• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1773-1780
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• 2005

The process of mould design in the foundry industry has been based on the intuition and experience of foundry engineers and designers. To bring the industry to a more scientific basis the design process should be integrated with scientific analysis such as heat transfer. The production by foundry techniques is influenced by the geometry configuration, which affects the solidification conditions and subsequent cooling. Numerical simulation and/or experiments make possible the selection of adequate materials, reducing cycle times and minimizing production costs. The main propose of this work is to study the heat transfer phenomena in the mould considering the phase change of the cast-part. Due to complex geometry of the mould, a block unstructured grid and a generalized curvilinear formulation engaged with the finite volume method is described and applied. Two types of boundary conditions, diffusive and Newtonian, are used and compared. The developed numerical code is tested in real case and the main results are compared with experimental data. The results showed that the solidification time is about 6 seconds for diffusive boundary conditions and 14.8 seconds for Newtonian boundary conditions. The use of the block unstructured grid in combination with a generalized curvilinear formulation works well with the finite volume method and allows the development of more efficient algorithms with better capacity to describe the part contours through a lesser number of elements.

• Computational Structural Engineering
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• v.7 no.1
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• pp.117-124
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• 1994

Multi-level Multi-objective optimization(MLMO) for reinforced concrete framed structure is performed, and compared with the results of single-level single-objective optimization. MLMO method allows flexibility to meet the design needs such as deflection and cost of structures using weighting factors. Using Multi-level formulation, the numbers of constraints and variables are reduced at each levels, and the optimization formulation becomes simplified. The force approximation method is used to reflect the variation in design variables between the substructures, and thus coupling is maintained. And the linear approximated constraints and objective function are used to reduce the number of structural analysis in optimization process. It is shown that the developed algorithm with move limit can converge effectively to optimal solution.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.183-194
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• 2002

A general procedure to evaluate the sensitivity of design variables to stresses and strains in PSC flexural members is proposed. To accomplish the purpose of this study, long-term losses including creep, shrinkage, and PS steel relaxation are formulated based on the equilibrium states of the deformed sectional geometry. Thereby, the formulation follows the basic steps which consider the fundamental formulas adopted by CEB-FIP, ACI, and KCI rather than the age adjusted effective modulus concept. Twenty-one design variable including the material and geometrical properties of concrete, nonprestressing steel and prestressing steel, and the geometry of the cross section are considered in the sensitivity analysis. The gradients of the stresses and strains needed for the sensitivity assessment are calculated in a closed format. The derived formulation is applied to the T-type section PSC beam with prestressing and nonprestressing steels for the sensitivity analysis. The analytically calculated sensitivity results are compared with those numerically calculated to ensure the validity of the proposed procedure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.29-34
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• 2020

In this study, a sensitivity formulation was applied to analyze the dynamic response due to the effect of the excitation force for the undamped vibration of the cantilever beam. The theoretically fundamental formulations were derived considering an eigenvalue problem and its modal analysis to govern the second order algebraic differential equation in terms of the change in the modal coordinate with respect to the design parameters. A representative physical quantity pertaining to the dynamic response, that is, the rate of change in the dynamic displacement, was observed by changing the design variables, such as the cross-sectional area of the beam. The numerical results were obtained at various locations, considering the application of the external forces and observation of the dynamic displacement. When the detection position was closer to the free end of the cantilever beam, the sensitivity of the dynamic displacement was higher, as predicted through the oscillating motion of the beam. The presented findings can provide guidance to compute the dynamic sensitivity for a flexibly connected structure under dynamic excitations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.257-260
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• 1999

It is very important to design the shape of container in HIPing process since the final shape and relative density distribution of the product are decisively dependent on the shape of container. A derivative based approach to determine the shape of container in HIPing process is presented. In this approach the optimal design problem is formulated on the basis of the finite element process. The process model the formulation for process optimal design and the schemes for the evaluation of the design sensitivity and an iterative procedure for optimization are described. In comparison with finite difference scheme the validity of the schemes for the evaluation of the design sensitivity is examined.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.10
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• pp.842-846
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• 2002

