• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1583-1588
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• 2000

The dynamic characteristics of a HDD suspension system are investigated by finite element analysis and experimental modal analysis. A finite element model of the suspension Type850 was developed for unloaded case. The calculated vibration modes were compared with measurements and agree well in shape and frequency except some local modes. Local thickness and Young's modulus of the finite element model are updated by modal tuning method to develop the precise FE model. A sensitivity matrix of the natural frequencies for some design variables was calculated using finite difference method. Most natural frequencies calculated by the tuned FE model coincide with the measurements and the errors between them are less than 2%.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.140-145
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• 2001

The tape carrier package(TCD) is one of the most important components in a liquid crystal display(LCD) module. It has a role to transmit electrical signals from a printed circular board(PCB) to a display panel. If TCP is damaged under mechanical shock, the signals can not be transmitted to the panel and as a result, some dead lines are generated on the panel. This kind of phenomenon is commonly called as 'line defects'. In this paper, new structural design concepts of TCP are proposed to guarantee its reliability by using Taguchi's approach and dynamic FE-analysis. The line defects problem of TCP module is solved by replacing the original TCP with the newly designed one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.840-840
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• 2003

Operational Modal Analysis (OMA) is a technique for identification of modal parameters by measurement of only the system's response. On many lightweight structures, such as load-speaker cones and disk drive read/write heads, is impossible or impractical to measure the input forces. Another characteristic of lightweight structure is their sensitivity to mass loading from sensors. The Scanning Laser Doppler Vibrometry(SLDV) allows response measurements to be taken without mass loading. One disadvantage of OMA testing compared to tradition input output modal testing is the OMA mode shapes are un-scaled. This means that the mode shape obtained from an OMA test can not used for analytical structural modification studies. However, the un-scaled mode shapes from an OMA test can be used to update a Finite Element Model (FEM). The updated FEM can then be used to analytically predict the effect of structural modifications. This paper will present the results of an OMA test performed on a simple plate and motor in operating conditions. The un-scaled mode shapes from this test will be used to update a FEM model of the system. The updated FEM model will be then be used to predict the effect of attaching a mass to the plate. The shapes predicted by the FEM for the modified system will be compared to a second OMA test on the modified system

• The KSFM Journal of Fluid Machinery
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• v.5 no.3 s.16
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• pp.40-45
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• 2002

Since the previous cut-and-try design algorithm requires much cost and time, the automated design technique with the CFD and optimum design algorithm has recently been concerned. In this work, the Navier-Stokes equation was solved to gain more detailed viscous flow information of cascade with rotor-stator interactions. The H-grid embedded by O-grid was generated to obtain more accurate solution by eliminating the branch cut of H-grid near airfoil surface. To handle the relative motion of the rotor to the stationary stator, the sliding multiblock method was applied and the cubic-spline interpolation was used on the block interface boundary. To validate present procedure, the time-averaged aerodynamic loads were compared with experimeatal data. A good agreement was obtained. The Modified Method of Feasible Direction (MMFD) was used to carry out the sensitivity analysis of the change of aerodynamic performance by the changes of the cascade geometry. The present optimization of the cascade gave a dramatic reduction of the drag while the lift maintains at the value within the user-specified tolerance.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.123-134
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• 2004

In this research, a multilevel decomposition technique to enhance the efficiency of the configuration optimization of truss structures was proposed. On the first level, the nonlinear programming problem was formulated considering cross-sectional areas as design variables, weight, or volume as objective function and behavior under multiloading condition as design constraint. Said nonlinear programming problem was transformed into a sequential linear programming problem. which was effective in calculation through the approximation of member forces using behavior space approach. Such approach has proven to be efficient in sensitivity analysis and different form existing shape optimization studies. The modified method of feasible direction (MMFD) was used for the optimization process. On the second level, by treating only shape design variables, the optimum problem was transformed into and unconstrained optimal design problem. A unidirectional search technique was used. As numerical examples, some truss structures were applied to illustrate the applicability. and validity of the formulated algorithm.

