• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.6
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• pp.411-418
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• 2020

In this paper, approximation and optimization methods are proposed for the structural performance of the composite fan blade. Using these methods, we perform the optimal design of the stacking sequence to maximize stiffnesses without changing the mass and the geometric shape of the composite fan blade. In this study, the lamination parameters are introduced to reduce the design variables and space. From the characteristics of lamination parameters, we generate response surface model having a high fitness value. Considering the requirements of the optimal stacking sequence, the multi-objective optimization problem is formulated. We apply the two-step optimization method that combines gradient-based method and genetic algorithm for efficient search of an optimal solution. Finally, the finite element analysis results of the initial and the optimized model are compared to validate the approximation and optimization methods based on the lamination parameters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1129-1136
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• 2010

Damper springs in a drive-line absorb the impulsive torque generated when a lock-up clutch is connected directly, instead of via a fluid coupling. Design optimization and finite element analysis were performed to improve the shock- and vibration-absorption capacity of the lock-up clutch. For this purpose, a multi-body dynamics model was developed by including the main parts of a vehicle, such as an engine with a clutch, a transmission, drive shafts and wheels, and a whole mass of a vehicle. The spring constants were selected so that resonance of a system could be avoided. Damper springs were optimized on the basis of the spring constants, impulsive torques, compressed angles, spring counts, fatigue constraints, etc. Topology optimization was performed for three plates with the damper springs. The compliance was set up as an objective function, and volume fraction was fixed below 0.3. A new shape for the plates was proposed on the basis of the topology result.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.73-89
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• 2016

To assure maximum economic benefits and the energy performance of solar water heating systems, the proper sizing of components and operating conditions need to be optimized. In recent years, a number of studies to design optimally solar water heating systems have been tried. This paper presents a design method for optimizing the various capacity-related and installation-related design variables based on life cycle cost using a genetic algorithm. The design variables considered in this study included the types and numbers of solar collector and auxiliary heaters; the types of storage tanks and heat exchangers; the solar collector slope; mass flow rates of the fluid on the hot and cold sides. The suggested method was applied for optimizing a solar water heating system for an elementary school in Seoul, South Korea. In addition, the effectiveness of the proposed optimization method was assessed by analyzing the obtained optimal solutions of six case studies, each of which was simulated with different solar fractions. It is observed that a trade-off between the equipment cost and the energy cost results in an optimal design that yields the lowest life cycle cost. Therefore, it could be helpful to apply the optimal solar water heating system by comparing the various design solutions obtained by using the optimization method instead of the engineer's experience and intuition.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1340-1345
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• 2003

In this paper, an integrated optimal design software system for structural components has been developed which interfaces existing commercial codes for CAD, CAE and Optimization. They include specialized optimal design software codes such as iSIGHT and VisualDOC, optimization module imbedded in CAD software developed by CAD developers, and optimal design software systems based on API of commercial CAD software. The advantages of the CAD imbedded optimal design approach and those of specialized optimal design software are taken to develop the system. The user defines optimal design formulation in the user interface for problem definition in the CAD control stage, where design variables are directly selectable from the CAD model and various properties and performance functions defined. The commercial CAD codes, Open I-DEAS are used for the development. The resulting software is minimally connected to CAD and CAE systems while keeping maximum independence from each other. This assures flexibility and freedom for problem definition. Fatigue life optimization is taken as a nontrivial application area. As a specific example, the shape design of a knuckle part of an automobile is performed, where the minimum fatigue life over the material domain in terms of the number of cycles of a curb strike are maximized under the constraint of not exceeding the current mass. The fatigue life has been improved by four times of the initial life. The developed software is illustrated to maintain the advantages of existing optimal design software systems while improving independency and flexibility.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.71-78
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• 2014

Door hinges of large refrigerators are required to ensure that the doors open and close smoothly in addition to supporting door weights and enduring the impact loads due to door opening and closing. However, door hinge design is difficult because of complex hinge mechanisms and sensitive structural safety. In this study, the mechanism satisfying the required spring response, space constraints, and structural strength is optimized, and the volume of the outer frame covering the hinge mechanism is minimized for reducing production costs. The entire design process is automated using the PIDO(Progress Integration and Design Optimization) technique, which achieves an efficient design process. Therefore, the frame mass is reduced to 24%, and the mechanism performance and structural stability are improved.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.5
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• pp.351-358
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• 2013

