• The Journal of the Acoustical Society of Korea
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• v.34 no.3
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• pp.219-226
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• 2015

In this paper, derivation of the STL (Sound Transmission Loss) of a square plate installed in an impedance tube is discussed using an analytic method. Coupled motion of the plate vibration and acoustic field is considered. Vibration of the plate and pressure field inside the tube are expressed in terms of the infinite series of modal functions. Under the plane wave assumption, it is shown that consideration of the first few modes yields sufficiently accurate results. When the boundary of the plate is clamped, vibration mode is assumed as a multiplication of the beam modes corresponding to the crosswise directions. The natural frequencies of the clamped plate are calculated using the Rayleigh-Ritz method. It is found that the STL shows a dip at the lowest natural frequency of the plate, and increases as the frequency decreases below the natural frequency. Comparison of the result in this paper with the STL obtained by measurements and FE computations in the reference shows an excellent agreement.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.99-108
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• 2015

The partially restrained smart CFT (concrete filled tube) column-to-beam connections with top-seat split T connections show various behavior characteristics according to the changes in the diameter and tightening force of the fastener, the geometric shape of T-stub, and material properties. This paper presents results from a systematic three-dimensional nonlinear finite element study on the structural behavior of the top-seat split T connections subjected to cyclic loadings. This connection includes super-elastic shape memory alloy (SMA) T-stub and rods to obtain the re-centering capabilities as well as great energy dissipation properties of the CFT composite frame. A wide scope of additional structural behaviors explain the influences of the top-seat split T connections parameters, such as the different thickness and gage distances of split T-stub.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.395-402
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• 2016

Space frame structures considering the components such as forms, layers, grids, etc. are possible to form a large space without interior columns. Here, steels having the yield strengths of 210 MPa to 450 MPa are generally used. The high strength steel (i.e., yield strength of 690 MPa) having suitable weldability, aseismicity and economics have been recently developed. In this paper, the high strength steel is applied to the space frame structures in order to analytically find out their transient responses considering the material and geometric nonlinearities. For various circular dome types of space frame structures, the modal analysis and nonlinear transient analysis are carried out using nonlinear three dimensional finite element analysis.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.149-150
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• 2013

Recently, various types of perforated breakwaters are being constructed for protecting offshore storm waves. In general, perforated breakwaters have wave chambers with perforated walls at seaside. Purposes of the wave chambers are to reduce wave reflections and maximum wave forces acting on the breakwater. Impact wave forces due to wave breaking can attack to the perforated wall directly, so the effects have to be considered in the design of the perforated wall carefully. Using resonance channels for wave energy dissipation, a new concept perforated breakwater is proposed, which is free from impact loads. Numerical simulation was made for wave reflection characteristics of the breakwater with respect to major design parameters. Numerical analysis was carried out using the Galerkin's FE model based on the linear potential theory considering energy dissipation on the perforated plate. Variations of wave reflection was investigated according to perforated ratios of perforated plate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.145-152
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• 2011

Current Bridge Specification for Highway Bridges adopts a simplified method to determine sectional forces of abutment wing by dividing its area into four sections. This simplified method was developed in Japan when numerical analysis was not mature and computer resources were expensive. This simplified method has been with us without modification. This study evaluates the problem of current design practice to improve the design guideline for abutment wing. In this study, a finite element model of abutment wing based on shell elements was developed to obtain accurate sectional force. In addition, foreign design specifications regarding abutment wing were thoroughly examined. It has been observed that sectional forces obtained from the simplified method produce inaccurate results under various geometric shapes. Thus, it is recommended that two dimensional plate analyses should be adopted for future design of abutment wing wall.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2565-2573
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• 2002