• The Journal of Advanced Prosthodontics
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• v.14 no.3
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• pp.182-202
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• 2022

PURPOSE. The aim of this study is to summarize various biomechanical aspects in evaluating the long-term stability of dental implants based on finite element method (FEM). MATERIALS AND METHODS. A comprehensive search was performed among published studies over the last 20 years in three databases; PubMed, Scopus, and Google Scholar. The studies are arranged in a comparative table based on their publication date. Also, the variety of modeling is shown in the form of graphs and tables. Various aspects of the studies conducted were discussed here. RESULTS. By reviewing the titles and abstracts, 9 main categories were extracted and discussed as follows: implant materials, the focus of the study on bone or implant as well as the interface area, type of loading, element shape, parts of the model, boundary conditions, failure criteria, statistical analysis, and experimental tests performed to validate the results. It was found that most of the studied articles contain a model of the jaw bone (cortical and cancellous bone). The material properties were generally derived from the literature. Approximately 43% of the studies attempted to examine the implant and surrounding bone simultaneously. Almost 42% of the studies performed experimental tests to validate the modeling. CONCLUSION. Based on the results of the studies reviewed, there is no "optimal" design guideline, but more reliable design of implant is possible. This review study can be a starting point for more detailed investigations of dental implant longevity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.9-16
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• 2014

Using a level set method and topological derivatives, a topological shape optimization method that is independent of an initial design is developed for linearly elastic structures. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. The "Hamilton-Jacobi(H-J)" equation and computationally robust numerical technique of "up-wind scheme" lead the initial implicit boundary to an optimal one according to the normal velocity field while minimizing the objective function of compliance and satisfying the constraint of allowable volume. Based on the asymptotic regularization concept, the topological derivative is considered as the limit of shape derivative as the radius of hole approaches to zero. The required velocity field to update the H-J equation is determined from the descent direction of Lagrangian derived from optimality conditions. It turns out that the initial holes are not required to get the optimal result since the developed method can create holes whenever and wherever necessary using indicators obtained from the topological derivatives. It is demonstrated that the proper choice of control parameters for nucleation is crucial for efficient optimization process.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.49-54
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• 2015

Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.205-208
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• 2008

Generally, there are several types in rear suspension. The rear suspension of subframe type consisting of side member and front/rear cross member is widely used in a medium car and full car. In the small car case, the beam of tubular type without independent suspension system is used to reduce manufacturing cost. The optimized rear suspension of subframe type using hydroforming method has been developed in this study. In designing suspension, the driving stability and durability performance should be considered as an important factor. The stability is related to dynamic frequency and durability is connected with stress analysis of structure. We focus on increasing the stiffness of suspension and decreasing the maximum stress relating to durability cycle life. For making use of the merits of hydroforming which is possible to make the bead, tube expansion, and feeding in desiring position, several optimization design techniques such as shape, size, and topology optimization are proposed. This optimization scheme based on the sensitivity can provide distinguished performance improvement in using hydroforming. Through commercial software based on the finite element, the superiority of this design method is demonstrated.

• Journal of the Regional Association of Architectural Institute of Korea
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• v.20 no.6
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• pp.63-70
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• 2018

This study is aimed to reflect the current status survey, analysis and response of 10 railway stations using geographical names in one of 19 stations located on Gyeongbu, Honam and Chungbuk line. Most railway stations in the study have shown normal images that are close to the standard type by selecting similar building materials rather than reflecting geographical features. Aside from the shape of the traditional Korean house in Cheongju, almost all newly constructed stations tend to incorporate light gray plating material on their modern exterior to produce Family look design as a railroad station. According to a survey of the sensitivity of the station's name, Osong Station was 73.6 percent, Gyeryong Station 67.3 percent, Heukseok-ri Station was 64.5 percent, Shintan-jin 62.6 percent, and Yeonsan Station 57 percent, more than half. Therefore, the results of the five stations were presented as a calculation and proposed design release focusing on the facades of each station. Each of these stations suggested a way to express the facade design image, considering the railway operation status of Korea Railroad, the area of the station and other surroundings.