineering
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• v.6 no.4
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• pp.15-25
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• 2001

Numerical prediction of the diffusion controlled transition in a turbine gas pass is important because it can change the local heat transfer rate over a turbine blade as much as three times. In this study, the gas flow over turbine blade is simplified to the flat plate boundary layer, and an adaptive grid scheme redistributing grid points within the computation domain is proposed with a great emphasis on the construction of the grid control function. The function is sensitized to the second invariant of the mean strain tensor, its spatial gradient, and the interaction of pressure gradient and flow deformation. The transition process is assumed to be described with a κ-ε turbulence model. An elliptic solver is employed to integrate governing equations. Numerical results show that the proposed adaptive grid scheme is very effective in obtaining grid independent numerical solution with a very low grid number. It is expected that present scheme is helpful in predicting actual flow within a turbine to improve computation efficiency.