A basic research was performed to ensure the usefulness of Small Punch-creep(SP-creep) test for residual life evaluation of heat resistant components effectively. This paper presents analytical results of initial stress and strain distributions in SP specimen caused by constant loading for SP-creep test and its experimental correlations with uniaxial creep(Ten-creep) test on 9Cr1MoVNb steel. It was shown that the initial maximum equivalent stress, ${\sigma}_{eq{\cdot}max}$ from FE analysis was correlated with steady-state equivalent creep strain rate, ${\epsilon}_{qf-ss'}$ rupture time, $t_r$, activation energy, Q and Larson-Miller Parameter, LMP during SP-creep deformation. The simple correlation laws, ${\sigma}_{sp}-{\sigma}_{TEN}$, $P_{sp}-{\sigma}_{TEN}\; and\; Q_{sp}-Q_{TEN}$ adopted to established a quantitative correlation between SP-creep and Ten-creep test data. Especially, the activation energy obtained from SP-creep test is linearly related to that from Ten-creep test at $650^{\circ}C$ as follows : $Q_{SP-P}\;{\risingdotseq}\;1.37 \;Q_{TEN},\; Q_{SP-{\sigma}}{\risingdotseq}1.53\; Q_{TEN}$.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.497-503
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• 2012

The aim of this study was to optimize S-tube shape of heat exchanger in term of reducing the size of tube bundle and improving the mechanical properties such as the thermal stress and resonance. The geometric parameters such as offset length, the straight distance between one end and other end of tube, the tube length in straight portion and fillet radius was assessed as a valid parameters. The structural analysis was performed to estimate the structural characteristics. Main effect analysis was performed to investigate the main effect for the various geometric parameters. The response surface methodology was employed to establish mathematical approximation models as a function of the geometric parameters of the S-tube. Also, The optimization was performed to optimize geometric parameters of S-tube using the regression equations and optimization tool. The optimized tube shape has been proposed. Those could be used in the heat exchanger design used in high temperature.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.3
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• pp.183-190
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• 2017

Carton clamp truck is widely perceived as the high-efficient handling equipment of factory premises and warehouse by its capability of palletless handling. Therefore, the significance of a lab-based handling simulation is becoming higher with the growth of clamp truck usage. In this study, preliminary FEA and design of handling test courses for the lab-based simulation of carton clamp truck handling were performed, and the PSD analyses were performed for the modified one for the test course proposed by Park et al. (2017) as well as ASTM D 6055 and ISTA 3B standards. For the vibration in all directions, the vibration energy intensity analyzed by ISTA 3B standard showed higher than that by the other two cases. A FEA was performed for the handling operation of the sudden stop of the clamps after lifting the target HCP (heavyweight refrigerator corrugated package, w=180 kgf) up to the specified height. The slip distance between the clamp arm and the target HCP was 0.85 mm. The simulation result of 0.85 mm was 3.7 times lower than the experimental result (3.2 mm) obtained by Park et al. (2017), and it was estimated that the deviation comes from both the experimental error by weight imbalance of target HCP, and excessive simplification during the FE modelling of target HCP.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.5
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• pp.553-560
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• 2015

Fracture mechanics analysis for cracked pipes is essential for applying the leak-before-break (LBB) concept to nuclear piping design. For LBB assessment, crack instability and leak rate should be predicted accurately for through-wall cracked pipes. In a nuclear piping system, elbows are connected with straight pipes by circumferential welding; this weld region is often considered a critical location. Hence, accurate crack assessment is necessary for cracks in the interface between elbows and straight pipes. In this study, the stress intensity factor (SIF) and elastic crack opening displacement (COD) were estimated through detailed 3D elastic finite element (FE) analyses. Based on the results, closed-form solutions of shape factors for calculating the SIFs and elastic CODs were proposed for circumferential through-wall cracks in the abovementioned interfaces under internal pressure. In addition, the effect of the elbow on shape factors was investigated by comparing the results with the existing solutions for a straight pipe.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.2 s.23
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• pp.77-82
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• 2005

Previously sailing yachts or leisure yachts were mainly made from FRP(Fiber glass reinforced plastic) in the small shipbuilding, but recently there is a trend to replace it for steel or aluminum to substitute FRP for environmental friendly materials. Although It have to need a many checked item in case of hull girder strength and transverse strength normally evaluate base on calculation of class guideline so called direct calculation method. Otherwise. this method of initial structural design considered enough for safety margin on the structure. But, case of small craft must consider for evaluating local strength through rational method. In this paper, check the bow structure members for satisfying results base on allowable stress criterion of damaged bow structure by dynamic load due to slamming and bottom impact load due to pitching motion through finite element analysis. and investigate engine bed structure considering engine weight load and transverse wave load.