In the electric power supplying industry, outdoor sealing end (pothead) is used and sometimes it is necessary to check the seismic qualification analysis or test which is intended to demonstrate that the equipment have adequate integrity to withstand stress of the specified seismic event and still performs their function. And since the pothead is mounted on the supporting jig, the avoidance of resonance between the pothead and jig is required. In order to design jig, three types of optimization are performed to get the minimum weight while satisfying the natural frequency constraint using ANSYS. Optimal array, position and thickness of truss members of the jig are obtained through topology, shape and sizing optimization process, respectively. And seismic analysis of the pothead on the jig for given RRS acceleration computes the displacement and stress of the pothead which shows the safety of the pothead. The obtained natural frequency, mass, and member thickness of the jig are compared with those of the reference jig which was used for seismic experimental test. The numerical results of the jig in the research is more optimized than the jig used in the experimental test.

• 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.

• Earthquakes and Structures
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• v.5 no.1
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• pp.83-109
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• 2013

A simple damper optimization method is proposed to find optimal damper allocation for shear buildings under both target added damping ratio and interstorey drift ratio (IDR). The damping coefficients of added dampers are considered as design variables. The cost, which is defined as the sum of damping coefficient of added dampers, is minimized under a target added damping ratio and the upper and the lower constraint of the design variables. In the first stage of proposed algorithm, Simulated Annealing, Nelder Mead and Differential Evolution numerical algorithms are used to solve the proposed optimization problem. The candidate optimal design obtained in the first stage is tested in terms of the IDRs using linear time history analyses for a design earthquake in the second stage. If all IDRs are below the allowable level, iteration of the algorithm is stopped; otherwise, the iteration continues increasing the target damping ratio. By this way, a structural response IDR is also taken into consideration using a snap-back test. In this study, the effects of the selection of upper limit for added dampers, the storey mass distribution and the storey stiffness distribution are all investigated in terms of damper distributions, cost function, added damping ratio and IDRs for 6-storey shear building models. The results of the proposed method are compared with two existing methods in the literature. Optimal designs are also compared with uniform designs according to both IDRs and added damping ratios. The numerical results show that the proposed damper optimization method is easy to apply and is efficient to find optimal damper distribution for a target damping ratio and allowable IDR value.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.89-98
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• 2011

This study examined the energy performance according to the main design parameters of a solar water heating system for an office building using the life cycle cost (LCC) optimization simulations. The LCC optimization simulations of the system were conducted with TRNSYS and GenOpt employing the Hooke-Jeeves algorithm for cases where water temperature was $60^{\circ}C$ and $50^{\circ}C$. The results showed that for water temperature at $60^{\circ}C$ and $50^{\circ}C$ the global radiation incident on the collector could be decreased by 16.98% and 28.52%, collector useful energy gain could be decreased by 15.04% and 22.59%, energy to load from storage tank could be decreased by 10.86% and 18.06% and AH energy to load could be increased by 16.86% and 38.50% respectively compared to a non-optimized system. The annual average collection efficiency of the collector was increased by 0.88% for $60^{\circ}C$ and 2.78% for $50^{\circ}C$ because of increase of collector slope and decrease of the mass flow rate per collector area. The annual average efficiency of the system was increased by 1.74% and 3.47% compared to the basis system. However, the annual solar fraction of the system was decreased by 6.68% for $60^{\circ}C$ and 11.26% for $50^{\circ}C$ due to decrease of collector area and storage tank volume.

• Journal of Korea Water Resources Association
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• v.41 no.3
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• pp.243-249
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• 2008

Continuous stirred tank reactor(CSTR) model which can be applied to control and management of the surface flow wetland is developed to simulate the water quality in this research. The model solution is obtained from the optimization model using the least-squares and 4th-order Runge-Kutta methods. The model is applied to simulate BOD and TSS in the wetland database of U.S. EPA, in which the hydraulic and water quality data are enough and the number of pond is just one for simple analysis of running results. The model is tested in two different cases, one constant volume case and another constant volume and flow rate case considering only reaction term, mass flux term and both reaction and mass flux terms respectively. It is found that the model simulates the real water quality very well with both reaction and mass flux terms rather than only reaction term and the settling velocity of TSS becomes $0.3{\sim}0.4\;m/d$. The model can be applied in wetlands treatment efficiently.