• 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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.723-734
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• 2018

A structural weight estimation methodology for the multicopter design process is presented. In general, a multicopter is composed of an airframe, motors, propellers, battery and so on. Among these, the weight of motors, propellers and battery can be obtained from the weight trends with respect to design parameters. However, the structural weight is hard to be estimated due to the various configurations and design concepts of multicopters. Moreover, the airframe weights of most commercial multicopter products are not provided. Thus, an accurate airframe weight model is required for the reliable mutlcopter design process. Firstly, the standard configuration of multicopters is defined. Then, we proposed the structural weight estimation method using the number and diameter of propellers determined from the initial step of sizing process. Finally, we validated our suggested method using the commerical products.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.117-131
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• 2009

In this study, a detail design was conducted for KSLV-1 1st stage Rear Fuselage Upper Compartment assembly. A basic structural sizing was done by the aircraft fuselage sizing in-house program. The frame structural design and the interface check were conducted by the FE and the CAD program. The structural margin of safety was conformed by FE analysis for the normal section model and duct cut-out section models which are the weakest parts of the rear fuselage. The shear stress analysis was performed for a fastener design of the skin-stringer which is most affected by the shear stress induced by the shear load.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.211-220
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• 2014

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.145.1-145.1
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.797-798
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• 2013

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.05a
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• pp.122-125
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• 2000

The paper describes the adaptation of evolutionary fuzzy model ins (EFM) in developing global function approximation tools for use in genetic algorithm based optimization of nonlinear structural systems. EFM is an optimization process to determine the fuzzy membership parameters for constructing global approximation model in a case where the training data are not sufficiently provided or uncertain information is included in design process. The paper presents the performance of EFM in terms of numbers of fuzzy rules and training data, and then explores the EFM based sizing of automotive component for passenger protection.

• Structural Engineering and Mechanics
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• v.50 no.3
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• pp.323-347
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• 2014

This paper proposes a Particle Swarm Optimization (PSO) algorithm, which is improved by making use of the Harmony Search (HS) approach and called HS-PSO algorithm. A computer code is developed for optimal sizing design of non-linear steel frames with various semi-rigid and rigid beam-to-column connections based on the HS-PSO algorithm. The developed code selects suitable sections for beams and columns, from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange W-shapes, such that the minimum total cost, which comprises total member plus connection costs, is obtained. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposed on the frame in the optimal design procedure. The nonlinear moment-rotation behavior of connections is modeled using the Frye-Morris polynomial model. Moreover, the P-${\Delta}$ effects of beam-column members are taken into account in the non-linear structural analysis. Three benchmark design examples with several types of connections are presented and the results are compared with those of standard PSO and of other researches as well. The comparison shows that the proposed HS-PSO algorithm performs better both than the PSO and the Big Bang-Big Crunch (BB-BC) methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.108-113
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• 2002

This paper presents a multi-step structural design optimization method fur machine tool structures using a genetic algorithm with dynamic penalty. The first step is a sectional topology optimization, which is to determine the best sectional construction that minimize the structural weight and the compliance responses subjected to some constraints. The second step is a static design optimization, in which the weight and the static compliance response are minimized under some dimensional and safety constraints. The third step is a dynamic design optimization, where the weight static compliance, and dynamic compliance of the structure are minimized under the same constraints. The proposed design method was examined on the 10-bar truss problem of topology and sizing optimization. And the results showed that our solution is better than or just about the same as the best one of the previous researches. Furthermore, we applied this method to the topology and sizing optimization of a crossbeam slider for a high-speed machining center. The topology optimization result gives the best desirable cross-section shape whose weight was reduced by 38.8% than the original configuration. The subsequent static and dynamic design optimization reduced the weight, static and dynamic compliances by 5.7 %, 2.1% and 19.1% respectively from the topology-optimized model. The examples demonstrated the feasibility of the suggested design optimization method.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.89-97
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• 1997

A genetic algorithm (GA) is a stochastic direct search strategy that mimics the process of genetic evolution. The GA applied herein works on a population of structural designs at any one time, and uses a structured information exchange based on the principles of natural selection and wurvival of the fittest to recombine the most desirable features of the designs over a sequence of generations until the process converges to a "maximum fitness" design. Principles of genetics are adapted into a search procedure for structural optimization. The methods consist of three genetics operations mainly named selection, cross- over and mutation. In this study, a method of finding the optimum topology of truss/beam structure is pro- posed by using the GA. In order to use GA in the optimum topology problem, chromosomes to FEM elements are assigned, and a penalty function is used to include constraints into fitness function. The results show that the GA has the potential to be an effective tool for the optimal design of structures accounting for sizing, geometrical and topological variables.variables.