• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.63-69
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• 2013

In order to find the optimum design of structures that have characteristic natural frequency range, a numerical optimization method to solving eigenvalue problems is a widely used approach. However in the most cases, it is difficult to decide the accurate thickness and shape of structures that have allowable natural frequency in design constraints. Parallel analysis algorithm involving the feasible direction optimization method and Rayleigh-Ritz eigenvalue solving method is developed. The method is implemented by using finite element method. It calculates the optimal thickness and the thickness ratio of individual elements of the 2-D plane element through a parallel algorithm method which satisfy the design constraint of natural frequency. As a result this method of optimization for natural frequency by using finite element method can determine the optimal size or its ratio of geometrically complicated shape and large scale structure.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.410-415
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• 2000

In this paper feasible direction method which is one of the optimization method is adopted to natural frequency optimization. In order to find the optimum design of structures that have characteristic natural frequency range, a numerical optimization method to solving eigenvalue problems is a widely used approach. However most cases, it is difficult to decide the accurate thickness and shape of structures that have allowable natural frequency in design constraints. Parallel analysis algorithm involving the feasible direction optimization method and Rayleight-Ritz eigenvalue solving method is developed. The method is implemented by using finite element method. It calculated the optimal thickness and the thickness ratio of each element of 2-D plane element through the parallel algorithm method which satisfy the design constraint of natural frequency.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.66-77
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• 1996

Optimal topology design is to search the optimal configuration of a structure which can be used as a shape at the conceptual design stage. Our objective is to maximize the stiffness of the structures and ribs under a material usage constraintl. The density of each finite element is the design variable and its relationship with Young's modulus is expressed by quadratic form. The configuration is represented by the entire density distribution, the structural analysis is performed by finite element method and the optimiza- tion is performed by Feasible Direction Method. Feasible Direction Method can handle various problems simultaneously, that is, mult-objectives and multi-constraints. Total computation time can be reduced by the quadratic relationship between the density and the material property and fewer design variables than Homogenization Method. Toplogy optimization technique developed in this research is applied to design the shapes of the ribs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.857-865
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• 2001

In finite element analysis, engineering optimizations are divided two major parts that are topology and structural optimization. Until these days most structural optimizations usually concentrate on single disciplinary optimization. Therefore numerical analysis and methodology which can optimize thermo-elastic creep and frequency phenomena are not suggested. In this paper finite element analysis methodology and algorithm of thermo -elastic creep and frequency optimizations are suggested and corroborate the efficiency of suggested new numerical methodology and algorithm by solving example problem.

• Journal of applied mathematics & informatics
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• v.28 no.3_4
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• pp.823-835
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• 2010

In this paper, A FSQP algorithm for degenerate inequality constraints optimization problems is proposed. At each iteration of the proposed algorithm, a feasible direction of descent is obtained by solving a quadratic programming subproblem. To overcome the Maratos effect, a higher-order correction direction is obtained by solving another quadratic programming subproblem. The algorithm is proved to be globally convergent and superlinearly convergent under some mild conditions. Finally, some preliminary numerical results are reported.

• Structural Engineering and Mechanics
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• v.24 no.4
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• pp.479-491
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• 2006

This paper deals with optimal fibre orientations of symmetrically laminated fibre reinforced composite structures for maximising the fundamental frequency of small-amplitude. A set of fiber orientation angles in the layers are considered as design variable. The Modified Feasible Direction method is used in order to obtain the optimal designs. The effects of number of layers, boundary conditions, laminate thicknesses, aspect ratios and in-plane loads on the optimal designs are studied.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.852-859
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• 1994

Optmal topology design is to search the optimal layout of the structure which can be used fot the shape of the conceptual design stage. Our objective is to maximize the stiffness of the structure under a material usage constraint. The density of each finite element is the design variable and its relationship with Young's modulus is expressed by quadratic form. The shape is represented by the entire density distribution, the structural analysis is performed by finite element method and the optimization is achieved by feasible direction method. Unlike optimality criteria method,feasible direction method can handle various problems simultaneously, that is, multi- objectives and multi-constraints. Total optimization time can be reduced by the approximation of the material property and fewer design variables than homogenization method. Topology optimization is applied to design the shape of ribs.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.530-533
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• 1996

This paper deals with finding an initial solution and modifying search direction by the centrering force in the predictor-corrector method which is a variant of the primal-dual barrier method. These methods were tested with NETLIB problems. Initial solutions which are located close to the center of the feasible set lower the number of iterations, as they enlarge the step length. Three heuristic methods to find such initial solution are suggested. The new methods reduce the average number of iterations by 52% to at most, compared with the old method assigning 1 to initial valurs. Solutions can move closer to the central path fast by enlarging the centering force in early steps. It enlarge the step length, so reduces the number of iterations. The more effective this method is the closer the initial solution is to the boundary of the feasible set.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.1-7
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• 2003

The aerodynamic optimization method for airfoil design was described in this paper. The Navier-Stokes equations were solved to consider the viscous flow information around an airfoil. The Modified Method of Feasible Direction(MMFD) was used for sensitivity analysis and the polynomial interpolation was used for distance calculation of the minimization. The Message Passing Interface(MPI) library of parallel computation was adopted to reduce the computation time of flow solver by decomposing the entire computational domain into 8 sub-domains and one-to-one allocating 8 processors to 8 sub-domains. The parallel computation was also used to compute the sensitivity analysis by allocating each search direction to each processor. The present optimization reduced the drag of airfoil while the lift is maintained at the tolerable design value.

• Journal of Biosystems Engineering
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• v.35 no.5
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• pp.287-293
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• 2010

In order to optimize an agricultural tractor clutch mechanism system, its structural static and kinematic mechanism were analyzed. The operating force of the mechanical tractor clutch system is currently not appropriate to drive comfortably. So it is needed to reduce the clutch operating force by applying advanced engineering design techniques. In the present study, an optimization technology is applied to the design of tractor clutch systems to reduce the operating force. As a result of the optimization using 2 link-angles and 1 link-length which are the main design variables of the clutch linkage system, the maximum pushing force of the maximum clutch pedal was found 182.8N, 14% decreased compared to the existing clutch system. The effectiveness of the optimum design is certified by menas of an experiment.