• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.639-646
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• 1995

The objective of this study is to minimize the weight of a damped anisotropic roto-bearing system considering whirl natural frequency and stability. The system is modeled as an assemblage of rigid disks, flexible shafts and discrete bearings. The system design variables are the crosssectional areas of shaft elements and the properties of bearings. To analyze the system, the polynomial method which is derived by rearranging the calculations performed by a transfer matrix method is adopted. For the optimization, the optimization software IDOL (Integrated Design Optimization Library) which is based on the Augmented Lagrange Multiplier (ALM) method is employed. Also, an analytical design sensitivity analysis of the system is used for high accuracy and efficiency. To demonstrate the usefulness of the proposed optimal design program incorporating analysis, design sensitivity analysis, and optimization modules, a damped anisotropic rotor-bearing system is optimized to obtain 34$ weight reduction.

• Structural Engineering and Mechanics
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• v.14 no.4
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• pp.473-489
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• 2002

A static linear programming formulation for minimum weight design of frames that is based on a matrix displacement method is presented in this paper. According to elementary theory of plasticity, minimum weight design of frames can be carried out by using only the equilibrium equations, because the system is statically determinate when at an incipient collapse state. In the present formulation, a statically determinate released frame is defined by introducing hinges into the real frame and the bending moments in yield constraints are expressed in terms of unit hinge rotations and the external loads respectively, by utilizing the matrix displacement method. Conventional Simplex algorithm with some modifications is utilized for the solution of linear programming problem. As the formulation is based on matrix displacement method, it may be easily adopted to the weight optimization of frames with displacement and deformation limitations. Four illustrative examples are also given for comparing the results to those obtained in previous studies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.389-394
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• 2017

In a conventional ship structure, stiffeners with an asymmetric section, such as inverted angles, are used widely despite the disadvantage of strength compared to the stiffeners with a symmetric section, such as a built-up T. On the other hand, T-type built-up members are attracting more attention than L-type inverted angles due to the increased size of ships. The purpose of this study was to develop an optimal design program for a built-up T, and apply an evolution strategy as an optimization technique. In the optimization process, the gross thickness concept was adopted for the design variables and objective function, and the constraints are set up based on HCSR (Harmonized Common Structural Rules). Using the developed program in this study, the optimal stiffener design was carried out for 300K VLCC and 158K COT of which the orders were obtained lately. The optimal results revealed the weight reduction effect of 144 tons and 60 tons, respectively.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.11
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• pp.541-546
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• 2006

In a levitation magnet system with large air gap, numerical method is needed because analytic method cannot consider the leakage flux properly. This paper conducted an optimal design of a levitation magnet system with large air gap which was used for an OLED system, where evolution strategy was adopted for optimal design algorithm. Levitation forces near the initial design were calculated first by using finite element method to reduce the computation time. During the optimization process, levitation forces of arbitrary dimension were obtained using the interpolation of the levitation forces which were calculated previously Weight of the maget system was chosen as the object function and it was used minimized.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.129-134
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• 2001

The paper presents the optimal design of a oil-free two-stage compressor, which is driven by 75 kW motor at an operating speed of 39,000 rpm, and the pressure ratio of which is up to 4. First, an attempt is made to obtain the optimal design of a bump bearing which supports a compressor rotor. Second, bump bearings and shaft are considered simultaneously, and the weighted sum of rotor weight and frictional torque is minimized. Finally, the optimal geometry of compressor wheel is considered. The mean efficiency and the - minimum efficiency are maximized respectively. The results presented in this paper provide important design information necessary to reduce the energy loss.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.293-300
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• 2008