Design of gas concentration process using a fully thermally coupled distillation is conducted with the commercial design software HYSYS. Detailed procedure of the design is explained, and the performance of the process is compared with that of a conventional system A structural design is exercised for the design convenience. The design outcome indicates that the procedure is simple and efficient. The structural information yielded from equilibrium distillation gives an easy formulation of distillation system which is the initial input required from the setup of the distillation system The performance of the new process indicates that an energy saving of 17.6 % is obtained compared with the conventional process while total number of trays maintains at the same.

• Korean Journal of Computational Design and Engineering
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• v.14 no.3
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• pp.207-216
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• 2009

Modern engineering design problems involve complexity of disciplinary coupling and difficulty of problem formulation. Multidisciplinary design optimization can overcome the complexity and design optimization software or frameworks can lessen the difficulty. Recently, a growing number of new multidisciplinary design optimization techniques have been proposed. However, each technique has its own pros and cons and it is hard to predict a priori which technique is more efficient than others for a specific problem. In this study, a software system has been developed to directly solve MDO problems with minimal input required. Since the system is based on MATLAB, it can exploit the optimization toolbox which is already developed and proven to be effective and robust. The framework is devised to change an MDO technique to another as the optimization goes on and it is called a reconfigurable MDO framework. Several numerical examples are shown to prove the validity of the reconfiguration idea and its effectiveness.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.253-255
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• 1999

In this paper, a shape optimization algorithm of superconducting magnet using finite element method is presented. Since the superconductor loses its superconductivity over the critical magnetic field and critical current density, this material property should be taken into account in the design process. Trial and error approach of repeating the change of the design variables costs much time and it sometimes does not guarantee an optimal design. This paper presents a systematic and efficient design algorithm for the superconducting magnet. We employ the sensitivity analysis based on finite element formulation. As for optimization algorithm, the inequality constraint for the superconducting state is removed by modifying the objective function and the nonlinear equality constraint of constant volume is satisfied by the gradient projection method. This design algorithm is applied to an optimal design problem of a solenoid air-cored superconducting magnet that has a design objective of the maximum energy storage.

• Journal of Ship and Ocean Technology
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• v.12 no.4
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• pp.7-19
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• 2008

In preliminary ship design, a parametric study is a more realistic way to explore design space and analyze design problem than an optimization technique due to time-consuming computational work or a difficulty in incorporating all constraints into the optimization formulation. In the parametric study, feasible alternatives are examined in various aspects; the best one can be selected. Among the aspects, the strength assessment by FE analysis is an essential process in the ship design. This paper proposes a system to facilitate a parametric study for FE model based on design of experiment (DOE). It works on a FE pre-processor environment and assists a user to define a parametric study by interacting with FE model. It also provides an interface module with a FE solver in order to control the input file and extract predefined FE results from the output file. Based on the proposed system, a better understating and a better design are expected to be achieved.

• Korean Journal of Food Science and Technology
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• v.53 no.2
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• pp.174-180
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• 2021

The optimal recipe for manufacturing composite honey-based herbal pills mainly comprising Rubus coreanus powder (RCP), black mulberry powder (BMP), and vitamin C was investigated. Honey-based herbal pills were prepared by mixing these powders, binding them with honey, and then forming a round shape. The experiment was designed based on the D-optimal mixture design, which included 12 experimental points with one replicate for three independent variables as follows: RCP (10~35%), BMP (10~35%), and vitamin C (5~10%). In addition, the dependent variables (total phenolic and flavonoid content and antioxidant activity) were measured and used to optimize the manufacturing conditions. The results showed that high amounts of RCP were correlated with high total flavonoid content, whereas the addition of high amounts of vitamin C resulted in higher antioxidant activity. In conclusion, an optimized formulation for the honey-based herbal pill was found to contain 35% RCP, 10% BMP, and 10% vitamin C.