• Proceedings of the KSME Conference
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• 2003.04a
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• pp.746-751
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• 2003

When a cantilever beam rotates about the axis perpendicular to its longitudinal axis, its natural frequencies vary. This phenomenon which is caused by centrifugal inertia forces is often referred to as the stiffening effects. Since the variation of natural frequencies often creates critical problems for the rotating structures, it is necessary to control the variation of natural frequencies. As the cross section of a rotating cantilever beam varies, natural frequencies can be changed. The thickness and the width of the cantilever beam are assumed to be cubic spline functions in the present work. An optimization method is employed to find the optimal thickness and width of the rotating beam. This result can be used for the design of rotating structures such as turbine and helicopter blades.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.684-689
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• 2003

When structures undergo rotating motion, their modal characteristics often vary significantly. The variations of modal characteristics are determined from their geometric shapes and their rotating angular speed. Since the modal characteristics vary during the operation of the structures, they should be carefully scrutinized. In this paper, rotating cantilever beams are chosen as design targets which need to meet some specific design requirements. The thickness and the width of the rotating beams are assumed as multi-stage spline functions and the stage values for the thickness and the width are used as design variables for the optimization problems.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.411-416
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• 2014

In this research we present design optimization methods for a vehicle-mounted satellite antenna positioner. Our initial antenna positioner was conservatively designed to satisfy a worst case scenario where wind blew across the positioner at the speed of 120 km/h. Investigating stresses and safety based on Finite Element Methods (FEM), we find reflector support frames can be optimized to significantly reduce the weight of the positioner system. Thus, we optimize the reflector support frame from the given initial design while considering weight, maximum stress, maximum allowable deflection, cross section, and thickness. As a result, Shape C and the thickness of 2 mm are determined for the cross section of the reflector support frame. Applying this result, the weight of the new antenna positioner is 57.343 kg, which is decreased by 10.74% compared to the initial conservative design.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.95-99
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• 2005

This paper presents the optimum design of cylindrical shell under external pressure loading. Two kinds of material, Al7075-T6, Ti-6Al-4V, are considered. For each material, the design variable is a thickness of the unstiffened parallel middle body shell, and the state variable, constraint, is hoop stress and the object .function is total weight of the cylindrical shell. Optimization is performed by conventional FE Program, ANSYS. In addition, buckling analysis is performed for the middle body of the cylindrical shell. Finally, we calculates the payload of the cylindrical shell to keep neutral buoyancy with optimized thickness in deep-sea applications.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.7
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• pp.602-609
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• 2008

This paper presents experimental optimization of process parameters for a newly developed SFF(Solid Freeform Fabrication) system. Two critical process parameters, layering thickness and curing period, which have a large effect on the quality of the product, are optimized through experiments. Specimens are produced using layering thicknesses of 60, 80, 100, 120, 140, and $160\;{\mu}m$ and curing periods of 0, 10, 20, and 30 minutes under the same processing conditions, i.e., build-room temperature, feed-room temperature, roller speed, laser power, scan speed, and scan spacing. The specimens are tested to compare and analyze performance indices such as thickness accuracy, flatness, stress-strain characteristics, and porosity. The experimental result indicates that layering thickness of $80{\sim}100\;{\mu}m$ and curing period of $20{\sim}30$ minutes are recommended for the developed industrial SFF system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.434-440
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• 2013

With polymer properties and ceramic volume fraction as design variables, the optimal structure of 1-3 piezocomposites has been determined to maximize the thickness mode electromechanical coupling factor. When the piezocomposite vibrates in a thickness mode, inter-pillar resonant modes are likely to occur between lattice-structured piezoceramic pillars and polymer matrix, which significantly deteriorates the performance of the piezocomposite. In this work, a new method to design the structure of the 1-3 type piezocomposite is proposed to maximize the thickness mode electromechanical coupling factor while preventing the occurrence of the inter-pillar modes. Genetic algorithm was used for the optimal design, and the finite element analysis method was used for the analysis of the inter-pillar mode.

• New & Renewable Energy
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• v.3 no.1 s.9
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• pp.13-19
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• 2007

A triangular fin with variable fin base thickness and base height is analyzed and optimized for the fixed fin base height using a two-dimensional analytical method. At the middle of the fin length, the variation of the temperature along the fin height is listed. The influences of the fin length, base thickness and base height on the heat loss and fin efficiency are analyzed, The optimum heat loss, corresponding optimum efficiency and optimum fin length as a function of the fin base thickness are presented. The optimum heat loss and optimum fin tip length as a function of the convection characteristic number are represented.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.51-56
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• 2008

Thermoforming is one of the most versatile and economical processes available for shaping polymer products, but obtaining a uniform thickness of the final product using this method is difficult. Heater power adjustment is very important because the thickness distribution depends strongly on the distribution of the sheet temperature. In this paper, the steady-state optimum distribution of heater power is first ascertained by a numerical optimization to obtain a uniform sheet temperature. The time-dependent optimal heater input is then determined to decrease the temperature difference through the direction of the thickness using the response surface method and the D-optimal method. The optimal results show that the time-dependent optimum heater power distribution gives an acceptable uniform sheet temperature in the forming temperature range by the end of the heating process.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.169-172
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• 2000

Although extensive efforts have been devoted to the optimal design of composite laminated plates in recent years, some practical issues still need further research. One of them is the handling of the uncertainties in material properties, which were ignored in most researches in the past. In this paper, the convex modeling is used in calculating the failure criterion, given as constraint, to consider the uncertain material properties in the thickness optimization. Numerical results show that the optimal thickness increases when the uncertainties of elastic moduli considered, which shows such uncertainties should not be ignored for safe and reliable designs.

• International Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.10-14
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• 2015

To design airfoils for novel airplanes, new knowledge of aerodynamics is required. In this study, modified Parametric SECtion (PARSEC) which is a airfoil representation is applied to airfoil design using a multi-objective genetic algorithm to obtain an optimal airfoil for consideration in the development of a Martian airplane. In this study, an airfoil that can obtain a sufficient lift and glide ratio under lower thrust is considered. The objective functions are to maximize maximum lift-to-drag ratio and to maximize the trailing edge thickness. In this way, information on the low Reynolds number airfoil could be extracted efficiently. The optimization results suggest that the airfoil with a sharper thickness at the leading edge and higher camber at the trailing edge is more suitable for a Martian airplane. In addition, several solutions which has thicker trailing edge thickness were found.