Efficient designing of SRM Grains in the field of Rocketry is still the main test for most of the nations of world for scientific studies, commercial and military applications. There is a strong need to enhance thrust, improve the effectiveness of SRM and reduce mass of motor and burning time so as to allow the general design to increase the weight of payload/on board electronics. Moreover burning time can be increased while keeping the weight of the propellant and thrust in desired range, so as to give the time to control / general design group in active phase for incorporating delayed cut off if required. A mathematical design, optimization & analysis technique for Slotted Tube Grain has been discussed in this paper. In order to avoid the uncertainties that whether the Slotted Tube grain configuration being designed is best suited for achieving the set design goals and optimal of all the available designs or not, an efficient technique for designing SRM Grain and then getting optimal solution is must. The research work proposed herein addresses and emphasizes a design methodology to design and optimize Slotted Tube Grain considering particular test cases for which the design objectives and constraints have been given. In depth study of the optimized solution have been conducted thereby affects of all the independent parametric design variables on optimal solution & design objectives have been examined and analyzed in detail. In doing so, the design objectives and constraints have been set, geometric parameters of slotted tube grain have been identified, performance prediction parameters have been calculated, thereafter preliminary designs completed and finally optimal design reached. A Software has been developed in MATLAB for designing and optimization of Slotted Tube grains.

• Journal of Drive and Control
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• v.11 no.4
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• pp.46-52
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• 2014

This study suggests a small-sized screw decanter specialized for dredging sites. Generally, conventional screw decanters are composed of a cylinder and a cone. However, the suggested screw decanter simply has a cone based on a cone-type bowl structure. In this research, a commercial analysis tool is used to establish an optimal design for the bowl and the screw conveyor. Moreover, the base frame, where the main bearings that support the spindle of the bowl and the screw conveyor are installed, is optimally designed considering the weight of the rotating body and the deflection caused by the high centrifugal force. Furthermore, the natural frequency range of the spinning body, the bowl and the screw conveyor, is applied to this base frame; it is designed not to correspond to the resonance frequency range and achieves stability as a result. This study suggests an optimal design for the rotating body and the base frame of a screw decanter considering its vibration characteristics. Such a design will prevent overuse of materials and help to reduce the weight and volume-and the price-of a screw decanter.

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.64-70
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• 1991

The design theory of roller gate has been systematized laying more emphasis on practical formulas than theoretical ones and the design procedure of the existing gate facilites is reviewed and analyaed on economical viewpoint and safety factor. The design theory of timoshenko, the thechnical standards for hydraulic gate and penstock of Japan, and the design standards for waterworks structures of Germany are applied to the study of optimal design of a gate leaf. In this study, gate leaf which is now being operated for water control at the seadike, estuary dam and reservoir dam are adopted as a mode, and a new design method by the computer is proposed through the variation of design elements within practical ranges. As a result, safety factor and economical design can be made by using T-beams to the horizontal and vertical beam of the gate leaf instead of H-beams used in the existing seadike roller gate at Asan, and total weight of gate leaf is reduced by the present optimization.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.58-63
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• 2005

In order to minimize weight of vehicle seat, an optimum design of aluminum seat is presented while satisfying stress and fatigue life constraints. In this study, the analysis model is validated by comparing it's stress with that of test. Then, two-level orthogonal array is used to estimate the design sensitivity for 7 design variables. Finally, the sequential approximate optimization (SAO) is performed using the constructed RSM models. The approximate RSM models are sequentially updated using the analysis results corresponding to the approximate optimum obtained during the SAO. After 14 analyses, the SAO gives an optimal design that can reduce 16.7$\%$ of weight while increasing 369$\%$ of fatigue life and satisfying stress constraint.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.2
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• pp.27-33
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• 2014

There are several methods to improve the flight efficiency of HALE(High Altitude Long Endurance) UAV(Unmaned Aerial Vehicle). Airframe structural point of view, weight reduction of the airframe structure is the most important method to improve the flight efficiency. In order to reduce the weight of airframe structures, new concepts which are different from traditional airframe structure design such as the mylar wing skin should be introduced. The spar is the most important component in a mylar skin wing structure, so the spar weight reduction is the key point for reduction of the wing structural weight. In this study, design trade-off study for the front spar of the HALE UAV wing is conducted in order to reduce the weight. Design and analysis procedure of high aspect ratio wing spar are introduced. Several front spar structures are designed and trade-off study regarding the weight and strength for the each spar are performed. Spar design configurations are verified by the static strength test. Finally, optimal front spar design is decided and applied to the HALE UAV wing design.